ImagineNano2015 Poster book by Phantoms Foundation

/ŵĂŐŝŶĞEĂŶŽϮϬϭϱ /ŶĚĞǆ

&ŽƌĞǁŽƌĚ KƌŐĂŶŝƐĞƌƐ ^ƉŽŶƐŽƌƐ ǆŚŝďŝƚŽƌƐ WŽƐƚĞƌƐ

ϱ ϳ ϭϭ ϭϱ

'ƌĂƉŚĞŶĞ

ϭϵ

EĂŶŽ^ƉĂŝŶ ŝŽΘDĞĚ

Ϯϰϳ

EĂŶŽ^ƉĂŝŶ ŚĞŵŝƐƚƌǇ

Ϯϴϳ

EĂŶŽ^ƉĂŝŶ dŽǆŝĐŽůŽŐǇ

ϯϭϵ

WWD

ϯϯϵ

/ŵĂŐĞ ĐƌĞĚŝƚ͗ DƵůƚŝĐĂůĞ ƐŝŵƵůĂƚŝŽŶƐ ŽĨ ƚŚĞ ŐƌŽǁƚŚ ŽĨ ŐƌĂƉŚĞŶĞ ŽŶ ĐŽƉƉĞƌ͘ >͘ ,ĞŶƌĂƌĚ͕ W͘ 'ĂŝůůĂƌĚ͕ d͘ ŚĂŶŝĞƌ͕ W͘ DŽƐŬŽǀŬŝŶ ĂŶĚ ^͘ >ƵĐĂƐ ;hŶŝǀĞƌƐŝƚǇ ŽĨ EĂŵƵƌ͕ ĞůŐƵŝŵͿ

ĚǀĞƌƚŝƐĞŵĞŶƚ ͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺͺ

/ŵĂŐŝŶĞEĂŶŽϮϬϭϱ

KŶ ďĞŚĂůĨ ŽĨ ƚŚĞ /ŶƚĞƌŶĂƚŝŽŶĂů͕ ^ĐŝĞŶƚŝĨŝĐ ĂŶĚ dĞĐŚŶŝĐĂů ŽŵŵŝƚƚĞĞƐ ǁĞ ƚĂŬĞ ŐƌĞĂƚ ƉůĞĂƐƵƌĞ ŝŶ ǁĞůĐŽŵŝŶŐ ǇŽƵ ƚŽ ŝůďĂŽ ĨŽƌ ƚŚĞ ƚŚŝƌĚ ĞĚŝƚŝŽŶ ŽĨ /ŵĂŐŝŶĞEĂŶŽ͘

/ŵĂŐŝŶĞEĂŶŽϮϬϭϱ

&ŽƌĞǁŽƌĚ

KƌŐĂŶŝƐĞƌƐ

ĂĐŬ ŝŶ ϮϬϭϯ͕ /ŵĂŐŝŶĞEĂŶŽ ĞǀĞŶƚ ŚĂƐ ƐƚƌĞŶŐƚŚĞŶĞĚ ŝƚƐ ƉŽƐŝƚŝŽŶ ĂƐ ƚŚĞ ŵĂŝŶ ĞǀĞŶƚ ĚĞĚŝĐĂƚĞĚ ƚŽ ŶĂŶŽƐĐŝĞŶĐĞ ĂŶĚ ŶĂŶŽƚĞĐŚŶŽůŽŐǇ ŝŶ ƵƌŽƉĞ͘ dŚĞ ŽƵƚƐƚĂŶĚŝŶŐ ƌĞƐƵůƚƐ ŽĨ ƉĂƌƚŝĐŝƉĂƚŝŽŶ ƚŚĂƚ ŚĂǀĞ ďĞĞŶ ƌĞĂĐŚĞĚ ĂŶĚ ƚŚĞ ŝŶƚĞƌĞƐƚ ĐƌĞĂƚĞĚ ďǇ ƚŚĞ ĚŝƐĐƵƐƐŝŽŶƐ͕ ŚĂǀĞ ůĂŝĚ ƚŚĞ ĨŽƵŶĚĂƚŝŽŶƐ ĨŽƌ ƚŚĞ ƵƉĐŽŵŝŶŐ ĞĚŝƚŝŽŶ͘ /ŵĂŐŝŶĞEĂŶŽ ϮϬϭϱ ŝƐ ŶŽǁ ĂŶ ĞƐƚĂďůŝƐŚĞĚ ĞǀĞŶƚ ĂŶĚ ŝƐ ĐŽŶƐŝĚĞƌĞĚ ŽŶĞ ŽĨ ƚŚĞ ůĂƌŐĞƐƚ ƵƌŽƉĞĂŶ ŝŶ ƚŚĞ ĨŝĞůĚ͘ dŚĞ ĞǀĞŶƚ ŝƐ ĂŶ ĞǆĐĞůůĞŶƚ ƉůĂƚĨŽƌŵ ĨŽƌ ĐŽŵŵƵŶŝĐĂƚŝŽŶ ďĞƚǁĞĞŶ ƐĐŝĞŶĐĞ ĂŶĚ ďƵƐŝŶĞƐƐ͕ ďƌŝŶŐŝŶŐ ƚŽŐĞƚŚĞƌ EĂŶŽƐĐŝĞŶĐĞ ĂŶĚ EĂŶŽƚĞĐŚŶŽůŽŐǇ ŝŶ ƚŚĞ ƐĂŵĞ ƉůĂĐĞ͘ /ŶƚĞƌŶĂƚŝŽŶĂůůǇ ƌĞŶŽǁŶĞĚ ƐƉĞĂŬĞƌƐ ǁŝůů ďĞ ƉƌĞƐĞŶƚŝŶŐ ƚŚĞ ůĂƚĞƐƚ ƚƌĞŶĚƐ ĂŶĚ ĚŝƐĐŽǀĞƌŝĞƐ ŝŶ EĂŶŽƐĐŝĞŶĐĞ ĂŶĚ EĂŶŽƚĞĐŚŶŽůŽŐǇ͘ hŶĚĞƌ ƚŚĞ ƐĂŵĞ ƌŽŽĨ ǁŝůů ďĞ ŚĞůĚ ϱ /ŶƚĞƌŶĂƚŝŽŶĂů ŽŶĨĞƌĞŶĐĞƐ ;'ƌĂƉŚĞŶĞ͕ EĂŶŽ^ƉĂŝŶ ŚĞŵŝƐƚƌǇ͕ ŝŽΘDĞĚ͕ dŽǆŝĐŽůŽŐǇ ĂŶĚ WWDͿ͕ Ă ŚƵŐĞ ĞǆŚŝďŝƚŝŽŶ ƐŚŽǁĐĂƐŝŶŐ ĐƵƚƚŝŶŐͲĞĚŐĞ ĂĚǀĂŶĐĞƐ ŝŶ ŶĂŶŽƚĞĐŚŶŽůŽŐǇ ƌĞƐĞĂƌĐŚ ĂŶĚ ĚĞǀĞůŽƉŵĞŶƚ͕ ĂŶ ŝŶĚƵƐƚƌŝĂů ĨŽƌƵŵ ĂŶĚ Ă ďƌŽŬĞƌĂŐĞ ĞǀĞŶƚ͘ /ŵĂŐŝŶĞEĂŶŽ ǁŝůů ŐĂƚŚĞƌ ƚŚĞ ŐůŽďĂů ŶĂŶŽƚĞĐŚŶŽůŽŐǇ ĐŽŵŵƵŶŝƚǇ͕ ŝŶĐůƵĚŝŶŐ ƌĞƐĞĂƌĐŚĞƌƐ͕ ŝŶĚƵƐƚƌǇ͕ ƉŽůŝĐǇŵĂŬĞƌƐ ĂŶĚ ŝŶǀĞƐƚŽƌƐ͘dŚĞ ůĂƚĞƐƚ ƚƌĞŶĚƐ ĂŶĚ ĚŝƐĐŽǀĞƌŝĞƐ ŝŶ EΘE ĨƌŽŵ ƐŽŵĞ ŽĨ ƚŚĞ ǁŽƌůĚǲƐ ůĞĂĚŝŶŐ ƉůĂǇĞƌƐ ŝŶ ƚŚĞ ĨŝĞůĚ ǁŝůů ďĞ ĚŝƐĐƵƐƐĞĚ͘ tĞ ǁŽƵůĚ ůŝŬĞ ƚŽ ƚŚĂŶŬ Ăůů ƉĂƌƚŝĐŝƉĂŶƚƐ͕ ƐƉŽŶƐŽƌƐ ĂŶĚ ĞǆŚŝďŝƚŽƌƐ ƚŚĂƚ ũŽŝŶĞĚ ƵƐ ƚŚŝƐ ǇĞĂƌ͘ dŚĞ ĂƐƋƵĞ ŽƵŶƚƌǇ ĚĞŵŽŶƐƚƌĂƚĞƐ ŝƚƐ ƐƚƌĞŶŐƚŚƐ ŝŶ ŶĂŶŽƐĐŝĞŶĐĞ͕ ŵŝĐƌŽ ĂŶĚ ŶĂŶŽƚĞĐŚŶŽůŽŐǇ͕ ĂŶĚ ƉŽƐŝƚŝŽŶƐ ŝƚƐĞůĨ ĂƐ Ă ŵĂũŽƌ ƉůĂǇĞƌ ŝŶ ƚŚĞ ͞ŶĂŶŽ͟ ǁŽƌůĚ͕ ƌĞĂƐŽŶ ǁŚǇ /ŵĂŐŝŶĞEĂŶŽ ŝƐ ŽƌŐĂŶŝǌĞĚ ĨŽƌ ƚŚĞ ϯƌĚ ƚŝŵĞ ŝŶ ŝůďĂŽ͘ dŚĞƌĞǲƐ ŶŽ ĚŽƵďƚ ƚŚĂƚ /ŵĂŐŝŶĞEĂŶŽ ϮϬϭϱ ŝƐ ƚŚĞ ƌŝŐŚƚ ƉůĂĐĞ ƚŽ ƐĞĞ ĂŶĚ ďĞ ƐĞĞŶ͘ ,ŽƉĞ ƚŽ ƐĞĞ ǇŽƵ ĂŐĂŝŶ ŝŶ ƚŚĞ ŶĞǆƚ ĞĚŝƚŝŽŶ ŽĨ /ŵĂŐŝŶĞEĂŶŽ ;ϮϬϭϳͿ͘

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'ƌĂƉŚĞŶĞ ϮϬϭϱ

21 | G r a p h e n e

Lorcan Brennan, Alexander Loudon, Yuri Gun’ko and Tatiana Perova

Baldycheva, Anna

Thomas Dieing and Ute Schmidt

Bailo, Elena

Sonia Haddad

Assili, Mohamed

Ratter K., Gilles B., Bendiab N., Magaud L., Coraux J.,Chapelier C

Artaud, Alexandre

Darnel Allen, Sharadha Sambasivan

Archibald, Wayne

Marc Delaunay, Gérard Bidan, Jan Wimberg, Thomas J. S. Schubert, Jean-Michel Gérard, Saïd Sadki

Aradilla, David

Zheling Li, Ian A. Kinloch, Robert J. Young, Kostya S. Novoselov, John Parthenios, Costas Galiotis, Konstantinos Papagelis

Anagnostopoulos, George

Eun-Jeong Lee, Hye-Jung Kim, Ikpyo Hong

An, Jung-Chul

Johan Stiens, Gennady Shkerdin

Alkorre, Hameda

Jean-Christophe Charlier

Adjizian, Jean-Joseph

authors

Germany

Tunisia

France

Virgin Islands

France

Greece

Korea

Belgium

country

Investigation of composite structures based on graphene and graphene oxide

Visualizing Graphene Properties at Highest Performance and Resolution Using Confocal Raman, AFM, SNOM and SEM

Long-wavelength optical phonon behavior in uniaxial strained graphene: Role of electron-phonon interaction

Graphene growth by “magical sizes” graphene nanoclusters assembly on Re(0001)

Investigating the electrical properties of doped graphene using near-edge X-ray absorption fine structure spectroscopy

Symmetric micro-supercapacitors based on vertical graphene nanosheet electrodes with high power and energy density performances

CVD graphene on polymer substrate under tension

Preparation of Graphene Nanoplatelets from Polymer-derived Graphite Film by GIC (Graphite Intercalation Compound) via Process

Planar four layers waveguide structure at sub-THz frequencies comprising metal and garphene: a complex scenery of coupled modes

Modelling atomic force microscopy nano-indentation in copper covered by graphene

poster title

Graphene 2015 Posters list: alphabetical order

22 | G r a p h e n e

D. Kostiuk, P. Siffalovic, M. Hodas, M. Pelletta, M. Jergel and E. Majkova

Bodik, Michal

Pablo M. Romero, Nerea O. Otero

Bobrinetskiy, Ivan

Patricia Álvarez, Clara Blanco, M. Victoria Jiménez, Javier Fernández-Tornos, Jesús J. Pérez-Torrente, Luis A. Oro and Rosa Menéndez

Blanco, Matías

Adolfo De Sanctis, Plablo Alonso, Iban Amenabar, Jianing Chen, Thomas H. Bointon, Monica F. Craciun, Javier García de Abajo, Saverio Russo, Rainer Hillenbrand, and Frank Koppens

Bezares, Francisco

Daniel Emmrich, Emanuel Marschewski, Achim Nadzeyka, Frank Nouvertné, Armin Gölzhäuser

Beyer, Andre

Andreas Inhofer

Bercioux, Dario

R. Y. Sato Berrú, and D. Mendoza

Bautista Flores, Claudia

Aron W. Cummings, Max Seifert, Marco Bobinger, Matthias Sachsenhauser, Jose A. Garrido and Stephan Roche

Barrios Vargas, Jose Eduardo

W. Yan, L. C. Phillips, S. Hämäläinen, A. Lombardo, M. Ghidini, X. Moya, F. Maccherozzi, S. van Dijken, S. S. Dhesi, N. D. Mathur and A. C. Ferrari

Barbone, Matteo

Sejal Doshi, A. S. Panwar, D. Bahadur

Bansal, Prerna

authors

Slovakia

Spain

Germany

Spain

Mexico

Spain

India

country

Large-area deposition of few-layer graphene produced by liquid phase exfoliation of expanded graphite

Differences in the changes of the optical and morphological properties depending on the number of graphene layers under UV oxidation

The effect of the support in the catalytic activity of iridium NHC complexes covalently bonded to carbon nanotubes and graphene oxide

Surface Plasmons in Highly-Doped Graphene

Nanopores in Silicon Nitride Membranes, Graphene and CNM: Milling and Imaging Techniques at the Helium Ion Microscope

Driven Topological Insulator Quantum Dot: A spin-particle source (SpPS)

Negative photoconductivity in the fullerene C60-few layer graphene system

Electronic transport in doped polycrystalline graphene

Spin diffusion length in LSMO–graphene spin valves

Exoelectrogens leading to precise reduction of graphene oxide

poster title

23 | G r a p h e n e

Ferney Chaves, David Jimenez

Chaves Romero, Ferney Alveiro

E. Bertran , J.L. Andújar and E.Pascual

Chaitoglou, Stefanos

Laure Fillaud, Xavier Lefevre, Renaud Cornut, Bruno Jousselme,Vincent Derycke

Casademont, Hugo

Marco Pala, Alessandro Cresti and David Esseni

Cao, Jiang

I. Wlasny, A. Busiakiewicz, P. Dabrowski, M. Rogala, P. J. Kowalczyk, I. Pasternak, W. Strupinski, J. M. Baranowski, Z. Klusek

Busiakiewicz, Adam

F. Pizzocchero, B. S. Jessen, P. Bøggild, P. U. Jepsen, D. H. Petersen

Buron, Jonas

P. Kühne, I.G. Ivanov, F. Giannazzo, V. Stanishev, A. A. Zakharov, T. Hofmann, M. Schubert, T. Iakimov, F. Roccaforte, R. Yakimova, V. Darakchieva

Bouhafs, Chamseddine

Daniel Carriazo, Teófilo Rojo, Gurpreet Singh

Botas, Cristina

J. Pedrós, J. Martínez, F. Calle

Bosca Mojena, Alberto

Filippo Pizzocchero, Marco Vanin, Jens Kling, Thomas W. Hansen, Karsten W. Jacobsen, Peter Bøggild

Booth, Timothy

Igor Píš and S. Nappini, M. Parravicini, A. Papagni, E. Magnano

Bondino, Federica

authors

Spain

Greece

France

Poland

Denmark

Sweden

Spain

Denmark

Italy

country

A Theoretical Study of the Electrostatics and Electronic Transport of the Graphene Barristor

Effect of a balanced concentration of hydrogen on a high quality graphene CVD growth

MoS2 Transistors with Electrografted Organic Ultrathin Film as Efficient Gate Dielectric

Quantum simulation of tunnel field-effect transistors based on transition metal dichalcogenides

The study of corrosion of copper protected by graphene coatings

Large-scale electrical characterization of graphene

Large-area mono-and decoupled bilayer graphene grown on C-face 4H-SiC(0001) by high temperature sublimation

Novel Sn/SnO2@rGO self-standing 3D architectures as anodes for Lithium ion batteries

Lab-scale system for automated graphene transfer

Dynamics of the graphene-metal nanoparticle catalyst interface during catalytic channeling

X-ray Spectroscopy Study of Surface-Assisted Graphene Growth from Brominated Molecular Precursors on Silver Substrates

poster title

24 | G r a p h e n e

F. Javier García de Abajo

Cox, Joel

Johan Ek Weis, Otakar Frank, Martin Kalbac

Costa, Sara

Qian Wu, Marc Porti, Narcis Mestres, Montserrat Nafría, Xavier Aymerich

Claramunt, Sergi

M. Dudynski, G. Kowalski, M. Tokarczyk, I. Jozwik ,P. Gebarowski

Ciepielewski, Pawel

S. Katsiaounis, E. Michail, M. Fakis,V.Drakopoulos,I. Polyzos, J. Parthenios, C. Galiotis,And K. Papagelis

Chourdakis, Nikolaos

Jinsik Choi, Seung-Bok Yang, Il-Doo Kim, Sung-Yool Choi, Young-Jun Yu, Choon-Gi Choi

Choi, HongKyw

Suguna Perumal, Mi Ri Kim, Kyungtae Park

Cheong, In Woo

A Davies, A. Summerfield, I. Cebula, A. N. Khlobystov, P. H. Beton, C. T. Foxon, L. Eaves, S. V. Novikov

Cheng, Tin

Irene Calizo, Angela R. Hight Walker

Cheng, Guangjun

Frederic Lafollet, Saioa Cobo, Guy Royal, Emmanuel Flahaut, Dipankar Kalita, Vincent Bouchiat, Laëtitia Marty, Nedjma Bendiab

Chen, Yani

authors

Spain

Czech Republic

Spain

Poland

Greece

Korea

USA

France

country

Nonlinear Graphene Plasmonics

Study of face-dependent graphene-copper interaction by heat treatment

Improvement of the transfer process of CVD graphene

Graphene structures obtained from biomass

Controlled induced defects on CVD graphene using ultrashort pulsed excitation

Graphene-based gas molecular sensor and hybrid transparent electrode applications

Amphiphilic block copolymers for graphene dispersions

Molecular beam epitaxial growth of graphene on sapphire substrates at extremely high temperatures

Probing the Ni(111)-graphene interface using Raman spectroscopy

Transistors based on graphene or double wall carbon nanotube hybrids for optoelectronics

poster title

25 | G r a p h e n e

C. Agnès, Q. Palomar, Y. Chenavier, L. Dubois, G.Bidan

Duclairoir, Florence

Jean-Christophe Charlier

Dubois, Simon

P. Kazmierczak, E. Karpierz, R. Bozek, A. Wolos, M. Kaminska, A. Wysmolek, I. Pasternak, A. Krajewska, W. Strupinski

Drabinska, Aneta

A. Usher, J. Martin

Downs, Christopher

Chernozatonskii L.A.

Demin, Victor

I. Goykhman, M. Bruna, A. Eiden, U. Sassi, M. Barbone, D. Dumcenco, K. Marinov, A. Kis and A.C. Ferrari

De Fazio, Domenico

A. R. Piacenti, M. Autore, F. Giorgianni, Y. Ito, M. Chenand S. Lupi

Dapuzzo, Fausto

Helena Rocha, Maria C. Paiva, M. Fernanda Proença, Paulo E. C. Lopes, Mariam Debs, Manuel Melle-Franco, Francis L. Deepak, Robert Young, Liv Hornekaer

Cunha, Eunice

Ibon Aranberri, Juan José Campos

Cuevas, José Mª

Dinh Van Tuan, David Soriano, Aron W. Cummings and Stephan Roche

Cresti, Alessandro

authors

France

Belgium

Poland

Russia

Italy

Portugal

Spain

France

country

Bi-functional organic linkers for 3D graphene oxide frameworks fabrication

Magnetism and spin-orbit coupling in defective graphene from first-principles

Electron scattering in graphene with NaCl nanoparticles adsorbed

Novel strain devices to observe pseudo-magnetic fields in suspended graphene membranes

Nanomeshes based on BN-graphene bilayer

Graphene/MoS2 Flexible Photo-detector

THz and Mid-Infrared Plasmonic Excitation in 3D Nanoporous Graphene

Controlled functionalized graphene nanoribbons produced from carbon nanotubes

Nanocomposites reinforced with carbon nanofibres for 3D printing

Graphene with enhanced spin-orbit coupling: Multiple quantum phases

poster title

26 | G r a p h e n e

Ana M. Pérez, Clara Blanco, Ricardo Santamaría, Marcos Granda, Patricia Álvarez, Rosa Menéndez

González, Zoraida

César Bernardo, Michael Belsley and Peter Schellenberg

Gonçalves, Hugo

Jason Christopher, Bo Wen, Zheng Han, Cory Dean, Anna Swan

Goldberg, Bennett

M. Insausti, B. Iraola, I. Bustero, F. FernándezCarretero, D. A. Pacheco Tanaka

Garcia, Alberto

James Huang

Galbiati, Arnaldo

Andreas Pospischil, Armin A. Zechmeister, Florian Libisch, Joachim Burgdörfer and Thomas Mueller

Furchi, Marco M.

H. Kim, D. Rouchon, N. Chevalier, V. Derycke, J. Bleuse, M. Chhowalla and O. Renault

Fregnaux, Mathieu

Patricia Álvarez, Marcos Granda, Clara Blanco, Ricardo Santamaría, Patricia Blanco, Zoraida González, Uriel Sierra, Antonio Páez, Rosa Menéndez

Fernandez, Laura

Xavier Cartoixà, David Jiménez

Feijoo Guerro, Pedro Carlos

Spain

Portugal

USA

Spain

Austria

France

Spain

Czech Republic

Ek Weis, Johan

Sara D. Costa, Otakar Frank and Martin Kalbac

country

I. Goykhman, D. De Fazio, U. Sassi, M. Barbone, A.C. Ferrari

Eiden, Anna

authors

Graphene modified graphite felts as effective electrodes in the positive half-cell of vanadium redox flow batteries

Evidence for enhanced longtime scale molecular fluorescence mediated by graphene

Strain and Friction in Few Layer 2D Crystals

Composite graphene/MnO2 as catalyst for air electrodes in metal-air batteries

Large-area Graphene Production using Roll-to-roll (R2R) Technology

Solar energy conversion in van der Waals heterostructures

Influence of substrate transfer process on the band structure and the optoelectronic properties of chemical vapor deposited MoS2 monolayers

Tuning graphene properties by a multi-step thermal reduction process

Channel Length Scaling of Graphene Field-Effect Transistors targeting Radio Frequency Applications

Isotopic labeling of bilayer graphene for advanced studies

High Responsivity Silicon-Graphene Schottky Avalanche Photodetectors for Visible and Telecom Wavelengths

poster title

27 | G r a p h e n e

P. Castell, A. Fernández Cuello, R. Guzmán de Villoria

Herrera-Ramírez, Luis Carlos

Camilo Acuña

Hernández, Yenny

P. Gaillard, T. Chanier, P. Moskovkin, S. Lucas

Henrard, Luc

Tim Batten, Mickael Febvre

Hayward, Ian

T. Iwai, S. Sato

Hayashi, Kenjiro

Koji Matsuzaki, Natsumi Saitou, Takaaki Taniguchi, and Yasumichi Matsumoto

Hara, Masahiro

A. F. Page, F. Ballout, O. Hess

Hamm, Joachim

Ick-Joon Park, Hamin Park, Sung-Yool Choi

Ha, Young Wook

Aleksandar Petrovski, Roberto Avolio, Perica Paunovic, Maria E.Errico,Beti Andonovic, Maria Cristina Coca, Gennaro Gentile,Francesca De Falco, Aleksandar Dimitrov, Maurizio Avella

Grozdanov, Anita

Stephen R. Power, Jesper Goor Pedersen, Antti-Pekka Jauho

Gregersen, Søren

A. Sindona, M. Pisarra, C. Vacacela, G. Falcone

Gravina, Mario

Dawn T. H. Tan and Brian Corbett

Gosciniak, Jacek

E. Puma, J. Piqueras, J. C. Cifuentes, G. Navickaite, T. Lasanta, I. Nikitskiy, R. Peréz, G. Konstantatos, F. Koppens

Goossens, Stijn

authors

Spain

Colombia

Belgium

Japan

Korea

Republic of Macedonia

Denmark

Italy

Ireland

Spain

country

The role of graphite nanoplatelets and carbon nanotubes on the enhanced fracture toughness and electrical conductivity of polypropylene composites

Layer by layer decoration of graphene and carbon nanotubes with magnetic nanoparticles

Multicale simulations of the growth of graphene on copper

Tip enhanced Raman analysis of graphene

Effects of Substrate Crystallinity on MoS2 Grown by CVD

UV photoresponse and magnetic control of single-layer titania nanosheets

Non-equilibrium plasmons with gain in graphene

Work-function engineering of CVD-grown graphene using Cs2CO3

Synthesis of polyaniline/graphene nanocomposite and its thermal, optical and electrochemical properties

Graphene on Antidot Lattice: Electronic and Transport Properties

Surface plasmons in the new generation of low dimensional materials: full wave modelling through linear response density functional theory

Theoretical investigation of graphene-based waveguide integrated photonic and plasmonic modulators

Prototype hybrid graphene quantum dot photodetector for VIS, NIR and SWIR

poster title

28 | G r a p h e n e

Sibel Kasap, Süleyman Çelik, Hasan Özkaya, Cenk Yanık, and Ismet I. Kaya

Khaksaran, Mohammad Hadi

Hadi Khaksaran, Süleyman Çelik, Hasan Özkaya, Cenk Yanık and Ismet I. Kaya

Kasap, Sibel

S. Sonuen, Ü. Çelik, Y. Uysall, E. Özgönül and A. Oral

Karamat , Shumaila

Pulickel M. Ajayan

Kabbani, Mohamad

Khang June Lee, Sang Yoon Yang, Sung-Yool Choi

Jung, Dae Yoo

Hyejeong Seong, Jong Yun Kim, Beom Jun Koo, Sung Kyu Kim, Sang Yoon Yang, Sung Gap Im, Sung-Yool Choi

Jang, Byung Chul

M. Waltl, A.D. Smith, S. Vaziri, M. Ostling, M.C. Lemme and T. Grasser

Illarionov, Yury

Mª Jesús Martín, Raúl Rengel

Iglesias, José M.

Po-Yuan Yu

Hsieh, Chien-Te

Alexander Zöpfl, Günther Ruhl, FrankMichael Matysik

Hirsch, Thomas

authors

Turkey

USA

Korea

Austria

Spain

Taiwan

Germany

country

Generating and Detecting the Spin Current in Y-shaped Semiconductor Nanowire with Quantum Point Contact

Optimization of CVD Growth Graphene on Nickel using Taguchi Method

Growth of Few Layer Single Crystal and Coalesced Graphene Grains on Platinum by Chemical Vapour Deposition

Synthesis and characterization of Kevlar’s analog graphene material

Control of nucleation density in CVD -grown grapheme using pre-treated Cu foil

Highly uniform and reliable polymer memory via iCVD using multilayer graphene barrier electrode

Temperature Dependence of Hot Carrier and Positive Bias Stress Degradation in Double-Gated Graphene Field Effect Transistors

High electric field transport in graphene: impact of screened coulomb interactions

Synthesis of Bimetallic Pd-Rh nanoparticles onto Graphene Nanosheets as Electrochemical Catalysts

Graphene Nanocomposites for Online Monitoring of Individual Gases at Moderate Temperature

poster title

29 | G r a p h e n e

Silke Seyock, Jan Schnitker, Vanessa Maybeck, Bernhard Wolfrum and Andreas Offenhäusser

Kireev, Dmitry

Hyun Kyung Kim, Suk Woo Lee and Kwang Bum Kim

Kim, Myeong Seong

Seon-Myeong Choi , Ho Ang Yoon , Jung Cheol Kim , Sang Wook Lee , Young-Woo Son , and Hyeonsik Cheong

Kim, Minjung

Seong-Yong Cho, Hyun-Mi Kim, Min-Su Kim, Ki-Ju Kim, Sang-Hoon Lee, and Ki-Bum Kim

Kim, Min-Sik

Seong-Yong Cho, Sang-Hoon Lee, Min-Su Kim, Ki-Ju Kim, and Ki-Bum Kim

Kim, Min-Sik

Suk Woo Lee, Yoen-Jun Choi, Kwang Chul Roh and Kwang-Bum Kim

Kim, Hyun-Kyung

Piotr Kaźmierczak, Aneta Drabioska, Krzysztof Korona, Andrzej Wysmołek, Maria Kamioska, Iwona Pasternak, Aleksandra Krajewska, Krzysztof Pakuła, Zbigniew R. Żytkiewicz

Kierdaszuk, Jakub

Rainer Bornemann, Andreas Bablich, Heiko Schäfer-Eberwein, Jintong Li, Michael Östling, Peter Haring-Bolívar , Max Lemme

Khandan Del, Sepideh

authors

Germany

Korea

Poland

Germany

country

Wafer-scale fabrication of graphene field effect transistors for neuronal interfacing

One pot synthesis of micrometer-sized spherical Li4Ti5O12/reduced graphene oxide as anode material for high-rate lithium ion batterie

Thermoelectric effect with band offset at lateral junction between ABA and ABC tri-layer graphene

Mesoepitaxy of graphene: continuous film formation

Liquid Cu catalyst phase effect on graphene growth

Nanomesh Graphene for Supercapacitor Applications

Large enhancement of Raman spectra in graphene deposited on GaN nanowires

Laser Annealing as an Enhancement Technique for the Optical and Electrical Properties of Graphene Ink based Films

poster title

30 | G r a p h e n e

Gotthard Seifert, Leonid A. Chernozatonskii

Kvashnin, Dmitry

D. Tomanek, P. B. Sorokin

Kvashnin, Alexander

Chun-Hu Chen

Kuo, Cheng-Chi

Rohit Srivastava

Kumawat, Mukesh Kumar

Pankaj Chamoli and Kamal K. Kar

Kumar, Manish

Kalyan Raidongia, Jiaojing Shao, Jiaxing Huang

Krishnan, Deepti

P. Dabrowski, I. Wlasny,M. Rogala, J.M. Baranowski, W. Strupinski, M.Kopciuszynski R. Zdyb, M. Jalochowski, Z. Klusek

Kozlowski, Witold

M. Rogala, W. Kozlowski, A. Busiakiewicz, I. Wlasny, S. Pawlowski, G. Dobinski, M. Smolny, L. Lipinska, R. Kozinski, K. Librant, P. Dabrowski, J. M. Baranowski, K. Szot, Z. Klusek

Kowalczyk, Pawel

Jong Yun Kim, Byung Chul Jang, Sung-Yool Choi

Koo, Beom Jun

Mikkel Kongsfelt, Søren Ulstrup, Antonija Grubišid Čabo, Andrew Cassidy, Patrick R. Whelan, Marco Bianchi, Maciej Dendzik, Filippo Pizzocchero, Bjarke Jørgensen, Peter Bøggild, Liv Hornekær, Philip Hofmann, Steen U. Pedersen, Kim Daasbjerg

Koefoed, Line

authors

Russia

Taiwan

India

USA

Poland

Korea

Denmark

country

MoS2 decoration study. Origin of strong binding and inertness

Prediction of formation of layered ultrathin graphene-type films of ionic compound

Graphene thickness-controlled Interface for Enhanced Photocatalysis and SERS Applications

Synthesis of highly dispersible and ultra pure graphene oxide

Photocatalytic degradation performance driven by UV and Visible irradiation of reduced graphene oxide–Fe3O4nanocomposite

Graphene oxide assisted hydrothermal carbonization of carbon hydrates

Nitrogen-doped graphene: chemical and morphological properties

The characterization of resistive switching in graphene oxide layer prepared by inkjet printing

Unipolar resistive switching memory using graphene oxide for flexible one diode-one resistor(1D1R) cell array

Electrochemical Transfer of Large-Area Single Crystal Epitaxial Graphene from Ir(111)

poster title

31 | G r a p h e n e

Young Hee Lee

Ly, Thuc Hue

A. Wolff, T. Schroeder, and G. Lupina

Lukosius, Mindaugas

Amirhasan Nourbakhsh, Inge Asselberghs, Cedric Huyghebaert,Iuliana Radu, Stefan De Gendt, and Marc Heyns

Lockhart de la Rosa, CĂŠsar Javier

Luc Henrard, Philippe Lambi

Lobet, Michael

Chao-Kuang chen and Zhen-Yu Juang

Liu, YingHan

Seki Park, , Min Su Kim, Hyun Kim, Jubok Lee, Young Hee Lee and Jeongyong Kim

Lee, Yongjun

Seong-Min Bak, Chang- Wook Lee, Cherno Jaye, Daniel A. Fischer, Xiao-Qing Yang, Kyung-Wan Nam and Kwang-Bum Kim

Lee, Suk Woo

Nojoon Myoung, Hee Chul Park

Lee, Seung Joo

Mi Ri Kim, and In Woo Cheong

Lee, Hyang Moo

Felipe Lipp Bregolin, Alexandre Artaud, Claude Chapelier, Vincent Renard

Le Quang, Toai

C. G. Rocha, M. S. Ferreira

Lawlor, James

authors

Korea

Germany

Belgium

Taiwan

Korea

France

Ireland

country

Grain Boundaries in CVD-Grown Monolayer Transition Metal Dichalcogenides

Graphene synthesis on insulating substrates via Ni-assisted CVD

n-type doping of MoS2 with polyvinyl alcohol

Robust optical absorption of graphene-polymer heterostructures for GHz electromagnetic radiation versus defects

Study of Cross-plane Electrical Conductivity of Graphene-based Heterostructure by Atomic Force Microscopy

Near-field optical imaging of monolayer MoS2 grown by chemical vapor deposition: Identification of grain boundaries and line defects

Study on Carbon Structural Changes in Manganese Dioxide/Graphene composites prepared by direct redox deposition

Vertical Heterojunctions Based on Ferromagnetic Graphene and Ferroelectric Tunnel Barrier

Synthesis for Graphene Dispersant via Reversible Addition-Fragmentation Chain Transfer Polymerization

Simultaneous growth of superconducting NbC and graphene on SiC

Electronic Structure of Impurity Doped Graphene: An Inverse Modelling Approach

poster title

32 | G r a p h e n e

M. Barbone, M. Bruna, M.K.Ijäs, D. Yoon, U. Sassi and A. C. Ferrari

Ott, Anna

A. M. Goossens, G. Navickaite, J. J. Piqueras, G. Konstantatos and F.H. L. Koppens

Nikitskiy, Ivan

Lozano N, Zhang M, Yudasaka M, Bussy C, Kostarelos K

Newman , Leon

Igor Píš, Tevfik Onur Mentes, Alessandro Sala, Mattia Cattelan, Stefano Agnoli, Federica Bondino, Elena Magnano

Nappini, Silvia

G. Plechinger, P. Tonndorf, S. Michaelis de Vasconcellos, R. Bratschitsch, C. SchüLler and T. Korn

Nagler, Philipp

Ryan J.Wu , Jong Seo Jeong

Mkhoyan, Andre

D. Yoon, M. Ijäs, W. P. Han, P. H. Tan, N. M. Pugno, T. Bjorkman, A. Krashenninnikov ,A. C. Ferrari

Milana, Silvia

Rocío Rincón, Margarita Jiménez, José Muñoz and María Dolores Calzada

Melero, Cristobal

Lidia Martínez, Javier Hernández-Ferrer

Martinez, María Teresa

Yanfeng Zhang, Zhongfan Liu

Ma, Donglin

authors

Spain

Italy

Germany

USA

Spain

China

country

Contaminations and Doping in Defected Graphene by Raman Spectroscopy

Hybrid graphene–quantum dot phototransistors for IR-imaging applications

Environmental remediation of oxidised graphene nanocarbons: 2D sheets degrade faster than 1D tubular-shaped structures

Evidence of the formation of a single layer of graphene and hexagonal boron nitride on Pt(111) from a single molecular precursor

Low-temperature photoluminescence of 2D Dichalcogenides and indirect excitons in their heterostructures

Analyzing Thickness Dependent Electronic Properties of MoS2

Determination of Shear Modulus and Out of Plane Young's Modulus of Layered Materials by Raman spectroscopy

Production of Nanostructured Carbon Materials and Hydrogen by Microwave Plasma at Atmospheric Pressure

Strategies of Graphene Quantum Dots synthesis and application of quantum dots/graphene nanoribbons hybrid materials as electrochemical sensors

Etching-free transfer of wafer-scale MoS2 films

poster title

33 | G r a p h e n e

Jukka Aumanen, Andreas Johansson, Juha Koivistoinen, Pasi Myllyperkiö

Pettersson, Mika

Thomas Garm Pedersen

Petersen, René

Laura Fernández-García, Patricia Álvarez, Patricia Blanco, Ricardo Santamaría, Marcos Granda, Clara Blanco, Rosa Menéndez

Pérez-Mas, Ana Matilde

Olivier Riant, Sophie Hermans

Pennetreau, Florence

David Jiménez, Mario Iannazzo, and Eduard Alarcón

Pasadas Cantos, Francisco

C.Galiotis and K. Papagelis

Parthenios, John

Achim Woessner, Michela Badioli, Klaas-Jan Tielrooij, Sebastien Nanot, Gabriele Navickaite, Tobias Stauber, F. Javier García de Abajo and Frank H. L. Koppens

Parret, Romain

Chang-Woo Song, Young-Wook Ha, Hamin Park and Sung-Yool Choi

Park, Ick-Joon

Ick-Joon Park, Young-Wook Ha and SungYool Choi

Park, Hamin

Hirokazu Fukidome, Tetsuya Suemitsu, Taiichi Otsuji, and Maki Suemitsu

Park, Goon-Ho

authors

Finland

Denmark

Spain

Belgium

Spain

Greece

Spain

Korea

Japan

country

Patterning and tuning of electrical and optical properties of graphene by laser induced twophoton oxidation

Bandgap scaling in bilayer graphene antidot lattices

Thermal reduction of thin graphene films on different substrates monitored by AFM

Graphene double functionalization with xanthates and peroxides

Capacitance compact modeling of four-terminal graphene FETs preserving charge conservation: A circuit-oriented device model benchmark

Decomposing strain and doping in graphene

Substrate-enhanced photo current in graphene

Investigation of Graphene N-type Doping Effects for S/D Electrodes via Cs2CO3 Doping in Amorphous InGaZnO Thin-Film Transistors

Bottom-gate graphene field-effect transistors with enhanced reliability based on passivation layer

Graphene field-effect transistor with a solution-processed gate dielectrics and UV-ozone-treated graphene/metal electrodes

poster title

34 | G r a p h e n e

Chiara Grotta, Cecilia Mattevi

Reale, Francesco

Vivek Pandey, Rajeev O Dusane

Ramakrishna, Shilpa

Marin Radu, Florica Radu, Valentin Radu, Florian Cioroianu, Mariana Cioroianu

Radu, Daniela

M. Zarenia, Andrey Chaves, G. A. Farias, J. M. Pereira Jr., F. M. Peeters

Rabelo da Costa, Diego

P. Q. Liu, M. Tamagnone, Clara Moldovan, J. Perruiseau-Carrier, J. Faist, A. B. Kuzmenko

Poumirol, Jean-Marie

Massimiliano Bianchi, Laura Rizzi, John Parthenios, Konstantinos Papagelis, Roman Sordan and Costas Galiotis

Polyzos, Ioannis

S. Dal Conte, M. Marsili, D. Prezzi, D. Sangalli, C.Manzoni, A. Marini, D. De Fazio, M. Bruna, I. Goykhman, A. C. Ferrari, G. Cerullo

Pogna, Eva Arianna Aurelia

Carolina Gonçalves, Inês C. Gonçalves, Fernão D. Magalhães

Pinto, Artur

Cristiane N. Santos, Frédéric Joucken, Benoît Hackens, Jean-Pierre Raskin and Robert Sporken

Pham Thanh, Trung

J. Lagoute, O. Mouhoub, Y. Tison, V. Repain, C. Chacon, A. Bellec, Y. Girard ,F.Joucken, S. Rousse

Pham, Van Dong

authors

Poland

Romania

Brazil

Switzerland

Greece

Italy

Portugal

Belgium

France

country

Epitaxial synthesis of WS2

Low Temperature Growth of Graphene by Hot Wire Chemical Vapour Deposition

Properties of the carbon found in the atomic state and nanoparticles used to generate hydrogen from water with applications to thermal plants

Monolayer-bilayer graphene quantum dots

Electrically tunable terahertz magneto-absorption and Faraday rotation in graphene

Suspended graphene under moderate intrinsic strain

Ultrafast broadband study of photocarrier dynamics in MoS2 single layer

Biodegradation influence on PLA/graphene-nanoplatelets composite biomaterials mechanical properties and biocompatibility

Influence of substrate temperature and SiC buffer layer on the quality of graphene formation directly on Si(111)

Electronic Interaction between Nitrogen-Doped Graphene and Porphyrin Molecules

poster title

35 | G r a p h e n e

S. C. Martin, B. Sacépé, A. Kimouche, J. Coraux, F. Fuchs, B. Grévin, H. Courtois and C. B. Winkelmann

Samaddar, Sayanti

A. V. Malyshev, and F. Domínguez-Adame

Saiz Bretín, Marta

Esaam Jamil, Sajjad Ghobadi, Vildan Bayram, Selmiye Alkan Gürsel

Sadhu, Veera

Marc Gluba, Guoguang Sun, Karsten Hinrichs, Norbert Nickel, Jörg Rappich

Rösicke, Felix

I. Wlasny, P. Dabrowski, P. J. Kowalczyk, A.Busiakiewicz, W. Kozlowski, L. Lipinska, J. Jagiello, M. Aksienionek, W. Strupinski, A. Krajewska, Z. Sieradzki, I. Krucinska, M. Puchalski, E. Skrzetuska, Z. Klusek

Rogala, Maciej

M.-H. Liu, P. Makk, S. Hess, R. Maurand, E. Tovari, M. Weiss, K. Richter and C. Schönenberger

Rickhaus, Peter

Alexys Bruno-Alfonso

Ribeiro, Allan Victor

F. Ramirez, M. Gonzalez-Barriuso, Maria J. Rivero, A. Yedra and Inmaculada Ortiz

Ribao, Paula

Daniel Schneider, Chanyoung Yim, Satender Kataria, Vikram Passi, Andreas Bablich, Georg S. Duesberg and Max C. Lemme

Riazimehr, Sarah

authors

France

Spain

Turkey

Germany

Poland

Switzerland

Brazil

Spain

Germany

country

Disorder and Screening in Decoupled Graphene on a Metallic Substrate

High thermoelectric figure of merit in graphene nanorings

Modification of Graphene Oxide as Catalyst Support for Fuel Cells

Covalent modification of large area monolayer graphene towards biosensing

The graphene oxide-based inkjet technology for flexible electronics

Electron optics in graphene

Use of the tight-binding approach to investigate the Wannier functions of graphene

Synthesis of GO/TiO2 composite through hydrothermal method for photocatalytic application

Spectral Sensitivity of pn-junction Photodetectors based on 2D materials

poster title

36 | G r a p h e n e

S. M. Badalyan, F. M. Peeters, and A.-P. Jauho

Shylau, Artsem

Yanfengzhang

Shi, Jianping

Laurent Syavoch Bernard, Antonios Bazigos, Arnaud Magrez and Adrian M. Ionescu

Sharma, Pankaj

Stephen R. Power, Dirch H. Petersen, and Antti-Pekka Jauho

Settnes, Mikkel

J.Michalik, J. Rodríguez-Fernández, L. Fernández-Barquín, M.R. Ibarra, J.M. de Teresa

Serrano-Esparza, Inés

Gi Woong Shim, Sang Yoon Yang, Dae Yool Jung, Gwang Hyuk Shin and Sung-Yool Choi

Seo, Seung-Bum

B. Pigeau, A. Kuhn, D. Kalita, Z. Han, L. Marty, O. Arcizet, N. Bendiab,V. Bouchiat

Schwarz, Cornelia

A. Pierret, F. Fossard, F.Ducastelle, J. Barjon and A. Loiseau

Schue, Leonard

Mathieu Massicotte, Fabien Vialla, and Frank H. L. Koppens

Schmidt, Peter

T. Preis, C. Schell, P.Giudici, K. Watanabe, T. Taniguchi, D. Weiss and J. Eroms

Sandner, Andreas

authors

Denmark

China

Switzerland

Denmark

Spain

Korea

France

Spain

Germany

country

Electron polarization function and plasmons in metallic armchair graphene nanoribbons

Controllable Growth and On-Site Domain Boundary Imaging of Monolayer MoS2 on Au foils and Its Potential Application in Hydrogen Evolution Reaction

Negative Differential Resistance in Top-Gated Chemical Vapor Deposition Grown Graphene Transistors

Bubbles and perforations in graphene using a patched Green’s function technique

Superconductive-graphene hybrid devices

Contact Resistance of Molybdenum Disulfide Field Effect Transistor with Doped-Graphene Electrodes

Local Optical Probe for Motion and Strain Detection of Resonances in Graphene Membrane Drums

Structural and optical characterization of h-BN layers

Charge carrier extraction in a graphene-WSe2-graphene heterostructure

Magnetotransport in high-mobility graphene antidot arrays

poster title

37 | G r a p h e n e

Lamprini Sygellou, Georgios Paterakis, and Costas Galiotis

Tasis, Dimitrios

D. Cox, T. Nieminen, P. Lähteenmäki ,D. Golubev, G. B. Lesovik, and P. J. Hakonen

Tan, Zhenbing

Christian Lang, Matthew Hiscock, Jonathan Moffat, Kim Larsen

Sundaram, Ravi

Antonio Esau Del Rio Castillo, Andrea Capasso, Vittorio Pellegrini, Bruno Scrosati, and Francesco Bonaccorso

Sun, Haiyan

Aleksandra Krajewska, Iwona Pasternak, Alejandro Gutierrez, Carmen Munuera, Mar Garcia Hernandez, J.A. Martin-Gago

Strupinski, Wlodek

Luca Camilli, Susie-Ann Spiegelhauer, Line E. Bergmann, Peter Bøggild

Stoot, Adam C.

Stefano Dal Conte, Cristian Manzoni, Francesco Scotognella, Akimitsu Narita, Xinliang Feng, Klaus Müllen, Giulio Cerullo

Soavi, Giancarlo

Richard Pincak

Smotlacha, Jan

M. Bodik, D. Kostiuk, M. Hodas, M. Pelletta, M. Jergel and E. Majkova

Siffalovic, Peter

Patricia Álvarez, Clara Blanco, Marcos Granda, Ricardo Santamaría and Rosa Menéndez

Sierra, Uriel

authors

Greece

Finland

Italy

Poland

Denmark

Italy

Russia

Slovakia

Spain

country

Tuning work function values in graphene oxide–derived films

Cooper Pair Splitting by means of Graphene Quantum Dots

Structural Characterization of 2D materials in the SEM using EDS and EBSD

Binder-free graphene film via solvent exchange process as anode in Li-ion battery

CVD graphene’s doping with Au nanoparticles

Single and multilayer 2D-coatings for corrosion protection

Exciton-exciton annihilation and Stimulated Emission in Graphene Nanoribbons

Spin–orbit interaction in the graphitic nanocone

Large-area deposition of few-layer graphene produced by liquid phase exfoliation of expanded graphite

New alternatives to graphite for graphene production by solvent exfoliation

poster title

38 | G r a p h e n e

A. Briancon-Marjollet, A.Bourrier, D.Kalita, V.Bouchiat and C. Delacour

Veliev, Farida

M. I. Katsnelson

Ulybyshev, Maksim

Jérôme Saint-Martin and Philippe Dollfus

Tran, Van Truong

J.L. Pinilla, R. Moliner, I. Suelves

Torres, Daniel

L.Lombardi, R. Agaiby, M.Banach, F.Torrisi, A.C. Ferrari

Tomarchio, Flavia

R.K. Singh Raman

Tiwari, Abhishek

Christian Schönenberger, Michel Calame F. Lüönd,Frederic Overney, Beat Jeckelmann, Blaise Jeanneret

Thodkar, Kishan

Niklas Reineking, Dirk Hönig

Thiesen, Peter H.

Wout Frederickx, Oleksandr Ivasenko, Tatyana Balandina, Kunal S. Mali, Akimitsu Narita, Søren A. Jensen, Michael R. Hansen, Xinliang Feng, Klaus Müllen and Steven De Feyter

Teyssandier, Joan

Philipp Leicht, Felix Blumenschein, Anders Bergvall, Tomas Löfwander, Luca Gragnaniello, Mikhail Fonin

Tesch, Julia

authors

France

Germany

France

Spain

Australia

Switzerland

Germany

Belgium

Germany

country

Graphene Transistors for Detection of Neuronal Activity

Hybrid Monte Carlo simulations of emergent magnetism in graphene in presence of hydrogen adatoms

Hybrid states at interfaces of zigzag Graphene/BN heterostructures

Structural differences between few-layer graphene oxide suspensions obtained from carbon nanotubes and fishbone nanofibers

Flexible, graphene-integrated, 122,880 pixels, electrophoretic display

Graphene Coating for Corrosion Resistance of Metals

CVD Graphene Electrical Quantum Metrology

Imaging Spectroscopic Ellipsometry and Spectral Reflectometry with Ellipsometric Contrast (SREC), Two Methods for Optical Characterization of 2D-Material

Imaging and analysis of liquid-phase-processable graphene nanoribbons

Size quantization effects in quasiparticle interference on epitaxial graphene nanoflakes

poster title

39 | G r a p h e n e

Hyung Gyu Park

Yang, Ning

K. E. Aretouli, P. Tsipas, D. Tsoutsou, J. Marquez-Velasco, S.A. Giamini, E. Vassalou and A. Dimoulas

Xenogiannopoulou, Evangelia

Catherine Drosou, Konstantina Tyrovola, Dimitris Christofilos, Jiannis Arvanitidis, Gerasimos S. Armatas, Labrini Sygellou, Despo Fata-Kassinos

Xekoukoulotakis, Nikolaos

Jong Seok Jeong, Matt Robbins, Nazila Haratipour, Mehmet Topsakal, Renata M.M. Wentzcovich, Steven J. Koester, K. Andre Mkhoyan

Wu, Ryan

Pablo Alonso-Gonzalez, Mark B. Lundeberg, Gabriele Navickaite, Yuanda Gao, Qiong Ma, Davide Janner, Kenji Watanabe, Takashi Taniguchi, Valerio Pruneri, Pablo JarilloHerrero, James Hone, Rainer Hillenbrand, and Frank H.L. Koppens

Woessner, Achim

Magdalena Twardowska, Aneta Prymaczek, Johannes Sommerkamp, Piotr Nyga, Izabela Kamioska, Sebastian Madkowski

Wiwatowski, Kamil

Xuechao Yu

Wang, Qijie

H. Lux, P. Steglich, J. Bauer, S. D端mecke, M. A. Schubert, and S. Schrader

Villringer, Claus

authors

Switzerland

Greece

USA

Spain

Poland

Singapore

Germany

country

Secondary Layer Evolution of Bilayer Graphene on Copper

Molecular Beam Epitaxy of atomically thin 2D dichalcogenide Van der Waals semiconductor heterostructures

Adsorption of emerging organic pollutants on graphene-based materials in the aqueous phase

The Atomic and Electronic Structure of Phosphorene

High resolution near-field photocurrent measurements reveal optoelectronic properties of graphene

Energy transfer in graphene-based nanostructures

High performance photodetectors based on graphene and other 2D materials

Optical properties of highly transparent conductive uniaxial carbon films

poster title

40 | G r a p h e n e

Guobao Li, Jijun Zhao

Zhou, Si

Yanfeng Zhang, Zhongfan Liu

Zhang, Yu

Woochul Yang

Zhang, Shaolin

Dasol Cheang, Jiyeon Hyun, Aeran Roh, Sun Heo, Lanxia Cheng, Jiyoung Kim, Pil-Ryung Cha, Jagab Lee, Ho-Seok Nam

Yun, Kayoung

F. Javier GarcĂa de Abajo

Yu, Renwen

Kwang-Bum Kim

Youn, Hee-chang

authors

China

Korea

Spain

Korea

country

The effect of oxygen content on lithium storage in graphite oxide by first principles studies

Dendritic, Transferable, Strictly Monolayer MoS2 Flakes Synthesized on SrTiO3 Single Crystals for Efficient Electrocatalytic Applications

Solvent co-exfoliated graphene/MoS2 nanocomposite for photoactivated VOCs gas detection

Growth Mechanism of Multi-Layer Graphene at Low-Temperature by Plasma Enhanced Chemical Vapor Deposition

Visible Light Modulation with Graphene

High-Surface-Area Nitrogen-doped Reduced Graphene Oxide for Electric Double Layer Capacitors

poster title

Modelling atomic force microscopy nano-indentation in copper covered by graphene 1

Jean-Joseph Adjizian and Jean-Christophe Charlier 1

Université catholique de Louvain, Institute of Condensed Matter and Nanosciences, chemin des étoiles, 8, 1348, Louvain-la-Neuve, Belgium jean.adjizian@uclouvain.be

Abstract Graphene is known to sustain up to 25% in plane tensile strains when measured using AFM nano1 2 indentation technique , also in agreement with recent molecular dynamics (MD) simulations . In the present work, MD simulations are performed in order to investigate the effect of graphene on the deformation of a conventional copper surface using nano-indentation. In our simulations, the AFM tip is modelled by a rigid fullerene (C60 - see Fig.1) that directly interacts with a (111) copper surface covered (or not) by a graphene sheet during the loading process. Experimentally, the load-displacement curves are frequently fitted by a power law following the Hertz theory of a spherical indenter on a elastic body. Indeed, the theoretical relation between the applied n force (F) and the indent (δ) is F δ where n=1.5. 3

Our simulations reveal that load-displacement data for the pristine (111) copper surface exhibit a non4 linear response (n~2.1) as frequently observed in several other thin film materials . However, the loaddisplacement curve presents a better agreement with the Hertz law (n~1.4) when the (111) copper surface is covered by a graphene sheet. Such a difference in power law can be explained by nonadhesive effects between the copper surface and the AFM tip due to the presence of graphene as suggested by start-of-the-art ab initio simulations.

References [1] C. Lee, X. Wei, J.W. Kysar, and J. Hone, Science 321, 385 (2008). [2] W. Wang, S. Li, J. Min, C. Yi, Y. Zhan, and M. Li, Nanoscale Research Letters 9, 41 (2014). [3] J.-J. Adjizian, M. Hammad, J.-P. Raskin, T. Pardoen, and J.-C. Charlier, in preparation (2014). [4] A. Gouldstone, H.J. Koh, K.Y. Zeng, Yu, A.E. Giannakopoulos and S. Suresh, Acta mater. 48, 2277 (2000).

Figures:

Figure 1: Model of nano-indentation in graphene on top of a (111) copper surface.

Graphene | 41

Planar four layers waveguide structure at sub-THz frequencies comprising metal and garphene: a complex scenery of coupled modes 1

Hameda Alkorre , Johan Stiens , Gennady Shkerdin

Department of Electronics and Informatics (ETRO), Laboratory for micro- and photon electronics (LAMI),Vrije 2 Universiteit Brussel (VUB), Pleinlaan 2, B-1050 - Brussels ± Belgium , .RWHO¶QLNRY ,QVWLWXWH RI 5DGLR (QJLQHHULQJ and Electronics RAS- Vvedenskogo Square 1, 141120 Fryazino (Moscow region), Russia. hailkorr@etro.vub.ac.be

Abstract In spite of the fact that graphene plasmons were investigated in a number of structures containing a few graphene monolayers or graphene bilayers, the case of coupled graphene plasmons with other types of structure modes (surface metal-plasmon or waveguide modes) has not been thoroughly examined. The coupling of graphene plasmons with surface metal plasmons in a structure containing a graphene layer and metal substrate separated by an air gap was studied [1]: the solution of the coupled plasmon mode shows a linear dispersion behavior in a specific parameter range. We propose a multilayer structure containing a metal substrate, dielectric buffer layer, a monolayer of graphene, and air as the superstrate, aimed to unravel the complex solution space: coupled graphenemetal plasmons and waveguide modes which are supported by this structure. Hereto we present interesting results for these plasmon modes, by employing analytical models [1], we described these plasmon modes behavior at the sub-THz range, to our knowledge, this could be the first study of its kind. The solution of the dispersion relation for the structure is explained in [2] [3]. We focused on the impact of the Fermi level in graphene and the geometrical parameters of the structure on the dispersion characteristics of various plasmonic solutions starting with a single frequency such as 300 GHz and then extending our model to different frequency values where we expect a strong coupling at sub-THz frequency range. This model has been verified numerically, where the surface plasmon characteristics of the multilayer structure under consideration have been analyzed for sub-THz frequencies [4],[5]. It was noted that the difference of decoupled metal surface plasmon and graphene surface plasmon wavevectors vanishes for low THz and GHz frequencies. Hence we may expect stronger coupling effects in this frequency range. The TM surface plasmons are represented by metal-like and graphene-like branches depending on their behavior for very thick buffer layers. For instance; for frequencies smaller than 0.75 THz (for the concrete structure under study), the metal-like surface plasmons split up into two branches depending on the graphene electron concentration: one of the branches exists in the whole range of the buffer thickness and being a shortrange mode for small thicknesses, another one undergoes cutoff and exists only within a limited range of buffer thicknesses smaller than the cutoff thickness. Further increase of the surface plasmon frequency leads to the disappearance of the splitting effect for metal like surface plasmon, also the TM waveguide modes split up into two branches for small frequencies analogously to that of the metal-like surface plasmon [6]. The coupled graphene-metal plasmon modes and waveguide modes can depend very strongly on the electron concentration in the graphene layer, and the buffer layer thickness and this gives advantages to use in a wide range of applications in sub-THz frequency for example as sensors and modulators. References

[1] N J M Horing Phys. Rev. B 80, 193401 (2009) [2] H. Alkorre, G. Shkerdin, C. De Tandt, R.Vounckx and J. Stiens, ImagineNano, conference, Bilbao: Spain, April (2013).

[3] J. Stiens , H. Alkorre ,G. Shkerdin and R. Vounckx , Optical and Quantum Electronics, special issue edition, (2014).

[4] H. Alkorre, G. Shkerdin, J. Stiens, R. Vounckx, Journal of Optics-under review. [5] H. Alkorre , G. Shkerdin, J. Stiens ,Y. Trabelsi, R, IAMOT special issue edition, vol.9, n. 6,(2014), pp.453 ± 459.

[6] G. Shkerdin, H. Alkorre, J. Stiens and R. Vounckx, Journal of Optics-under review. 1

42 | Graphene

Preparation of Graphene Nanoplatelets from Polymer-derived Graphite Film by GIC (Graphite Intercalation Compound) via Process Jung-Chul An, Eun-Jeong Lee, Hye-Jung Kim, Ikpyo Hong RIST, 67, Cheongam-Ro, Nam-Gu, Pohang, 790-330, Korea jcan@rist.re.kr Abstract A few-nanometer-thick at micrometer-wide graphene platelets were successfully prepared from the graphitized polymer (i.e., polyimide) film by simple GIC (Graphite Intercalation Compound) via exfoliation process. The intrinsic high crystalline structure of graphitized polyimide film were found to be beneficial in yielding thinner, wider and defectless graphene nanoplatelets. Sulfuric acid was served as the functional intercalating agent in the GIC formation step. XRD results revealed the stable and clear stage-one state formed in the GIC. Concentration of chemical agent, intercaltion temperature were found to influence the average thickness of prepared graphene nanoplatelets. Pulverization condiation such as sonication time and power influenced the averaged lateral size of the graphene platelets with variations from 5 to 30 micro meters. References [1] H. W. Kim, A. A. Abdala, C. W. Macosko, Macromolecules, 16 (2010) 6515. [2] M. Rashad, F. Pan, M. Asif, A. Tang, J. Ind. Eng. Chem., 20 (2014) 4250. [3] S. H. Song, H. K. Jeong, Y. G. Kang, J. Ind. Eng. Chem., 16 (2010) 1059. [4] S. M. Park, E. J. Yoo, I. Honma, Nano Letters, 1, (2009) 72. [5] L. Zhu, X. Zhao, Y. Li, X. Yu, C. Li, Q. Zhang, Mater. Chem. Phys. 137 (2013) 984.

Graphene | 43

CVD graphene on polymer substrate under tension 1

George Anagnostopoulos, Zheling Li , Ian A. Kinloch , Robert J. Young , Kostya S. Novoselov , John 1 1,4 1,5 Parthenios , Costas Galiotis , Konstantinos Papagelis Institute of Chemical Engineering Sciences, Foundation for Research and Technology Âą Hellas (FORTH/ ICE-HT), P.O. Box 1414, Patras 265 04, Greece

School of Materials and School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL, UK 4

Department of Chemical Engineering and Department of Materials Science, University of Patras, Patras 26504, Greece

Abstract In general, CVD is suitable to apply highly dense and pure graphene based coatings such as pristine 1 2 graphene on a substrate . Skakalova et al. have studied the growth mechanism of graphene sheets using the CVD method in order to fabricate high-quality large-area graphene sheet while a characterization regarding structure, electrical, optical and mechanical properties took place. As for the 3-5 latter, plenty of work has been done over the last years in order to investigate its behavior on external loading (tension and/or compression) in different substrates. In this work, Raman spectroscopy has been employed to monitor the deformation mechanics of monolayer CVD graphene on a poly(ethylene terephthalate) substrate (CVD graphene/PET) where the PET film is flat but the graphene is wrinkled The wrinkles have the effect of separating the graphene into isolated islands with size of about 1.5 Č?P, in which the wrinkle height is of the order of 15 nm (fig. 1a). Furthermore, it is found that upon deformation of the film, the shift of the Raman 2D band with strain for the graphene and the band broadening behavior is quite different from that of exfoliated monolayer graphene flakes (fig 1b). It is shown that the wrinkles have the effect of separating the graphene mechanically into isolated islands, with each island being similar in size to the Raman laser spot. It is demonstrated that inside each island the stress will be transferred non-uniformly from the PET (fig 1c) to the graphene and this allows the unusual Raman band shift and broadening behavior to be explained. References 1. Tong Y, B. S., Song M. Graphene Based Materials and Their Composites as Coatings. Austin Journal of Nanomedicine & Nanotechnology 2013, 1, 1003. 2. 3DUN + - 0H\HU - 5RWK 6 6NiNDORYi 9 *URZWK DQG 3URSHUWLHV RI )HZ-Layer Graphene Prepared by Chemical Vapor Deposition. Carbon 2010, 48, 1088-1094. 3. Androulidakis, C.; Tsoukleri, G.; Koutroumanis, N.; Gkikas, G.; Pappas, P.; Parthenios, J.; Papagelis, K.; Galiotis, C. Experimentally Derived Axial StressÂąStrain Relations for Two-Dimensional Materials Such as Monolayer Graphene. Carbon 2015, 81, 322-328. 4. Young, R. J.; Kinloch, I. A.; Gong, L.; Novoselov, K. S. The Mechanics of Graphene Nanocomposites: A Review. Composites Science and Technology 2012, 72, 1459-1476. 5. Mohiuddin, T. M. G.; Lombardo, A.; Nair, R. R.; Bonetti, A.; Savini, G.; Jalil, R.; Bonini, N.; Basko, D. M.; Galiotis, C.; Marzari, N.; Novoselov, K. S.; Geim, A. K.; Ferrari, A. C. Uniaxial Strain in Graphene by Raman Spectroscopy: G Peak Splitting, Gruneisen Parameters, and Sample Orientation. Phys Rev B 2009, 79. Figures

Fig. 1a: AFM image showing an isolated island formed by wrinkling. The height scale bar is in nm.

44 | Graphene

Fig. 1b: Pos(2D) and the corresponding FWHM(2D) as a function of the applied and the extracted actual strain for the graphene membrane on the PET substrate

Fig.1c: Graph explaining the proposed stress transfer mechanism (Li is the length of the i-crystallite and Lc the critical transfer length)

Symmetric micro-supercapacitors based on vertical graphene nanosheet electrodes with high power and energy density performances 1,2

David Aradilla , Marc Delaunay , Gérard Bidan , Jan Wimberg , Thomas J. S. Schubert , Jean-Michel 3 1 Gérard , Saïd Sadki 1

LEMOH/SPrAM/UMR 5819 (CEA, CNRS, UJF), CEA/INAC Grenoble, France 2 SiNaPS Lab.-SP2M, UMR-E CEA/UJF, CEA/INAC, Grenoble, France 3 Commissariat à l´Energie Atomique, Direction des Sciences de la Matière, Institut Nanoscience et Cryogénie, CEA/INAC Grenoble, France. 4 INAC/Dir, CEA/INAC Grenoble, 17 rue des Martyrs, 38054-Grenoble, France 5 IOLITEC Ionic Liquids Technologies GmbH, Salzstrasse 184, 74076 Heilbronn, Germany david.aradilla@cea.fr Abstract In recent years, tremendous research efforts have been devoted to the development of high performance micro-supercapacitors ȝ-SCs) due to their unique properties in terms of high power 1 density, long cycling stability, excellent reversibility and fast high-frequency response. Within this context, the synthesis of novel nanostructured material based on carbon or derivatives will play a crucial and key role on the design of advanced electrodes for micro-supercapacitor devices. Precisely, graphene has recently aroused a great deal of attention as nanostructured carbonaceous material in the field RI ȝ-SCs owing to its peculiar characteristics such as high surface-to-volume ratio or large surface 2 -1 area (2630 m g ), which make it a potential and prominent candidate for on-chip electrochemical 2 energy storage into miniaturized electronic devices (e.g. micro-robots) in the near future. In this work, we report the performance of a novel 2-D planar micro-supercapacitor using vertical graphene nanosheet (VGN) electrodes grown by electron cyclotron resonance-chemical vapor deposition (ECR-CVD) on silicon substrates. The morphological and structural characterization of the electrodes was examined by scanning electron microscopy (SEM), transmission scanning electron microscopy (TEM) and RAMAN spectroscopy respectively. From an application perspective, the symmetric micro-supercapacitor was analyzed using cyclic voltammetry, galvanostatic charge-discharge cycles and electrochemical impedance spectroscopy employing an aprotic ionic liquid (PYR13TFSI) as electrolyte. The device exhibits a quasi-ideal electrical double layer capacitive behaviour as well as a -2 -2 high power density value of 4 mW cm and a specific energy of 15 mJ cm at a wide cell voltage of 4V. In addition, an outstanding cycling stability after 300000 galvanostatic cycles at a high current density of -2 1 mA cm was tested. These results reflects that the synergistic combination of both VGNs as electroactive material and PYR13TFSI as electrolyte pave the way towards advanced high performance micro-supercapacitors with high power and energy densities. References [1] M. Beidaghi, Y. Gogotsi, Capacitive energy storqge in micro-scale devices: Recent advances in desin and fabrication of micro-supercapacitors, Energy Environ. Sci. 7 (2014) 867 - 884. [2] G. Xiong, C. Meng, R. G. Reifenberger, P. P. Irazoqui, T. S. Fisher, A review of graphene-based electrochemical microsupercapacitors, Electroanalysis 26 (1) (2014) 30 - 54. Figures

200 nm

Figure. SEM micrograph of VGNs grown by ECR-CVD on highly n-doped Si (111) substrates.

Graphene | 45

Investigating the electrical properties of doped graphene using near-edge X-ray absorption fine structure spectroscopy 1

Wayne Archibald , Darnel Allen , Sharadha Sambasivan

1. College of Science and Mathematics, University of the Virgin Islands, St Thomas, United States Virgin Islands 00802 warchib@live.uvi.edu 2. Chemistry, Suffolk County Community College, Selden, New York 11784 sambass@sunysuffolk.edu

Abstract This project sought to explore the electronic properties of doped chemical vapor deposition (CVD) graphene. Single layer CVD graphene samples were doped with 0.5Å of gold, 1Å of silver and 1Å of titanium via thermal/e-beam evaporation. Compared to our pristine graphene sample, the titanium doped, gold doped and silver doped samples exhibited an increase in hall mobility of about 19%, a decrease of 24% and a decrease of 8% respectively. Near-edge X-ray Absorption Fine Structure (NEXAFS) Spectroscopy of the pristine graphene sample and the doped samples illustrated that there ZDV D VOLJKW VKLIW LQ WKH SRVLWLRQ RI WKH ʌ UHVRQDQFH SHDN LQ WKH GRSHG VDPSOHV ZKHQ FRPSDUHG WR WKDW of the pristine graphene sample. Differences were also noticed in the interlayer states of all the samples.

References

M. Weser, Y. Rehder, K. Horn, M. Sicot, M. Fonin, A. B. Preobrajenski, E. N. Voloshina, E. Goering and Y. S. Dedkov, Appl. Phys. Lett., 2010, 96, 012504 G. Giovannetti, P. A. Khomyakov, G. Brocks, V. M. Karpan, J. van den Brink and P. J. Kelly, Phys. Rev. Lett., 2008, 101, 026803. Lee, V, Park C, Jaye, C, Fischer, D. A, Yu, Q, Wu W, Liu Z, Bao, J, Pei, S, Smith C, Lysaght, P and Banerjee, S: J. Phys. Chem. Lett. 2010, 1, 1247±1253

46 | Graphene

Graphene growth by Âłmagical sizeVÂ´ graphene nanoclusters assembly on Re(0001) Artaud A.

123

, Ratter K.

234

, Gilles B. , Bendiab N. , Magaud L. , Coraux J. , Chapelier C.

INAC-SPSMS, CEA, 17 rue des Martyrs, F-38054 Grenoble cedex 9, France Institut NEEL, CNRS and UniversitĂŠ Joseph Fourier, BP166, F-38042 Grenoble Cedex 9, France 2 8QLYHUVLWH Ň&#x201C; *UHQREOH $OSHV ,QVW 1((/ )-38042 Grenoble, France 3 CNRS, Inst NEEL, F-38042 Grenoble, France 4 SIMAP, Grenoble INP, 1130 rue de la Piscine, BP 75, F-38402 Saint-Martin-GÂś+qUHV Cedex, France Contact: alexandre.artaud@neel.cnrs.fr 2

Abstract: Monolayer graphene shows unique electronic properties, among which ballistic electronic transport at the micrometer scale [1]. This makes graphene an ideal candidate for coherent Cooper pair transport via Andreev Bound States (ABS) between two superconducting reservoirs. Whereas evidence of a supercurrent in graphene has been given as soon as 2007 [2], no signature of ballistic ABS was found yet, due to low transparency of the graphene-superconductor interface and extrinsic disorder induced by the fabrication of the junction or by its environment. These problems can be circumvented by growing graphene epitaxially on a superconducting substrate such as Re(0001) (gr/Re). In this system, superconducting correlations have been measured using scanning tunneling microscopy-spectroscopy (STM/STS) [3]. Gaining control over graphene growth on Re(0001) is mandatory in view of designing advanced graphene-superconductor epitaxial systems, such as graphene billiards and perpendicular-to-the-plane junctions with tunable graphene doping and interaction with the metal. With the help of STM and reflection-high energy electron diffraction performed in situ, in the same ultra-high vacuum where the sample has been prepared, we have explored the nucleation and first steps of the growth of gr/Re. We have found that graphene coexists with a dilute carbon phase forming a surface reconstruction, and that graphene nanoclusters of well-defined sizes ÂłPDJLFDO VL]HVÂ´ preferentially form (Figure 1). These ÂłPDJLFDO VL]HsÂ´-nanoclusters are mobile and assemble to form graphene sheets [4]. They are therefore the key-intermediate to grow graphene, though their formation has only been predicted thus far. Our density functional theory calculation (Figure 2a,b) help us deciphering their electronic and structural properties. References: [1] Mayorov et al., Nano Letters, 12 (2012) pp.4629-4634 [2] Heersche et al., Nature, 446 (2007) pp.56-59 [3] Tonnoir et al., Physical Review Letters, 111 (2013) 246805 [4] Artaud et al., to be submitted Figures: (a)

Figure 1: STM topograph (ÍłÇ¤Íś ŕľ&#x2C6; ÍłÇ¤Íś Â?Â?) of a typical 3-C6 graphene nanocluster on Re(0001).

(b)

Figure 2: DFT-simulated 3-C6 graphene nanocluster on a á&#x2C6;şÍš ŕľ&#x2C6; Íšá&#x2C6;ť cell of Re(0001). (a) Integrated Č ß°Č ŕŹś over the Í˛ ŕľ&#x2020; Í˛Ç¤Í´ Â&#x2021; range. C atom sizes are proportional to their distance from the Re surface. (b) Side-view showing the dome-like shape of the graphene nanocluster.

Graphene | 47

Phys. Rev. B 90, 125401 (2014)

Long-wavelength optical phonon behavior in uniaxial strained graphene: Role of electron-phonon interaction Mohamed Assili, Sonia Haddad Laboratoire de Physique de la Matière Condensée, Département de Physique, Faculté des Sciences de Tunis, Université Tunis El Manar, Campus Universitaire 1060 Tunis,Tunisia We derive the frequency shifts and the broadening of Γ-point longitudinal optical (LO) and transverse optical (TO) phonon modes, due to electron-phonon interaction1 , in graphene under uniaxial strain2 as a function of the electron density and the disorder amount. We show that, in the absence of a shear strain component, such interaction gives rise to a lifting of the degeneracy of the LO and TO modes which contributes to the splitting of the G Raman band. The anisotropy of the electronic spectrum, induced by the strain2–4 , results in a polarization dependence of the LO and TO modes. This dependence is in agreement with the experimental results showing a periodic modulation of the Raman intensity of the splitted G peak. Moreover, the anomalous behavior of the frequency shift reported in undeformed graphene is found to be robust under strain.

1 2

T. Ando, J. Phys. Soc. Jpn. 75, 084713 (2006). T. M. G. Mohiuddin, A. Lombardo, R. R. Nair, A. Bonetti, G. Savini, R. Jalil, N. Bonini, D. M. Basko, C. Galiotis, N. Marzari, K. S. Novoselov, A. K. Geim, and A. C. Ferrari, Phys. Rev. B 79, 205433 (2009). M. O. Goerbig, J.-N. Fuchs, and G. Montambaux, F. Pi´echon, Phys. Rev. B, 78, 045415 (2008). M. O. Goerbig, J.-N. Fuchs, G. Montambaux and F. Pi´echon, Eur. Phys. Lett. 85, 57005 (2009).

48 | Graphene

Visualizing Graphene Properties at Highest Performance and Resolution Using Confocal Raman, AFM, SNOM and SEM Elena Bailo, Thomas Dieing and Ute Schmidt WITec GmbH, Ulm 89081, Germany elena.bailo@witec.de Graphene is used in a multitude of macroscopic and microscopic devices. The combination of various analytical techniques often leads to the most appropriate understanding of graphene. The aim of this contribution is to illustrate the various fields of application of combined confocal Raman, AFM, SNOM and/or SEM measurements with a focus on graphene. New microscopic techniques are developed continuously to improve resolution but also to increase the amount of information obtainable from the samples. The confocal Raman microscope, a combination of a confocal microscope with high sensitivity Raman spectroscopy, provides chemical imaging with diffraction-limited resolution [1]. For graphene a combination of the confocal Raman microscope with AFM and SNOM leads to their more comprehensive characterization. AFM provides information about the geometric dimensions of graphene, whereas SNOM enables optical resolution beyond the diffraction limit while maintaining all optical contrast methods. Furthermore, by combining these two methods with Raman spectroscopy, the resolution of molecular imaging can be improved tremendously. The Raman image presented in Fig. 1a is the integrated intensity of the G band which reveals the presence of a graphene sheet consisting of a monolayer, a double layer and a multilayered graphene (brightest areas). Furthermore, from the intensity distribution of the D band, it is possible to determine the chirality of graphene based on a diffraction limited optical method [2]. Fig. 1b highlights the same sample area, but this time measured in SNOM mode, revealing the transparency of the graphene layers as a function of number of layers (Fig. 1c).

Fig. 1: Raman SNOM study of graphene: intensity of Raman G band (a), SNOM image (b), and decrease of transparency of graphene as a function of number of layers. Additionally RISE Microscopy is a novel correlative microscopy technique that combines confocal Raman Imaging and Scanning Electron (RISE) Microscopy within one integrated microscope system. A new dimension in imaging: ultra-structural SEM complemented with chemical compound information and molecular Raman imaging (fig. 2).

Fig. 2 - (a) SEM image of a graphene sample. (b) Color-coded confocal Raman image. (c) SEM image overlaid with the confocal Raman image. References [1] T. Dieng, O. Hollricher, and J. Toporski `Confocal Raman MicroscopyÂ´ Springer Series in Optical Sciences 158, 2010. [2] Y. M. You, ZhenHua Ni, Ting Yu, and ZeXiang Shen, 'Edge Chirality Determination of Graphene by Raman Spectroscopy', Applied Physics Letters, 93 (2008), 163112

Graphene | 49

Investigation of composite structures based on graphene and graphene oxide 1,2

3,4

Anna Baldycheva , Lorcan Brennan , Alexander Loudon , Yuri Gun’ko

2,4

and Tatiana Perova

University of Exeter, College of Engineering Mathematics and Physical Sciences, Exeter, EX4 4QF, UK 2 Department of Electronic and Electrical Engineering, Trinity College, The University of Dublin, Ireland 3 School of Chemistry, Trinity College, The University of Dublin, Dublin 2, Ireland 4 ITMO University, 49 Kronverskiy pr., St.-Petersburg, 197101, Russia A.Baldycheva@exeter.ac.uk

Abstract Carbon materials and in particular carbon nanomaterials (graphene, graphene oxide and carbon nanotubes) have received huge attention as replacement materials for a wide range of solar-cells components [1]. Graphene has been employed effectively as a replacement for ITO/FTO transparent conducting substrates and also as an alternative counter electrode material. The conversion of graphite to graphene oxide results in the functionalisation of the graphene oxide sheet with carboxyl, epoxide and alcohol moieties and leads to certain advantages of this material over the pure graphene. In this paper the properties and possible applications of two types of composite structures based on graphene and graphene oxide (GO) were investigated. For the first type, the GO (and reduced graphene oxide (rGO)) was used as a template for the deposition of platinum and gold nanoparticles. For the second type, the graphene (or graphene oxide) mixture with nematic liquid crystals was used for infiltration into grooved Si structures acting as a one-dimensional photonic crystal. It was found that platinum and gold nanoparticles could be successfully deposited, with a small size distribution and in high concentration (Fig. 1a) onto the surface of GO. Multiple techniques were investigated for the deposition of these materials onto fluorine tin oxide (FTO) glass substrates. The main aim was the formation of a stable and catalytically active electrode on FTO glass substrates. Such an electrode could then be tested electrochemically and in dye synthesized solar-cells and potentially offer new routes towards fabrication of low cost solar energy devices. A number of different characterization techniques such as XRD, SEM, TEM, electrical testing, FTIR and micro-Raman spectroscopies were employed to study the properties of the fabricated composites. Raman spectroscopy, in particular, is a powerful tool for identifying the number of layers, the structural quality, the degrees of doping and disorder in graphene and GO structures as well as for unique investigation of alignment of liquid crystals inside the Si micro-channels [2]. Changes observed in the Raman spectra of GO are due to the disruption of the delocalised ʌ-ʌ network that extends across the graphene oxide layer. Raman area-mapping was also employed for characterization of different graphene and GO-based samples deposited on a Si/SiO2 substrate. Figure 1b shows the comparison between Raman spectra of GO, rGO and rGO with deposited Pt and Au nanoparticles (PtrGO and AurGO) in the region of G and D bands. The red shift of G-band is observed upon oxidation of graphite as well as for AurGO and PtrGO. The observed increase in the G and D bands intensity ratio (ID/IG) has been linked to the creation of new graphitic domains, which are smaller in size than that present in GO but more numerous in number. The possible applications of the obtained structures are discussed. References [1] L.J. Brennan, M.T. Byrne, M. Bari, Y.K. Gun'ko, Advanced Energy Materials, 1 (2011) 472. [2] E.V. Astrova, T.S. Perova, S.A. Grudinkin et al., Semiconductors, 39 (2005) 759. Figures Figure 1. a) TEM image of rGO with Pt nanoparticles (PtrGO), b) Raman spectra of D and G bands for GO, rGO, PtrGO and AurGO structures.

50 | Graphene

Exoelectrogens leading to precise reduction of graphene oxide Prerna Bansal, Sejal Doshi, A. S. Panwar, D. Bahadur Indian Institute of Technology Bombay, Powai, Mumbai, India prerna.bansal@iitb.ac.in

Abstract Graphene is an adept material with applications ranging from electronics to biosensors. Mass production of graphene in a cost effective manner has been a major challenge for utilizing the full potential of this excellent material. In the present study, reduced graphene oxide (RGO) has been prepared by a simple, cost effective green biological route. In this work, graphene oxide (GO) has been reduced using gram negative facultative anaerobe S. dysenteriae having exogenic properties of electron transfer. Apparently, different concentrations of GO were successfully reduced with almost complete mass recovery. Effective role of lipopolysaccharides has been observed while comparing RGO reduced by gram negative S. dysenteriae and gram positive S. Aureus. Bacterially reduced RGO (Br-RGO) prepared in our work has been characterized by X-Ray diffraction, Zeta potential, X-ray photoelectron spectroscopy and Raman spectroscopy techniques and results were found to be in good agreement with chemically reduced GO. As agglomeration of RGO is a major issue to overcome while chemically reducing GO [1], we observed that Br-RGO prepared in our work has zeta potential value -26.62mV, good enough to avoid restacking of Br-RGO. Figure 1 presents fourier-transform infrared (FTIR) spectra of GO and Br-RGO recorded using KBr as reference. FTIR results confirmed the efficient reduction of GO in presence of S. dysenteriae cells, indicated by a significant decrease in the intensity of peaks corresponding to various oxygen functionalities due to removal of partial carboxyl, hydroxyl and epoxide groups from GO and also due to cracking of aromatic C=C bonds [2]. Our results lead to a path that microbe with redox potential has a promising impendence to reduce GO. With this study it is shown that lipopolysaccharide along with exoelectrogens are responsible for reducing GO in gram negative bacterial cells. This was a successful attempt to use green biological route for reduction of GO, which is otherwise done using hazardous chemicals. References [1] Stankovich S, Dikin DA, Piner RD, Kohlhaas KA, Kleinhammes A, Jia Y, Carbon, 45 (2007)1558 [2] Li D, Muller MB, Gilje S, Kaner RB, Wallace GG. Nature Nanotechnology, 3 (2008)101 Figures

Figure 1 FTIR spectra of Graphite Oxide and Br-RGO reduced by S. dysenteriae cells.

Graphene | 51

Spin diffusion length in LSMOÂągraphene spin valves M. Barbone1, W. Yan2, L. C. Phillips2, S. HĂ¤mĂ¤lĂ¤inen3, A. Lombardo1, M. Ghidini2,4, X. Moya2, F. Maccherozzi5, S. van Dijken3, S. S. Dhesi5, N. D. Mathur2 and A. C. Ferrari1 1

Cambridge Graphene Centre, University of Cambridge, CB3 0FA, Cambridge, UK of Materials Science & Metallurgy, University of Cambridge, Cambridge, UK 3 Department of Applied Physics, Aalto University School of Science, FI-00076, Aalto Finland 4 Department of Physics, University of Parma, 43100, Parma, Italy 5 Diamond Light Source, Chilton, Didcot, OX11 0DE UK 2Department

mb901@cam.ac.uk Significant progress has been made in graphene spintronics since the first demonstration of a graphene-based spin valve [[1]]. Due to low spin-orbit coupling [[2]] and hyperfine interaction [[2]], spin diffusion lengths have been measured in the range from 1.5 Pm [[3]] up to 285 Pm [[4]]. Here we present spin valves formed by combining La2/3Sr1/3MnO3 (LSMO) electrodes and few layer graphene channels. LSMO exhibits interfacial spin-polarization close to 100% at low temperature [[5]], making it a promising material for spin valves with highly spin-polarized electrodes [[6]]. We report spin transport on a device fabricated combining a 5 layer graphene and LSMO. The electrodes show a 20% X-ray magnetic circular dichroism contrast (XMCD) asymmetry at remanence after magnetic pulses, as confirmed by photoemission electron microscopy with XMCD. The transition between parallel and anti-parallel states occurs at distinct and well defined magnetic fields. This is further confirmed by magneto-optic Kerr effect PLFURVFRS\ 7KH UHVLVWDQFH GLIIHUHQFH EHWZHHQ WKH DQWLSDUDOOHO DQG SDUDOOHO FRQILJXUDWLRQV LV Çť5 0Č? FRUUHVSRQGLQJ WR D PDJQHWRUHVLVWDQFH RI DW . (Fig. 1), and a spin diffusion length~100 Č?P (Fig.2). Importantly, our analysis excludes the contribution from tunnelling anisotropic magnetoresistance (TAMR), and allows us to attribute the recorded magnetoresistance entirely to spin transport. References [1] [2] [3] [4] [5] [6]

E.W. Hill et al., IEEE Trans. Magn. 42 (2006) 2694. D. Huertas-Hernando et al., Pys. Rev. B 74 (2006) 155426. N. Tombros et al., Nature. 448 (2007) 571. B. Dlubak et al., Nat. Phys. 8 (2012) 557. M.Bowen et al., Appl. Phys. Lett. 82 (2003) 233. L. Hueso et al., Nature 445 (2007) 410.

Figures

Figure 1: Magneto-transport measurements on a 5layer graphene on LSMO electrodes. Blue and black line correspond to the directions of magnetic field sweep indicated by the arrows.

52 | Graphene

Figure 2: Simulated magnetoresistance (MR) as a function of interfacial spin polarisation Č&#x2013; spin diffusion length lsf , and interfacial resistance r b * using the driftdiffusion model. The blue line indicates the range of values derived for our device.

Electronic transport in doped polycrystalline graphene J. E. Barrios-Vargas1, Aron W. Cummings1, Max Seifert2, Marco Bobinger2, Matthias Sachsenhauser2, Jose A. Garrido2 and Stephan Roche1,3 1

ICN2 – Institut Català de Nanociència i Nanotecnologia, Campus UAB, 08193 Bellaterra, Spain Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany 3 ICREA, Institució Catalana de Recerca i Estudis Avançats, 08070 Barcelona, Spain jose.barrios@icn.cat Abstract Graphene as a raw material for electronic devices is frequently synthetized using chemical vapor deposition (CVD), which is a reliable way to get a large area graphene sample [1]. Usually, CVD graphene consists of a variety of misoriented graphene grains with grain boundary interfaces. These grain boundaries are made up of non-hexagonal carbon rings which degrade the electrical and mechanical properties. Also, these interfaces have a high chemical reactivity that suggests a promising chemical detection mechanism that is not fully understood so far. We present numerical simulations of quantum transport in functionalized polycrystalline graphene samples using tight binding parameters extracted from the literature for hydrogen and epoxide groups [2, 3]. To carry out the transport calculations we use a real-space order-N quantum wave packet approach to compute the Kubo-Greenwood formula, which we then relate to the mobility as a function of carrier concentration in order to match with experimental measurements [4, 5]. In order to understand the effect of the dopants on the CVD graphene we set up two different situations: a random doping distribution and an accumulation of the doping at the grain boundaries. Our calculations support experimental measurements that reveal distinct electronic transport regimes depending on the density and distribution of induced defects on the polycrystalline graphene films (Figure 1, [5]). Our findings provide a novel perspective to tailor the properties of polycrystalline graphene 2

References [1] Jaechul Ryu et al., ACS Nano, 8 (1) (2014) 950–956 [2] T. O. Wehling et al., Phys. Rev. Lett. 105 (2010) 056802. [3] Nicolas Leconte et al., ACS Nano 4 (2010), 4033-4038. [4] Dinh van Tuan et al., Nano Lett. 13 (2013), 1730-1735. [5] Max Seifert et al., Role of Grain Boundaries in Tailoring Electronic Properties of Polycrystalline Graphene by Chemical Functionalization (Submitted 2014). Figure 1. Electronic transport in functionalized CVD graphene. a and b, Field-effect mobility as a function of the relative defect density for six different transistors (each symbol representing a device) for graphene oxidation and hydrogenation, respectively. The mobility data are normalized to the mobility of clean devices. Open symbols represent ozone treatments at substrate temperatures above 70°C. The relative defect density nD/nC was calculated from the integrated area D/G Raman intensity ratio; nine measurement 2 spots within the 10x10 ȝm transistor channels were averaged to create one data point. b (inset), Simulation of ȝ/ȝ0 for increasing amount of hydrogen defects with a random distribution (green) and accumulated at grain boundaries (yellow). The vertical dashed line represents the saturation of the grain boundaries with hydrogen. c, Simulation of ȝ/ȝ0 for an increasing amount of epoxide defects with random distribution (blue) and accumulated at grain boundaries (red). After reaching the saturation threshold of the grain boundaries by epoxide defects (vertical dashed line), vacancies are gradually added (open symbol data points).

Graphene | 53

Negative photoconductivity in the fullerene C60-few layer graphene system 1

C. Bautista Flores , R. Y. Sato Berrú and D. Mendoza

Instituto de Investigaciones en Materiales Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, 04510, México, DF. claudiabautistaf@gmail.com, doroteo@unam.mx 2

In situ electrical measurements of few layer graphene during thermal evaporation of fullerene C 60, and the behavior of this bilayer junction under illumination is reported. We obtained few layer graphene films by chemical vapor deposition technique, then fullerene C60 was thermally evaporated on them. We found an increase in conductance of few layer graphene during the thermal evaporation of C60. When the bilayer junction was under illumination, we observed a kind of negative photoconductivity [1] at low light intensities, and it is p-type doped, we propose that its behavior changes to n-type for high light intensities of illumination [2]. We also found that the Raman signal of C60 is enhanced when it is on graphene, this effect is probably due to the so called Graphene Enhanced Raman Scattering [3]. We believe that the present findings may be useful for the design of devices using the C60/graphene system for optoelectronic applications.

References [1] A. Rose, Concepts in photoconductivity and allied problems, Interscience, New York, (1963), 64. [2] C. Bautista-Flores, R. Y. Sato-Berrú and D. Mendoza, Applied Physics Letters, 105 (2014) 191116. [3] X. Ling, W. Fang, Y.-H. Lee, P. T. Araujo, X. Zhang, J. F. Rodriguez-Nieva, Y. Lin, J. Zhang, J. Kong, and M. S. Dresselhaus, Nano Letters, 14 (2014), 3033.

Figure 1: Conductance of C60-Few layer graphene system as a function of light intensity, and schematic energy band diagram showing the position of Fermi level for low and high light intensities. In this case, a green filter centered at 550 nm was used. The arrows indicate the direction in which the light intensity was varied. For the results presented in the inset, a filter centered at 620 nm was used.

54 | Graphene

Driven Topological Insulator Quantum Dot: A spin-particle source (SpPS) Dario Bercioux, Andreas Inhofer Donostia International Physics Center, Donostia-San Sebastian,Spain dario_bercioux001@ehu.es Abstract We propose a device that allows for the emission of pairs of spin-polarized electrons into the edge states of a two-dimensional topological insulator [1]. Charge and spin emission is achieved using a periodically driven quantum dot weakly [2] coupled to the edge states of the host topological insulator. We present calculations of the emitted time-dependent charge and spin currents of such a dynamical scatterer using the Floquet scattering matrix approach. Experimental signatures of spin-polarized twoparticle emission can be found in noise measurements [3,4]. Here we introduce a new form of noise suppression, named Z2 anti-bunching. Additionally, we propose a setup in which entanglement of the emitted electrons is generated. This entanglement is based on a post-selection procedure and becomes manifest in a violation of a Clauser-Horne-Shimony-Holt inequality [3].

References [1] M.Z.Hasan & C. L. Kane Rev. Mod. Phys. 82, 3045 (2010). [2] G.Fève et al. Science 316, 1169 (2007) [3] A. Inhofer & D. Bercioux, Phys. Rev. B 88, 235412 (2013). [4] P. Hofer & M. Büttiker, Phys. Rev. B 88, 241308R (2013). Figures Zero-temperature emitted charge as a function of the height of the driving step U0. The various lines 2 2 correspond to different values of the reflection probability of the QPC |λpb| : |λpb| =0.95 (solid red line), 2 2 |λpb| =0.5 (dashed blue line), and |λpb| =0.1 (dotted green line). Please note that the steps are given in units of twice the electron charge. Upper inset: The density of states of the QD for various values of |λpb|. Lower inset: Model of driving we consider: the driving of the gate is switched on at time t0 and the potential is changed by a quantity U0.

Graphene | 55

Nanopores in Silicon Nitride Membranes, Graphene and CNM: Milling and Imaging Techniques at the Helium Ion Microscope 1

André Beyer , Daniel Emmrich , Emanuel Marschewski , Achim Nadzeyka , 2 1 Frank Nouvertné , Armin Gölzhäuser 1

Physics of Supramolecular Systems, University of Bielefeld, 33615 Bielefeld, Germany 2 Raith GmbH, Konrad-Adenauer-Allee 8, 44263 Dortmund, Germany andre.beyer@uni-bielefeld.de

The Helium Ion Microscope (HIM) is a charged particle microscope employing helium ions for probing the sample. In the low dose regime, the HIM operates as microscope, high doses enable material modification and sputtering. Compared to conventional focussed ion beams (FIB) using metal ions like Gallium, the HIM offers a very small focal spot size down to 0.35 nm and a strongly localized sputter interaction with the material. We employ the HIM for both milling nanopores in free standing membranes + as well as for the inspection of pores. The He beam with its unique properties overcomes the resolution limit of conventional FIB tools as we show in a comparison with a high resolution Ga-FIB. We achieve + smallest He -milled nanopores with a diameter of about 4 nm in all investigated membranes: 30 nm thick Silicon Nitride, Graphene and 1 nm thick carbon nanomembranes (CNM) made from aromatic selfassembled monolayers by electron-induced cross-linking. Different strategies for the characterization of pores with the HIM will be discussed. In particular, we compare the feasibility of the ion generated + secondary electron signal to the He transmission signal.

56 | Graphene

Surface Plasmons in Highly-doped Graphene 1

Francisco J. Bezares, Adolfo De Sanctis, Plablo Alonso, Iban Amenabar, Jianing Chen, Thomas 2 2 1 2 3 H. Bointon, Monica F. Craciun, Javier García de Abajo, Saverio Russo, Rainer Hillenbrand, and 1 Frank Koppens 1

ICFO – The Institute of Photonic Sciences, Av. Carl Friedrich Gauss 3, 08860 Barcelona, Spain, 2 Centre for Graphene Science, College of Engineering, Mathematical and Physical Sciences, 3 University of Exeter, CIC nanoGUNE Consolider, Tolosa Hiribidea 76, 20018 DonostiaSanSebastián, Spain francisco.bezares@icfo.es

Abstract The opto-electronic properties of graphene can be tuned by varying its charge carrier density via an applied voltage, surface chemical functionalization or interlayer intercalation. Although the former methods offer advantages for many applications, the carrier concentrations (n) that can be achieved 13 -2 with their use are limited to values corresponding to approximately ~10 cm using conventional 14 -2 methods and n ≤ 4X10 cm by using other methods such as ionic-liquid or solid polymer electrolyte gating[1-3]. Interlayer intercalation, however, has been shown to allow for significantly higher carrier 14 -2 concentrations, n > 5X10 cm , opening the way for experimental studies of the opto-electronic properties of graphene in an unprecedented energy regime[1,4]. Here, we show that highly-doped, FeCl3-intercalated graphene exhibits unique opto-electronic behaviour. For instance, we show that surface plasmons, i.e. collective oscillations of charged carriers, in this system can be coherently excited with propagation lengths significantly longer than any other non-encapsulated graphene system reported to-date. µ-Raman Spectroscopy, scattering-Scanning Near Field Microscopy (sSNOM) and nano-Fourier Transform Infrared (nano-FTIR) Spectroscopy were used to study plasmonic behavior which provided valuable insight into the physics governing such phenomena in graphene. Of particular interest for this work are intrinsic electron-phonon interactions in graphene as, in principle, a better understanding of such phenomena may lead to the electronic control of crystal lattice vibrations for the development of future applications. As such, near-field imaging was used to observe unconventional behavior near the frequency of the intrinsic optical phonon and a model describing this phenomenon will be discussed. References [1] Weijie Zhao, Ping Heng Tan, Jian Liu and Andrea C. Ferrari, Intercalation of Few-Layer Graphite Flakes with FeCl3: Raman Determination of Fermi Level, Layer by Layer Decoupling, and Stability, J. Am. Chem. Soc.133 (2011), 5941–5946. [2]!J. T. Ye, M. F. Craciun, M. Koshino, S. Russo, S. Inoue, H. T. Yuan, H. Shimotani, A. F. Morpurgo and Y. Iwasa, Accessing the Transport Properties of Graphene and its Multi-layers at High Carrier Density, Archive, arXiv:1010.4679v1 (2010) 1-4 [3] Dmitri K. Efetov and Philip Kim, Controlling Electron-Phonon Interactions in Graphene at Ultrahigh Carrier Densities, PRL, 105 (2010) 256805 [4] Ivan Khrapach, Freddie Withers, Thomas H. Bointon, Dmitry K. Polyushkin, William L. Barnes Saverio Russo and Monica F. Craciun, Novel Highly Conductive and Transparent Graphene-Based Conductors, Adv. Mater., 24 (2012) 2844–2849

Graphene | 57

The effect of the support in the catalytic activity of iridium NHC complexes covalently bonded to carbon nanotubes and graphene oxide 1

Matías Blanco , Patricia Álvarez , Clara Blanco , M. Victoria Jiménez , Javier Fernández-Tornos , 2 2 1 Jesús J. Pérez-Torrente , Luis A. Oro and Rosa Menéndez 1 Instituto Nacional del Carbón INCAR-CSIC, P.O. Box 73, 33080, Oviedo, Spain 2 Department of Inorganic Chemistry, Instituto de Síntesis Química y Catálisis Homogénea (ISQCHCSIC). University of Zaragoza, 50009, Zaragoza, Spain rosmenen@incar.csic.es Abstract Carbon nanomaterials, highlighting carbon nanotubes (CNT) and graphene oxide (GO), have been recently applied as supports to generate proactive heterogeneous catalysts [1],[2]. However, the aromatic degree of the support structure and the amount of oxygen functional groups could play an important role in the catalytic performance. In this work, both carbon nanomaterials are covalently modified through their surface OH groups to develop active catalysts based on supported iridium Nheterocyclic carbene (NHC) complexes. The effect of the inherent structure of the support will be studied. GO [2] obtained by a modified Hummers method, acid-oxidized CNT [1] and their corresponding 400 ºC thermally reduced materials were covalently functionalized with an appropriate hydroxyl-ending imidazolium salt through their OH functional groups. Characterization of the imidazolium-modified samples using typical solid characterization techniques, such as TGA, elemental analysis or XPS, enables the amount of the imidazolic compounds in the nanomaterials to be determined with moderate to good conversions. In both cases, nanotubes exhibit a better aromatic structure presenting also fewer amounts of oxygen functionalities. Both samples were used to generate in situ iridium NHC complex derived from the later imidazolium salt. XPS and HRTEM analysis confirm the presence of the iridium NHC complexes bonded to the samples. The supported complexes were tested in the reduction of cyclohexanone to cyclohexanol by means of hydrogen transfer processes with 2-propanol/KOH as heterogeneous catalysts. The samples were found to be active in the reaction conditions, giving conversions over 90 % in the times depicted in table 1. However, CNT catalysts exhibit a better performance than their corresponding GO. The better sp2 structure of the tubes, combined with their fewer amount of structural defects and oxygen functional groups could be the responsible. Finally, good cyclability of the catalysts without any loss of activity and a good stability in air were observed, in sharp contrast with the poor air stability of the related homogeneous system developed before. References [1] M. Blanco, P. Álvarez, C. Blanco, M. V. Jiménez, J. Fernández-Tornos, J. J. Pérez-Torrente, L. A. Oro, Rosa Menéndez ACS Catal. 3 (2013), 1307. [2] M. Blanco, P. Álvarez, C. Blanco, M. V. Jiménez, J. Fernández-Tornos, J. J. Pérez-Torrente, L. A. Oro, Rosa Menéndez. Carbon 83 (2015), 21. Figures

Figure 1. XPS C1s of functionalized oxidized and reduced supports

Figure 2. Recycling studies of the catalysts.

Table 1. Catalytic performance Sample Time for 90% (min) CNT-1-Ir 210 GO-1-Ir 760 CNT-TR400-1-Ir 120 TRGO-1-Ir 150 CNT-Ir CNT-TR400-Ir GO-Ir GO-TR400-Ir -

TON TOF0 (h-1) TOF50 (h-1) TOF90 (h-1) 934 11214 1220 267 947 11364 758 75 942 11336 3000 471 964 11568 1607 385 101 30 70 21 147 441 203 609 -

Acknowledgments The authors thank MICINN (Projects CONSOLIDER INGENIO 2010 CSD2009-00050, MAT2010-16194 and CTQ 2010-15221), and the Diputación General de Aragón (E07) for their financial support. Dr. Patricia Álvarez thanks MICINN for her Ramón y Cajal contract. Matias Blanco acknowledges his fellowship from and MECD (AP2010-0025).

58 | Graphene

Differences in the changes of the optical and morphological properties depending on the number of graphene layers under UV oxidation Ivan. I. Bobrinetskiy, Pablo M. Romero, Nerea O. Otero AIMEN - AsociaciĂłn de InvestigaciĂłn MetalĂşrgica del Noroeste, Relva 27A, 36410 PorriĂąo, Spain ivan.bobrinetskiy@aimen.es Aleksei V. Emelianov, Denis D. Levin National Research University of Electronic Technology, pass. 4805, bld. 5, Moscow, Zelenograd, Russia emmsowton@gmail.com Graphene, like other carbon nanomaterials, is considered as a promising component for organic and non-organic electronics. Because of molecular-scale nature, its properties highly depend on the number RI OD\HUV *UDSKHQHÂśV PRUSKRORJ\ FDQ EH JUHDWO\ FKDQJHG XQGHU WKH LQIOXHQFH RI KHDW SODVPD RU ultraviolet oxidation, and in the presence of various chemicals. Thus, there is a noticeable change in the electronic properties of carbon materials, which makes these methods promising for use in electronic applications that require surface functionalization or modification to the energy levels in the graphene. In this work we investigated the difference in chemical reactions with environment for graphene with various number of layers. Graphene has been transferred by the modified method of mechanical exfoliation on the Si substrate with thermal oxide thickness of 300 nm. For UV treatment we used a 240 W high pressure mercury lamp. UV photooxidation lasted for 3 hours in a wet atmosphere. We measured Raman spectra (Fig. 1), made AFM (Fig. 2) and SEM images for pristine and oxidized sheets. Treating graphene in a wet atmosphere under high pressure mercury UV lamp may involve several mechanisms: graphene oxidation, etching and doping. We found the process of UV oxidation during prolonged treatment is different. It depends on the graphene number of layers associated with increased activity of monolayer graphene energy and high resistivity to oxidation of multilayer graphene 3 associated with a high energy barrier for the formation of sp hybridized carbon atoms induced by UV photons. The p-doping of graphene takes place in all cases. The chemical doping results from the charge transfer by absorbed or bound to the o[\JHQ VSHFLHV RQ WKH JUDSKHQHÂśV VXUIDFH 7KH SURFHVV RI UV oxidation in a wet atmosphere allows a controlled method for carrying out the functionalization and doping of graphene, and its removal. Also we addressed the interest to photocatalytic oxidation with making use of titanium oxide nanoparticles. We demonstrated now effect in difference for photocatalytic oxidation under UV lamp because of very low energy transferred to nanoparticles. We suggest the rapid photocatalytic oxidation by pulsed laser irradiation. Calculation shows that it possible to provide sufficient energy to nanoparticals during single laser pulse to initialize the local graphene oxidation. It can be widely used in the formation of active electrode elements based on graphene containing different number of layers.

Fig. 1. Raman spectra for pristine (dotted) and oxidized (solid) graphene(a Âą 1-layer, b Âą 2-layer) for 3 h under UV photooxidation in a wet atmosphere.

Fig. 2. AFM images of single-layered graphene flake: a - pristine graphene on 300nm thermal SiO2, b Âą graphene sheet after oxidation in wet air for 3 h under UV irradiation. Arrows marks the non-oxidized parts of the graphene with lateral size less than 300 nm.

Graphene | 59

Large-area deposition of few-layer graphene produced by liquid phase exfoliation of expanded graphite M. Bodik, D. Kostiuk, P. Siffalovic, M. Hodas, M. Pelletta, M. Jergel and E. Majkova Institute of Physics, Dubravska cesta 9, 845 11 Bratislava, Slovakia peter.siffalovic@savba.sk Abstract Liquid phase exfoliation of graphene [1] presents a promising route for large-scale graphene production. Herein, we describe controlled deposition of few-layer graphene (FLG) using modified LangmuirSchaefer deposition. The FLG sheets were exfoliated from the expanded graphite by ultrasonic treatment or high-shear mixing in DMA, DMF and NMP solvents. Our studies confirmed better exfoliation rate for the expanded graphite when compared to natural graphite flakes. The FLG dispersions were further purified by centrifugation and mixed with chloroform to increase the spreading coefficient. The FLG dispersion was dropwise applied onto water surface in a Langmuir-Blodgett trough. The FLG surface coverage was monitored by the Brewster angle microscopy. The closed FLG layer was transferred onto different substrates such as Si wafers and float glass substrates using controlled removal of the water subphase. This deposition technology guarantees large-scale homogenous deposition of nanomaterials in general [2]. The structural, optical and electrical properties of FLG layers were inspected by the grazing-incidence X-ray diffraction and reflectometry, AFM, confocal Raman microscopy, imaging ellipsometry, optical spectroscopy and sheet resistance measurements. A typical AFM image of the deposited FLG film is shown in Fig. 1. The quality of the prepared FLG films is superior to the films prepared by more conventional techniques such as spin- and/or dip-coating. The utilization of the FLG films is wide, ranging from transparent electrodes to special interface hole transport layers for organic electronics. References [1] K. R. Paton et al., Nat Mater 13, 624 (2014). [2] P. Siffalovic et al., Self-Assembly of Nanoparticles at Solid and Liquid Surfaces, chapter in "Smart Nanoparticles Technology" edited by Abbass Hashim, ISBN 978-953-51-0500-8, InTech (2012) Figures

Fig. 1 - Densely packed FLG sheet after deposition.

60 | Graphene

X-ray Spectroscopy Study of Surface-Assisted Graphene Growth from Brominated Molecular Precursors on Silver Substrates ,JRU 3t達

1,2

and S. Nappini , M. Parravicini , A. Papagni ,E. Magnano and F. Bondino

IOM CNR, Laboratorio TASC S.S. 14 Km. 163 5 I-34149 Basovizza (TS) (Italy) Elettra-Sincrotrone Trieste S.C.p.A. S.S. 14 Km 163.5 I-34149 Basovizza (TS) (Italy) -Bicocca, Via Cozzi 55, 20125 Milano (Italy)

2 3

bondino@iom.cnr.it Abstract The bottom-up surface-confined fabrication of graphene architectures employing 1,6-dibromopyrene has been tracked by a combination of X-ray spectroscopy techniques: angle-resolved photoelectron spectroscopy (ARPES), high-resolution core level photoemission (HR-XPS), near-edge absorption spectroscopy (NEXAFS) and work function measurements. The formation of different precursor layers have been investigated on Ag(110) and Ag(111) surfaces as a function of temperature and coverage and monitoring the evolution of the system we have clearly observed a progressive rearrangement of intermolecular architectures. In particular, the correlation of temperature-dependent work function measurements with temperature-dependent core level photoemission has given important clues on the adlayer-substrate interaction and the progressive formation of intermediate species. The adlayers arise from organometallic units formed through homolytic dissociation of the C-Br bonds and carbon-Ag adatom bond evolution into structures with the spectroscopy signatures typical of graphene formed by the on-surface polymerization of debrominated molecular units. The evidence of graphene formation is given by UPS, ARPES, C 1s core level and C K edge NEXAFS. We observe that besides the temperature, the initial coverage is an important parameter for the surface-assisted growth of graphene by brominated molecular precursors on silver substrates under UHV conditions.

Graphene | 61

Dynamics of the graphene-metal nanoparticle catalyst interface during catalytic channeling Timothy J. Booth1, Filippo Pizzocchero1, Marco Vanin2, Jens Kling3, Thomas W. Hansen3, Karsten W. Jacobsen2, Peter Bøggild1 1) DTU Nanotech, Technical University of Denmark, Ørsteds Plads, 345E, Kgs, Lyngby 2800, Denmark 2) DTU Physics, Technical University of Denmark, Fysikvej 311, Kgs, Lyngby 2800, Denmark 3) DTU CEN, Technical University of Denmark, Fysikvej 307, Kgs, Lyngby 2800, Denmark tim.booth@nanotech.dtu.dk Abstract The catalytic hydrogenation and reduction of graphene has received renewed attention as one feasible route for the patterning of graphene structures at the nanoscale [1–5] which is applicable to suspended graphene and does not require the use of lithographic resists. An enhanced understanding of the dynamics of this process is required to see where metal nanoparticle channeling might prove technologically applicable, and to enable control of the process - the exact mechanism of the etching process is difficult to ascertain without the help of in-situ studies capable of resolving the dynamics at sufficient spatial and temporal resolution. We describe the results of in-situ nanoparticle channeling carried out by silver nanoparticles on suspended graphene in-situ in an environmental transmission electron microscope. Along with an understanding of the energetics and rate of the process [1] we have also made observations of the metal nanoparticle-graphene interface [2], including the three-dimensional structure of the nanoparticles. In contrast to some of the assumptions of recent studies [3], we find that the morphology of the nanoparticles is dynamic, and changes over time in response to the type of graphene edge it is in contact with. This behavior is particularly pronounced during turning of the nanoparticles, where a loss of crystalline faceting (but not of bulk crystallinity) is observed in our in-situ experiments. These observations highlight the importance of dynamic in-situ studies in the understanding of this process, and contradict assumptions about the metal-graphene interface and therefore the energetics of the system. By combining our observations with DFT calculations, we are able to provide a model for the long straight channels that we observe which are perfectly oriented with the graphene zig-zag direction. References [1] T.J. Booth, F. Pizzocchero, H. Andersen, T.W. Hansen, J.B. Wagner, J.R. Jinschek, R.E. DuninBorkowski, O. Hansen, P. Bøggild, Nano Lett. 11 (2011) 2689. [2] F. Pizzocchero, M. Vanin, J. Kling, T.W. Hansen, K.W. Jacobsen, P. Bøggild, T.J. Booth, J. Phys. Chem. C 118 (2014) 4296. [3] L. Ma, J. Wang, J. Yip, F. Ding, J. Phys. Chem. Lett. 5 (2014) 1192. [4] M. Lukas, V. Meded, A. Vijayaraghavan, L. Song, P.M. Ajayan, K. Fink, W. Wenzel, R. Krupke, Nat. Commun. 4 (2013) 1379. [5] G. Melinte, I. Florea, S. Moldovan, I. Janowska, W. Baaziz, R. Arenal, A. Wisnet, C. Scheu, S. Begin-Colin, D. Begin, C. Pham-Huu, O. Ersen, Nat. Commun. 5 (2014).

Figure 1. Left – HRTEM image of channeling nanoparticle. Center – HRTEM image of graphene corner at a turning point. Right – FFT of nanoparticle and graphene with angular mismatch between the graphene (100) and Ag (111) and (002) planes.

62 | Graphene

Lab-scale system for automated graphene transfer Alberto Boscá1, 2, J. Pedrós1, 3, J. Martínez1, 4, F. Calle1, 2, 3 1Instituto

de Sistemas Optoelectrónicos y Microtecnología, UPM, Madrid, 28040, Spain de Ingeniería Electrónica, E.T.S.I de Telecomunicación, UPM, Madrid, 28040, Spain 3Campus de Excelencia Internacional, Campus Moncloa UCM-UPM, Madrid, 28040, Spain 4Dpto. de Ciencia de Materiales, E.T.S.I de Caminos, Canales y Puertos, UPM, Madrid, 28040, Spain alberto.bosca@upm.es 2Dpto.

Abstract Although chemical vapor deposition (CVD) has proven to be an excellent method for growing electronic-quality graphene, its main disadvantage is the need of transferring the graphene layer from the metal catalyst to a suitable final substrate. A manual transfer method [1] was developed to overcome this issue. It consists of protecting the graphene with a thin polymer layer, wet-etching the growth substrate, rinsing with deionized water, and finally depositing the resulting polymer/graphene membrane onto the desired target substrate. Despite this method has been strongly optimized [2,3], it still requires strong handling skills, is time consuming, and is not suitable for an industrial process. An alternative method based on a roll-to-roll system [4] can overcome some limitations of the manual method, but it is limited to flexible substrates. In this work we report on a lab-scale system designed to transfer graphene automatically to arbitrary substrates, which could be easily scaled up for industrial applications. The system is composed of several modules (Fig. 1) that control the process temperature, the liquid flow and the overall system state. An Arduino UNO microcontroller is used as the real-time control system, timing and activating the rest of modules. It also allows communication with a computer for logging purposes. The passive components of the system are depicted in Fig. 2. A polytetrafluoroethylene (PTFE) tube encloses the graphene sample during the whole process. This enclosing tube has a surface treatment that centers the polymer/graphene membrane that floats inside it. The treatment avoids mechanical stress or induced ripples in the graphene during the process. A fixed platform and a substrate holder ensure a fixed position between the final substrate and the tube center. All these pieces are immersed into a liquid, starting with an etchant solution and changing gradually into deionized water for the final rinsing steps. Finally, graphene field-effect transistors (GFETs) were processed on the same CVD material but transferred using both the standard manual method and the novel automatic method for comparison. Raman and electrical assessment of the GFETs demonstrate that devices on the automaticallytransferred graphene present systematically higher mobilities and less impurity contamination. Acknowledgements Supported by MINECO projects RUE (CSD2009-0046) and GRAFAGEN (ENE2013-47904-C3) References [1] Alfonso Reina, Xiaoting Jia, et al., Nano Lett., vol. 9, 1 (2009), p. 30. [2] Wei-Hsiang Lin, Ting-Hui Chen, et al., ACS Nano, vol. 8, 2 (2014), p. 1784. [3] Hai Li, Jumiati Wu, et al., ACS Nano, vol. 8, 7 (2014), p. 6563. [4] Sukang Bae, Hyeongkeun Ri Kim, et al., Nat. Nanotechnol., vol. 5, August (2010), p. 1. Figures

Figure 1: System modules. An Arduino UNO board is used for interconnection and control

Figure 2: PTFE passive components (in liquid) and the sample and final substrate positions

Graphene | 63

Novel Sn/SnO2@rGO self-standing 3D architectures as anodes for Lithium ion batteries Cristina Botas (1), Daniel Carriazo (1,2), Teófilo Rojo (1), Gurpreet Singh (1) (1) CICenergigune, Alava, Spain. (2) IKERBASQUE, Basque Foundation for Science, Bilbao, Spain cbotas@cicenergigune.com Abstract The rapid development of portable electronic devices and electric vehicles requires high energy density rechargeable batteries. Lithium-ion batteries (LIBs) are the promising candidates for such applications. Graphene and graphene based materials are gaining interest as anode in LIBs due to their great properties, such as excellent mechanical flexibility and high electrical conductivity, surface area and chemical diffusivity of Li. The beneficial role of graphene composites and the synergistic effects between metals and graphene has been demonstrated [1] in the earlier literature. Metallic Sn offers high capacity anodes for the lithium ion batteries; the theoretical capacity of Li4.4Sn is 993 mAh/g [2]. However, it has several problems: i) volume change during the lithiation/delithiation process (it can be up to 300 %); ii) the material is highly degraded by these volume changes and the cyclability is affected; iii) high decomposition of the electrolyte. To overcome these problems and improve the stability of Sn anodes different Sn/C composites have been developed. The carbon matrixes can accommodate the volume change of Sn during charge–discharge process and thereby provide a better cyclability. These composites show better cycle performance than pure metallic Sn anode material. Recently, Sn/Graphene composites have been developed. These LIBs anodes present better rate capacity (680 mAh/g at 2 A/g) and longer cycle life (1000 cycles) than other Sn/C composites [2]. However, in our knowledge, self-standing Sn/SnO2@reduced graphene oxide (rGO) composites (without any binder and any support) as electrodes for LIBs have not been reported so far. The aim of this work, in order to obtain a good specific capacity while maintaining structural stability, was to evaluate different novel self-standing composites of Sn/SnO2@rGO 3D architectures as anodes for Lithium ion batteries. For this, different composites were synthesized by dissolving a certain amount of a Sn precursor within the GO suspension previously prepared by modified Hummer method [3]. The mixture was then processed and further reduced at different temperatures to obtain the Sn/SnO2@rGO self-standing composites. Electrochemical measurements were carried in CR2032 type coin cells assembled inside a glove box under Argon atmosphere. The electrolyte employed was 1.2 M LiPF6 in ethylene carbonate and dimethyl carbonate 1:1 (v/v). Lithium metal foil was used as counter/reference and glass fiber as -1 -1 separator. The Sn@rGO self standing film presented a capacity higher than 600 mA g at 50 mA g and a stable feature after 40 cycles. References [1] Z. Wu, G. Zhoua, L.Yina, W. R., F. Lia, H. Cheng. Nano Energy, 1 (2012) 107. [2] J. Qin, C. He, N. Zhao, Z. Wang, C. Shi, E. Liu, J. Li. ACS Nano, 8 (2014), 1728. [3] C. Botas, P. Álvarez, C. Blanco, R. Santamaría, M. Granda, P. Ares, F. Rodríguez-Reinoso, R. Menéndez. Carbon, 50 (2012), 275. 120

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Figure 1. a) Charge/discharge curves and b) galvanostatic cycling of c) 3D-Sn/SnO2@rGO electrode.

Acknowledgment. The authors thank European Commission (Graphene Flagship) for their financial support.

64 | Graphene

Large-area mono- and decoupled bilayer graphene grown on C-face 4H-SiC(0001) by high temperature sublimation C.Bouhafs1, P. KĂźhne1, I.G. Ivanov1, F. Giannazzo2, V. Stanishev1, A. A. Zakharov3, T. Hofmann4, M. Schubert4, T. Iakimov1, F. Roccaforte2, R. Yakimova1, V. Darakchieva1 1Department

of Physics, Chemistry and Biology, IFM, LinkĂśping University, SE-581 83 LinkĂśping, Sweden 2CNR-IMM, Strada VIII, 5 Zona Industriale, 95121 Catania, Italy 3Lund University, Maxlab, S-22100 Lund, Sweden 4Department of Engineering, University of Nebraska-Lincoln, Lincoln, 68588-0511 Nebraska, USA chabo@ifm.liu.se

Abstract Graphene grown by sublimation on C-terminated surface of SiC (0001) has attracted significant attention due its high free carrier mobility and the possibility of wafer scale production. However, C-face graphene typically grows in three-dimensional mode resulting in multi-layer graphene (MLG), with small domains and rough surface. Another issue with C-face graphene is that the individual layers of the MLG show a gradual doping profile with different mobility parameters which limit the use of C-face graphene in device application. Therefore, it is critical to achieve growth of monolayer and bilayer graphene with good surface morphology and controlled electronic properties. In this work, we demonstrated the growth of large-area mono- and decoupled bilayer graphene on C-face 4H-SiC (0001). Graphene was grown by high-temperature sublimation at 1950Â°C in Ar atmosphere. The number of graphene layers was determined using reflectance mapping and low-energy electron microscopy (LEEM). The transport properties were investigated using conductive atomic force microscopy (C-AFM), micro-Raman spectroscopy and mid-infrared optical Hall effect (OHE). The microRaman spectroscopy maps were measured simultaneously with reflectance maps, which allowed precise determination of the graphene layers properties such as doping. The LEEM and reflectance mapping showed large-area mono- and decoupled bilayer graphene with size of 600 Âľm 2 and 200 Âľm2 over the total probed area of 900 Âľm2, respectively and small domains of thick graphene layers [Fig.1 (a)]. The correlation between the C-AFM, reflectance and micro-Raman spectroscopy showed that the mono- and the decoupled bilayer graphene are n-type doped with different electron concentrations: the doping concentration of monolayer graphene was of the order of 1013 cm-2 and the decoupled bilayers were quasi-neutral. The OHE measurements showed Landau transition energies with a root square dependence on the magnetic field [Fig.1 (b)], which can be attributed to monolayer graphene or stacks of decoupled graphene layers. This result was confirmed by micro- Raman spectroscopy that showed a symmetric 2D Raman peak with a full width at half maximum varying between 26 cm-1 and 40 cm-1. Further a splitting of the Landau levels was observed [Fig.1 (b)], indicating different Fermi velocities. By comparing the doping concentration obtained from C-AFM and micro-Raman spectroscopy on one hand, and the inter-Landau-level transition energies obtained from magneto optical hall effect on the other hand, we attributed the observed Landau levels to the decoupled multilayer graphene layers. The splitting of the Landau levels was attributed to the different strain environment of the layers such as uniaxial strain. Figures

Fig. 1. (a) 30Ă&#x2014;30 Âľm2 color-coded thickness map for the graphene deduced from the reflectance measurement. (b) Inter-Landau level transitions of graphene on C-face 4H-6L& VKRZLQJ ÂĽ% GHSHQGHQFH ZKLFK LPSOLHV D VWDFN RI monolayers or decoupled multilayers. The Fermi velocities of different sets of Landau levels are indicated.

Graphene | 65

Large-scale electrical characterization of graphene Jonas D. Buron, F. Pizzocchero, B.S. Jessen, P. Bøggild, P.U. Jepsen, D.H. Petersen DTU Nanotech, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark jonas.buron@nanotech.dtu.dk Abstract There is a profound interest in the commercial adaptation of large-area graphene of high electrical quality for electronics and optoelectronics applications, including terahertz (THz) electronics and transparent, flexible, and durable electrodes for graphene-based touch-screens and solar cells. However promising, synthesized graphene shows large variations in quality, highlighting a need for electrical characterization on a large scale, for development of the material towards a position as a real alternative for electronic applications. In spite of very impressive advances in the available processes for large-scale synthesis, however, development of techniques targeting such electrical characterization of graphene on a large scale has not kept pace. We have introduced micro four-point probe (M4PP) and terahertz time-domain spectroscopy1, which are two non-invasive methods for characterization of the electrical properties of graphene, including sheet conductance2, carrier mobility3, sheet carrier density3, Dirac point3 and carrier scattering rate1. In addition to accurate and direct observation of fundamental transport properties as well as carrier dynamics at terahertz frequencies1, we show that THz-TDS and M4PP are capable of rapid, noninvasive and reliable large-scale mapping of graphene that might be viewed as a vital requirement for industrial implementation of graphene. Through back-gated THz-TDS carrier mobility mapping experiments3, we demonstrate large-scale carrier mobility and carrier density mapping, and show that mm-scale variations in the sheet conductance CVD graphene is attributed primarily to variations in carrier mobility rather than the chemical doping level, which is highly homogeneous. We show how ultra-broadband THz-TDS can identify the characteristic carrier dynamics regimes of barrier free (Drude) and restrained (Drude-Smith) carriers in a sheet of graphene. We show that the presence of extended line defects can be identified by ultra-broadband THz-TDS as well as M4PP on the scale of nano- and micro-meter, respectively. Using this method we find that graphene synthesised on single crystal Cu(111) shows clear signs of being barrier free, which stands in contrast with our observations on graphene grown on copper foil. References 1. Buron, J. D. et al., Nano Lett. 14, (2014) 6348±6355. 2. Buron, J. D. et al., Nano Lett. 12, (2012) 5074±5081. 3. Buron, J. D. et al., in preparation. (2014). Figures

Examples of THz-TDS and M4PP characterization of graphene. (Blue) Large-area field-effect mobility map of CVD graphene film. Gate-voltage dependence in 3 selected areas. Orange circles/triangles: THz conductance spectrum for discontinuous CVD graphene grown on poly-crystal Cu exhibits Drude-Smith behavior. Green circles/triangles: THz conductance spectrum for continuous CVD graphene grown on single crystal Cu(111) shows Drude behavior. Beneath: schematic of non-contact transmission THz-TDS measurement. (gray) Switched configuration M4PP can be used to evaluate graphene film continuity on the length scale of the electrode pitch. Red columns: RA/RB distribution of CVD graphene grown on poly-crystal Cu shows fingerprints of non-2D, non-continuous conduction. Green columns: RA/RB distribution of CVD graphene grown on single-crystal Cu shows fingerprints 2D continuous conduction

66 | Graphene

The study of corrosion of copper protected by graphene coatings I. Wlasny1, A. Busiakiewicz1, P. Dabrowski1, M. Rogala1, P. J. Kowalczyk1, I. Pasternak2, W. Strupinski2, J. M. Baranowski2, Z. Klusek1 1

Copper is widely known to exhibit nearly outmatched electrical and thermal conductance. Because of it, this metal is widely used in electronic industry in form of wires or heatsinks. However, in the ambient atmosphere the surface of copper interacts with air molecules and the layer of oxides is formed. As the conductive properties of the oxides of copper are far inferior to those of the metal in its pure state, means of the corrosion prevention are often being taken. The side effect of nearly all of the methods is the controlled degradation of the properties of copper and in case of coatings Âą increase of the dimensions of the device. One of the most promising methods for corrosion inhibition for copper is graphene coating due to impermeability of single sheets to gases [1]. The graphene is very attractive as not only it is good conductor for heat and electricity by itself, but it also can withstand high pressures. Also, using the CVD method it can be grown directly on copper surface. Because of this, the graphene is believed to be one of the most promising corrosion inhibiting coatings for copper. The CVD graphene grown on the surface of copper is not continuous, however. Instead, it is composed of numerous islands, which are either not connected to each other, or their joint boundaries are heavily defected due to misalignment of the lattices of the islands. These areas serve as the gateways for the air molecules, and in the proximity of those areas the corrosion reactions are enabled [2]. We present our investigation of this phenomenon. We show that while globally the amount of copper oxides in air exposed graphene-coated copper negligible, during the nanoscale investigations by STM/STS signs of corrosion can be found. We show the characteristic of those changes and alterations in the local electronic structure of graphene-coated copper they introduce. This work was financially supported by Polish Ministry of Science and Higher Education under Project No. N202 204737, the National Centre Projects DEC-2012/05/B/ST5/00354 and DEC2012/04/S/ST3/00186, the National Center for Research and Development Projects GRAF TECH/NCBiR/01/32/2012, GRAF TECH/NCBR/15/25/2013. References [1] Bunch, J. S., Verbridge, S. S., Alden, J. S., van der Zande, A. M., Parpia, J. M., Craighead, H. G., McEuen, P. L., Nano Letters, 8 (2008) 2458Âą2462. [2] Wlasny, I., Dabrowski, P., Rogala, M., Kowalczyk, P. J., Pasternak, I., Strupinski, W., Baranowski, J. M., Klusek, Z., Applied Physics Letters, 102 (2013) 111601.

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Quantum simulation of tunnel field-effect transistors based on transition metal dichalcogenides Jiang Cao1, Marco Pala1, Alessandro Cresti1 and David Esseni2 1

IMEP-LAHC, Univ. Grenoble Alpes, CNRS, F-38016 Grenoble, France 2 DIEG-IUNET, Via delle Scienze 208, 33100 Udine, Italy jiang.cao@minatec.inpg.fr

Abstract The tunnel field-effect transistors (TFETs) may enable a more aggressive reduction of the supply voltage than the MOSFETs, by lowering the sub-threshold swing (SS) under the thermionic limit of 60mV/dec at room temperature. Promising experimental results were reported for TFETs based on silicon and III-V semiconductors. However, in nanoscale devices, quantum confinement widens the band gaps and precludes the implementation of truly broken band gap alignments in 3D semiconductors [1], while interface states degrade the SS [2]. The use of semiconducting transition metal dichalcogenides (TMDs) may represent an extremely advantageous alternative thanks to their intrinsic 2D geometry and thinness, the absence of dangling bonds, and the variety of available materials, which results in a large range of energy band gaps and band alignments. In this contribution, we predict an extremely steep sub-threshold swing for inter-layer TFETs based on WTe2 and MoS2 layers with a 1 nm thick h-BN interlayer [3]. Figure 1 shows a sketch of the device and its equivalent 2D structure. Our full-quantum simulations are based on the non-HTXLOLEULXP *UHHQÂśV function formalism and accurately account for the device electrostatics by a self-consistent coupling to the Poisson equation. Electron-phonon scattering is calibrated to make the simulations consistent with available mobility experiments. By means of this numerical apparatus, we investigate the role of several relevant design parameters such as chemical doping, top gate geometrical alignment and back-gate biasing (see Fig.2). Our analysis reveals that carefully designed TMD TFETs can offer excellent SS values (<30 mV/dec) and represent a promising technology for future low-power nanoelectronics. References [1] S. Brocard et al., IEDM Proceedings (2013) 5.4.1. [2] M. Pala et al., IEEE TED 60 (2013) 2795. [3] M. Li et al., J. Appl. Phys. 115 (2014) 074508 . Figures

Fig1: (a) Sketch of the TFET under study. (b) Equivalent 2D model used in the simulations. The x2D axis corresponds to the y-direction for MoS2 and to xdirection for WTe2. (a)

(b)

(c)

Fig.2: (a) Transfer characteristics as a function of the top-gate voltage VTG for different values of the gate extension in the contact regions. The SS is 100, 27 and 17 mV/dec for Lext = 0, 5 and 10nm, respectively. (b) Output characteristics for different top-layer dopant concentration ND and back-gate voltage VBG. (c) Band profile and energy spectrum of the inter-layer current density in the transistor on-state (VTG=0.3V).

68 | Graphene

MoS2 Transistors with Electrografted Organic Ultrathin Film as Efficient Gate Dielectric Hugo CASADEMONT, Laure FILLAUD, Xavier LEFEVRE, Renaud CORNUT, Bruno JOUSSELME, Vincent DERYCKE CEA Saclay, IRAMIS / NIMBE / LICSEN, F-91191 Gif sur Yvette, France hugo.casademont@cea.fr

Abstract Two dimensional layered semiconductors, and in particular transition metal dichalcogenides such as molybdenum disulfide (MoS2), have recently received increasing attention due to the combination of their unique electronic properties with their atomically thin geometry. Contrary to graphene, MoS 2 has a finite band gap of 1.2-1.9 eV (depending on the number of layers), thus complying with the requirements of digital electronic applications. To maximize the potential of MoS2 as channel material in field effect transistors, it must be associated with an efficient gate dielectric. Beside the mainstream CMOS technology, other fields such as large-area and/or printable electronics, sensors and display technologies could also benefit from the combination of 2D materials and new dielectrics, especially if these dielectrics present additional advantages in terms of mechanical flexibility, low temperature processes, conformability to structured substrates, cost and simplicity of equipment and processes, etc. In this respect, the development of robust organic nano-dielectrics and their combination with new semiconductors represent a high potential route. In this context, we developed new dielectrics based on electrografted organic thin films on metallic electrodes. These dielectrics are produced at room temperature and under mild conditions. The process yields uniform films of nanometer thickness (4-8 nm range). In this work [1], we demonstrated the first transistors combining MoS2 as channel material and an electrografted organic ultrathin film as gate dielectric. The transistors exhibit high ION/IOFF ratio together with steep subthreshold slope as low as 110 mV/decade. Besides, the transfer characteristics of these transistors have no-hysteresis due to the hydrophobic and trap-free nature of our electrografted dielectric. The transistors reported in [1] were fabricated on rigid substrates and using mechanically exfoliated MoS2. Their potential in large scale (based on CVD MoS2) and flexible electronics will be discussed on the basis of our latest results. References [1] H. Casademont, L. Fillaud, X. LefĂ¨vre, B. Jousselme, V. Derycke, submitted

Figures

Graphene | 69

Effect of a balanced concentration of hydrogen on a high quality graphene CVD growthS. Chaitoglou*,E. Bertran :͘>͘ ŶĚƷũĂƌ ĂŶĚ ͘ Pascual Universitat de Barcelona, FEMAN Group, IN2UB, Department of Applied Physics and Optics ͬ DĂƌƚş ŝ &ƌĂŶƋƵğƐ͕ ϭ͕ 08028,Barcelona, Spain. Ύ ƵƚŚŽƌ͛Ɛ ĐŽŶƚĂĐƚ͗ ƐƚĞĨĂŶŽƐĐŚĂŝƚŽŐůŽƵΛƵď͘ĞĚƵ Abstract The extraordinary properties of graphene make it one of the most interesting materials for future applications in electronics, optics and structural materials. Between the different synthetic methods, chemical vapor deposition (CVD) is the one that permits to obtain large areas of monolayer graphene without defects. To achieve this, it is important to find the appropriate conditions for each experimental system. In our CVD reactor working at low pressure, important factors appear to be the pretreatment of the copper substrate, considering both its cleaning and its annealing before the growing process. The carbon ƉƌĞĐƵƌƐŽƌͬ ŚǇĚƌŽŐĞŶ ĨůŽǁ ƌĂƚŝŽ ĂŶĚ ŝƚ͛Ɛ ŵŽĚŝĨŝĐĂƚŝŽŶ ĚƵƌŝŶŐ ƚŚĞ ŐƌŽǁƚŚ is significant in order to obtain large area graphene crystals without defects. Copper substrate is usually exposed ƚŽ ŵĞƚŚĂŶĞ ĂŶĚ ŚǇĚƌŽŐĞŶ ŐĂƐĞƐ ĂŶĚ͕ ƚŚĞ ŐƌŽǁƚŚ ŝƐ ƚĂŬŝŶŐ ƉůĂĐĞ Ăƚ ϭϬϰϬΣ ͘ /Ŷ ƚŚŝƐ ǁŽƌŬ͕ ǁĞ have focused on the study of the methane and the hydrogen flows to control the production of monolayer graphene as well as the growth time. . In particular, we observe that hydrogen concentration increases during a usual growing process (keeping stable the methane/ hydrogen flow ratio) resulting in etched and not continuous domains. But, a modification of the hydrogen flow in order to balance this increase results in the growth of smooth hexagonal graphene domains. This is a result of the etching effect that hydrogen performs on the growing graphene. It is important, therefore, to study the moderated presence of hydrogen, which allows the form of large hexagonal domains. Also, by increasing the growth time we observe an increase in the nucleation density of the crystals.

Figure 1: Optical emission spectra where can be seen the reduction of the OH radical peak

70 | Graphene

&ŝŐƵƌĞ Ϯ͗ ƐĐĂŶŶŝŶŐ ĞůĞĐƚƌŽŶ ŵŝĐƌŽƐĐŽƉĞ ƉŝĐƚƵƌĞƐ ŽĨ ŐƌĂƉŚĞŶĞ ĐƌǇƐƚĂůƐ ŽŶ ĐŽƉƉĞƌ ĨŽŝů ĂĨƚĞƌ ϮϬ͛ growth (sample A)

Figure 3: scanning electron microscope pictures of graphene crystals on copper ĨŽŝů ĂĨƚĞƌ ϰϬ͛ growth (sample B)

&ŝŐƵƌĞ ϰ͗ ƐĐĂŶŶŝŶŐ ĞůĞĐƚƌŽŶ ŵŝĐƌŽƐĐŽƉĞ ƉŝĐƚƵƌĞƐ ŽĨ ŐƌĂƉŚĞŶĞ ĐƌǇƐƚĂůƐ ŽŶ ĐŽƉƉĞƌ ĨŽŝů ĂĨƚĞƌ ϰϬ͛ growth with reduced hydrogen flow (sample C)

Graphene | 71

Figure 5: Raman spectra of the obtained graphene referring to sample C References - >ŝ͕ yƵĞƐŽŶŐ͕ Ăŝ͕ tĞŝǁĞŝ͕ Ŷ͕ :ŝŶŚŽ͕ Ğƚ Ąů͕͟>ĂƌŐĞ-Area Synthesis of High-Quality and Uniform 'ƌĂƉŚĞŶĞ &ŝůŵƐ ŽŶ ŽƉƉĞƌ &ŽŝůƐ͕͟^ / E ͕ ϯϮϰ ͕ ϱϵϯϮ ͕ϮϬϬϵ ͕ ϭϯϭϮ-1314 -Sreekar Bhaviripudi Ğƚ Ăů͕ ͚͛ ZŽůĞ ŽĨ <ŝŶĞƚŝĐ &ĂĐƚŽƌƐ ŝŶ ŚĞŵŝĐĂů sĂƉŽƌ ĞƉŽƐŝƚŝŽŶ ^ǇŶƚŚĞƐŝƐ ŽĨ hŶŝĨŽƌŵ >ĂƌŐĞ ƌĞĂ 'ƌĂƉŚĞŶĞ hƐŝŶŐ ŽƉƉĞƌ ĂƚĂůǇƐƚ͕͛͛ E EK > dd Z^ ͕ ϭϬ ͕ ϭϬ ͕ ϮϬϭϬ͕ 4128-4133 - >ŝ͕ yƵĞƐŽŶŐ͖ DĂŐŶƵƐŽŶ͕ Ăƌů t͖͘ sĞŶƵŐŽƉĂů͕ ƌĐŚĂŶĂ͖ Ğƚ Ăů͕͚͛͘'ƌĂƉŚĞŶĞ &ŝůŵs with Large Domain Size by a Two-^ƚĞƉ ŚĞŵŝĐĂů sĂƉŽƌ ĞƉŽƐŝƚŝŽŶ WƌŽĐĞƐƐ͕͛͛ E EK > dd Z^ ͕ ϭϬ ͕ ϭϭ͕ 2010 , 4328-4334 -^͘ ,ƵƐƐĂŝŶ Ğƚ Ăů͕͛͛ Z&-PECVD growth and nitrogen plasma functionalization of CNTs on ĐŽƉƉĞƌ ĨŽŝů ĨŽƌ ĞůĞĐƚƌŽĐŚĞŵŝĐĂů ĂƉƉůŝĐĂƚŝŽŶƐ͕͛͛ ŝĂŵŽŶĚ Θ ZĞůĂƚĞĚ DĂƚĞƌŝĂůƐ͕ ϰϵ͕ ϮϬϭϰ͕ ϱϱʹ61

72 | Graphene

A Theoretical Study of the Electrostatics and Electronic Transport of the Graphene Barristor

Ferney Chaves, David Jiménez Departament d'Enginyeria Electrònica, Escola d'Enginyeria, Universitat Autònoma de Barcelona, Campus UAB, 08193 Bellaterra (Barcelona), Spain. Abstract Although transistors based on silicon technology have continued improving their speed and integration density over the years, their extreme reduction of the channel length causes inevitable leakage currents, being increasingly difficult to follow Moore’s law. To overcome the problems related with scalability, a variety of technologies and active materials have been proposed over the past years. Among them, the graphene-based transistor came up as a potential candidate because its appealing physical properties such as a very large mobility and saturation velocity. However, because graphene has no band gap, only a small on/off current ratio can be obtained on conventional graphene transistors [1]. To circumvent the problem, Samsung researchers introduced a class of three-terminal devices based on a graphene5

silicon hybrid device that exhibits a large current ratio Ion/Ioff (a10 ) [2]. They have named this barrier variable device as “barristor” (GB) (Fig.1a). The key GB function takes place at the electrostatically gated graphene/silicon interface where a tunable Schottky barrier controls charge transport across a vertically stacked structure (Fig. 1b). In order to gain a deeper insight into the GB operation, we present a theoretical study of GB electrostatics, so the relation between the applied biases and both the graphene shift Fermi level ('E) and the Schottky barrier height (Ib) could be properly understood, even in the presence of a chemical doping in the graphene. Other important aspect we have looked into is to what extent the transport theory of the conventional metal-silicon Schottky junction, where the metal is a bulk (3D) material, is appropriate in describing the GB characteristics. In this regard, we have explored the fundamentally different case of graphene-silicon Schottky junction, where graphene is a flat (2D) material.

We acknowledge support from SAMSUNG within the Global Research Outreach Program.

[1] Frank Schwierz, “Graphene transistors”, Nature Nanotechnology 5, 487 (2010). [2] Heejun Yang et al., “Graphene Barristor, a Triode Device with a Gate-Controlled Schottky Barrier”, Science 336, 1140 (2012).

Figure 1.(a) Scheme of the Graphene Barristor proposed by Samsung in Ref. [2]; (b) Band diagram along a vertical cut along the gate stack.

Graphene | 73

Transistors based on graphene or double wall carbon nanotube hybrids for optoelectronics Yani Chen1*, Frederic Lafollet2, Saioa Cobo2, Guy Royal2, Emmanuel Flahaut3, Dipankar Kalita1, Vincent 1 1 1 Bouchiat , Laëtitia Marty , Nedjma Bendiab 1 Institut Néel /CNRS, Univ. Grenoble Alpes, F-38000 F Grenoble, FRANCE 2 Département de Chimie Moléculaire, UMR CNRS CNRS-5250, 5250, Institut de Chimie Moléculaire de Grenoble, FR CNRS-2607, 2607, Université Joseph Fourier Grenoble I, BP 53, 38041 Grenoble Cedex 9, FRANCE 3 Université de Toulouse, UPS, INP, Institut Carnot CIRIMAT,, 118 Route de Narbonne, 31062 Toulouse Cedex 9, FRANCE Contact at: yani.chen@neel.cnrs.fr Abstract platform for realizing new functional devices such as ultrasensitive ultrasensi Carbon nanotubes (CNTs) are ideal platforms gas detectors, molecular scale logics and quantum devices devices, due to their outstanding electrical properties. properties Particularly, double walled nanotubes (DWNTs) consist consisting of two concentric single walled CNTs, CNTs can be treated as structures of two twisted and stretched graphene bilayers that exhibit complicated but relatively independent electronic properties, properties visible using sing molecule grafting on the outer wall [1]. Photo active molecules such as porphyrin po molecules and osmium smium terpyridine complex have the ability to reversibly switch between two or more stable states in response to external external stimuli such as light, temperature or an electrical current, current and can thus find application in molecular electronics electron [2]. A few studies have already demonstrated demonstrate the efficient photo induced charge transfer ansfer in CNT/porphyrin hybrid systems by using electrochemical methods, photoluminescence excitation experiments [3] as well as absorption spectra. Here we use Raman spectroscopy as a powerful tool both for the investigation of isolated DWNT and graphene and to study the charge transfer between the chemical dopants d and DWNT or graphene. We demonstrate transistors based on isolated DWNT (or graphene) and photo active molecules probed with combined Raman spectroscopy and electrical transport measurements. The he role of light in the control of the state of the hybrid will be manifested and elucidated in terms of photo-induced induced charge transfer. References [1] D. Bouilly, et al. ACS nano 5,, (2011), pp. 4927 4927-4934. [2] C. B. Winkelmann, et al. Nano lett. 7 (2007), pp. 1454-1458. [3] F. Vialla, et al. Phys. Rev. Lett. 111 (2013), pp.137402 Figures

Figure :Principle of the chromophore chromophore-DWNT DWNT transistors. The molecule is deposited on chip on the transistor. Light excitation of the chromophore acts as an optical ga gate.

74 | Graphene

Probing the Ni(111)-graphene interface using Raman spectroscopy Guangjun Cheng, Irene Calizo, Angela R. Hight Walker Physical Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, MS 8443, Gaithersburg, MD 20899, USA guangjun.cheng@nist.gov Abstract Theoretical simulations have shown that due to the hybridization of Ni d-HOHFWURQV ZLWK WKH Ę&#x152;-orbitals of graphene, graphene phonon dispersion is significantly altered [1]. There is no Raman signal from graphene on Ni(111) due to the suppression of the Kohn anomaly. In our work, we deposit a Ni thin film by thermal evaporation onto mechanically exfoliated graphene, few-layer graphene (FLG), and graphite, and probe the Ni-graphene interface using Raman spectroscopy. When the sample is annealed in forming gas, a Ni(111) thin film is produced on graphene, FLG, and graphite. We observe the disappearance of Raman signals from graphene underneath Ni(111) when using low laser power and the re-appearance of the Raman signals from the graphene with a higher power excitation laser. This work provides direct experimental evidence for the strong interaction between Ni(111) and graphene. References [1] Adrien A., Ludger W., Nano Lett, 10 (2010) 4335-4340 Figures

Figure1. Representative micro-Raman spectra collected from 1L, 2L and 3L graphene regions after the deposition of 10 nm Ni thin film.

Graphene | 75

Molecular beam epitaxial growth of graphene on sapphire substrates at extremely high temperatures

1,2

T.S. Cheng , A Davies , A. Summerfield , I. Cebula , A.N. Khlobystov , P.H. Beton , C.T. Foxon , L. 1 1 Eaves , S.V. Novikov 1

School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK 2 School of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK Tin.Cheng@nottingham.ac.uk

The discovery of graphene and its remarkable electronic properties has provided scientists and engineers with a material system for revolutionising electronics and opto-electronics. At present, the highest quality graphene is obtained by exfoliating small area (~10 ß¤m square) flakes from graphite. Whilst the quality of graphene grown by chemical vapour deposition continues to be improved, molecular beam epitaxy is a complementary technique which offers the possibility of producing large area, high quality heterostructures with atomic level control of layer thickness, composition and doping. Here we report the growth of graphene using a custom-designed dual chamber molecular beam epitaxy (MBE) system, based on the GENxplor from Veeco. The standard GENxplor has been specially o modified by Veeco to reach growth temperatures of up to 1850 C in high vacuum conditions and is capable of growth on substrates up to 3 inches in diameter. The growth chambers have a vertical configuration with the heater on top. In MBE, the substrate temperature is normally measured using an optical pyrometer. However, because we use transparent SiC and sapphire, the pyrometer measures the temperature of the substrate heater, not the substrate. Therefore, our estimate of the growth temperature is based on a thermocouple reading. In order to calibrate the temperature we have formed o graphene on the Si-face of SiC by heating wafers to temperatures above 1400 C. To demonstrate the scalability of the developed process, we have grown graphene on SiC substrate sizes ranging from 2 10x10 mm up to 3-inch diameter. We have also grown graphene layers on sapphire substrates using a SUKO-63 carbon sublimation source from Dr. Eberl MBE-Komponenten GmbH. Growth at substrate temperatures between ~1000 o and ~1650 C (thermocouple temperatures) have been investigated. We report the results of a wide range of techniques (reflection high energy electron diffraction (RHEED), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy, scanning tunnelling microscopy and sheet resistance measurements) that we have used to characterise these layers.

76 | Graphene

Amphiphilic block copolymers for graphene dispersions Suguna Perumal, Mi Ri Kim, Kyungtae Park, and In Woo Cheong Department of Applied Chemistry, Kyungpook National University, Daegu 702-701, South Korea. inwoo@knu.ac.kr Abstract Synthesis and characterization of different types of amphiphilic block copolymers and as graphene dispersants in water and ethanol will be presented. Graphene has been the center of attention during past few years with outstanding physical and mechanical properties. Particularly, affording singelayer graphene sheets without structural defects remains as difficult task. This single layer graphene has proved suitable toward various applications.1 In the present work, different graphene-phililic block copolymers, PSt-b-mPEG/PVP-b-mPEG (styrene (St) and vinyl pyridine (VP)), were prepared using reversible addition fragmentation chain transfer polymerization (RAFT). The hydrophobic block lengths (PSt/PVP) are varied whereas hydrophilic length was fixed as 8k PEG. The commercially available graphene M25 was used. The graphenes were dispersed in ethanol and water and characterized using UV-Vis (adsorption spectrum), goniometry (surface tension), and AFM (surface morphology and adhesion energy). The results revealed that the PVP-b-mPEG amphiphilic block copolymer showed good dispersibility of graphene than compared to that of PSt-b-mPEG and P-123. NVC (Nvinylcarbazole) based block copolymers were also prepared and their dispersibility results was presented. (Acknowledgement: This work was supported by the Ministry of Trade, Industry and Energy, Grant No. 10044338)

References [1] Guardia, L.; fernández-Merino, M. J.; Paredes, J. I.; Solís-Fernández, P.; Villar-Rodil, S.; MartínezAlonso, A.; Tascón, J. M. D. Carbon 49 (2011) 1653.

Figures

Graphene | 77

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78 | Graphene

Controlled induced defects on CVD graphene using ultrashort pulsed excitation 1

N. Chourdakis , S. Katsiaounis , E. Michail , M. Fakis , V. Drakopoulos , I. Polyzos , J. Parthenios , 1,3 1,4 C. Galiotis and K. Papagelis 1

Foundation of Research and Technology Hellas, Institute of Chemical Engineering Sciences, P.O. Box 1414, GR-26504 Patras (Greece) 2 Department of Physics, Univ. of Patras, GR-26504 Patras (Greece) 3 Department of Chemical Engineering, Univ. of Patras, GR-26504 Patras (Greece) 4 Department of Materials Science, Univ. of Patras, GR-26504 Patras (Greece) Contact e-mail: nhurdaki@iceht.forth.gr

It has been recently shown experimentally that two-photon absorption in graphene is an extremely intense phenomenon[1]. Besides, graphene is an ideal memory material because of its transparency, conduction properties and solution processability[2]. The goal of this work is to investigate the creation of defects onto graphene lattice, after illumination by a focused femtosecond laser beam and then to optimize the procedure in order to develop a novel three dimensional optical data storage memory, with high spatial resolution consisting of graphene/polymer layers. In a first step, we examine the generation of defects on chemically deposited graphene on the top of Si/SiO2 substrate. The graphene lattice is illuminated using 80fs pulses centered at 820nm and a repetition rate of 80MHz with different laser power and exposure time in order to create defects which will be both as large as needed for being clearly detected and as small as needed for giving high storage density. The fabricated samples are characterized by SEM imaging as well as Raman spectroscopy. Detailed Raman mapping of graphene took place before and after the laser illumination using a laser excitation of 514nm and a 100x objective lens. The Raman spectrum of pristine graphene consists of two distinctive features, known as G and 2D peaks. The presence of defects gives rise to another two features, D and D` peaks, which initially are forbidden in nondefected graphene as a result of Raman selection rule. The defected areas exhibit much higher I(D)/I(G) ratio compared to the non-defected ones indicating successful generation of defects[3,4] (Figure 1a). Defects of different sizes can be obtained by varying the exposure time at relatively low laser power levels. SEM images verify the size and shape of the defected areas (Figure 1b). This work is funded by the SURJUDPPH ³$5,67(,$ ,, *5$3+(1( 3+<6,&6 ,1 7+( 7,0( '20$,1 $1' $33/,&$7,21 72 ' 237,&$/ 0(025,(6´ LPSOHPHQWHG LQ WKH IUDPH RI WKH 2SHUDWLRQDO 3URJUDP ³(GXFDWLRQ DQG /LIHORQJ /HDUQLQJ´ DQG LV FR-financed by the European Union (European Social Fund) and Greek national funds. References [1] H. Yang et al, Nano Letters 11, (2011) 2622-2627 [2] D.I. Son et al, Nano Letters 10, (2010) 2441 [3] S. Hang et al, Carbon 72, (2014) 233-241 [4] L.G. Cancado et al, Nano Letters 11(8), (2011) 3190-3196

Figure 1. (a) Raman map of the D to G peak ratio I(D)/I(G) measured with 0.2ȝm mesh of CVD graphene after illumination with 3mW laser power for 20sec and (b) SEM image of the same defected area.

Graphene | 79

GRAPHENE STRUCTURES OBTAINED FROM BIOMASS P. Ciepielewski*, M. Dudynski**, G. Kowalski^, M. Tokarczyk^, I. Jozwik*, P. Gebarowski ^^ *Institute of Electronic Materials Technology, Warsaw, Poland **MTF and Institute for Theoretical Physics, Warsaw University, Warsaw, Poland ^Faculty of Physics, University of Warsaw, Warsaw, Poland ^^Institute of Ceramics and Building Materials, Warsaw, Poland Pawel.Ciepielewski@itme.edu.pl The possibility of obtaining graphene flakes directly from the charcoal (wood) is presented. The Raman and XRD (X-ray diffraction) experimental data for the charcoal and activated charcoal (birchwood) have been analyzed before and after high Ar pressure (150 and 300 MPa) and high temperature (1700C and 2000C) sintering . Before thermal and pressure treatment the Raman spectra were similar to that usually observed in GO (graphene oxide) [1]. After the treatment, the Raman data revealed, for both materials, existence of characteristic for graphene sharp * ' 'Âś DQG 2D modes . The energies and widths (FWHM) of these modes and their relative intensities indicated the existence of monolayers and multilayers graphene structures with estimated flakes sizes ranging from 15nm to 150 nm (according to I(G)/I(D) relation proposed in [2]) . The example of the Raman spectrum and the spatial map of one of the flakes (removed from the sintered charcoal in ultrasonic washer), corresponding to graphene monolayer, is presented in Fig1. Neither characteristic features of graphitic structure as observed in [3] nor 3D carbon structures (fullerenes, nanotubes) have been found in the Raman spectra. The XRD data before sintering shows some features characteristic for amorphous carbon. After sintering XRD data revealed the existence of few-layer graphene structures along thick, turbostratic stocked graphene layers. The experimental results gives an insight in the process of carbonization of biomass and allowed the verification of many theoretical models concerning the mechanisms of creation of the carbon nanostructures and their properties.

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[1]. Adarsh Kaniyoor and Sundara Ramaprabhu, AIP Advances 2, 032183 (2012). [2]. L.G. Cancado et al. (2008) Appl. Phys. Lett., (2006), 88, 163106. [3]. Jinggeng Zhao et al. Carbon 47 (2009) 744-751

80 | Graphene

Improvement of the transfer process of CVD graphene a

Sergi Claramunt , Qian Wu , Marc Porti , Narcis Mestres , Montserrat Nafría , Xavier Aymerich a

Electronic Engineering Department, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Spain sergi.claramunt@uab.cat

Abstract From the very beginning, graphene has shown incredible electrical properties [1]. Different electronic devices, like radiofrequency transistors, actuators, sensors, etc. may benefit of the inclusion of graphene as a material in the device. There are different approaches for the synthesis of graphene, but, for electronic applications, one of the preferred methods is the chemical vapor deposition (CVD) process [2]. Its main drawback is that it is necessary to separate the graphene layer from the Cu foil that acts as a catalytic seed. Nowadays various methods exists to do this process, and the most common used at laboratory scale is the spread of a PMMA layer over the graphene and then etch away the Cu foil [3]. Afterwards, the PMMA/Graphene stack can be deposited over the substrate objective. Finally, the PMMA layer is dissolved using acetone to uncover the graphene layer that will be ready for further treatment. Although with this method of separation we may obtain fairly good graphene layers, we detected some issues that affect its final quality and the reproducibility of the graphene layer transference. For example, the flexibility of the PMMA/graphene stack may favor the formation of wrinkles during the transference process that can prevent the contact between the graphene layer and the substrate, increasing the chances of the generation of defects and holes (Fig. 1a). Moreover, we also found that another source of defects is the PMMA cleaning. Usually, the PMMA is eliminated using acetone, which is very effective for this polymer. But because of the fast reaction, chunks of the graphene layer can be stripped out, especially if the contact with the substrate is not good. Also, it is known that acetone cannot eliminate completely PMMA, leaving a residue that in some cases can be detected by Raman spectroscopy (Fig. 2a). In this work we propose the addition of several steps to the standard process in order to improve the transference of a CVD graphene layer. First of all, after the PMMA/graphene stack is deposited over the substrate, the system is heated in order to relax the PMMA layer. In this way, the number of wrinkles will be decreased, assuring an intimate contact between the graphene layer and the substrate. After that, the PMMA layer is eliminated using acetic acid instead of acetone. With this solvent we achieve two things: first, a slower reaction, lowering the possibility of the stripping of the graphene during the layer dissolving process (Fig. 1b) and second, using acetic acid we ensure a good cleaning of the graphene layer (Fig. 2b), avoiding any additional annealing step. By adding and combining these two simple steps, the quality of the final graphene layer is improved and the repeatability of the process assured. Optical microscopy, Raman spectroscopy and Atomic Force Microscopy analysis show that the final graphene layer is almost continuous, with all the defects concentrated on the edges of the graphene layer. References [1] K.S. Novoselov et.al., Science, 306 (2004) 666. [2] Li, X. S. et al., Science 324, (2009) 1312. [3] Reina A. et. al, J Phys Chem C 112 (2008) 17741. Figures

(a)

(b)

. Fig. 1. Optical images of a graphene layer transferred using the standard method (a) and with our proposed additional steps (b)

Fig 2. Raman spectra of graphene cleaned with (a) acetone and (b) acetic acid.

Graphene | 81

Study of face-dependent graphene-copper interaction by heat treatment Sara D. Costa, Johan Ek Weis, Otakar Frank, Martin Kalbac J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3, CZ-18223 Prague 8, Czech Republic. sara.costa@jh-inst.cas.cz

Abstract The interaction between graphene and metals represents an ever more pressing issue because it determines the quality of contacts, an essential prerequisite for the correct function of intended graphene devices. In the present work we propose a simple method to estimate the level of interaction between graphene and copper single crystals with differently oriented faces – (111), (110) and (100). Insitu Raman spectroscopy under heat treatment clearly shows Cu face-specific behavior of the overlying graphene. Whereas for graphene on Cu(111) the interaction is in agreement with theoretical predictions and remains identical after several heating cycles, in the other two cases, the initially very weak interaction becomes even stronger after the heating than for Cu(111), resulting also in a larger charge transfer to graphene. In this way, a simple and coherent model to compare the level of interaction between graphene and copper, and its temperature-dependent evolution is provided. Furthermore, these face- and temperature-dependent variations in Cu-graphene interaction can prove imperative in successful graphene large-area growth and in the ease of its subsequent transfer to target substrates.

82 | Graphene

Nonlinear Graphene Plasmonics 1

1,2

Joel D. Cox and F. Javier García de Abajo 1

ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels, Spain 2 ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Spain joel.cox@icfo.es

Nonlinear optical processes host a wide range of applications in nanophotonics, including all-optical signal processing, ultrafast switching, and sensing, all of which are inhibited by the inherently weak nonlinear optical susceptibilities found in conventional materials. Noble metal nanoparticles can help overcome this limitation on the nanoscale, as they enhance optical nonlinearities through the strong electromagnetic field concentration enabled by localized plasmons. Due to plasmonic enhancement, noble metal nanoparticles have demonstrated nonlinear frequency conversion with the highest recorded efficiencies per volume [1], and are generally regarded as the best available nonlinear materials. Compared to noble metals, doped graphene nanostructures support plasmon excitations that couple more strongly with light, possess longer lifetimes, and are electrically tunable [2]. Here we show that nonlinear optical processes, including second- and third-harmonic generation, sum and difference frequency generation, and four-wave mixing, can be realized in small, doped graphene nanoislands with extraordinarily high efficiencies, surpassing those of noble metal nanoparticles with much greater size by several orders of magnitude. We model the optical response of these nanoislands using rigorous quantum mechanical simulations, taking into account significant contributions from nonlocal and finitesize effects. Due to quantum effects, a graphene nanoisland is capable of supporting multiple plasmon resonances, facilitating strong nonlinear frequency conversion for illumination with light of one or more incident frequencies that target these plasmons. [1] M. Kauranen and A. V. Zayats, Nat. Photon. 6 (2012) 737. [2] F. J. García de Abajo, ACS Photon. 1 (2014) 135.

Wave mixing in graphene nanoislands: (a) Illustration of a triangular graphene nanoisland illuminated by multifrequency collinear light pulses. (b) Spectral density of the induced dipole moment under excitation by light polarized along a direction parallel (upper panel) or perpendicular (middle panel) to one of the nanotriangle sides. The filled curves show the spectra produced by individual pulses of FHQWUDO IUHTXHQF\ Ȧ1 UHG RU Ȧ2 (green), while the black curves show the response when these pulses are applied simultaneously. The linear absorption cross-section of the nanoisland, which reveals the presence of multiple plasmonic resonances with electrical doping, is presented in the lower panel.

Graphene | 83

Graphene with enhanced spin-orbit coupling: Multiple quantum phases 1

Alessandro Cresti , Dinh Van Tuan , David Soriano , Aron W. Cummings and Stephan Roche

IMEP-LAHC, Univ. Grenoble Alpes, CNRS, F-38016 Grenoble, France CIN2 (ICN-CSIC) and Universitat Autonoma de Barcelona, E-08193 Bellaterra, Spain

alessandro.cresti@minatec.inpg.fr Abstract Functionalization with heavy atoms has been predicted to locally enhance the spin-orbit coupling in graphene [1] and turn it into a topological insulator [2]. For graphene ribbons, this would result in a 2 quantum spin Hall phase, with polarized edge channels and a 2e /h quantized conductance in the energy region of the topological gap. However, at present, any experimental confirmation of such a phenomenon is critically lacking. In this contribution, we focus on the case of thallium adatoms and show how their clustering might be responsible for this failure. Our numerical codes based on the Landauer-Büttiker and Kubo-Greenwood approaches, allow us to simulate both edge (in graphene ribbons) and bulk (in 2D graphene) electronic transport for samples of realistic size. Adatom clustering is shown to have a detrimental effect on the formation of the topological phase (see Fig.1), since it leaves large areas of graphene uncovered, where the effective spin-orbit coupling vanishes. Very intriguingly, we report a transition from the quantum spin Hall phase to the spin Hall effect upon thallium segregation [3], with a residual spin accumulation at the sample edges (see Fig.2). Such a phenomenon is related to the rise of local currents around the clusters, whose chirality depends on the spin orientation and that result in low-energy bulk extended 2 states, as evidenced by a robust minimum conductivity ‫׽‬4e /h (see Fig.3). References [1] C.L. Kane and E.J. Mele, Phys. Rev. Lett. 95 (2005) 226801. [2] C. Weeks et al, Phys. Rev. X 1 (2011) 021001. [3] A. Cresti, D. Van Tuan, D. Soriano, A.W. Cummings, and S. Roche, Phys. Rev. Lett. 113 (2014) 246603. Figures Fig.1: Conductance as a function of the electron energy E for a 50 nm wide and 50 nm long graphene ribbon with doped contacts and a 15% of thallium adatoms in clusters with radius r from 0.1 nm to 2 nm. Note the detrimental effect of clustering on the conductance plateau in the region of the topological gap (from about -50 meV to 50 meV).

Fig.2: Local distribution of spin-resolved spectral current and polarization in the ribbon described in Fig.1 for r=1.5 nm at E=15 meV. The current flows through the bulk (breakdown of the topological gap) and forms spindependent chiral currents around the clusters (the indicated arrows are an example). The local spin polarization shows accumulation at edges resulting from a spin Hall effect.

84 | Graphene

Fig.3: Conductivity of 2D graphene with a 15% of clustered thallium atoms and different densities of long-range impurities.

Nanocomposites reinforced with carbon nanofibres for 3D printing Jose María Cuevas, Ibon Aranberri, Juan José Campos GAIKER-IK4, Parque Tecnológico Ed. 202, 48170 Zamudio, Spain cuevas@gaiker.es Abstract Additive manufacturing is a group of emerging technologies that create objects from the bottom-up by adding material one cross-sectional layer a time. In 3D printing in particular, the additive process of the successive layers of material is laid down under computer control and these objects can be of almost any shape or geometry, and are produced from a 3D model or other electronic data source. The majority of materials used presently by modern 3D printing techniques are proprietary polymers and therefore big efforts are being done in order to find new materials with interesting functionalities such as thermal conductivity, electrical conductivity, mechanical resistance, etc.... As material science advances, one of the more exciting developments over the last several years has been the utilization of carbon nanofibres, a material which is extremely lightweight, strong, and electrically conductive. In the present poster, new polymeric films and tensile test samples reinforced with these graphenic nanofibres and manufactured by 3D printing are shown. The development of these materials suitable for 3D printing is only the beginning of a new era within the material science is applied to this kind of bottom-up manufacturing.

References [1] Olga Ivanova, Christopher Williams, Thomas Campbell, Rapid Prototyping Journal, 19/5 (2013) 353. [2] Ignacio Martin-Gullon, José Vera, Juan A. Conesa, José L. González, César Merino, Carbon 44 (2006) 1572.

Figures

Figures a) 3D printing of a nanocomposite film

b) Tensile test samples manufactured by 3D printing

Graphene | 85

Controlled functionalized graphene nanoribbons produced from carbon nanotubes. 1

Eunice Cunha , Helena Rocha , Maria C. Paiva , M. Fernanda ProenĂ§a , Paulo E. C. Lopes , Mariam 4 5 4 6 7 Debs , Manuel Melle-Franco , Francis L. Deepak , Robert Young , Liv Hornekaer 1

Institute for Polymers and Composites/I3N, University of Minho, Campus de AzurĂŠm, 4800-058 GuimarĂŁes, Portugal, 2 Department of Chemistry, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal 3 Pole for Innovation in Polymer Engineering (PIEP), University of Minho, Campus de AzurĂŠm, 4800-058 GuimarĂŁes, Portugal, 4 International Iberian Nanotechnology Laboratory (INL), Av. Mestre JosĂŠ Veiga, 4715-330 Braga, Portugal 5 Computer Science and Technology Center, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal 6 Materials Science Centre, School of Materials, University of Manchester, Oxford Road, Manchester M13 9PL, U.K. 7 Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, Building 1521, Ny Munkegade, 8000 Aarhus C, Denmark

eunice.cunha@dep.uminho.pt

Abstract Graphene nanoribbons (GNR) have received a great deal of attention due their promise for electronics and optoelectronic applications [1]. 5HFHQWO\ WKH IRUPDWLRQ RI *15 ZDV REVHUYHG ÂłLQ VLWXÂ´ E\ XQ]LSSLQJ of carbon nanotubes under ultra-high vacuum scanning tunneling microscopy (UHV STM) [2]. The CNT under observation were functionalized by the 1,3-dipolar cycloaddition reaction [3], in which the concentration of covalently bonded functional groups can be controlled by the experimental functionalization conditions. This functionalization route was responsible for the unzipping of the CNT, and thus the GNR formation by unzipping of functionalized CNT was repeated in ethanol suspension. The present work demonstrates the formation of graphene nanoribbons in solution by unzipping of functionalized carbon nanotubes. The formation of the GNR prepared in solution was studied by UV-visible spectroscopy, and the GNR obtained by solvent evaporation were analyzed by Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and scanning tunneling microscopy (STM). TEM and STM images demonstrated the formation of few layer graphene ribbons, and this result was confirmed by Raman spectroscopy. Molecular modeling was applied to study the crystalline stacking of functionalized GNRs yielding interlayer distances of 0.51 nm, in agreement with STM and XRD analysis. It was demonstrated that this interlayer distance was required to accommodate the functional groups attached to the graphene. Figure 1 depicts the Raman spectra of the functionalized carbon nanotubes and resulting GNR, showing evidence for the formation of few-layer graphene.

References [1] M. Terrones, A. Botello-MĂŠndez, J. Campos-Delgado, F. LĂłpez-UrĂas, Y. Vega-CantĂş, F. RodrĂguezMacĂas, A. ElĂas, E. MuĂąoz-Sandoval, A. Cano-MĂĄrquez, J. Charlier, H. Terrones, Nano Today, 5 (2010) 351. [2] M. C. Paiva, W. Xu, M. F. ProenĂ§a, R. M. Novais, E. LĂŚgsgaard, F. Besenbacher, Nano Letters, 10 (2010) 1764. [3] M. C. Paiva, F. Simon, R. M. Novais, T. Ferreira, M. F. ProenĂ§a, W. Xu, F. Besenbacher, ACS Nano 4, (2010) 7379.

86 | Graphene

Intensity (a.u.)

Acknowledgments The authors acknowledge Fundação para a Ciência e Tecnologia (FCT) for project PEstC/CTM/LA0025/2013 (Strategic Project - LA 25 - 2013-2014), and for ( &XQKD¶V PhD grant SFRH/BD/87214/2012. M. Melle-Franco acknowledges support by FCT through the program Ciência 2008 and the project SeARCH (Services and Advanced Research Computing with HTC/HPC clusters) funded under contract CONC-REEQ/443/2005.

CNT

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Graphene | 87

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88 | Graphene

Graphene/MoS2 Flexible Photo-detector ‡

‡

D. De Fazio , I. Goykhman , M. Bruna , A. Eiden , U. Sassi , M. Barbone , D. Dumcenco , K. Marinov , §

‡

A. Kis and A.C. Ferrari

‡ Cambridge Graphene Centre, University of Cambridge, Cambridge, UK § Electrical Engineering Institute, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland dd429@cam.ac.uk Abstract We present a large area, flexible photodetector for visible wavelengths fabricated by stacking centimetre-scale chemical vapor deposited (CVD) graphene and CVD MoS2, both wet transferred onto a flexible polyethylene terephthalate (PET) substrate (fig. 1). In this configuration, MoS2 acts as an absorbing material for visible wavelengths, while graphene is primarily used as a conductive channel for photocurrent flow. When electron-hole pairs are generated in MoS2 upon illumination of the stack, MoS2 donates electrons to the p-doped graphene channel [1], resulting in a decrease of the total source-drain current. In this configuration, the device responsivity can be enhanced either by promoting the injection process from MoS2 to graphene through side-gating using a polymer electrolyte (fig. 2), a technique that is suitable for a flexible platform [2,3], or by increasing the photoconductive gain in the graphene channel by applying larger source-drain voltage. The photodetector has an internal responsivity as high as ~30A/W at 642nm. This is at least two orders of magnitude higher than previously reported values for bulk-semiconductor flexible membranes [4,5] and for other flexible photodetectors based on a combination of graphene and MoS2 [6,7,8]. The photocurrent is stable at different bending angles, with variations less than 15% for radiuses of curvature down to 6cm.

References [1] W. J. Zhang, et al. Sci. Rep. 4 (2014). [2] H. Sirringhaus et al. Science 290 (2000) 2123. [3] A. Das et al. Nature Nanotech. 3 (2008) 210. [4] W. Yang et al. Appl. Phys. Lett. 96 (2010) 121107. [5] H. C. Yuan et al. Appl. Phys. Lett. 94 (2009) 013102. [6] F. Withers et al. Nano Lett. 14 (2014) 3987. [7] D. J. Finn et al. J. Mater. Chem. C 2 (2014) 925. [8] Koppens et al. Nature Nanotech. 9, (2014) 780.

Figures

Fig 1. Sketch of the flexible photodetector

Fig 2. I – V trans-characteristics of the device at different optical powers

Graphene | 89

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90 | Graphene

Novel strain devices to observe pseudo-magnetic fields in suspended graphene membranes 1

C. Downs *, A. Usher , J. Martin

School of Physics, University of Exeter, Stocker Road, Exeter, United Kingdom Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore

*C.Downs@exeter.ac.uk The interplay between a mechanical deformation of a graphene membrane and the change in electronic transport gives rise to novel physics, such as the formation of pseudo-magnetic fields, and offers a route WR ÂłVWUDLQWURQLFÂ´ GHYLFHV LQ ZKLFK WKH EHKDYLRXU RI WKH FKDUJH FDUULHUV FDQ EH PRGLILHG E\ FRQWUROOLQJ WKH amount of local strain [1]. These devices have the advantage of exhibiting a range of conduction phenomena arising purely from the strain pattern within the graphene membrane, without the need to cut the graphene sheet. Furthermore, neighbouring devices on a single substrate can display different transport effects, despite common external parameters such as applied magnetic field. Pseudo-magnetic fields can be induced by the introduction of non-uniform strain in the membrane and are expected to lead to unusual transport features in the quantum Hall regime, such as the prospect of the quantum Hall effect in the absence of applied field [2,3]. Furthermore, time-reversal symmetry is preserved for lattice deformations, and so the pseudo-magnetic field takes opposite values for electrons LQ WKH . DQG .Âś YDOOH\V 7KLV HQDEOHV WKH YDOOH\V WR be examined individually. Thus far, only non-uniform pseudo-magnetic fields have been observed in scanning tunnelling spectroscopy measurements in zero external magnetic field, probing the local density of states of highly strained graphene nanobubbles [4,5]. We have fabricated novel devices to produce the required strain configuration to produce uniform pseudo-magnetic fields in metalÂągraphene suspended structures for conventional two-terminal electron transport measurements. Conventional nanofabrication techniques, such as electron beam lithography, are used to pattern the structures. After partially etching the supporting oxide layer with hydrofluoric acid, the difference in the thermal expansion coefficients within the device structure leads to the metallic contacts selectively deforming upon cooling to cryogenic temperatures, producing the desired nonuniform strain. Finite element modelling was used to develop the contact design, which was verified with prototypes imaged in a low temperature electron microscope. The magnitude of the pseudo-magnetic field in these devices is designed to be ~1 T enabling the effects of the pseudo-magnetic field to be explored in conjunction with an experimentally-realisable external magnetic field. Electrical measurements in the electron-densityÂąmagnetic-field plane on these strained devices are on-going. This work can easily be adapted to produce other strain configurations, providing a route to strain engineering the electrical properties of graphene, an area which has developed a large body of theoretical work but thus far little experimental work. This work is funded by EPSRC and HEFCE, UK, and by the National Research Foundation, Singapore. References [1] V. M. Pereira and A. H. Castro Neto, Phys. Rev. Lett., 103 (2009) 046801 [2] F. Guinea, M. I. Katsnelson and A. K. Geim Nat. Phys., 6 (2010) 30 [3] F. Guinea, A. K. Geim, M. I. Katsnelson and K. S. Novoselov, Phys. Rev. B, 81 (2010) 035408 [4] N. Levy et al., Science, 329 (2010) 544 [5] J. Lu, A.H. Castro Neto and K.P. Loh, Nat. Commun., 3 (2012) 823

Graphene | 91

Electron scattering in graphene with NaCl nanoparticles adsorbed Aneta Drabinska,1 P. Kazmierczak, 1 E. Karpierz,1,2 R. Bozek,1 A. Wolos,1,3 M. Kaminska,1 A. Wysmolek,1 I. Pasternak,4 A. Krajewska,4,5 W. Strupinski4 1Faculty

of Physics, University of Warsaw, Warsaw, Poland of Chemistry, Warsaw University of Technology, Warsaw, Poland 3 Institute of Physics, Polish Academy of Sciences, Warsaw, Poland 4Institute of Electronic Materials Technology, Warsaw, Poland 5Institute of Optoelectronics, Military University of Technology, Warsaw, Poland *Aneta.Drabinska@fuw.edu.pl 2Faculty

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Fig. 1. Weak localization signal measured at different temperatures for graphene after (a) and before (b) immersion in NaCl solution and the temperature dependence of coherence length (c).

92 | Graphene

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Since planar, two-dimensional graphene structures enable facile and homogeneous functionalization, it is commonly expected that graphene will find a wide range of applications in many devices like ultrasensitive, label-free miniaturized electrostatic or electrochemical sensors. Recently, the use of graphene in an active fluid flow sensor has been considered. When thinking about this particular DSSOLFDWLRQ EHVLGHV GHWHUPLQLQJ WKH LQIOXHQFH RI WKH OLTXLG IORZ UDWH RQ JUDSKHQHÂśV HOHFWULF UHVSRQVH LW is very important to study the impact of fluids themselves on JUDSKHQH OD\HUÂśV SURSHUWLHV In our studies, using Atomic Force Microscopy (AFM), Electron Spin Resonance (ESR), contactless electron transport measurements and Raman spectroscopy, we investigated electron scattering mechanisms in epitaxial graphene, grown on Cu, transferred into SiC substrate and exposed to 0.06 M NaCl solution. The functionalization of graphene with NaCl microcrystals was confirmed by AFM and ESR techniques. Contactless magnetoconductance measurements showed the weak localization effect for temperatures below 50 K (fig. 1a and b). The elastic intervalley and long-range scattering lengths did not change after NaCl treatment, whereas the coherence length was reduced. Temperature dependence of the coherence length showed electron-electron scattering as the main inelastic scattering mechanism, and a change from ballistic to diffusive regime in electron transport after NaCl treatment (fig. 1c). However, the main reason for the reduction of the coherence length at low temperatures for the NaCl-treated graphene sample was additional temperature independent inelastic scattering responsible for electron spin flip scattering, which we associated with the presence of NaCl nanoparticles on the graphene surface. The Raman spectroscopy showed that the intensLW\ RI WKH ' DQG 'Âś EDQGV LQFUHDVHG IRU WKH sample after its immersion in NaCl solution (fig. 2a). Statistical DQDO\VLV RI WKH LQWHQVLWLHV RI WKH ' 'Âś and G bands indicated that the scattering is caused by both decoration of the existing defects (vacancies and grain boundaries) with NaCl nanoparticles which increased the efficiency of the scattering processes, and creation of a new type of defects, i.e. on-site defects caused by the decoration of the graphene surface with NaCl nanoparticles. The energy shifts of the 2D and G bands proved that NaCl deposition on the graphene surface did not change carrier concentration but reduced compressive biaxial strain in a graphene layer (fig. 2b). This work was partially supported by the NCN grant no 2012/07/B/ST3/03220 (Poland), NCBiR grant GRAF-TECH/NCBR/02/19/2012 (Poland), and European Union Seventh Framework Programme grant agreement no 604391 Graphene Flagship.

1590

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2680

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Magnetism and spin-orbit coupling in defective graphene from first-principles Simon M.-M. Dubois, Jean-Christophe Charlier Institute of Condensed Matter and Nanoscopic Physics (IMCN), UCL, Chemin des étoiles 8, bte L7.03.01, B-1348, Louvain-La-Neuve, Belgium Simon.Dubois@uclouvain.be Abstract Owing to the weak spin-orbit coupling, vanishing hyperfine interaction and ultra-high mobilities of its low-energy carriers, graphene is a promising material for spin channel applications. However, while theory predicts spin lifetimes of ~1 µs [1,2], experiments consistently report much shorter values [3-7]. The elucidation of these discrepancies is very important in order to enable future applications of graphene for spin processing and it would contribute to the elaboration of a unifed picture of spin relaxation in graphene based nanostructures. Potential culprits for the enhanced spin relaxation are adatoms, structural defects such as ripples or substrate induced effects. As an example, it has been recently shown that a small amount of covalently bonded hydrogen atoms is sufficient to increase the spin-orbit interaction of graphene by several orders of magnitude [8,9]. In this work, we investigate the magnetic structure and spin-orbit interaction induced by structural point defects (i.e. vacancies and Stone-Wales) and light adatoms by means of first-principles methods. We first detail the impact of the defects on the spin-orbit coupling strength both in the dense and dilute limits. As some defects such as vacancies and H-adatoms come with local magnetic moments, we then investigate the interplay between spin-orbit and exchange couplings, unravelling a rather large effect not easily explained by phenomenological models. Eventually, the spin-textures for in-plane and out-plane magnetic configurations are computed and the magnetic anisotropy of defective graphene is discussed.

References [1] S. Konschuh, M. Gmitra, and J. Fabian, Phys. Rev. B, 82 (2010) 245412. [2] D. Pesin and A.H. MacDonald, Nat. Mater., 11 (2012) 409. [3] N. Tombros, C. Jozsa, et al., Nature, 448 (2007) 571. [4] B. Dlubak, M.-B. Martin, et al., Nat. Phys, 8 (2012) 557. [5] M. H. D. Guimarães, A. Veligura , et al., Nano Lett., 12 (2012) 3512. [6] K. Pi, Wei Han, K. M. McCreary, et al., Phys. Rev. Lett., 104 (2010) 187201. [7] W. Han, K. M. McCreary, et al., J. Magn. Magn. Mater. 324 (2012) 369. [8] J. Balakrishnan, et al., Nat. Phys., 9 (2013) 284. [9] M. Gmitra, D. Kochan, and J. Fabian, Phys. Rev. Lett., 110 (2013) 246602.

Graphene | 93

Bi-functional organic linkers for 3D graphene oxide frameworks fabrication F. Duclairoir, C. Agnès, Q. Palomar, Y. Chenavier, L. Dubois, G. Bidan Laboratoire de Chimie Inorganique et Biologique, UMR-E3 CEA-UJF, Institute for Nanoscience and Cryogenics, Commissariat à l'énergie atomique (CEA), 17 rue des martyrs, 38054, Grenoble, cedex 9, France florence.duclairoir@cea.fr Abstract The expectations around graphene come from huge potentialities for various applications (RF transistor, (bio)sensors…).[1] Graphene high specific surface, mechanical resistance and conductivity make it specifically attractive for energy related applications. Its interfacing with various compounds has been shown to make it more processable, to tune its electrical/optical properties and to create functional materials.[2] Its use in the energy field is widely studied and lately questions have arose on whether graphene would be a good conductive additive or a relevant active material for electrochemical storage. For the latter purpose, 3D graphene scaffolds or graphene organic framework (GOF) are a class of material that seems to be promising to generate a new family of activated carbons.[3] In this poster, the routes developed in the laboratory to yield graphene frameworks will be presented starting from the fabrication of graphene using the chemical exfoliation route consisting on the oxidation of graphite followed by its reduction. The characterization of the starting graphene materials by XRD, XPS, TGA will be shown. The rGO obtained displays a high surface area (BET, SEM, TEM) and its degree of exfoliation is important. These graphene derivatives have been modified by diazonium salts possessing two anchoring sites enabling graphene sheets cross-linking, thereby targeting the formation of a graphene scaffold. Another route followed is to use diamine compounds to generate the graphene sheets inter-linking. In this case, the chemical reaction involved is not a radical reaction but an epoxide ring opening. For both approaches, different molecular bridge lengths and number of equivalents have been tested. The characterization of these matrixes will be shown (Fig. 1a), highlighting the impact of rGO re-stacking but also displaying a graphene hydrogel formation (Fig. 1b) following the diamine route. These results will be compared to examples found in the literature.[3,5] References [1] S. Yang, R. E. Bachman, X. Feng and K. Müllen, Acc. Chem. Res., 46 (2013) 116. [2] T. Kuila, S. Bose, A. K. Mishra, P. Khanra, N. H. Kim and J. H. Lee, Prog. Mat. Sci., 57 (2012) 1061. [3] P. Chen, J.-J. Yang, S.-S. Li, Z. Wang, T. Y. Xiao, Y.-H. Qian and S.-H. Yu, Nano Energy 2 (2013) 249. [4] N. A. Kumar, S. Gambarelli, F. Duclairoir, G. Bidan and L. Dubois, J. Mater. Chem. A, 1 (2013) 2789. [5] M. H. Alonso, A. A. Abdala, M. J. McAllister, I. A. Aksay and R. K. Prud’homme, Langmuir 23 (2007) 10644. Figures

Figure 1: (a) XRD patterns obtained for graphene oxide matrixes functionalized with various amines (hexyldiamine – black line, butyldiamine – black dotted line, graphene oxide – grey line); (b) Picture and SEM image of the graphene hydrogel obtained with ethylenediamine.

94 | Graphene

High Responsivity Silicon-Graphene Schottky Avalanche Photodetectors for Visible and Telecom Wavelengths A. Eiden, I. Goykhman, D. De Fazio, U. Sassi, M. Barbone, A.C. Ferrari Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 OFA,UK ale26@cam.ac.uk Abstract We present a high (A/W range) responsivity Si-graphene Schottky avalanche photodetector (PD) for visible (642nm) and telecom (1550nm) wavelengths. The device is fabricated by contacting chemical vapor deposited (CVD) graphene with a p-type Si substrate forming a Schottky junction [1,2]. Upon device illumination with photon energy above the Si bandgap (1.12eV), photodetection happens due to direct (band-to-band) photo-generation of electron-hole pairs in Si [3]. At 1550nm the photon energy (0.8eV) is below the Si bandgap, and the PD operation relies on internal photoemission, where photoexcited free carriers are injected from the graphene electrode to Si above a Schottky barrier [3]. To achieve a photogain, the PD is designed to perform under avalanche multiplication of the photoexcited carriers in the Si depletion region for elevated (higher than 4V) reverse biases. As a result, the device has an external responsivity up to ~1A/W for 642nm and ~0.5A/W for 1550nm. The latter responsivity is the highest achieved so far amongst Si-PDs for telecom wavelengths [4], and comparable with state-of-the-art Si-Ge devices currently employed in Si photonics [5,6]. Our device paves the way towards graphene-Si optoelectronic integration. References [1] X. An et al., Nano Lett. 13, 909 (2013). [2] S. Tongay et al., Phys. Rev. X 2 (2012). [3] S. Sze et al, Wiley, New York (2006). [4] M.Casalino, Int. J. Opt. Applications 2, 1 (2012) [5] Y. Kang et al., Nat. Photonics 3 (2009). [6] J. Michel et al., Nat. Photonics 4 (2010).

Figures

Fig 1. Schematic of Graphene-Si Schottky PD.

Fig 2. I-V characteristics under illumination showing photoresponse for visible and telecom wavelengths.

Graphene | 95

Isotopic labeling of bilayer graphene for advanced studies Johan Ek Weis, Sara D. Costa, Otakar Frank and Martin Kalbac J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejskova 3, CZ-18223 Prague 8, Czech Republic johan.ekweis@jh-inst.cas.cz Abstract Graphene has been proposed for many different applications, but the lack of a band gap limits its possible uses [1]. It has been found that the band gap of graphene bilayers can be controlled easier than for monolayers [2]. This study is therefore focused on bilayer graphene. Raman spectroscopy is one of the main characterization techniques of graphene. However, conventional Raman spectroscopy does not allow separation of the different layers in bilayers. We 12 13 therefore use isotopic labeling, where one layer is constituted of C and the other layer of C, which allows differentiating of the properties of the bottom and top layer. We have used this technique to establish that the adlayer in CVD growth of graphene on copper grows underneath the first layer [3]. We have investigated the different effect heat treatment has on the individual layers [4]. We have also found how fluorination influences the top and bottom layers depending on the stacking order of the bilayer [5]. References [1] K. S. Novoselov, V. I. Fal'ko, L. Colombo, P. R. Gellert, M. G. Schwab, K. Kim, Nature, 490, (2012) 192 [2] Y. B. Zhang, T. T. Tang, C. Girit, Z. Hao, M. C. Martin, A. Zettl, M. F. Crommie, Y. R. Shen, F. Wang, Nature, 459 (2009) 820 [3] J. Ek Weis, S. D. Costa, O. Frank, M. Kalbac, Phys. Status Solidi B. (2014) doi: 10.1002/pssb.201451169 [4] J. Ek Weis, S. D. Costa, O. Frank, M. Kalbac, J. Phys. Chem. Lett. 5, (2014) 549 [5] J. Ek Weis, S. D. Costa, O. Frank, Z. Bastl, M. Kalbac, Chem. Eur. J. (2014) doi: 10.1002/chem.201404813

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Channel Length Scaling of Graphene Field-Effect Transistors targeting Radio Frequency Applications Pedro C. Feijoo, Xavier Cartoixà, David Jiménez Department d’Enginyeria Electrònica, Escola d`Enginyeria, Edifici Q, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallès, Spain pedrocarlos.feijoo@uab.cat Abstract Graphene Field-Effect Transistors (GFETs) are expected to play an important role in the radio frequency electronic applications due to the outstanding graphene carrier mobility and velocity saturation [1]. The best reported cut-off frequency fT and maximum oscillation frequency fmax -figures of merit in radio frequency electronics- are, respectively, 427 GHz [2] and 45 GHz [3]. Although that record fT is below state-of-the-art III-V transistors (e.g., InP or GaAs), this figure of merit has rapidly increased over the years [1]. By contrast, fmax has not followed a similar progression and there is still much room for improvement. The theoretical limit of both key frequencies is estimated to be over 1 THz for GFETs [4]. To make it happen, transistor channel lengths (L) must shrink dramatically to push forward the current figures of merit. But in doing so, short channel effects (SCE) can come into play, severely impacting on both fT and fmax. To gain a deeper insight on the impact of SCE in GFETs figures of merit, we have developed a model under a drift-diffusion scheme that is based on the solution of the 2D Poisson equation in the GFET active region coupled with the current continuity equation. As an illustrative example, Fig. 1 shows the simulated output and transfer characteristics of a prototypical GFET with a channel length of 100 nm and a 40 nm thick HfO2 dielectric [5]. From them we can infer the transconductance gm, (=dIds/dVgs) and the output conductance gd (=dIds/dVds) which are key in determining both fT and fmax [1]. In summary, our work allows the assessment of the SCE impact on the high frequency performance of the GFETs by solving the 2D Poisson equation coupled with a drift-diffusion model for the carrier transport. The proposed model has been benchmarked against reported experimental results [6]. Acknowledgements This work is supported by the Spanish MINECO (TEC2012-31330) and the European Union (No. th 604391, 7 FP Graphene Flagship). References [1] F. Schwierz, Proceedings of the IEEE, vol. 101, No. 7 (2013) 1567. [2] R. Cheng, J. Bai, L. Liao, H. Zhou, Y. Chen, L. Liu, Y.-C. Lin, S. Jiang, Y. Huang, X. Duan, Proc. Nat. Acad. Sci., 109 (2012) 11588. [3] Y. Wu, K. A. Jenkins, A. Valdes-Garcia, D. B. Farmer, Y. Zhu, A. A. Bol, C. Dimitrakopoulos, W. Zhu, F. Xia, P. Avouris, Y.-M. Lin, Nano Lett., 12 (2012) 3062. [4] J. Zheng, L. Wang, R. Quhe, Q. Liu, H. Li, D. Yu, W.-N. Mei, J. Shi, Z. Gao, J. Lu, Sci. Rep. 3 (2013) 1314. [5] D. Jimenez, O. Moldovan, IEEE Trans. On Electron Dev., vol. 58, No. 11 (2011) 4049. [6] S.-H. Jan, Y. Sun, A. A. Bol, W. Haensch, Z. Chen, VLSI Tech. Dig. (2010) 231. Figures

Figure 1. Output (a) and transfer (b) characteristics of the GFET under test including SCE.

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TUNING GRAPHENE PROPERTIES BY A MULTI-STEP THERMAL REDUCTION PROCESS a

Laura Fernández-García , Patricia Álvarez , Marcos Granda , Clara Blanco , Ricardo Santamaría , a a a b a Patricia Blanco , Zoraida González , Uriel Sierra , Antonio Páez, Rosa Menéndez, * . a

Instituto Nacional del Carbón, INCAR-CSIC, Apdo. 73, 33080 Oviedo, Spain. REPSOL, Centro de Tecnología, Carretera de Extremadura, km 18, 28935 Mostoles, Madrid rosmenen@incar.csic.es

The chemical methods for producing graphene materials, via the formation of graphite oxide which must be subsequently exfoliated and reduced to obtain the final graphene, are among the most valuable due to their simplicity and easy scalability. The characteristics of the graphene materials obtained (rGO), which will determine their applicability, are greatly affected by the experimental conditions.[1,2] In any case, the use of single-step thermal treatment does not allow the properties of the materials obtained to be tuned as once the final temperature has been fixed, the resulting properties (C/O ratio, BET surface area, processability into suitable electroders, etc.) are also fixed. The aim of this work is to design a route for the preparation of rGOs of enhanced BET surface area as well as maximizing their suitability as electrodes in energy devices. For that, a GO obtained by a modified Hummers method was thermally exfoliated/reduced at 700 and 1000ºC by two single step procedures (ramp and flash pyrolisis) and by a novel multi-step procedure. The ramp pyrolisis in a single step gave rise to rGOs with low BET surface areas (~200 m2g-1) which are easily conformed into stable electrodes (Figure 1a). In contrast, by flash pyrolisis in a single step, high BET surface areas were obtained (~500 m2g-1) but it is not possible to conform them into stable electrodes (Figure 1b). By using the multi-step procedure developed herein it is possible to prepare rGOs that have an increased BET surface area (compared to that of the material prepared by the single-step ramp-heated material) and that are easily conformed into stable electrodes for electrochemical energy storage devices (Figure 1c). SEM images of the rGOs indicate the formation of tridimensional structures derived from the expansion of the graphite oxide on heating, which is the factor responsible for the development of porosity in these graphene materials. In the case of the flash-pyrolized sample (Figure 2a) cavities with sizes more in the range of mesopores are observed, contributing to an increment in the BET surface area and to the loss of suitability as electrodes. These structures are not so abundant in the ramp-heated sample, which explains its lower BET surface area (Figure 2b). An intermediate situation is obtained by the multi-step procedure, which explains the high BET surface area and good suitability as electrode of these materials. ACKNOWLEDGMENT: The authors thank REPSOL for their financial support, project SAVE Dr. P. Alvarez also acknowledges MICINN for her Ramon y Cajal contract. Work patented (ref: EP14382352.4) References [1] McAllister MJ et al. Chem Mater 19 (2007) 4396. [2] Botas C et al. Carbon 50 (2012) 275.

Figures

Figure 1: Electrodes from rGO obtained by ramp single steps: ramp (a,b) and flash (c,d) and multistep (e,f)

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Figure2: SEM image (up) and BET curves (down) of rGO obtained by ramp single steps: ramp (a) and flash (b) and multi-step (c)

Influence of substrate transfer process on the band structure and the optoelectronic properties of chemical vapor deposited MoS2 monolayers 1

M. Frégnaux , H. Kim , D. Rouchon , N. Chevalier , 2 3 4 1 V. Derycke , J. Bleuse , M. Chhowalla and O. Renault 1

Univ. Grenoble Alpes, F-38000 Grenoble, France CEA, LETI, MINATEC Campus, F-38054 Grenoble, France. 2 CEA, IRAMIS, F-91191 Gif-sur-Yvette, France. 3 Univ. Grenoble Alpes, F-38000 Grenoble, France CEA, INAC, F-38054 Grenoble, France. 4 Materials Science and Engineering, Rutgers University, 607 Taylor Road, Piscataway, New Jersey, 088854, USA mathieu.fregnaux@cea.fr Abstract: Two-dimensional transition metal dichalcogenides (2D TMDs), such as molybdenum disulfide (MoS 2), are very promising materials for optoelectronic application purpose. Having an ultrathin layered structure and a remarkable direct band gap of 1.9 eV in the monolayer (1L) regime, few micrometer MoS2 domains can be obtained by chemical vapor deposition (CVD). However, integration of these nanosheets into electronic devices may require a substrate transfer process step. In this paper, we present a combined characterization protocol developed in our group to compare the structural, optical and electronic properties of both as-deposited and substrate transferred MoS2 1L. Such preliminary study is primordial for subsequent application tests on devices. The use of X-ray PhotoElectron Emission Microscope (XPEEM) [1] allows us to identify large MoS2 microdomains (few ten microns) and to control their good stoichiometry. The effective presence of MoS2 1L and their good crystallinity is verified by atomic force microscopy and Raman spectrometry, respectively. In addition, XPEEM can be used in the momentum microscopy mode (k-PEEM) to perform parallel angular imaging in a one shot experiment. [2] It provides energy-filtered valence band mapping of a -1 single domain in the reciprocal space, within ± 2 Å and at an energy resolution better than 100 meV. The band structure of MoS2 1L is then directly generated by projection along the high symmetry directions of the first Brillouin zone. These results are discussed in regards to microphotoluminescence measurements at low and room temperature. Finally, this combined photoemission and photoluminescence protocol provides complementary and fundamental information about the influence of substrate transfer process on the optoelectronic properties of these alternative semi-conductors. This work was performed on the Nanocharacterization Platform (PFNC) of CEA Grenoble. References [1] H. Kim, O. Renault et al., Appl. Phys. Lett., 105 (2014) 011605. [2] C. Mathieu et al., Phys. Rev. B., 83 (2011) 235436.

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Solar energy conversion in van der Waals heterostructures 1

Marco M. Furchi , Andreas Pospischil , Armin A. Zechmeister , Florian Libisch , Joachim BurgdĂśrfer 1 and Thomas Mueller 1 2

Institute of Photonics, Vienna University of Technology, Gusshausstrasse 27-29, 1040 Vienna, Austria Institute for Theoretical Physics, Vienna University of Technology, Wiedener Hauptstrasse 8-10, 1040 Vienna, Austria marco.furchi@tuwien.ac.at

Abstract Photovoltaic cells for solar energy harvesting are today mainly made out of crystalline semiconductors or organic compounds. Beside the high production costs, crystalline semiconductor cells have the drawback of being heavy and bulky. Organic cells, on the other hand, suffer from low carrier mobility and short lifetime of the organic material. To overcome these drawbacks, we engineered a new type of solar cell based on atomically thin transition metal dichalcogenide (TMDC) layers. Due to the thickness of the used materials the advantages of low raw material costs, high flexibility and semi-transparency are intrinsic parameters. This, combined with the wide range of available band gaps and the good carrier mobility make atomically thin TMDC crystals a promising candidate for next generation solar [1] cells . Recent work demonstrated that atomically thin WSe2 can be electrostatically doped such that hole and electron conduction is achieved and that it can be used to realize a lateral hetero-junction [2] which can be operated as a solar cell . The main drawback of the mentioned structure is the small interaction area. To overcome this limitation, [3] we fabricated planar van der Waals heterojunctions by stacking two , and also multiple, atomically thin TMDC layers. Figure 1a shows that such a planar p-n can indeed be used for efficient solar energy harvesting. Besides measurements of electrical transport and the photovoltaic properties, we will present photoluminescence measurements that clarify the working principle of these devices. In addition we will present improved cells, formed by a triple TMDC heterojunction as schematically depicted in Figure 1b.

References [1] D. Jariwala et al., ACS Nano, 8 (2014) 1102-1120. [2] A. Pospischil et al., Nature Nanotechnology, 9 (2014) 257-261. [3] M.M. Furchi et al., Nano Letters, 14 (2014) 4785-4791.

Figures

(a)

(b)

Drain Source

0.10

6400 W/m2

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0.05

180 W/m2

0.00

TMDC TMDC 1 TMDC 2 3

-0.05

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Fig. 1(a) I-V characteristic of the MoS2 â&#x20AC;&#x201C; WSe2 heterostructure device under optical illumination 2 with Popt =180!6400 W/m . (b) Schematic illustration of a triple junction heterostructure device.

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Large-area Graphene Production using Roll-to-roll (R2R) Technology Arnaldo Galbiati(1), James Huang(2) (1)

SOLARIS PHOTONICS, London, U.K. KINGYOUP OPTRONICS, Taipei, Taiwan (R.O.C) admin@solaris-photonics.com

(2)

Abstract Only 10 years have passed since Geim and Novoselov first used adhesive tape to isolate graphene from graphite, since then, tens of graphene manufacturing companies have been created all over the world, which can produce small graphene sheets as well as large-area, high-quality graphene films on an industrial scale exceeding 400 tonnes and 110,000 m2 per year. The Chemical Vapor Deposition (CVD) technique produces high-quality graphene films by the catalytic decomposition of hydrocarbons on a metal (for example, Cu, Ni, Pt or alloy) surface at high temperatures, and the films are then transferred to transparent substrates such as glass and polymers by etching away the metal or by non-destructive electrochemical bubbling for transparent conductive film (TCF) applications. In this paper we will present state-of-the-art Roll-to-roll (R2R) CVD growth and transfer techniques that have been developed to fabricate large-area graphene for various applications such as functional coatings, conductive inks, batteries and supercapacitors, transparent electrodes in touch panels, displays and photovoltaic devices as well as for novel flexible electronic devices. References [1] Novoselov, K. S. et al. Science 306, (2004) 666–669 [2] Zhu, Y. W. et al. Adv. Mater. 22, (2010) 3906–3924 [3] Novoselov, K. S. et al. Nature 490, (2012) 192–200 [4] Bonaccorso, F., Sun, Z., Hasan, T. & Ferrari, A. C. Nature Photon. 4, (2010) 611–622 [5] Kim, K. S. et al. Nature 457, (2009) 706–710 [6] Li, X. S. et al. Science 324, (2009) 1312–1314 [7] Bae, S. et al. Nature Nanotech. 5, (2010) 574–578 [8] Kobayashi, T. et al. Appl. Phys. Lett. 102, (2013) 023112 [9] Gao, L. B. et al. Nature Commun. 3, (2012) 699 [10] Dai, B. Y. et al. Nature Commun. 2, (2011) 522

Figure: 1, Large-area Graphene production equipment using Roll-to-roll (R2R) technology

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Composite graphene/MnO2 as catalyst for air electrodes in metal-air batteries M. Insausti, B. Iraola, I. Bustero, F. Fernández-Carretero, D. A. Pacheco Tanaka, A. García-Luis TECNALIA, Mikeletegi Pasealekua, 2, San Sebastián (Spain) alberto.garcia@tecnalia.com Abstract Metal-air batteries have the potential to store more energy than lithium-ion batteries with a relative lower cost, simplicity and without the lithium safety concerns. The performance of this battery is mainly determined by the oxygen reduction reaction (ORR) at the air cathode, and a considerable effort has been dedicated to develop new air electrodes composed by an ORR catalyst supported in an electrical conductive material (e.g. carbon based materials) [1]. Transition metal oxides have been proved as good catalysts for the ORR in alkaline media, replacing the expensive noble metals (e.g. platinum). In particular, MnO2 presents a high catalytic activity, specific capacitance and it is inexpensive, abundant and environmentally friendly. On the other hand, graphene is an advantageous support material to replace conventional carbon materials in air electrodes. The combination of high surface area, elevated mobility of charge carriers, high conductivity, unique graphitized basal plane structure and potential low manufacturing cost makes graphene a promising candidate to be used in this application. Additionally, an improvement in the ORR catalytic activity has been demonstrated with the synergetic interaction of graphene and the metal-oxide [2]. In this work, we present the study of a MnO2/graphene catalyst, synthesized by a simple in-situ hydrothermal method [3] that leads to an uniform distribution of the metal oxide particles over the graphene platelets. X-ray diffraction (XRD) analysis shows an amorphous structure for the manganese oxide, which can increase its catalytic activity due to the high concentration of lattice defects and active sites in the material. The electrochemical characterization of this MnO2/graphene composite catalyst includes the evaluation of the ORR activity using the rotating disc electrode (RDE) technique in KOH 1M at 25 °C. Promising results have been achieved, demonstrating that the ORR follows the 4e pathway and with an activation overpotential only 80mV greater than the Pt/C used as reference. References [1] F. Cheng, and J. Chen, Chem. Soc. Rev., 41 (2012) 2172. [2] Y. Liang, Y. Li, H. Wang, J. Zhou, J. Wang, T. Regier and H. Dai, Nature Materials,10 (2011) 780. [3] L. Feng, Z. Xuan, H. Zhao, Y. Bai, J. Guo, C.-H. Su and X. Chen, Nanoscale Research Letters, 9 (2014) 290. Figures

SEM micrograph of MnO2/graphene composite catalyst

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Linear sweep voltammograms (LSV), at 1600 rpm rotating rate, comparing MnO2/graphene sample with Pt/C catalyst

Strain and Friction in Few Layer 2D Crystals Bennett Goldberg, Jason Christopher, Bo Wen, Zheng Han, Cory Dean, Anna Swan Boston University, 590 Commonwealth Ave., Boston, MA 02215, USA goldberg@bu.edu Abstract Strain in 2D crystals can tune material properties [1], controllably breaking crystal symmetry [2], and inducing pseudo magnetic fields [3]. Friction plays a central role in these applications because of its effect on the strain field’s engineering, orientation and magnitude. We have developed a simple experiment for generating known strain fields in 2D crystals to explore phonon response and friction. We suspend a 2D crystal over a hole etched in a Si substrate creating a sealed micro-chamber. We place these chambers into a pressure vessel with an optical window for Raman measurements while simultaneously applying external pressure (figure 1). The external pressure deforms and slides the 2D material into the hole, and we measure the strained Raman spectra with high spatial resolution (figure 2). The friction force and phonon strain response are determined by fitting a global set of parameters to an extended continuum model that improves precision (figure 3). Our method is applicable to a wide variety of 2D crystals and substrates. In previous work we studied graphene [4], and most recently we focused on hexagonal Boron Nitride (hBN). The coefficient of friction (COF) between hBN and SiO2 is µ=0.37 ± 0.19, which is more than three times larger than trilayer graphene’s COF, 0.11 ± 0.01. The Gruneisen parameter and shear deformation potential for the E2g mode in hBN, a degenerate mode analogous to the G mode in graphene, are measured to be 1.84 ± 0.09 and 1.0 ± 4.6 respectively. Measurement of the shear deformation potential through analysis of polarized Raman spectra highlights the utility of our technique considering this parameter has eluded decades of experiments on bulk material. Measurements of Molybdenum disulfide (MoS2) and phosphorene are under way. We have also begun to alter the substrate chemically with silanization and replacing it with other materials such as hBN. The multitude of possibilities fosters an understanding of the structural, chemical and geometric aspects of tribology as has never been available before. Figure 1: Micro-chamber and pressure vessel geometry (Argon Ion Laser: λ = 512nm, Beam Width = 0.75µm.)

Figure 3: Phonon strain response global fitting over multiple pressures (Pressure is in PSI. Error bars represent one standard deviation, and the material is hBN.)

Figure 2: Strained Raman spectra of a 7 layer hBN flake over a 6µm hole.

References [1] Y.Y. Hui et al., ACS Nano, 7 (2013) 7126 [2] P. Koskinen et al., PRL, 112 (2014) 186802 [3] N. Levy et al., Science, 329 (2010) 544 [4] A. Kitt et al., Nano Lett., 13 (2013) 2605-2610

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Evidence for enhanced longtime scale molecular fluorescence mediated by graphene H. Gonçalves1*, C. Bernardo1, M. Belsley1 and P. Schellenberg1 1

University of Minho, Campus Gualtar, Braga, Portugal Goncavels.hmc@outlook.pt

Abstract Graphene, being an ultra-thin, strong, high transparency, flexible conductor, has excellent potential for a wide variety of applications[1]. Graphene plasmonics is a new topic[2] that can be explored to manipulate light at nanoscale. For example, it has been predicted that the transfer of energy (FRET) between a donor-acceptor pair in close vicinity to a graphene sheet can be enhanced due to the excitation of plasmons in the graphene sheet[3]. The predicted broadband property of the plasmon enhancement is very advantageous since one can expect large enhancement also in cases where the emission and absorption spectra of the donor and acceptor do not fully overlap. Fluorescent molecules in close proximity to graphene can efficiently excite graphene plasmons[4], since they provide the large wave vectors, existing in the near-field of the emitters, necessary for graphene plasmon excitation. In this work we show experimentally that the presence of single layer graphene flakes in close proximity to an ensemble of perylene organic dye molecules induces both quenching of the perylene on a fast time scale and an enhanced emission on longer timescales. We take the enhanced emission at later timescales as evidence that these plasmons once excited in the graphene can serve as an energy reservoir which is capable of exciting other molecules at a later time, leading to an extended tail in the fluorescence decay curve of the ensemble. The enhanced fluorescence at long time scales is all the more noteworthy given the initial fast quenching induced by the presence of the graphene. References [1] Geim A K and Novoselov K S, Nat. Mater., 6 (2007) 183±91. [2] Stauber T J, Phys. Condens. Matter, 26 (2014) 123201. [3] Biehs S-A and Agarwal G S, Appl. Phys. Lett., 103 (2013) 243112. [4] Gaudreau L, Tielrooij K J, Prawiroatmodjo G E D K, Osmond J, García de Abajo F J and Koppens F H L, Nano Lett., 13 (2013) 2030±5. Figures

A schematic of the excitation transfer between molecular dipoles via the plasmonic waves excited in a nearby graphene sheet (left figure); Fluorescence decays curves for high concentrations of perylene molecules in a thin PMMA film (less that 2 nm) on top of or away from a single layer graphene flake. The increased emission at time scales of several nominal lifetimes of perylene is taken as evidence of the excitation transfer process.

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Graphene modified graphite felts as effective electrodes in the positive half-cell of vanadium redox flow batteries *

Zoraida González , Ana M. Pérez, Clara Blanco, Ricardo Santamaría, Marcos Granda, Patricia Álvarez, Rosa Menéndez

Instituto Nacional del Carbón, INCAR-CSIC, Apto. 73, 33080- Oviedo zoraidag@incar.csic.es Abstract Vanadium Redox Flow Batteries (VRFBs) have emerged as promising energy storage systems [1]. Although they store energy through the chemical changes of the electroactive species dissolved in two separate solutions, the selection of proper electrode materials is of fundamental importance in order to maximize their efficiency [2]. With this aim, this work proposes graphene modified graphite felts (G-GFs) as low cost, easy to handle and more efficient active electrode materials for VRFBs. Two G-GFs were prepared following an electrophoretical deposition (EPD) method. Firstly, two pieces of GF were immersed in home-made cells containing a graphene oxide (GO) suspension of 3 (3G-GF) or 6 (6G-GF) mg/mL and a voltage of 10 V was applied for 3 h. Then, the samples were dried at 100ºC and electrochemically reduced in KOH 3M by means of cyclic voltammetry (CV) experiments. In addition, a commonly utilized electrode material (thermally treated graphite felt, TTGF) was used for comparative purposes. The electrochemical performance of the materials as positive electrodes in a VRFB was studied by means of CV experiments in a Teflon three electrode cell where GF, TTGF and 2 G-GFs were the working electrodes (disk-shaped, 1 cm of exposed area). As electrolyte a 0.05M VOSO4/1.0M H2SO4 solution was used. The better electrochemical activity (mainly in terms of the overpotential of the redox reactions) and reversibility on the G-GFs electrodes (Fig. 1) could be attributed to the presence of the graphene sheets, which lead to a higher electrical conductivity and an increased heterogeneous electron transfer rate. Moreover, the increased surface area of 6G-GF may improve the Ip of the vanadium reactions in a real flow system, without the diffusion limitations existing in our static test device. Thus, taking advantages of both graphite felts and graphenes, we produced more effective electrode materials for the positive half-cell of a VRFB which would contribute to the development of batteries with higher energy efficiencies. References [1] C. Ponce de León, A. Frías-Ferrer, J. González-García, D.A. Szánto, F.C. Walsh, J. Power Sources 160 (2006) 716. [2] V. Haddadi-Asl, M. Kazacos, M. Skyllas-Kazacos, J. Appl. Electrochem. 25 (1995) 29. Figures 6G-GF 3G-GF TTGF GF

I(mA)

5 0 -5

-15 0.40

0.60 0.80 1.00 E(V) vs. Ag/AgCl / 3.5M KCl

Fig. 1 CVs recorded on the materials at 1 mVs

-1

Graphene | 105

Prototype hybrid graphene quantum dot photodetector for VIS, NIR and SWIR A.M. Goossens, E. Puma, J. Piqueras, J. C. Cifuentes, G. Navickaite, T. Lasanta, I. Nikitskiy, R. Peréz, G. Konstantatos, F. Koppens ICFO ± The Institute of Photonic Sciences, Av. Carl Friedrich Gauss, 3, 08860 Castelldefels (Barcelona), Spain

stijn.goossens@icfo.es Abstract Hyperspectral imaging is becoming attractive in many areas. Extending imaging capabilities of visible cameras to the short wave infrared wavelength ranges enables powerful night vision systems. This combination of spectral ranges can also provide farmers with useful information about the hydration levels of their crops. Moreover, relevant health information such as the oxygen saturation level can only be extracted by employing spectrometric measurements in different wavelength ranges. Currently, hyperspectral imaging is performed by using different light sensitive materials for each wavelength range. This presents problems with the compactness and facile integrability of hyperspectral systems. There is currently a large need for one hyperspectral detector technology that can not only measure in the visible (VIS), but also in the near infrared (NIR) and short wave infrared (SWIR). Previously we demonstrated a hybrid graphene quantum dot photo detector that is sensitive to both visible light and short wave infrared radiation [1]. The broad spectral range combined with its extremely low noise-equivalent power smaller than a fW make it a promising light sensing technology. PbS colloidal quantum dots are deposited on top of graphene and induce a photogating effect when exposed to radiation. By tuning the size of the quantum dots, the band gap can be tuned and hence the absorption range. We have demonstrated absorption from the visible up to 1.6 µm. As a proof of concept for the robustness and facile integrability with wearables we have developed a demonstrator comprising an ultrasensitive photo detector on a PEN substrate and a customised readout board (see Fig. 1). This read-out board has balanced read-out, integrated amplification and video frame rate imaging capabilities. In this poster we will embed a live demo of a hybrid graphene quantum dot photo detector. The hybrid graphene quantum dot photo detector is based on large area CVD-graphene. Moreover the colloidal quantum dots are compatible with large volume production wet-chemistry methodologies and can be deposited atop substrates using standard solution-processed large area deposition techniques. These factors make it possible to integrate the photo detectors with currently existing electronic circuit fabrication processes. This paves the way for volume production and commercialization

References [1] G. Konstantatos, M. Badioli, L. Gaudreau, J. Osmond, M. Bernechea, F. P. Garcia de Arquer, F. Gatti and F. H. L. Koppens, Nature Nanotechnol., 7 (June 2012). Hybrid graphene-quantum dot detectors with ultrahigh gain.

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Figures Fig. 1 Photograph of the first version of the prototype of the hybrid graphene quantum dot light detector. The detector is interfaced with a read-out box and the signal is displayed on an iPad.

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Theoretical investigation of graphene-based waveguide integrated photonic and plasmonic modulators ,1,2

Jacek Gosciniak*

, Dawn T. H. Tan and Brian Corbett

Singapore University of Technology and Design, Engineering Product Design (EPS), 20 Dover Drive, Singapore 138682 2 Tyndall National Institute, University College Cork, Lee Maltings, Prospect Row, Cork, Ireland *Email: jacek.gosciniak@tyndall.ie *Phone: +353 021 234 6713

Abstract. Theoretical investigations of graphene-based electro-optic plasmonic and photonic modulators will be analyzed and the results will be presented. The effect of different ridge materials and different spacer dielectrics is analyzed showing that a 3 dB modulation with 65 nm-long waveguide is possible with dielectric-loaded surface plasmon polariton waveguides (DLSPPWs) resulting in an energy per bit only 0.08 fJ/bit. The figure of merit defined as the ratio between an extinction ratio and insertion loss was found to be about 5.2 with a low refractive index ridge and increases to over 17.3 for a high refractive index Si ridge compared to 3.5 calculated and measured with photonic graphene-based waveguides. Additionally, it is shown that further improvement in terms of a figure of merit is possible with the rib photonic waveguides with a double-layer graphene placed between slab and a ridge where it is calculated to exceed 250! For such photonic waveguides, a 3 dB modulation is DFKLHYHG ZLWK ȝmlong waveguides with the energy per bit of 0.3 fJ/bit. Additionally, the wavelength dependence of the graphene sheet was analyzed showing a redshift with increasing chemical potential what influences on the attenuation of the waveguide which redshifts as well ± increasing a gate voltage applied across a graphene layer shifts the attenuation curve to the shorter wavelengths with a 3 dB modulation bandwidth H[FHHGLQJ 7+] IRU D ȝP-long DLSPP waveguide.

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Surface plasmons in the new generation of low dimensional materials: full wave modelling through linear response density functional theory M. Gravina, A. Sindona, M. Pisarra, C. Vacacela, G. Falcone Dipartimento di Fisica, UniversitĂ della Calabria, Cubo 30C, 87036 Rende (CS), Italy

gravina@fis.unical.it Abstract Dielectric properties of low dimensional graphene-based materials are attracting much attention due to the fast development of experimental platforms in which plasmons are generated and controlled [1-4]. A reliable theoretical framework is needed in order to develop innovative technological solutions for highperformance next-generation nano-devices, integrating graphene with conventional silicon-based devices, and find the fundamental limits for functional graphene materials nano electronics. Here, we present the plasmonic responses of graphene nanoribbons, silicene and germanene, both in their free-standing and adsorbed forms on supporting substrates. The calculations are performed by density functional theory within the linear response regime. This full wave modelling improves the usual semi-phenomenological descriptions available in the literature.

References [1] L. Ju et al., Nature Nanotechnol. 6, 630-634 (2011) [2] P. Alonso-Gonzalez et al., Science 344 1369 2014 [3] Z. Fei et al., Nature 487 82-85 2012 [4] G. W. Hanson, Journal of Applied Physics 103 064302 (2008); G. W. Hanson, IEEE Transactions on antennas and propagation 56 (3), 747-757 (2008)

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Graphene on Antidot Lattice: Electronic and Transport Properties. S酶ren Schou Gregersen, Stephen R. Power, Jesper Goor Pedersen, Antti-Pekka Jauho Center for Nanostructured Graphene/DTU Nanotech - Department of Micro- and Nanotechnology, Technical University of Denmark, DTU, Building 345 East, DK-2800 Kongens Lyngby, Denmark sorgre@nanotech.dtu.dk Abstract

Graphene bilayer systems are known to exhibit a band gap when the layer symmetry is broken, which can be achieved by applying a perpendicular electric field, thereby inducing opposite onsite potentials in the top and bottom layers.[1] The resulting band structure resembles that of a conventional semiconductor with a parabolic dispersion, where the band gap scales approximately linear with the applied field. Unfortunately, like other gapped graphene systems, the linear dispersion of single layer graphene is usually lost, as in the bilayer system. The implication of the parabolic dispersion is a lower mobility and thus degraded device performance.[2] To overcome this, we propose using heterogeneous multilayered structures. Bilayer superlattices have been studied in detail, with e.g. periodic potential barriers,[3] and dual-layer antidot-lattices.[4] A 1- or 2D potential modulation of the potential in bilayer graphene has even been predicted to yield linear dispersion.[5] However, heterostructure bilayers composed of two different single-layer systems has little theoretical support. Stacked heterostructures from multiple 2D materials created and held together only by van der Waals (vdW) forces[6] is particularly interesting as the interfaces may be kept clean from processing chemicals. Here, we introduce a novel bilayer graphene heterostructure, where single-layer graphene is placed on top of another layer of graphene with a regular lattice of antidots, see Fig. 1. We dub this class of graphene systems GOAL: graphene on graphene antidot lattice. By varying the structure geometry, band structure engineering can be performed to obtain linearly dispersing bands (with a high concomitant mobility), Fig. 2, which nevertheless can be made gapped with the perpendicular field, Fig. 3. We have analyzed the electronic structure and transport properties of various types of GOALs, and found interesting behavior which should be possible to achieve in various similar bilayer heterostructures. References [1] E. McCann and M. Koshino, Reports Prog. Phys 76 (2013) 56503. [2] F. Schwierz, Nat. nano. 5 (2010) 487. [3] M. Barbier, P. Vasilopoulos, and F. M. Peeters, Philos. Trans. Ser. A Math. Phys. Eng. Sci. 368(2010) 5499. [4] D. G. Kvashnin, P. Vancs贸, L. Y. Antipina, G. I. M谩rk, L. P. Bir贸, P. B. Sorokin, and L. A. Chernozatonskii, Nano Research 1 (2014) 1.

[5] M. Killi, S. Wu, and A. Paramekanti, Phys. Rev. Lett. 107(2011) 086801. [6] A. K. Geim and I. V. Grigorieva, Nature 499(2013) 419. Figures

110 | Graphene

Figure 1 (a) Schematic illustration of the considered structures, consisting of a single graphene layer (blue) on top of a GAL layer (red), arranged in an AB stacking. (b) A closer view of the atomic structure of the Wigner-Seitz cell of a {L,R} = {6, 2} GOAL, with carbon atoms in the graphene (GAL) layer illustrated with blue filled circles (red open circles).

Figure 2 Band structures of f16;Rg GOALs. The left-most panel shows the full band structure within our model (solid blue lines), and for comparison the results obtained if skew scattering terms are included (red dashed lines). The right panels show a section of the band structure of GOALs near the ŕ¸&#x20AC; point, for increasing antidot sizes, in solid lines. Dashed gray lines show the corresponding single-layer graphene dispersion, while dotted gray lines illustrate the bilayer graphene dispersion.

Graphene | 111

Figure 3 Band structures and gaps of biased various GOALs.(a) Band structures for the {16, 3} (red, dashed) and {16, 6} GOALs (blue, solid) and pristine bilayer graphene (gray, dotted), with a bias U = 0:2 eV applied across the layers. Note the bands resembling biased bilayer graphene, i.e. the "Mexican hat" profile, for the small antidot {16, 3} and those resembling gapped single-layer graphene for the large antidote {16, 6} GOAL. (b) Band gaps for {16, R} GOALs with R = 3, 4, 5, 6, 7 and an increasing bias. Note the mostly linear dependence on the bias for all antidot sizes.

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SYNTHESIS OF POLYANILINE/GRAPHENE NANOCOMPOSITE AND ITS THERMAL, OPTICAL AND ELECTROCHEMICAL PROPERTIES

Anita Grozdanov , Aleksandar Petrovski , Roberto Avolio , Perica Paunovic , Maria E.Errico ,Beti 1 2 2 2 1 Andonovic , Maria Cristina Coca , Gennaro Gentile , Francesca De Falco , Aleksandar Dimitrov , 2 Maurizio Avella

1- Faculty of Technology and Metallurgy, University Ss Cyril and Methodius in Skopje, Republic of Macedonia 2- Institute for Polymers, Composites and Biomaterials- IPCB-CNR, Fabricato Oliveti, Via Campi Flegrei 78, Pozzuoli (NA) Italy anita.grozdanov@yahoo.com

Recently, nanocomposites based on conducting polymers and graphene have attracted a great interest of the scientists due to its potential applications in various fields such as sensors, catalysis, capacitors, displays. Among all the conducting polymers, Polyaniline (PANI) is one of the most intrigued materials owing to its easy method of preparation and its high stability on environmental exposition. On the other hand, Graphene nanosheets exhibit very high electrical conductivity due to their very high electron mobility. The nanocomposites were prepared by using electrochemical synthesis of conductive polymer matrix, Polyaniline-PANI and modified and unmodified Graphene. Two types of nanocomposites were synthesized: Ist with graphene deposited on the Pt-electrode and IInd with graphene dispersed in the electrolyte. Characterization was performed by several techniques: FTIR, UV-VIS, TGA/DTA, Raman, SEM, TEM and electrical measurements by resistivity and cyclic voltammetry. The morphological study of the modified Graphene based NC showed porous fibrilar morphology, Graphene structure is well included in PANI matrix. Compared to neat PANI, CV curves in the presence of MWCNT have shown remarkable higher anodic and cathode peaks. The obtained composites exhibited a higher value of conductivity which may be attributed to the synergy effect of the conductive polymer matrix and graphene nanostructure.

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Work-function engineering of CVD-grown graphene using Cs2CO3 Young-Wook Ha, Ick-Joon Park, Hamin Park, Sung-Yool Choi Department of Electrical Engineering and Graphene Research Center, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea daliah2000@kaist.ac.kr, sungyool.choi@kaist.ac.kr

Abstract Graphene has been considered as a candidate for electrodes or carrier transport layers in next generation electronic and optoelectronic devices due to its superior conductivity, transparency, and flexibility. However, chemical vapor deposition (CVD) grown graphene is easily p-doped by the absorbance of dipole molecules such as H2O [1, 2], so n-doping technology has been desired to utilize graphene as cathode or electron transport layer in devices [3, 4]. Here, we present the n-type doping of graphene using Cs2CO3 solution which resulted in the decrease of work-function in graphene. Workfunction decreasing of graphene (from 4.8 eV to 4.1eV) was confirmed via UV photoelectron spectroscopy (UPS) analysis. Doping time dependent characteristics of graphene was investigated by observing changes in Dirac voltage of fabricated graphene field effect transistors (GFETs). Besides, we confirmed that this doping method does not introduce any damages in graphene from no changes of carbon peak in X-ray photoelectron spectroscopy (XPS) measurement and no D-peak increase in Raman spectra analysis. References [1] O. Leenaerts et al., Phys. Rev. B, 77(2008), 125416 [2] T. O. Wehling et al., Chem. Phys. Lett., 476(2009), 125-134 [3] K. C. Kwon et al., J. Phys. Chem. C, 116(2012), 26586Ă26591 [4] J. H. Bong et al., Nanoscale, 6(2014), 8503-8508 Figures

0.10

GFET_Cs2CO3_0.5M VDS = 0.1V

ID (mA)

0.08

0min 1min 5min 10min 30min

0.06

0.04

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VG (V) Figure 1. Transfer curves of Cs2CO3 doped GFETs depending on the doping time Figure 2. UPS spectra of graphene before and after doping

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Non-equilibrium plasmons with gain in graphene J. M. Hamm, A. F. Page, F. Ballout, O. Hess Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom

joachim.hamm@imperial.ac.uk Abstract In calculating the gain spectra of photo-inverted graphene self-consistently from the exact complex-frequency dispersion curves, we provide evidence that graphene can, under realistic conditions, support plasmons with gain [1]. As the dispersion crosses through regimes where the plasmons couple to the particle/hole plasma via stimulated emission and absorption processes, it acquires an imaginary part that represents the gain and loss spectrum (see fig. 1b). Based on a comprehensive theory for the non-equilibrium polarizability, we systematically study the influence of doping, collision loss and temperature on both the plasmon dispersion and the gain/loss spectrum. While doping and temperature affect the shape of the emission spectrum, collision loss leads to a reduction of gain proportional to the collision rate. The frequency dispersion curves, in turn, are robust against collision loss and temperature but are distinctly affected by doping. When the imbalance in the particle/hole chemical potentials reaches a critical value, the plasmon dispersion passes through a singularity and undergoes a sudden change. Our results show that plasmon amplification is possible at under assumption of realistic collision loss and temperature. Carrier inversion does not only enable plasmon amplification via stimulated emission but also leads to spontaneous emission of plasmons. To investigate this incoherent channel, we extract the spontaneous plasmon emission spectra and associated carrier recombination rates directly from the complex-frequency dispersion and by application of Fermi's golden rule. We find that the emission spectra are weakly dependent on the collision rate, but strongly influenced by doping and temperature. Our results suggest that spontaneous plasmon emission is a significant channel for particle/hole recombination in photo-excited graphene, with rates that exceed those previously reported [2] by a factor of 5. In the light of these results, it appears evident that spontaneous plasmon emission plays an important role for the relaxation of the photo-excited plasma back to equilibrium, as observed in pump-probe and tr-ARPES experiments. References [1] A. Freddie Page, Fouad Ballout, Ortwin Hess, Joachim M. Hamm, arXiv:1412.3042 (2014). [2] Farhan Rana, Jared Wang Strait, Christina Haining Manolatou, Phys. Rev. B 84(4), 045437 (2011). Figures

Figure 1: Plasmon frequency dispersion (top panel) and decay rate (bottom panel) for (a) the equilibrium case and (b) the photo-inverted intrinsic case. The exact complex-frequency dispersion (solid red lines) is shown together with the dispersion in the real-frequency approximation (dashed black lines), in the classical Drude limit (dotted black lines) and using the optical conductivity (dash-dotted black lines).

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UV photoresponse and magnetic control of single-layer titania nanosheets Masahiro Hara, Koji Matsuzaki, Natsumi Saitou, Takaaki Taniguchi, and Yasumichi Matsumoto Kumamoto University, 2-39-1 Kurokami, Kumamoto, Japan mhara@sci.kumamoto-u.ac.jp

Two-dimensional materials have attracted great interests in the past decade from various fields. We have recently focused on titania (titanium oxide) nanosheets chemically exfoliated from layered titanate crystals [1]. In our earlier work, we found a drastic change in the conductivity of an individual singlelayer titania nanosheet under humid conditions [2]. In the present work, we will report photoresponse and magnetic control of titania nanosheets. We have demonstrated a phtoresponse of fabricated two-terminal devices with a single-layer titania nanosheet under periodic illuminations of ultra violet (UV) light. As shown in Fig.1, we observed a clear on/off switching with a short rise/fall time (< 0.2 sec). The photocurrent under UV illuminations strongly depends on environmental gas molecules. The reduction of the photocurrent even under inert nitrogen gas atmospheres implies that collisions of gas molecules affects annihilations of electron-hole pairs on the surface-sensitive two-dimensional nanosheet [3]. We have also investigated magnetic behaviors of Mn-doped titania nanosheets. Single-layer titania nanosheets with magnetic impurities deposited on a Si substrate were measured by X-ray magnetic circular dichroism (XMCD). The XMCD spectra as shown in Fig.2 revealed a weak ferromagnetic order of the nanosheets even at room temperature. Fe overlayers on the nanosheets induced antiferromagnetic couplings between the nanosheets and the Fe overlayers [4].

References [1] R. Ma and T. Sasaki, Adv. Mater. 22 (2010) 5082. [2] A. Tanaka et al., Appl. Phys. Lett. 104 (2014) 163106. [3] K. Matsuzaki et al., Appl. Phys. Lett. 106 (2015) 033104. [4] N. Saitou et al., submitted.

Figures

Figure 1: Photocurrent under periodic pulsed UV illuminations at bias voltage of 1.0 V.

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Figure 2: Normalized Mn L2,3 XMCD spectra for different thicknesses of Fe overlayers.

Effects of Substrate Crystallinity on MoS2 Grown by CVD K. Hayashi, T. Iwai, S. Sato Fujitsu Laboratories, 10-1 Morinosato-Wakamiya, Atsugi, Japan hayashi.kenjiro@jp.fujitsu.com Abstract Two-dimensional materials, represented by graphene, remain their structural stability even in an atomically thin film, in which confined electrons exhibit anomalous behavior compared to that in bulk crystals. Especially, transition metal dichalcogenides (TMDCs) have attracted considerable interest as emerging device materials for nanoelectronics because their electronic properties can be changed considerably by combinations of composed atoms [1]. Recently, chemical vapor deposition (CVD) of TMDC monolayers has been demonstrated directly on dielectric substrate by using solid sources [2]. Chemical reactions among precursor materials lead to TMDCs nucleation on the substrate surface. In this regard, surface diffusion of precursors would have a significant impact on the growth kinetics; however, it still remains unclear how substrate crystallinity and roughness affect the resultant film quality. To address this issue, we demonstrated atmospheric pressure CVD of MoS2 on c-plane sapphire and polycrystalline alumina substrates by using MoO3 and sulfur solid sources. Raman spectroscopy and photoluminescence (PL) measurements (Fig.1) revealed that monolayer MoS2 was grown on the sapphire substrate, which was confirmed by Raman peak distance (~19 cm -1) between two characteristic modes (E12g and A1g) and a strong PL emission peak at ~1.88 eV. The MoS2 on the alumina substrate showed broad Raman peaks and a relatively large peak distance while strong PL emission was confirmed. The MoS2 layers were then transferred onto SiO2/Si substrates to check the uniformity in thickness using the color contrast caused by light interference (Fig.2). While the MoS2 grown on the sapphire substrate consists of triangular-shaped islands, MoS2 islands grown on the alumina substrate are irregular in shape and partly have multilayer regions. This explains the Raman and PL results on the alumina substrate: the spectrum is the superposition of peaks from monolayer and multilayer regions in the island. The differences in the resultant islands are probably originated from differences in growth kinetics on each substrate surface. The growth kinetics, including adsorption, dissociation and diffusion processes of the precursors would correlate with surface orientations. The alumina substrate is composed of crystal grains with various orientations, thus providing the MoS2 islands different from those on sapphire. References [1] K. Dolui et al., Phys. Rev. B 88 (2013) 075420 [2] Y-H. Lee et al., Adv. Mater. 24 (2012) 2320

Fig.1 (a) Raman and (b) PL spectra

Fig.2 Optical microscope images of MoS2 grown on (a) sapphire and (b) alumina substrate after transfer onto SiO2/Si substrate.

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Tip enhanced Raman analysis of graphene Tim Batten, Ian Hayward, Mickael Febvre Renishaw plc, Old Town, Wotton-under-Edge, Gloucestershire, United Kingdom tim.batten@renishaw.com Abstract Graphene has huge potential in a wide range of technologies, however for this potential to be realized improvements must be made to enable the growth of higher quality large area graphene sheets. The properties of commercially grown graphene still typically lag behind those of mechanically exfoliated material and new techniques are required to better characterise these materials and optimise growth. In this work we apply tip enhanced Raman spectroscopy (TERS) to a variety of graphene samples, revealing chemical information and often inhomogeneity on the nanoscale. Raman spectroscopy is a well-established tool for charactering many aspects of graphene, including strain, electronic properties and number of layers [1]. Raman spectroscopy is an optical technique and as such the maximum spatial resolution it can achieve is determined by the diffraction limit, this equates to ~300 nm when using a visible wavelength. Tip enhanced Raman spectroscopy (TERS) is a novel technique that uses a special plasmonic tip to increase the electric field at the sample which, in turn, increases the Raman signal intensity. These tips are very small, with diameters on the order of 10 nm, and are held in close proximity to the sample using a scanning probe microscope (SPM) or atomic force microscope (AFM). The TERS enhancement originates within a few nanometers of the tip and is a near field effect, allowing the spatial resolution of Raman to surpass the diffraction limit and potentially achieve sub nm resolution [2]. TERS therefore has the unique advantage of increasing both the spatial resolution and sensitivity. Figure 1 illustrates the increase in Raman intensity seen from CVD graphene deposited on Cu. Here preferential enhancement of the D band suggests that a defect region is being directly probed. TERS mapping of the sample reveals variations in G/2D intensity ratio on the 10 nm scale demonstrating the increase in spatial resolution enabled by TERS and also the inhomogeneity of the sample on the nanoscale. References [1] A. C. Ferrari, and D. M. Basko, Nature nanotechnology 8.4 (2013): 235-246. [2] R. Zhang, Y. Zhang, Z. C. Dong, S. Jiang, C. Zhang, L. G. Chen, L. Zhang, Y. Liao, J. Aizpurua, Y. Luo, J. L. Yang and J. G. Hou, Nature 498.7452 (2013): 82-86. [3] P. R. Kidambi, C. Ducati, B. Dlubak, D. Gardiner, R. S. Weatherup, M-B. Martin, P. Seneor, H. Cole, and S. Hofmann, The Journal of Physical Chemistry C, 116 (2012): 22492-22501 Figures

Figure 1. TERS (red) and far field Raman spectra of graphene (blue). These results demonstrate the enhancement in signal provided by TERS. More details on this sample can be found in Ref. 3.

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Figure 2. TERS image showing sub-diffraction-limit changes in the G/2D ratio for a graphene sample. This ratio is often used to estimate CVD graphene thickness. Significant changes in this ratio over a 10 nm length scale shows graphene variation on the nanoscale. This variation is not seen using micro Raman which has a diffraction limited lateral resolution of ~ 300 nm.

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Graphene | 119

Layer by layer decoration of graphene and carbon nanotubes with magnetic nanoparticles. Yenny Hernandez Camilo AcuĂąa Universidad de los Andes, Carrera 1 18A-10 Bloque Ip, BogotĂĄ, Colombia yr.hernandez@uniandes.edu.co Abstract Functional nanocomposites of graphene and carbon nanotubes are of great interest for applications where temperature stability and alienation of the active component is necessary. These type of nanocomposites have been widely studied from graphene oxide (GO), however decoration of defect free graphene has proved challenging due to its unreactive surface. Here we present the successful decoration of graphene and carbon nanotubes using a combination of electrically active polymers that is reproducible to a variety of magnetic nanoparticles such as FeO3, CoFe2O4 and SrFe11O19.

120 | Graphene

The role of graphite nanoplatelets and carbon nanotubes on the enhanced fracture toughness and electrical conductivity of polypropylene composites 1

2,3

L. C. Herrera-Ramírez , P. Castell , A. Fernández Cuello , R. Guzmán de Villoria * [1] IMDEA Materials Institute, C/ Eric Kandel 2, 28906, Getafe, Madrid, Spain [2] AITIIP Centro Tecnológico, Polígono Industrial Empresarium, C/ Romero 12, 50720, Zaragoza, Spain [3] Department of Mechanical Engineering, University of Zaragoza, EINA, Av. María de Luna 3, 50018, Zaragoza, Spain roberto.guzman@imdea.org Abstract [1] In recent years, materials researchers have focused their interest on polymer nanocomposites , being carbon-based nanostructures envisioned as promising nanofillers, due to its outstanding mechanical, [2,3] electrical and thermal properties . In this work, commercially available carbon nanotubes (CNT) and graphite nanoplatelets (GNP), composed by multiple graphene layers stacked together by van der Waals forces, have been used to produce polypropylene (PP) nanocomposites. This materials were manufactured following an industrial [4,5] approach as it is the masterbatch technique . The CNT/PP composites, shows a significant increase in the electrical conductivity for the [6,7] nanocomposites with 5 and 10 wt.% of CNT. A processing-induced anisotropy is observed in the electrical conductivity, being different in the three directions of the injection-moulded bars. The fracture toughness has been determined applying a single-specimen technique, the Spb parameter [8] method . For the nanocomposites manufactured, the fracture mechanism has been identified as void nucleation and growth, by scanning electron microscopy. This is also the fracture mechanism that takes place in the neat PP. The manufactured nanocomposites presents an improved fracture toughness with loadings up to 10 and 2.5 wt.% of CNT and GNP, respectively. The results obtained by the strain field analysis around the crack tip, performed by digital image correlation, indicates that this may be explained in terms of variation of size of the deformation zone ahead the crack tip. Finally, in this work it has been demonstrated how an scalable machine and an industrial masterbatch compounding approach can be applied to a thermoplastic, in order to obtain nanocomposites with improved fracture toughness and electrical conductivity, opening the way to a wider industrial utilization of these materials. References [1] [2] [3] [4] [5] [6] [7] [8]

E. T. Thostenson, C. Li, T.-W. Chou, Compos. Sci. Technol., 65 (2005), 491. G. Mittal, V. Dhand, K. Y. Rhee, S.-J. Park, W. R. Lee, J. Ind. Eng. Chem. n.d., DOI 10.1016/j.jiec.2014.03.022. Y. Zhu, S. Murali, W. Cai, X. Li, J. W. Suk, J. R. Potts, R. S. Ruoff, Adv. Mater., 22 (2010), 3906. K. Prashantha, J. Soulestin, M. F. Lacrampe, P. Krawczak, G. Dupin, M. Claes, Compos. Sci. Technol., 69 (2009), 1756. Y.-C. Li, G.-H. Chen, Polym. Eng. Sci., 47 (2007), 882. M. Ganß, B. K. Satapathy, M. Thunga, R. Weidisch, P. Pötschke, D. Jehnichen, Acta Mater., 56 (2008), 2247. R. J. Kuriger, M. K. Alam, D. P. Anderson, R. L. Jacobsen, Compos. Part Appl. Sci. Manuf., 33 (2002), 53. L.C. Herrera-Ramírez, P. Castell, J.P. Fernández-Blázquez, A. Fernández Cuello, R. Guzmán de Villoria, Compos. Sci. Technol., Submitted article (2014)

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Graphene Nanocomposites for Online Monitoring of Individual Gases at Moderate Temperature Thomas Hirsch1, Alexander Zöpfl1, Günther Ruhl2, Frank-Michael Matysik1 1

Institute of Analytical Chemistry, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany 2 Infineon Technologies AG, 93049 Regensburg, Germany thomas.hirsch@chemie.uni-regensburg.de

Abstract Simple and reliable monitoring of gas concentration is important in everyday-life. Graphene based sensors could provide a cheap and versatile alternative to well established metal oxide chemiresistors which need to be operated at high temperature. The large surface-to-volume ratio is one of the outstanding properties of graphene as sensor material, due to the absence of any bulk phase. Fast response time, high sensitivity and reversibility are accompanied with this property. Any kind of interaction between graphene sheets and adsorbates, influencing the electronic structure of graphene, leads to an altered charge carrier concentration or respectively electrical conductance of the material, already at ambient temperature and conditions. Here, we report on reduced graphene oxide as a sensitive material for gas detection.1 It is obtained by oxidation of graphite with subsequent reduction and can be dispersed in water, enabling an easy transfer. Application via spin coating to pre-structured microelectrodes comprising an interdigital structure was optimized and resulted in consistent layers of reproducible quality. These sensors not only responded to various analyte gases and concentrations, but the signal was also influenced by parameters like air humidity and temperature, but there is also a lack on selectivity. To overcome this drawback, functional groups, metal oxide and metal nanoparticles were introduced in one pot synthesis, in order to form nanocomposite materials. Additional decoration of reduced graphene oxide already deposited on the sensor with metal nanoparticles was achieved by electrochemical deposition. Upon different functionalizations, it was possible to achieve altered sensor behavior for different ambient gases like NO2, N2, O2, CH4, CO and H2. Especially upon adsorption of NO2 the high signal changes allowed a limit of detection in the sub-ppm range. The signal pattern for each gas allowed an individual recognition. Using multivariate analysis based on principal component analysis it was possible to discriminate each individual gas. This approach could be extended to build up sensor arrays like an artificial nose, in order to detect individual gases in a complex gas mixture at ambient conditions. References [1] A. Zöpfl, M.-M. Lemberger, M. König, G. Ruhl, F.-M. Matysik, T. Hirsch, T. Faraday Discuss. 173 (2014), 403

122 | Graphene

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Graphene | 123

High electric field transport in graphene: impact of screened coulomb interactions José M. Iglesias*, Mª Jesús Martín, Raúl Rengel Universidad de Salamanca, Applied Physics dept., Plaza de la Merced, S/N, 37008 - Salamanca, Spain *e-mail: josem88@usal.es Abstract Since the breakthrough of the prime isolation of a single-atom-thick carbon crystalௗ[1] , graphene has attracted a huge amount of attention due to its outstanding electronic properties. At room temperature it exhibits extremely high mobilitiesௗ[2] and carrier population can be tuned by electrostatic gating, which makes it a promising material for future developments of a wide range of highly efficient electronic devicesௗ[3] . In our work we will study the role that electron-electron interaction plays on the electronic transport subjected to high longitudinal electric fields by means of the Monte Carlo method. Our simulator takes into account the graphene’s linear dispersion relation and includes the transverse-acoustic (TA), longitudinal-acoustic (LA), transverse-optic (TO), and longitudinal-optic (LO) phonon branchesௗ[4] , as well as surface polar phonons (SPPs) associated with WKH XQGHUO\LQJ VXEVWUDWHௗ[5] , a screened Coulomb potential model for electron-electron interactionsௗ[6] and impurity scattering. A proper treatment of the dual-carrier scattering probabilities implies its calculation depending on the electron wavevector orientation, resulting in a highly anisotropic probability, as it can be seen in Fig. 1, when the distribution of the carriers is noticeably displaced in the field direction (fig. 2). Further analysis steaming from carrier distribution in energy and in the K space is presented, taking into account the microscopic aspects of these collisions and their function as relaxation mechanisms. The influence on the carrier mobility is also analyzed, thus elucidating the importance of carrier-carrier interactions in graphene and their interplay with impurity and phonon scattering. References ௗ[1] K. S. Novoselov, A. K. Geim; S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva and A. A. Firsov, Science, 306 (2004) 666 ௗ[2] K. M. Borysenko, J. T. Mullen, E. A. Barry, S. Paul, Y. G. Semenov, J. M. Zavada, M. B. Nardelli, and K. W. Kim, Phys. Rev. B, 81 121412 (2010) ௗ[3] Y. M. Lin, C. Dimitrakopoulos, K. A. Jenkins, D. B. Farmer, H. Y. Chiu, A. Grill, and Ph. Avouris, Science 327, (2010) 662 ௗ[4] R. Rengel and M. J. Martín, J. Appl. Phys., 114 143702 (2013) ௗ[5] R. Rengel and M. J. Martín, Appl. Phys. Lett., 104, 233107 (2014) ௗ[6] X. Li, E. A. Barry, J.M. Zavada, M. Buongiorno Nardelli and K. W. Kim, Appl. Phys. Lett., 97 082101 (2010) Figures

1.0 0.5

60 Rate for a Fermi-Dirac distribution

40 20 0 -1 0 kx /n -1 1 m

-2

-1

m k y/n

Fig. 1: Comparison of the anisotropic dual carrier scattering probabilities for a distribution in an equilibrium Fermi-Dirac distribution, and for a steady-state distribution for a 20 kV/cm applied field.

124 | Graphene

ky/nm-1

-1

(τe-e) (ps)

1.5

Rate for a stationary state (E=20kV cm-1)

% particles 0.4 -0.5 0.3 0.2 -1.0 0.1 (a) (b) 0.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 -0.5 0.0 0.5 1.0 kx/nm-1 kx/nm-1 0.0

Fig. 2: Distribution functions for a reached stationary state when a 20 kV/cm electric field is applied on the y direction and dual carrier intraband interactions are (a) turned off, (b) turned on.

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Graphene | 125

Highly uniform and reliable polymer memory via iCVD using multilayer graphene barrier electrode Byung Chul Jang1, Hyejeong Seong2, Jong Yun Kim1,3, Beom Jun Koo1, Sung Kyu Kim4, Sang Yoon Yang1, Sung Gap Im2, Sung-Yool Choi1 1

Department of Electrical Engineering and Graphene Research Center, KAIST, Daejeon 305-701, Korea

Department of Chemical and Biomolecular Engineering and Graphene Research Center, KAIST, Daejeon 305-701, Korea 3 4

Department of Chemistry, Hanyang University, Seoul 133-701, Korea

Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Korea

mklone@kaist.ac.kr

Abstract Recently, there has been strong demand for flexible nonvolatile memory for large area, low cost, and low power flexible electronics. As a promising next-generation flexible nonvolatile memory, we present a poly(1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane) (pV3D3)-based resistive switching memory (RRAM) that can be easily fabricated using the initiated chemical vapor deposition (iCVD), which provides a solvent-free, low-temperature, and damage-free deposition of highly uniform polymer films on various substrates including flexible substrate. The Cu/pV3D3/Al RRAM device has reliable memory performance in terms of retention, but high reset power consumption, nonuniform resistive switching uniformity, poor endurance issues remain to be addressed. To realize lower power and reliable pV3D3based RRAM, we introduced a multilayer graphene (MLG) film as Cu diffusion barrier, which suppresses the diffusion of Cu ions through pV3D3 films, resulting in the ultralow reset current due to the high out-of-plane resistance of MLG. In addition, the high thermal conductivity of graphene suppresses the reset process by thermal effect and a high interfacial resistance at the pV3D3/MLG interface induces Cu filament formation/rupture at the interface by electrochemical redox reaction, improving the nonuniform resistive switching uniformity and poor endurance. These dramatic improvements of pV3D3-based RRAM by inserting MLG as interfacial layer are promising not only for filament type RRAM devices which are suffer from the nonuniform resistive switching but also for polymer-based RRAM devices which are suffer from thermal instability, thus paving the way of a new area of application for graphene in the nonvolatile memory devices.

126 | Graphene

Control of nucleation density in CVD-grown graphene using pre-treated Cu foil Dae Yool Jung, Khang June Lee, Sang Yoon Yang, Sung-Yool Choi Department of Electrical Engineering and Graphene Research Center, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea saram1823@kaist.ac.kr, sungyool.choi@kaist.ac.kr

Abstract After a decade of discovery of graphene flake which was exfoliated from graphite, we have now established large scale and fair quality graphene film synthesis technology using chemical vapor deposition (CVD). However, CVD-grown graphene have not yet shown such a high quality as compared to mechanically exfoliated graphene. While many factors influence the quality of graphene, the root causes are poly-crystallinity and domain boundaries in the CVD-grown graphene. Therefore, large size single crystal graphene has been desired and recent studies achieved remarkable size of single crystal graphene via pre-treated growth substrate using pre-oxidation [1-3] and planarization [4-6]. Here, we examined the utility of copper foil pre-treatment in the perspective of controlling nucleation density. Besides, we studied the growth of graphene domain from carbon nuclei by changing growth conditions during CVD process. Characterization of obtained graphene through above process was processed with scanning electron microscope, Raman spectroscopy, Hall effect measurement, and atomic force microscopy.

References [1] H. Zhou et al., Nat. Commun., 4 (2013), 2096 [2] Y. Hao et al., Science, 342 (2013), 720-723 [3] L. Gan et al., ACS Nano, 7 (2013), 9480-9488 [4] S. M. Kim et al., Nanotechnology, 24 (2013), 365602 [5] D. Lee et al., Nanoscale, 6 (2014), 12943-12951 [6] V. L. Nguyen et al., Adv. Mater., (2014), doi: 10.1002/adma.201404541 Figures

Figure 1. (a) Optical microscope image of partially oxidized Cu foil. (b) Optical microscope image of Cu foil covered with fully grown graphene (c) Raman spectrum of as grown graphene (on Cu foil) after growth steps.

Graphene | 127

Synthesis and characterization of Kevlar’s analog graphene material Mohamad A Kabbani, Pulickel M. Ajayan Rice University, 6100 Main MS-325, Houston, Texas 77005-1827,USA mak8@rice.edu

Kevlar, (structure A), the brand name for (poly paraphenylene terephthalamide) owes its high tensile strength of 3620 MPa to intermolecular hydrogen bonds between the carbonyl groups and NH centers and ! ! !!!"#$%&’(!!"!!!!!!"#$ !%&’!!"#$%!The present work discusses the synthesis of Kevlar’s analogs graphene material via the reaction of amino and hydroxylsubstituted CNTs with terphthaloyl chloride. The products are characterized using ATR-FT-IR, Raman and XPS spectroscopic techniques together with SEM and TEM to explore the effect of the graphene ! ! ! interaction on the mechanical properties of the product.

Structure A !!!

128 | Graphene

Growth of Few Layer Single Crystal and Coalesced Graphene Grains on Platinum by Chemical Vapour Deposition S. Karamat1, S. Sonuşen2, Ü. Çelik3, Y. Uysallı1, E. Özgönül1 and A. Oral1 1

Department of Physics, Middle East Technical University, Ankara Turkey 06800

Faculty of Engineering and Natural Sciences, Sabancı University, Istanbul, Turkey 34956 3

NanoMagnetics Instruments Ltd., Ankara, Turkey shumailakaramat@gmail.com

Abstract Graphene, one atom thick sp2-bonded graphite, received the attention of different disciplines of physics because of its marvelous properties [1–4]. To fully utilize the graphene in industry, fabrication of high quality graphene is essential. The most promising method to grow large area graphene on metal catalysts is chemical vapour deposition (CVD) [5-7]. The problem widely faced by the scientific community in the CVD growth is the presence of crystallographic graphene domains. The growth of graphene is initiated at different nucleation sites on the metal catalyst which give full coverage with the increase in growth time but also promote the growth of few layer grains having different crystallographic orientation. During the growth procedure, nucleation density of graphene played an important role because it controls grain boundaries which would affect the quality of graphene. The material properties like mechanical strength, mobility, doping percentage and thermal transport are greatly affected by these grain boundaries [8]. A lot more still needs to understand about the growth parameters and the nucleation of domains. The present work is about the growth of few layer single crystal graphene grains on Pt foil via chemical vapour deposition. The optical microscope images of the graphene grains show Bernal and twisted layer stacking. Grain boundaries of Pt provide low energy sites to the carbon species and the nucleation of grains are more at the boundaries. The stacking order and the number of layers in grains can be seen more clearly with scanning electron microscopy. 2D Raman peaks show dispersive nature for Bernal stacked grains and were fitted with four Lorentzian peaks. The shift in the 2D Raman peak clearly indicates the different stacking sequences in different grains. Atomic force microscopy analysis showed an increasing trend in grain height profile with an increase in the number of layers. Moreover, different coalesced grains showed clearly different stacking sequences and merging of different nucleation sites of different grains. We observed Bernal AB and twisted layer stacking in the grains when they were combining together in order to grow into a bigger size. The full width at half maximum -1 (FWHM) value of 2D Raman peaks appeared in the range of 52-69 cm which showed an increase from -1 the value of single layer graphene (30.18 cm ) and identify Bernal stacking in grains. In twisted stacking, FWHM values lie in the range of 19 -32 cm-1. Raman contour mapping also helps in understanding the number of layers. References

[1]. Novoselov K, et al., Science 306 (2004)666–9 [2]. Geim A K, Science 324 (2009)1530–4 [3]. Novoselov K, Rev. Mod. Phys. 83 (2011)837–49 [4]. Bonaccorso F, et al., Nature Photon. 4 (2010) 611–22 [5]. Reina A, et al., Nano Lett. 9 (2009) 30. [6]. Li X et al., Science, 324 (2009) 1312. [7]. Kim KS et al., Nature 457 (2009) 706. [8]. Vlassiouk I, et al., Nanotechnology 22 (2011) 275716

Graphene | 129

Optimization of CVD Growth Graphene on Nickel using Taguchi Method Sibel Kasap , Hadi Khaksaran , SĂźleyman Ă&#x2021;elik , Hasan Ă&#x2013;zkaya &HQN <DQĂ&#x2022;N 1,2* Ismet I. Kaya 2

1,2

and

Faculty of Engineering and Natural Sciences, Sabanci University, 34956 Istanbul, Turkey

Nanotechnology Research and Application Center, Sabanci University, 34956 Istanbul, Turkey skasap@sabanciuniv.edu

Abstract The chemical vapor deposition (CVD) is a fairly available method for the synthesis of large area graphene films with high quality for industrial applications [1]. Transition metals including Ni, Cu, Pt, Ir and Pd have been used as a substrate for graphene growth [2]. Among them, nickel is a well-known transition metal as a substrates for graphene growth, due to the high carbon solubility and low lattice mismatch with graphene [3]. In CVD method, where variables of parameters, such as temperature, gas flow rate and pressure are involved [3], since many experiments need to be performed for reaching at the optimum conditions. The Taguchi method, which is a combination of mathematical and statistical analyzing system to optimize synthetic processes of nanostructured materials [4-5] In this work, Taguchi method is applied to the optimization of the synthesis of graphene by nickel catalyzed chemical vapor deposition (CVD) with the aim of high transparency and low sheet resistance o of the growth process. Three parameters, growth temperature (X1: 800-900 C), concentration of CH4 (X2: %5-%50), and growth time (X3: 2-10 min.) are optimized using a 3-level Taguchi design. The characterization of graphene films are made by Raman spectroscopy, optical transmittance and sheet resistance after they were transferred on glass slides.

References [1] Bae S, Kim H, Lee Y, Xu X, Park JS, Zheng Y, Balakrishnan J, Lei T, Kim HR, Song YI, Kim YJ, Kim KS, Ă&#x2013;zyilmaz B, Ahn JH, Hong BH, Lijima S.,Nat. Nanotechnol. 5(2010)574-78. [2] Yu Q, Lian J, Siriponglert S, et al., Appl Phys Lett, 93(2008),113103. [3] Mattevi C, Kim H, Chhowalla M., Journal of Material Chemistry 21(2011) 3324-34. [4] Kim S.M, Park, K.S., Kim K.D., Park S.D., Kim H.D., Journal of Industrial and Engineering Chemistry 15(2009) 894-897. [5] Santangelo S., Lanza M., Piperopoulos E., Galvagno S., Milone C., Materials Research Bulletin 47(2012) 595-601.

130 | Graphene

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Graphene | 131

Laser Annealing as an Enhancement Technique for the Optical and Electrical Properties of Graphene Ink based Films 1

Sepideh Khandan Del , Rainer Bornemann , Andreas Bablich , Heiko SchĂ¤fer-Eberwein , Jintong Li , 3 2 1 Michael Ă&#x2013;stling , Peter Haring-BolĂvar , Max Lemme 1

Institute of Graphene-based Nanotechnology, University of Siegen, HĂślderlinstr 3, D-57076, Siegen, Germany 2 Institute of High Frequency and Quantum Electronics, University of Siegen, HĂślderlinstr. 3, D-57076 Siegen, Germany 3 School of Information and Communication Technology, KTH-Royal Institute of Technology, Electrum 229, SE-164 40 Kista, Sweden Contact: max.lemme@uni-siegen.de

In this work we propose a fast and on-demand technique to fabricate graphene-based transparent conductive films. Drop casting of high-concentration graphene ink accompanied with an efficient laser annealing process results in a homogenous graphene thin film. Graphene ink was produced by a liquid phase exfoliation (LPE) method through exfoliating graphite powders in dimethylformamide (DMF) and additional stabilizing polymers. Finally, DMF was exchanged by terpineol in order to increase graphene concentration, adjust ink viscosity, and reduce solvent toxicity [1]. The ink was deposited on substrates by drop casting and then annealed at 400Â°C for 30 min to remove stabilizing polymers. Subsequently, a 532 nm cw laser beam was scanned across the film with a power density of 55 MW/cm2 and integration times of 1-5 ms. The graphene thin films were characterized by a combination of optical microscopy, laser scanning microscope, scanning electron microscope (SEM), Raman spectroscopy and X-ray powder diffraction (XRD). While the drop casted films are highly UHVLVWLYH WKH ODVHU WUHDWPHQW UHVXOWV LQ VKHHW UHVLVWDQFHV RQ WKH RUGHU RI NÂ&#x; VT 0HDQZKLOH the transmittance of the films increases from 60% to more than 85 DW Č&#x153; QP Raman data indicate that by laser annealing the films, both the FWHM of the Raman G band and the integrated intensity ratio of the D band to the G band decrease significantly. This confirms that the laser treatment reduces structural disorder within the film. XRD data shows the intensity of the SHDN DW â&#x20AC;ŤÂ&#x192; ÝŞâ&#x20AC;Ź, which corresponds to the 002 plane of graphite layers, is higher for laser treated samples. This data indicate after laser treatment there are more graphene flakes overlapped in the (002) crystalline direction. AFM and SEM images show topography changes in the films after laser treatment. Laser annealed films have a significantly more homogenous and smooth surface with roughness of about 10 nm. Electrical and optical properties of fabricated films by this method are comparable to that of the state of the art in printed graphene films. Laser annealing enables the controlled transformation of a high resistive coating into a transparent conductive film with potential applications in electrostatic dissipation or touch displays. [1] J. Li, et al., Adv. Mater., vol. 25, (2013) 3985Âą3992

(a)

(b)

Figure 1: (a) schematic of laser annealing process (b) Transparency at 550 nm, the red area is glass substrate while the yellowish color indicates the laser treated film.

132 | Graphene

Large enhancement of Raman spectra in graphene deposited on GaN nanowires Jakub Kierdaszuk, 3LRWU .DÄ¨PLHUF]DN $QHWD 'UDELÄ&#x201D;VND Krzysztof Korona, $QGU]HM :\VPRĂĄHN 1 2 2,3 1 0DULD .DPLÄ&#x201D;VND Iwona Pasternak, Aleksandra Krajewska, .U]\V]WRI 3DNXĂĄD Zbigniew R. 4 ÄŠ\WNLHZLF] 1 Faculty of Physics, University of Warsaw, Pasteura 5 street, Warsaw, Poland 2 Institute of Electronic Materials Technology, Wolczynska 133 street, Warsaw, Poland 3 Institute of Optoelectronics, Military University of Technology, gen. Sylvester Kaliski 2 street, Warsaw, Poland 4 Institute of Physics, Polish Academy of Sciences, Lotnikow 32/46 street, Warsaw, Poland Contact e-mail: hessotia@gmail.com 1

Since graphene is transparent and has good conductivity, it is considered to be a proper candidate for replacing ITO in solar cells. On the other hand, it has been shown recently that nanowire structures can substantially increase efficiency of solar cells. 1 Therefore, possibility of using graphene as a transparent electrode deposited on GaN nanowires (NWs) is very attractive. In our studies we 2 focused on Raman spectroscopy and contactless microwave transport measurements of graphene grown by Chemical Vapor Deposition method, and transferred onto top of GaN NWs grown by Molecular Beam Epitaxy. The results were compared with the ones obtained for graphene deposited on epitaxial GaN layer. Large enhancement of Raman spectra deriving from graphene deposited on NWs in comparison with the corresponding spectra of graphene on epilayer was observed (Fig. 1). Value of enhancement varied from 55 times for the most enhanced 2' SHDN WR WLPHV IRU 'Âś SHDN Two dimensional Raman micro mapping showed correlations between Raman peak parameters and nanowires distribution underneath of graphene. Periodic modulation of electron concentration and homogenous strain found in graphene on NWs suggested that Raman enhancement could be explained by influence of strong electric field induced by electric charges located on the top of the 3 nanowires, similar to the Tip Enhancement Raman Scattering (TERS) mechanism. This effect is confirmed in transport measurements where positive magnetoconductance signal for low magnetic field for both samples was observed (Fig. 2). The signal amplitude was reduced for graphene on NWs which was caused by reduction of coherence scattering length LÄł comparing to graphene on epilayer. Nonzero offset in LÄł 2(T) linear dependence, present only for graphene on NWs, showed additional, temperature independent scattering mechanism reducing coherence scattering length. This can be related for example to charges induced on the NWs surface by spontaneous and piezoelectric 4 polarization of GaN, which due to a very small distance of NW from graphene sheet can modulate electron concentration in graphene, and furthermore be responsible for the enhancement of the Raman spectra. (1) Krogstrup, P. et al., Nat. Photonics 7 (2013), 1Âą5. 'UDELÄ&#x201D;VND $ HW DO 3K\V 5HYL % 045421 (3) Maximiano, R. V et al., Phys. Rev. B 85, (2012), 235434 (4) Ambacher, O. el al., Journal of Physics:Condensed Matter 14, (2002), 3399Âą3434

Figure 1. Raman spectra measured for graphene deposited on GaN nanowires, and on GaN epitaxial layer.

Figure 2. Magnetoconductance signal (a) and its derivative on magnetic field (b) for graphene deposited on GaN NWs, and on GaN epilayer.

Graphene | 133

Nanomesh Graphene for Supercapacitor Applications 1

Hyun-Kyung Kim , Suk Woo Lee , Yoen-Jun Choi , Kwang Chul Roh and Kwang-Bum Kim

Laboratory of Energy Storage Materials, Department of Material Science and Engineering, Yonsei University, Seoul, South Korea 2 Energy Efficient Materials Team, Energy & Environmental Division, Korea Institute of Ceramic Engineering & Technology, Seoul, South Korea khkme@yonsei.ac.kr

Abstract Supercapacitors (SCs), also known as electrochemical capacitors (ECs), have attracted increasing attention owing to their fast charge and discharge rates, long cycle life and their ability to complement Li-ion and other advanced secondary batteries [1]. Among the various kinds of carbonaceous materials that have been employed to fabricate SCs, the 2 one-atom-thick two-dimensional (2D) sp carbon structure of graphene has attracted considerable interest by virtue of the fact that its ideal structure offers a unique combination of good mechanical/chemical stability, high electrical/thermal conductivity, and a large surface area of over 2630 2 -1 m g . Especially, due to the high theoretical surface area of single layer graphene, it is expected to -1 have high specific capacitance (550 F g ) as an electrode material for SCs applications [2]. However, solution processing results in aggregation of graphene nanosheets due to strong van der Waals forces of attraction, leading to lower values of surface area and lesser number of electrochemically active sites thereby giving lower than the theoretically expected value [3]. Therefore, the current status calls for new and innovative strategies to enhance the charge storage properties of graphene-based materials. In this study, we report on nanomesh graphene as an electrode material for SCs applications (Fig. 1) The nanomesh graphene with nanoperforation shows edge effect from defects, dangling bonds and functional groups associated with the terminal edges of graphene and stronger quantum effects derived from neck-width (< 20 nm) in micron-size graphene [4, 5]. More details will be discussed at the meeting.

References [1] P. Simon, Y. Gogotsi, Nat. Mater., 7 (2008) 845. [2] C. Liu , Z. Yu , D. Neff , A. Zhamu , B. Z. Jang , Nano Lett., 10 (2010) 4863. [3] Y. Zhu, S. Murali, M. D. Stoller, A. Velamakanni, R. D. Piner, R. S. Ruoff, Carbon, 48 (2010), 2118. [4] Z. Zhang, J. Zhang, N. Chen and L. T. Qu, Energy Environ. Sci., 5 (2012), 8869. [5] W. Yuan, Y. Zhou, Y. Li, C. Li, H. Peng, J. Zhang, Z. Liu, L. Dai, G. Shi, Scientific Reports, 3 (2013) 2248.

Figure

Figure 1. Schematic illustration and TEM image of nanomesh graphene (inset: FT pattern)

134 | Graphene

Liquid Cu catalyst phase effect on graphene growth Min-Sik Kim, Seong-Yong Cho, Sang-Hoon Lee, Min-Su Kim, Ki-Ju Kim, and Ki-Bum Kim*

Department of Materials Science and Engineering, Seoul National University, Korea

The catalytic effect of liquid Cu was studied via post-annealing of graphene grown on solid Cu and melting catalyst phase. As-grown graphene samples were prepared on solid Cu, and heated up to higher than melting point of Cu in-situ. Nuclei density and grain size including growth morphologies were studied by electron microscopy and Raman spectrum analysis. Average size of graphene grains Č?P2 JURZQ RQ VROLG &X PHUJHG LQWR ODUJHU VL]H Č?P2) during the annealing on liquid Cu. Graphene growth shows self-assembly behavior on liquid Cu despite of its original irregular shape and orientation on solid Cu. Introduction of hydrogen results in well-aligned hexagon shape in the same direction graphene single crystal on liquid Cu. Each merged graphene grains shows single crystal by diffraction pattern studies. Even for the full coverage graphene on solid Cu, defect structure was healed on liquid Cu which was also verified Raman spectrum analysis. This simple postannealing by melting Cu catalyst can be used as enhancement of graphene property.

Graphene | 135

Mesoepitaxy of graphene: continuous film formation Seong-Yong Cho, Min-Sik Kim, Hyun-Mi Kim, Min-Su Kim, Ki-Ju Kim, Sang-Hoon Lee, and Ki-Bum Kim*

Department of Materials Science and Engineering, Seoul National University, Korea

Polycrystalline nature of graphene is a major issue to be overcame in real application of CVD graphene. Recently, liquid Cu was used as catalytic substrate for graphene growth, and due to liquid surface nature, self-assembly of graphene islands was observed. However, stitching of each graphene islands still need to be investigated since thermal stress may result cracks. We verified that typical growth conditions for self-assembly of graphene on liquid Cu are not adequate for obtaining continuous graphene film, due to low supersaturation ratio. Two-step growth method was suggested in order to reduce thermal induced cracks, and fill the narrow gaps between graphene islands. Also, the transport behavior was studied via Van der Pauw measurement of the graphene film, and TLM patterning of two adjacent graphene islands. Self-assembled graphene shows lower resistance compared to randomly grown graphene islands which are typically observed on solid Cu.

136 | Graphene

Thermoelectric effect with band offset at lateral junction between ABA and ABC tri-layer graphene 1

Minjung Kim , Seon-Myeong Choi , Ho Ang Yoon , Jung Cheol Kim , Sang Wook Lee , Young-Woo 2 1,* Son , and Hyeonsik Cheong 1

Department of Physics, Sogang University, Seoul, 121-742, Korea School of Computational Sciences, Korean Institute for Advanced Study, Seoul, 130-722, Korea 3 Division of Quantum Phases and Devices, School of Physics, Konkuk University, Seoul, 143-701, Korea 2

hcheong@sogang.ac.kr Abstract Photocurrent generated at a junction between ABA (Bernal) and ABC (Rhombohedral) stacking in trilayer graphene has been observed. The Raman spectra of ABA- and ABC- stacked tri-layer graphene have been studied [1], but the photocurrent in tri-layer graphene has not yet been investigated. The photocurrent and the Raman spectra of the tri-layer graphene were measured simultaneously to identify the exact position of the photocurrent and the ABA/ABC junction. We investigated the mechanism of the photocurrent by measuring the back-gate bias dependence of the photocurrent in vacuum. In general, there are two mechanisms for photocurrent without an external bias: the photovoltaic effect from Fermi energy difference and the thermoelectric effect from the Seebeck coefficient difference. Here, we studied the dominant mechanism of the photocurrent in the ABA/ABC stacking junction in tri-layer graphene. We calculated the Fermi energy and the Seebeck coefficients of ABA and ABC stacked trilayer graphene in order to explain the mechanism of the photocurrent at the junctions. The Fermi energy as a function of the number of electrons is calculated by the density functional theory. The Seebeck coefficient is calculated by the density functional theory and the Boltztrap program. In addition, we measured the photocurrent at junctions between single- and bi-layer graphene for comparison. The experimental photocurrent behavior is consistent with the calculated Seebeck coefficient difference if a band offset of 90 meV (240 meV) is assumed for the ABA/ABC (Single/Bi) junction. References [1] T. A. Nguyen, J.-U. Lee, D. Yoon, H. Cheong, Scientific Reports, 4 (2014) 4630. Figures

Figure 1 Schematic of ABA/ABC photodevice

Figure 2 (a) Raman and photocurrent image of ABA/ABC photodevice (b) Gate bias dependence of photocurrent at the lateral ABA/ABC junction

Graphene | 137

One pot synthesis of micrometer-sized spherical Li4Ti5O12/reduced graphene oxide as anode material for high-rate lithium ion batteries Myeong Seong Kim, Hyun Kyung Kim, Suk Woo Lee and Kwang Bum Kim* Laboratory of Energy Conversion and Storage Materials Department of Material Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemoon-gu, Seoul, 120-749, South Korea gom0505@hotmail.com Abstract Spinel Li4Ti5O12 has attracted much attention as an anode material for lithium-ion batteries because of its good Li-ion intercalation reversibility and extremely small structural changes during charge-discharge cycling. Despite these advantages, Li4Ti5O12 is not suitable for commercial use due to its low electronic -13 -1 1 conductivity (10 S cm ), which leads to poor rate capabiltiy. Several effective ways to improve the rate capability of Li4Ti5O12 have been reported, including reduction of the particle size to the nanoscale, doping Li, Ti, or O sites with small amounts of metal or nonmetal ions, surface modification or carbon 2-4 coating, and its incorporation into composites with carbonaceous materials. Among the various carbonaceous materials, reduced graphene oxide (RGO) or graphene nanosheets has attracted considerable interest as electrode materials for electrochemical energy storage because of their unique properties such as high electronic conductivity, large surface area, and good mechanical properties. Some recent studies have demonstrated the excellent rate capability and cycle stability of 4 Li4Ti5O12/RGO nanocomposites. However, in all these reports, the lithium±titanium±oxide (Li±Ti± O)/RGO nanocomposite as the precursor for Li4Ti5O12, was initially synthesized using a two-step or multistep process. In such multistep methods, Li4Ti5O12 particles can be limited the available sizes and morphologies. In addition, it is difficult to fabricate the phase-pure Li4Ti5O12 due to the formation of 5 titanates with several other phases. Previously reported Li4Ti5O12/RGO nanocomposites mostly have 2-dimension morphologies 4,5 with low tap density. The 2-dimentional Li4Ti5O12/RGO nanocomposites are not suitable for commercial use because their low tap density limits the volumetric energy density. Therefore, a simple and facile synthesis of micrometer-sized spherical Li4Ti5O12/RGO composites with a high tap density and superior rate capability is highly desirable. In this study, we report one-pot synthesis of micrometer-sized spherical Li4Ti5O12/RGO with high tap density, wherein the initial Li-Ti-O/RGO precursor is fabricated by the spray drying method in the presence of all precursors in a solution. Upon subsequent heat treatment, phase-pure micrometer-sized spherical Li4Ti5O12/RGO with high tap density was successfully synthesized. More detailed on the synthetic procedure, morpology, electrochemical and structural properties of micrometer-sized spherical Li4Ti5O12/RGO will be presented at the meeting. References [1] S. G. Doo et al, J. Am. Chem. Soc., 130 (2008) 14930 [2] N. Ohta et al, Adv. Mater., 18 (2006) 2226 [3] N. Jayaprakash et al, Appl. Nanosci., 1 (2011) 7 [4] H. K. Kim et al, Electrochem. Commun., 12 (2010) 1768 [5] H. K. Kim et al, J. Mater. Chem. A, 1 (2013) 14849 Figures

Figure 1 TEM images of micrometer-sized spherical Li4Ti5O12/RGO microspheres

138 | Graphene

Wafer-scale fabrication of graphene field effect transistors for neuronal interfacing Dmitry Kireev, Silke Seyock, Jan Schnitker, Vanessa Maybeck, Bernhard Wolfrum and Andreas OffenhĂ¤usser Institute RI %LRHOHFWURQLFV 3*,- ,&6- )RUVFKXQJV]HQWUXP -Â OLFK -Â OLFK *HUPDQ\ d.kireev@fz-juelich.de There are plenty of invasive methods for studying a neuronal networkÂśs activities [1]. Of course, the invasiveness of the processes makes them undesired. In recent years, there has been vast research in the field of non-invasive neuronal interfacing and extracellular neuronal recordings [2]. Different methods (passive Âą MEAs and active Âą FETs) and different materials (carbon, silicon, PEDOT:PSS) have been used for the purpose. *UDSKHQHÂśV H[FHOOHQW HOHFWULFDO PHFKDQLFDO DQG ELRORJLFDO SURSHUWLHV PDNH LW D SHUIHFW FDQGLGDWH for such a role. Firstly, liquid-gated graphene field effect transistors (GFETs, see fig. 1) show very high transconductance, and therefore sensitivity [3]. Secondly, graphene is a very stable and biocompatible material (fig.2). Thirdly, flexibility and bendability of graphene make it the most promising material for future bio-implantable devices [3]. Therefore we established our 4-inch wafer fabrication process based on CVD-grown graphene (fig. 3a). Each fabricated wafer results in 52 biocompatible chips (fig. 3b). Each chip comprises 32 GFETs (fig. 3c). The size of graphene active area is varied in order to study the noise of the system. Each chip is measured on a multi-channel measurement system, which allows us to measure all the GFETs simultaneously. Thus, it is possible to measure not just single action potentials of the electrogenic cells, but even propagation of the potential through the network. References [1] Mehdi Jorfi, John L Skousen, Christoph Weder and Jeffrey R Capadona, J. Neural Eng.12 (2015), 011001 [2] Xiaojie Duan (2014), Nanotechnology and Neuroscience: Nano-electronic, Photonic and Mechanical Neuronal Interfacing, pp 13-43 [3] L.H. Hess, M. Seifert, J.A. Garrido, Proceedings of the IEEE, 101, 7, (2013), 1780-1792

Figure 1 Schematic of the liquid-gated GFETs array. Inserts Âą the interface between graphene and a cell

Figure 3 Design of the wafer. (a) Âą the whole 4-inch wafer view; (b) Âą zoom in on a chip; (c) Âą zoom in on an active area with 32 GFETs visible; (d) Âą zoom in on a single GFET. Yellow Âąsource and drain, dashed area - graphene Figure 2 An SEM image of a neuronal network grown on top of a GFET

Graphene | 139

Electrochemical Transfer of Large-Area Single Crystal Epitaxial Graphene from Ir(111) Â&#x201A;

Â&#x201A;

Line Koefoed, Mikkel Kongsfelt, SĂ¸ren Ulstrup, $QWRQLMD *UXELĂŁLĂź Ă˝DER Andrew Cassidy, Patrick R. Â§ Ă Ă Â§ Ĺ? Â§ Whelan, Marco Bianchi, Maciej Dendzik, Filippo Pizzocchero, Bjarke JĂ¸rgensen, Peter BĂ¸ggild, Liv Ă Ă Â&#x201A; Â&#x201A; HornekĂŚr, Philip Hofmann, Steen U. Pedersen, Kim Daasbjerg Â&#x201A;

Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, Aarhus C, Denmark Department of Physics and Astronomy and iNANO, Aarhus University, Ny Munkegade 120, Aarhus C, Denmark Â§ Department of Micro- and Nanotechnology, Technical University of Denmark, Kgs. Lyngby, Denmark Ĺ? Newtec A/S, StĂŚrmosegĂĽrdsvej 18, Odense M, Denmark line88@chem.au.dk

Abstract Transfer of large single crystal graphene is highly desired and important for applications in [1] nanoelectronics. A promising and inexpensive approach for manufacturing high-quality graphene is chemical vapor deposition (CVD) onto transition metals. In particular, growth of strictly monatomic graphene of well-defined orientation and macroscopic extension can be achieved on metal single [2] crystals such as Ir(111). Unfortunately, the task of transferring such high-quality graphene to other [3] substrates is difficult, because of the strong interaction between the Ir surface and graphene. In this work we present a new electrochemical method, which in a two-step procedure can accomplish the transfer of large-area single crystalline graphene from Ir(111) under ambient conditions. + First, tetraoctylammonium ions (TOA ) are intercalated between the Ir(111) crystal and graphene by charging the latter. The graphene layer is supported with a drop coated polymer layer, before the second electrochemical step is applied. This step consists of electrochemical reduction of protons in aqueous solution to cause hydrogen evolution and, thereby, enabling transfer of large millimeter-sized and nearly perfect monolayer graphene from Ir to another substrate such as SiO 2/Si. This simple technique allows transfer of graphene single crystals having the same size as the substrate they are grown on (diameter | 7 mm). In addition, after delamination the substrate can be reused for further growth cycles and transfer of graphene. Raman mapping was used to analyze and determine the structural defects and strained wrinkles in the transferred graphene. References [1] [2] [3]

Morozov, S. V.; Novoselov, K. S.; Katsnelson, M. I.; Schedin, F.; Elias, D. C.; Jaszczak, J. A.; Geim, A. K. Phys. Rev. Lett. 100 (2008), 016602. Coraux, J.; NÂ´Diaye, A. T.; Busse, C.; Michely, T. Nano Lett.8 (2008), 565. %XVVH & /D]LĂź 3 'MHPRXU 5 &RUDX[ - *HUEHU 7 $WRGLUHVHL 1 &DFLXF 9 %UDNR 5 1Âś'LD\H $ 7 %OÂ JHO 6 =HJHQKDJHQ - 0LFKHO\ 7 Phys. Rev. Lett. 107 (2011), 036101.

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140 | Graphene

Unipolar resistive switching memory using graphene oxide for flexible one diode-one resistor (1D-1R) cell array Beom Jun Koo1, Jong Yun Kim1,2, Byung Chul Jang1, Sung-Yool Choi1 1

Department of Electrical Engineering and Graphene Research Center, KAIST, Daejeon 305-701, Korea 2

Department of Chemistry, Hanyang University, Seoul 133-701, Korea

azurite@kaist.ac.kr Abstract Resistive random access memory (RRAM) type flexible memory is attracting increasing attention as a promising candidate for future flexible nonvolatile memory (NVM) due to its good scalability, fast switching speed, and low-power consumption. Recently, the graphene oxide (GO) has been proposed as potential resistive switching material because GO can be readily fabricated using a room temperature spin-coating method and has reliable memory performance in terms of retention and endurance characteristics during bending test. Up to now, most of reported RRAM based on GO exhibited bipolar resistive switching memory (BRS) in which both SET and RESET processes are dependent of voltage polarities. However, unipolar resistive switching memory (URS), in which both SET and RESET processes occur at the same voltage polarities, is essential in RRAM for integration of the switching device with memory, to address the sneaky path problems in cross-bar arrays. To realize the stable URS memory based on GO, we investigated the effect of electrode metals and GO thickness on the Metal/GO/Metal RRAM. The Ni/GO/Au structure with 95-nm-thick GO shows good switching performance with the low set/reset voltages, and excellent endurance cycles, but its on/off current ratio has poor performance. The Al/GO/Au structure with 55-nm-thick GO has a high on/off current ratio, but it has poor endurance and the set/reset voltages are very variable. To improve the unstable memory performances, GO-based RRAM was annealed in the high vacuum condition for making reduced graphene oxide (rGO) which has lower oxygen functional group acted as trap sites at the interface than GO. With Al/rGO/Au structure with 55-nm-thick rGO, we successfully could show the URS behavior with the on/off ratio to over 103 which sustains over 100 cycling, and reduce the variation of set/reset voltages. This work provides an important step for developing understanding of the fundamental physics of unipolar resistive switching in GO, for the one diode â&#x20AC;&#x201C; one resistor (1D-1R) cell array to future flexible electronics.

Graphene | 141

The characterization of resistive switching in graphene oxide layer prepared by inkjet printing 1,2

M. Rogala , P. J. Kowalczyk , W. Kozlowski , A. Busiakiewicz , I. Wlasny , S. Pawlowski , 1 1 3 3 3 3 3 G. Dobinski , M. Smolny , L. Lipinska , R. Kozinski , K. Librant , P. Dabrowski , J.M. Baranowski , 2 1 K. Szot , Z. Klusek 1

Department of Solid State Physics, Faculty of Physics and Applied Informatics, University of Lodz, Pomorska 149/153, 90-236 Lodz, Poland 2 3HWHU *UÂ QEHUJ ,QVWLWXW -$5$-),7 )RUVFKXQJV]HQWUXP -Â OLFK -Â OLFK *HUPDQ\ 3 Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw, Poland pkowa@uni.lodz.pl

Abstract Resistive switching (RS) processes recently discovered in graphene oxide (GO) [1] shows a new way of non-volatile data storage in flexible solid state devices. The principles of operation of novel resistive random-access memory (ReRAM) consist of electrically inducted reversible changes of material resistivity between well distinguishable low resistance (ON) and high resistance (OFF) states [2]. The RS is closely related to the memristance according to "memory resistor" (memristor) which is a forth passive two terminal electrical component. We will discuss the conditions which must be met in order to achieve the effect of changes of resistance in GO. In our experiments we used graphene oxide produced using modified Hummers method. The GO thin films of various thicknesses (20 Âą 100 nm) were inkjet printed on a silicon substrate covered with platinum, which was the flat bottom electrode. The top electrode, which was in contact with GO film, was the Pt covered tip of atomic force microscope (AFM). Environmentally controlled AFM setup was used, which allows for investigations in vacuum, different gases and control of humidity in the range of up to 70%RH. The use of inert electrode material in combination with very low contact area of the top electrode allows us to analyse the influence of the environmental factors on resistive switching processes occurring in GO. By the use of atomic force microscope we were able to modify the electrical conductivity in nano-regions of GO thin film between ON and OFF states. The observed resistive switching has bipolar character, which is related to the asymmetry of the experimental setup (top of the sample is exposed to the environment which can be controlled during the experiment). We will present how the composition of the atmosphere around GO influences the strength of the RS effect. We will also focus on the dependence between the effectiveness of the electrical modification of the material and the thickness of GO film. We will discuss observed reduction/oxidation processes occurring in graphene oxide layer in terms of its spatial distribution and their consequences on the morphology changes of the thin film. Results of our investigations have a direct connection to the challenges the industry will face when GO will be used to construct ReRAM devices with the desired parameters. This work is supported by the National Science Centre under project DEC-2012/05/B/ST5/00354 and the National Centre for Research and Development under the project GRAF-TECH/NCBR/15/25/2013.

References [1] C.L. He et al., Appl. Phys. Lett. 95 (2009) 232101. [2] K. Szot, M. Rogala, W. Speier, Z. Klusek, A. Besmehn, R. Waser, Nanotechnology 22 (2011) 254001.

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Nitrogen-doped graphene: chemical and morphological properties 1

W. Kozlowski , P. Dabrowski , I. Wlasny , M. Rogala , J. M. Baranowski , W. Strupinski , 3 3 3 1 M. Kopciuszynski , R. Zdyb , M. Jalochowski , Z. Klusek 1

Department of Solid State Physics, Faculty of Physics and Applied Informatics, University of Lodz, Pomorska 149/153, 90-236 Lodz, Poland 2 Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw, Poland 3 Institute of Physics, M. Curie-6NรกRGRZVND 8QLYHUVLW\ 3ODFH 0 &XULH-6NรกRGRZVNLHM -031 Lublin, Poland wkozl@std2.phys.uni.lodz.pl Abstract Nitrogen-doped graphene has attracted major attention due to its ability to change electronic properties of the graphene and enhance biocompability of the devices. Nitrogen is able to create three main bonding configurations within graphene sheets: graphitic-like, pyridine-like and pyrrolic-like. However, it has been pointed out that only the graphitic-like configuration causes the position of the Dirac point relative to the Fermi level to change and enhances n-type carrier concentration in the graphene. In our work we studied nitrogen-doped graphene prepared by CVD method on Si face 4H SiC. Properties of the nitrogen-doped graphene were examined by LEED, Raman, XPS and ARPES. Local electronic properties of the graphene were studied using STM/STS techniques. Nitrogen dopants have been observed as a bright spots on STM topography. Dark spots are mainly structural defects in the graphene lattice associated with nitrogen incorporation. Presence of different bonding configurations of the nitrogen atoms in our sample has been confirmed by XPS measurements. We show that the presence of nitrogen causes defect creation within graphene sheets which can significantly reduce conductance of the graphene layers. However, we were able to create graphene sheets with different combinations of nitrogen-carbon bonds configurations and density of created structural defects by tuning the parameters during the graphene synthesis. This work is supported by the National Centre for Research and Development under the project GRAFTECH/NCBR/15/25/2013 and the National Science Centre under project DEC-2012/05/B/ST5/00354

Graphene | 143

Graphene oxide assisted hydrothermal carbonization of carbon hydrates Deepti Krishnan, Kalyan Raidongia, Jiaojing Shao, Jiaxing Huang Northwestern University, Evanston, IL, USA - 60208 deeptikrishnan2015@u.northwestern.edu Abstract Biomass is a cheap, ecofriendly and renewable raw material for the production of functional carbonaceous materials. Hydrothermal carbonization (HTC) of biomass typically produces carbon materials that are insulating. Using simple carbon hydrates such as glucose and cellulose as a model system for biomass, here we demonstrate that graphene oxide (GO) sheets can promote HTC conversion. Adding a very small amount of GO to glucose (e.g., 1:800 weight ratio) can significantly alter the morphology of its HTC product, resulting in more conductive carbon materials with higher degree of carbonization. HTC treatment of glucose is known to produce a dispersion of micron sized carbon spheres. In the presence of GO, HTC treatment results in dispersed carbon platelets of tens of nanometers in thickness at low mass loading level, and free-standing carbon monoliths at high mass loading levels. Control experiments with other carbon materials such as graphite, carbon nanotubes and carbon black show that only GO has significant effect in promoting HTC conversion, likely due to its good water processability, amphiphilicity and two-dimensional structure that may help to template the initially carbonized materials. GO offers an additional advantage in that its graphene product can act as an in-situ heating element to enable further carbonization of the HTC carbon monoliths upon microwave irradiation. Similar effect of GO is also observed for the HTC treatment of cellulose.

Figure

144 | Graphene

Photocatalytic degradation performance driven by UV and Visible irradiation of reduced graphene oxide± Fe3O4 nanocomposite Manish Kumar 1, Pankaj Chamoli2 and Kamal K. Kar1, 2* Nanoengineering Materials laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur-208016, India, 2Advanced Nanoengineering Materials laboratory, Materials Science Programme, Indian Institute of Technology Kanpur, Kanpur-208016, India * Email: kamalkk@iitk.ac.in, Phone: +91-512-2597687, Fax: +91-512-597408

1Advanced

Abstract Contamination in our aquatic system occurs mainly due to the presence of organic dyes dumped by leather, textile, pharmaceutical industries and heavy metal ions concentration (such as lead, mercury, arsenic, zinc, cobalt, chromium etc.).These taints are proving massive threat to human health by spreading into our food chain system. Our present work overviews incessant research interest to synthesis of highly efficient graphene based nanocomposite as photocatalyst and absorbent for removal of contamination from aquatic system. Reduced graphene oxide±Fe3O4 (rGO±Fe3O4) nanocomposite was synthesized by one-step solvothermal route. The as-synthesized nanocomposite was characterized by X-ray powder diffraction, scanning electron microscope, field emission scanning electron microscope, Raman spectroscopy, Fourier transform infrared spectroscopy and UV-VIS spectroscopy for confirmation of rGO±Fe3O4 formation. FESEM analysis shows the presence of Fe3O4 nanoparticles, distributed uniformly and anchored onto the wrinkled graphene sheets. The photocatalytic degradation performance of rGO±Fe3O4 nanocomposite was investigated under UV and Visible irradiation for methyl blue aqueous solution. UV-visible spectroscopy confirmed that the photo-decomposition of methyl blue from aqueous solution. In addition, the role of substituent Fe3O4 in nanocomposites in terms of adsorption for As(V) and As(III) were analyzed by Atomic absorption spectroscopy. Hence, rGO±Fe3O4 shown promising nanocomposite as photocatalyst and absorbent for treatment of contaminated water. Keywords: Graphene oxide, Nanocomposite, Photocatalysis, Organic dyes, UV-irradiation

Fig. (a) XRD of rGO-Fe3O4 nano composite (b) SEM of graphene oxide and rGO-Fe3O4 nano composite

Graphene | 145

_______________________________________________________________________________________________________________

Synthesis of highly dispersible and ultra pure graphene oxide

Mukesh K.Kumawat*, Rohit Srivastava Department of Biosciences and Bioengineering, IIT Bombay, Mumbai, India-400076

*mukesh87.iitb@gmail.com Graphene oxide (GO) synthesis by oxidation of graphite was pioneered by Brodie1 in 1859, its modification in 1898 by Staudenmaier2, thereafter Hummer’s method3 is most widely used method for synthesis of GO. Several modifications4-6 of Hummer’s method have been suggested in last decade. Here we report another modification wherein we chemically processed the graphite before it was used for Hummer’s method to produce GO. The prepared GO was purified by washing several times using centrifugation. The term for synthesized GO is m-GO (‘m’ stands for modified) and GO synthesized by Hummer’s method is h-GO. On comparison, m-GO with h-GO it was found that m-GO was highly dispersible and ultra pure (Figure 1). m-GO was characterized by TEM and AFM (Figure 2). TEM image (Figure 2A) showed residual carbon free pure graphene oxide sheets and SAED pattern was ordered. AFM image (Figure 2B) confirmed that m-GO sheets were well exfoliated and had thickness <1 nm. Comparison of UV-visible absorption spectra of equal concentration of m-GO and h-GO (Figure 3) revealed that m-GO had more ʌ-ʌ* transitions (higher Ȝmax). High dispersibility and high purity of m-GO makes it suitable for synthesis of GO based composite materials and biological applications.

References

[1] Brodie et al, Philos.Trans. R. Soc. London, 14 (1859) 249–259. [2] Staudenmaier et al, Ber. Dtsch. Chem. Ges. 31 (1898) 1481–1487. [3] Hummers et al, J. Am. Chem. Soc. 80 (1958) 1339. [4] Wang et al, CARBON 47 (2009) 68–72. [5] Sun et al, Nano Res 1 (2008) 203-212. [6] Daniela et al, ACS Nano, 4, 8 (2010) 4806–4814.

146 | Graphene

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(A)

(B)

Figure 2: (A) TEM image of m-GO and its SAED pattern (inset). (B) AFM image of m-GO with its section analysis on right side displaying thickness of <1 nm.

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400

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600

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Graphene | 147

Graphene thickness-controlled Interface for Enhanced Photocatalysis and SERS Applications Cheng-Chi Kuo and Chun-Hu Chen*

Department of Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan 80424 chunhu.chen@mail.nsysu.edu.tw Abstract: Graphene has been widely studied in hybrid nanocomposites because of its unique chemical and electrical properties. Graphene thickness at the hybrid interface plays important roles in photocatalytic enhancement and SERS performance, but its enhancement mechanism has not been systematically studied due to the difficulty of controlling graphene hybridization. Our recent work shows that the graphene enhancement in the photocatalysis highly depends on the thickness of graphene with the best performance of three layers graphene stacking at the interface. To verify the thickness effect, we utilized a photo-assisted gold deposition to label the photocatalytic active sites at graphene hybrid surfaces. We also used UV-ozone or oxygen plasma to functionalize graphene hybrid interface. The results exhibit the highly photocatalytic enhancement after the increase of surface hydrophilicity. The numbers of graphene layer are found to govern the gold density and charge transfer efficiency in the graphene hybrid system. In Raman SERS study, the graphene hybrid composites with gold particle deposition have great SERS enhancement with the factor as large as ~108. Our results demonstrate that the enhancement of photocatalysis and SERS is highly associated with graphene thickness in graphene hybrid nanocomposites.

References: 1. .XR & & &KHQ & + 1DQRVFDOH 2. Novoselov, K. S. Rev. Mod. Phys. 2011, 50, 6986. 3. Meyer, J. C.; Geim, A. K.; Katsnelson, M. I.; Novoselov, K. S.; Booth, T. J.; Roth, S. Nature 2007, 446, 60 4. Hibino, H.; Kageshima, H.; Maeda, F.; Nagase, M.; Kobayashi, Y.; Yamaguchi, H. Phys. Rev. B 2008, 77, 75413.

148 | Graphene

Prediction of formation of layered ultrathin graphene-type films of ionic compound A.G. Kvashnin, D. Tomanek, P.B. Sorokin Moscow Institute of Physics and Technology, 9 Institutsky lane, Dolgoprudny, Russian Federation FSBI Technological Institute for Superhard and Novel Carbon Materials, 7a Centralnaya St., Troitsk, Moscow, Russian Federation Physics and Astronomy Department, Michigan State University, East Lansing, Michigan 48824, United States aleksandr.kvashnin@phystech.edu Abstract Structural changes at surfaces including atomic relaxation and reconstruction are a manifestation of their effort to minimize the total free energy. Atomic rearrangements are typically moderate at surfaces of semi-infinite systems and in thick slabs in order to minimize the energy penalty associated with structural mismatch at the interface between the reconstructed surface and the unreconstructed bulk. In ultra-thin slabs, surface contribution dominates the total energy, as only a small fraction of atoms experience bulk-like atomic environment. Our results based on ab initio density functional calculations indicate a general graphitization tendency in ultrathin slabs of ionic compound including rocksalt and cesium chloride-type structures. Whereas the bulk of many compounds show an energy preference for cubic rather than layered atomic arrangements, the surface energy of layered systems is commonly lower than that of their cubic counterparts. We determine the critical slab thickness for range of systems, below which spontaneous conversion from cubic to layered graphitic structure occurs, driven by surface energy reduction in surface-dominated structures. Such graphitization process was investigated in details for cubic sodium chloride thin slabs. Figures

Graphene | 149

MoS2 decoration study. Origin of strong binding and inertness Dmitry G. Kvashnin1, Gotthard Seifert2, Leonid A. Chernozatonskii1 1

Emanuel Institute of Biochemical Physics RAS, 119334, 4 Kosigina st., Moscow, Russia 2 Technische Universit채t Dresden, 01069 Dresden, Germany dgkvashnin@gmail.com

Nowadays the some of the most developing areas of investigations of two dimensional materials are the investigations of graphene and MoS2. Graphene is semimetall with zero band gap displays amazing electronic, mechanical and optical properties. MoS2 belongs to the family of transition metal dichalcogenides with semiconductor bulk band gap about 1.6 eV depending of the thickness. Graphene and MoS2 have a complementary physical properties. So it is natural to investigate possible ways to combine these materials to create heterostructures. Set of numbers of the layers of various compounds allows to create heterostructures by combining the layers between each other. Only the drawback of obtained heterostructure is the weak van der Waals interaction between the layers. To improve a weak interaction an individual metal atoms could be adsorbed on the layers surface before the creation of the hererostructure. In this work detailed investigation of decoration process of MoS2 layer by Mo atoms was performed. Using DFT calculations adsorption barrier was calculated. It was found the string binding between the MoS2 layer and Mo adatoms which states about energy favorability of adsorption process. Further detailed investigation of the step by step decoration process and migration barrier of adatom on the MoS2 surface to understand the origin of strong binding with taking into account inertness nature of MoS2 layer was carried out. Electronic properties were also studied during the decoration process. This work was supported by the Russian Scientific Foundation (project no 14-12-01217). We are grateful to the 'Chebishev' and 'Lomonosov' supercomputers of Moscow State University and the Joint Supercomputer Center of the Russian Academy of Sciences for the possibility of using a cluster computer for our quantum-chemical calculations. D.G.K. also acknowledges the support from the Russian Ministry of Education and Science (No. 948 from 21 of November 2012).

150 | Graphene

Electronic Structure of Impurity Doped Graphene: An Inverse Modelling Approach

J. A. Lawlor, C. G. Rocha, M. S. Ferreira, Physics Department, Trinity College Dublin, Ireland.

Calculations of the electronic transport properties of nanoscale systems is necessary to understand their possible applications in nanoelectronics and future devices. While there exists a range of techniques for studying transport in regular crystalline materials, there are technical limitations that make most techniques impractical or even unable to model disorder in the material, the exception being the Tight Binding (TB) method. The reliability and accuracy of these TB calculations relies directly on finding a suitable description of the system (e.g. "hopping" energies, onsite potentials etc.). While several methods exist for doing this, they can be both time-consuming and difficult to fine-tune. We present a simple and general method for obtaining a TB description of any pristine or disordered nanoscale system using converged numerical quantities, such as formation energy and charge transfer. Although the method is independent of the system, we use graphene as a guinea pig for our method due not only to the mathematical simplicity of its TB model, but also as understanding the controlled doping of graphene to tailor its electronic properties is of great importance to the wider scientific community currently.

Graphene | 151

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152 | Graphene

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Synthesis for Graphene Dispersant via Reversible Addition-Fragmentation Chain Transfer Polymerization Hyang Moo Lee, Mi Ri Kim, and In Woo Cheong Department of Applied Chemistry, Kyungpook National University, Daegu 702-701, South Korea. inwoo@knu.ac.kr Abstract In this research, synthesis of graphene dispersant and dispersing graphene using synthesized dispersant will be presented. Block copolymers are prepared as a dispersant via reversible addition1 fragmentation chain transfer (RAFT) polymerization. Poly 2,2,2-trifluoroethyl methacrylate (PTFEMA) is used as a solvophilic block, and poly 4-vinyl pyridine (PVP) is used as a graphene-philic block. The resulted polymers are characterized using gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR), and the graphene dispersions are characterized using ultraviolet-visible spectroscopy (UV-Vis) and transmission electron microscopy (TEM). (Acknowledgement: This work was supported by the Ministry of Trade, Industry and Energy, Grant No. 10044338)

References [1] Daniel J. Keddie; Graeme Moad; Ezio Rizzardo; San H. Thang Macromolecules 45 (2012) 5321.

Figures

Time dependent photographic images of graphene dispersions.

Graphene | 153

Vertical Heterojunctions Based on Ferromagnetic Graphene and Ferroelectric Tunnel Barrier Seung Joo Lee1, Nojoon Myoung2, Hee Chul Park3 1

Quantum-functional Semiconductor Research Center, Dongguk University, Seoul 100-715, Republic of Korea 2 Department of Material Science and Engineering, University of Ioannina, Ioannina 45100, Greece 3 School of Computational Science, Korea Institute of Advanced Study, Seoul 130-722, Republic of Korea leesj@dongguk.edu

Abstract Numerous studies of graphene-based vertical heterostructure have been devoted to the electronic applications making use of the extraordinary properties of graphene. Such layered structures have been proposed as a prototype field-effect transistor by using vertical quantum tunneling.[1,2] Since the range of possible candidates is almost infinite in nature, there are many combinations of layered materials to create novel heterostructures. Here, we predict the emergence of giant resistance in a vertically stacked heterojunction based on ferromagnetic graphene (FMG) with spin-resolved band structures. [3] We investigate tunneling current characteristics through atomically thin insulating layer sandwiched by two FMGs. Owing to the spinresolved band structures of FMG, spin configuration of FMGs can be controlled by electric fields, and quantum tunneling through FMG heterojunctions can be suppressed by giant electroresistance in ferroelectric tunnel junctions. [4] References

[1] L. Britnell, et al. Science, 335, (2012) 947 [2] N. Myoung, K. Seo, S. J. Lee, and G. Ihm, ACS Nano, 7, (2013) 7021 [3] H. X. Yang, et al. Phys. Rev. Lett., 110, (2013) 046603 [4] M. Y. Zhuravlev, et al. Phys. Rev. Lett., 94, (2005) 246802 Figures

Fig. 1. Emergence of giant resistance in FMG/FEI heterojunctions. The blockade of quantum tunneling through the heterojunction originates from the anti-parallel configuration of FMGs.

154 | Graphene

Study o on Carbon Structural S Changes C in M Manganese Dioxide/Gra aphene com mposites pre epared by direc ct redox dep position Suk W Woo Lee1, Seong-Min S Bak B 2, Chang--Wook Lee3, Cherno Jaye e2, Daniel A. Fischer2, Xia ao-Qing 2 3 Yang g , Kyung-Wa an Nam and d Kwang-Bum m Kim1,* 1

Department of Mate erials Scienc ce and Engin neering, Yonsei University, Shinchon Dong, Seod daemun Gu, Seo oul 120-749, Korea 2 Chemisstry Departm ment, Brookha aven Nationa al Laboratory y Upton, NY 11973, Uniteed States 3 Departtment of Ene ergy and Materials Engine eering, Dong gguk University, Pil-dong 3-ga, Jung-g gu, Seoul, Korea ste eyn@yonsei.ac.kr ct Abstrac Structura al changes of o the carbon in a MnO2/re reduced grap phene oxide (RGO) hybridd materials prepared p by the diirect redox re eaction betw ween carbon a and permang ganate ions (MnO4-) weree explored to o reach better un nderstaning for f the effectts of carbon ccorrosion on carbon loss and its bondding nature during d the hybrid syynthesis. We e have demonstrated the changes in the t RGO stru ucture that ooccur during synthesis of MnO2//RGO hybrid ds by the dire ect redox dep position of MnO M 2 onto RG GO. Our resuults demonsttrate that the redox reaction be etween MnO O4- ions and R RGO gives rise not only to quantitativve carbon los ss but also ges in the ele ectronic struc cture of the ccarbon remaiining after the redox depoosition of Mn nO2. The to chang direct red dox depositio on of MnO2 onto o RGO, w which is a carrbon-destruc ctive approacch, leads to a substanttial carbon lo oss from the initial RGO sstructure, as evidenced in n our EA res ults. In addittion, C Kedge NE EXAFS resultts suggest th hat there is a an oxidized carbon enviro onment at thee interface within w the hybrids tthat results in n a localized electronic sttructure of th he RGO remaining in the R-MnO2/RG GO hybrid after the carbon loss during redox deposition of MnO2. Th herefore, disrruption of thee sp2 carbon bonding of the RG GO and stron ng Mn-O-C covalent c bon nding interacttions betwee en the MnO2 and RGO in the RMnO2/RG GO hybrids may m have a detrimental d e effect on the electrical pro operties of thhe hybrids. Electrochemical mea asurements of o the MnO2//reduced graphene oxide hybrid usingg a Cavity Micro u electrochemi e es mainly due e to the poorr electrical co onductivity Electrode revealed unfavorable cal propertie of the hyybrid. This study provides s a useful gu uide for a rational approac ch to synthessizing metal//RGO or metal oxxide/RGO hybrid materialls

Referen nces [1] Li, Q.. Wang, Z. L. Li, G. R. Gu uo, R. Ding, L. X. Tong, Y. Y X., Nano Lett., L 12 (20112) 3803. [2] Kim, S. H. Kim, S. S J. Oh, S. M., M Chem. Ma ater., 11 (199 99) 557. [3] Yu, G G. H. Hu, L. B. B Vosgueritchian, M. Wa ang, H. L. Xie, X. McDon nough, J. R; Cui, X. Cui, Y. Bao, Z. N., Nano o Lett., 11 (2002) 2905. [4] Choi, H. C. Shim, M. Bangsarruntip, S; Daii, H. J., J. Am m. Chem. So oc, 124 (20022) 9058. Figures

Fiig1. Normalized d NEXAFS spec ctra for R-MnO2//RGO hybrids with w various MnO O2 contents andd the RGO precu ursor

Graphene | 155

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156 | Graphene

Study of Cross-plane Electrical Conductivity of Graphene-based Heterostructure by Atomic Force Microscopy YingHan Liu, Chao-Kuang chen and Zhen-Yu Juang* Center for Micro/Nano Science and Technology in National Cheng Kung University, No.1, University Road, Tainan City 701, Taiwan Department of Mechanical Engineering in National Cheng Kung University, No.1, University Road, Tainan City 701, Taiwan yinghan@mail.ncku.edu.tw; z.y.juang@gmail.com Abstract Designing thermoelectric (TE) structures by 2D-materials has been discussed for a long time. The graphene-based cross-plane thermoelectric (XPTE) heterostructures have great potential to achieve high figure of merit ZT due to its low cross-plane (XP) thermal conductivity. However, the cross-plane electricity hasnâ&#x20AC;&#x2122;t been investigated so far, which is crucial for designing a new potential TE heterostructure. Herein, we experimentally demonstrate the XP current distribution of graphene/C60cluster heterostructure by conducting AFM technology (Bruker Dimension ICON, PeakForce TUNA). The results show that the current tends to distribute around graphene/C60-cluster instead of blank area of graphene at low DC sample bias. After increasing applied voltage, the current tends to concentrate on graphene wrinkles rather than graphene/C60-cluster positions. These facts reveal that the XP electrical conductivity could be enhanced by the usage of intercalated C60 clusters and hence improve the XPTE properties. References [1] Authors, Journal, Issue (Year) page.

Figures

Graphene | 157

Robust optical absorption of graphene-polymer heterostructures for GHz electromagnetic radiation versus defects MichaĂŤl Lobet, Luc Henrard, Philippe Lambin University of Namur, Rue de Bruxelles 61, 5000 Namur, Belgium michael.lobet@unamur.be Abstract Graphene-PMMA heterostructures present good shielding efficiency against GHz electromagnetic radiations [1]. Theory and experiments demonstrate that there exist an optimum number of seven graphene sheets separated by thin polymer spacers to obtain maximal absorption. This is explained by an arithmetic addition of graphene sheet conductivies for small number of layers. In the present work, reflectivity, transmittance and absorbance of multilayered material are obtained using Rigorous Coupled Wave Analysis (RCWA) and compared to experimental measurements realized in the Ka band. When the material properties are no longer uniform in the directions parallel to the surface, absorption properties may be affected. For instance, the graphene layers produced by CVD present microscopic holes or microscopic dots (embryos of a second layer). Numerical calculations show that the absorption of the optimum graphene/PMMA sandwich is robust in the sense that it does not depend strongly on graphene defects to first order in concentration (Figure 1). This property is not true when the number of layers deviates from the optimum value N=7. We also demonstrate that grain boundaries in graphene do not compromise the good shielding efficiency of the proposed absorption device. This research was supported by a Marie Curie International Research Staff Exchange Scheme Fellowship within the 7th European Community Framework Programme (MC-IRSES proposal 318617 FAEMCAR project). It has also received funding from the European Union Seventh Framework Programme under grant agreement No 604391 Graphene Flagship.

References [1] K. Batrakov, P. Kuzhir, S. Maksimenko, A. Paddubskaya, S. Voronovich, Ph Lambin, T. Kaplas & Yu Svirko, Scientific Reports, 4 (2014) 7191.

Figures

Figure 1: Reflexion, transmission and absorption properties of graphene-PMMA heterostructures (N = 7 layers) versus filling fraction of random holes that may be present in graphene sheets.

158 | Graphene

n-type doping of MoS2 with polyvinyl alcohol César J. Lockhart de la Rosa1,2, Amirhasan Nourbakhsh1,2, Inge Asselberghs1,2, Cedric Huyghebaert1, Iuliana Radu1, Stefan De Gendt1,2, and Marc Heyns1,2 1 imec, 2KULeuven,

Kapeldreef 75, Leuven, Belgium Celestijnenlaan 200, B-3001 Leuven, Belgium Email: lockhart@imec.be

Abstract Molybdenum disulfide (MoS2) is one of the main member of the semiconducting transition metal dichalcogenides family with promising potential applications in optoelectronics. However MoS2 devices such as field effect transistors (FETs) have high sheet resistance (RSH) and high metal-to-MoS2 contact resistance (RC) limiting the device performance. One of the most effective techniques to reduce RSH and RC is doping the MoS2 thin films. Substitution doping of MoS2 with different atoms has been reported by several research groups [1-3]. However since this mechanism relies on covalent modification of MoS2 it introduces severe structural defects. Alternatively, efficient doping of MoS2 can be achieved by charge transfer from physisorbed species to MoS2 [4-5]. This work reports on a reversible doping method to achieve highly stable n-type MoS2, in which polyvinyl alcohol (PVA) serves as a non-covalent electron dopant layer. The chemically stable n-type characteristics of the PVA-doped-MoS2 FETs were evaluated by electrical characterization. RC and RSH were extracted using the transfer length method (TLM) and four-point-probe (4PP) method, respectively. Figure 1 shows optical micrographs of 4pp and TLM back gated MoS2-FETs with average thickness of about 5 nm. Thin films of PVA were obtained by spin coating from an aqueous solution onto the devices. The doping density of the MoS2 FETs was controlled by changing the PVA concentration. Upon PVA coating, the ON current (ION) increases by a factor of 2 (figure 2-a) which can be further improved by a factor of 6 by dehydrating the PVA film. The ION improvement is due to the increase in the 2D carrier concentration (N2D) resulting in a 30% reduction of RC (figure 2-b). Moreover, a mobility increase from 20 to 422 cm2V-1s-1 was observed (figure 2-c) after dehydration which can be attributed to charge impurity screening by PVA. The mobility boosting together with the increase of N2D reduced the RSH by more than one order of magnitude of its original value. After removal of the PVA film, all the parameters recovered to the pre-doping values indicating the reversibility of this doping process. In conclusion, we have shown a strong n-type doping of MoS2 FETs using PVA as dopant source. The significant improvement of device performance in ION and mobility is mainly attributed to the reduction of RSH and RC due to the strong doping from PVA coating. References [1] K. Dolui et al, Physical Review B, 88 (2013) 075420. [2] M. Chen et al, Applied Physic Letters, 103 (2013) 142110. [3] L. Yang et al, VLSI, T250 (2014). [4] Y. Du et al, IEEE Electron Devices Letters, 10 (2013) 1328. [5] D. Kiriya et al, J. Am. Chem. Soc. 113 (2014), 7853.

5µm

Figure 1: 4PP structure (right) and TLM structure (left).

Figures

Figure 2: a) Transfer characteristics of the device, b) Contact resistance, c) Field-effect mobility

Graphene | 159

Graphene synthesis on insulating substrates via Ni-assisted CVD M. Lukosius, A. Wolff, T. Schroeder, and G. Lupina IHP,Im Technologiepark 25, 15236 Frankfurt (Oder), Germany lukosius@ihp-microelectronics.com Abstract Recent years brought significant progress in the area of graphene synthesis. However, despite the immense research efforts, a direct method for the depositions of high quality graphene on arbitrary substrates (insulators or semiconductors) is still not available (except for graphene transfer). Although transfer of graphene may be a viable option in prototyping and even some commercial applications, in microelectronic manufacturing of novel graphene based devices, a direct, clean, and simple growth on arbitrary semiconducting and insulating substrates would be ideal. In addition, such a growth method should be also scalable and compatible with the mainstream Si technology manufacturing requirements. The growth of graphene on Ni has been already investigated by several groups so far, where graphene films were synthesized via chemical vapor and solid deposition methods at elevated temperatures (~1000 °C) [1-3]. In these cases, graphene growth occurred on top of the Ni, underneath the Ni and between the Ni dots. These approaches show the potential of Ni as a mediator for graphene synthesis, and are very promising, however, there also some drawbacks, like the inhomogeneous coverage and number of layers and defects in graphene. In the present work, we examined the possibility to develop Si-technology compatible, transfer-free, Ni-mediated graphene synthesis method, since new approaches for the fabrication of graphene-based nanostructures with high quality graphene and tailored interfaces are of the highest importance. The depositions were performed at the temperature of 800 ± 1000 °C, using C2H4 reactive gas as the source of carbon and Ar as a carrier gas. The typical pressures of 0.1 mbar were maintained during the deposition process. 50 nm Ni structures were evaporated at room temperature on Si wafers, covered with 100 nm thermally grown SiO2. The samples were annealed in the H2 atmosphere at 800 °C in order to crystallize Ni, followed by the exposure to C2H4 atmosphere for 20 minutes Two types of graphene synthesis (underneath and between the Ni structures) routes have been investigated in this study. The first results of the attempts to grow uniform layers of graphene underneath the Ni structures are presented in Fig. 1. The experiments revealed that the graphene successfully grew on the Ni bars as well as underneath the Ni, on the insulating SiO2 layers, as it was found by Raman spectroscopy (Fig. 3 c), after etching away the top graphene layer and the Ni film. In addition, an alternative route of growing graphene between Ni on the SiO2 will be also presented in this work. References [1] A. Reina et. al., Nano Res. 2, (2009) 509. [2] J. Kwak et. al., Nature Com. 3, (2012) 1. [3] P. J. Wessely et. al., Adv. Sci. Technol. 77 (2013)258. Figures

Fig. 1. SEM (a), optical microscope after Ni etch (b) and Raman mapping of the 2D intensity (c) images of the graphene, on structured Ni on SiO2/Si wafers.

160 | Graphene

Grain Boundaries in CVD-Grown Monolayer Transition Metal Dichalcogenides 1,2

Thuc Hue Ly , and Young Hee Lee

1,2,3

IBS Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon 440-746. Korea 2 Department of Energy Science, Sungkyunkwan University, Suwon 440-746. Korea 3 Department of Physics, Sungkyunkwan University, Suwon 440-746. Korea thuchue@skku.edu Abstract Two-dimensional monolayer transition metal dichalcogenides (TMdCs), driven by graphene science, revisit optical and electronic properties, which are markedly different from bulk characteristics. These properties are easily modified due to accessibility of all the atoms viable to ambient gases, and therefore there is no guarantee that impurities and defects such as vacancies, grain boundaries, and wrinkles behave as those of ideal bulk. On the other hand, this could be advantageous in engineering such defects. Here, we report a method of observing grain boundary distribution of monolayer TMdCs by a selective oxidation. This was implemented by exposing directly the TMdC layer grown on sapphire without transfer to ultraviolet light irradiation under moisture-rich conditions. The generated oxygen and hydroxyl radicals selectively functionalized defective grain boundaries in TMdCs to provoke morphological changes at the boundary, where the grain boundary distribution was observed by atomic force microscopy and scanning electron microscopy. This paves the way towards the investigation of transport properties engineered by defects and grain boundaries.

References [1] Duong, D. L. et al. Probing graphene grain boundaries with optical microscopy. Nature 490 (2012), 235±239. [2] Huang, J.-K. et al. Large-Area Synthesis of Highly Crystalline WSe2 Monolayers and Device Applications. ACS Nano 8 (2014), 923±930. [3] Ly, T. H. et al. Observing Grain Boundaries in CVD-Grown Monolayer Transition Metal Dichalcogenides. ACS Nano 8 (2014), 11401±11408.

Figures

(a) Schematic of the ultraviolet irradiation process. (b,c) SEM and AFM image of oxidized WSe 2. (d,e) SEM and AFM image of oxidized MoS2.

Graphene | 161

Etching-free transfer of wafer-scale MoS2 films Donglin Ma, Yanfeng Zhang*, Zhongfan Liu* Center for Nanochemistry (CNC), Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and 0ROHFXODU (QJLQHHULQJ 3HNLQJ 8QLYHUVLW\ %HLMLQJ 3HRSOHÂśV 5HSXEOLF RI &KLQD madl-cnc@pku.edu.cn Abstract Two dimensional MX2 (MoS2, WS2, etc.) materials have sparked wide interest in both basic and applied researches, such as optoelectronics, valleytronics, and hydrogen evolution reactions, etc. To realize the usage of MX2 in real applications, transfer of as-grown materials from the commonly used insulating substrates onto target substrates is an essential step. However, traditional wet chemical etching method cannot avoid the use of substrate etchants such as HF, which usually cause the degradation of film quality, the destruction and waste of substrates, as well as potentially environmental issues. Herein, we develop an etching-free transfer method for transferring wafer-scale MoS2 films onto arbitrary substrates by using ultrasonication. Briefly, the collapse of ultrasonication-generated microbubbles at the interface between polymer-coated MoS2 film and substrates induce sufficient force to delaminate the MoS2 films. Using this method the MoS2 films can be transferred from all the substrates (silica, mica, strontium titanate, sapphire) and remains the original sample morphology and quality. This method guarantees a simple transfer process, allows the reuse of growth substrates, without the presence of any hazardous etchants. The etching-free transfer method may promote the broad applications of MoS2 in electronics, optoelectronics and catalysis. References [1] Donglin Ma, Yanfeng Zhang, Zhongfan Liu, Arxiv:1501.00786. [2] Libo Gao, Kian Ping Loh, Nature, 505 (2014) 190-194. [3] Libo Gao, Huiming Chen, Nat. Commun. 3 (2012) 699. Figures

162 | Graphene

Strategies of Graphene Quantum Dots synthesis and application of quantum dots/graphene nanoribbons hybrid materials as electrochemical sensors Mª Teresa Martínez, Lidia Martínez, Javier Hernández-Ferrer Instituto de Carboquímica ICB-CSIC, Miguel Luesma Castán, 4, 50018 Zaragoza, Spain. mtmartinez@icb.csic.es Abstract Graphene quantum dots, GQDs, have been synthesized using two strategies: electrochemical (E) and wet chemical (W) methods. A simple, industrially up-scalable, two-electrode electrochemical setup, starting from graphite and a one-pot wet chemical synthesis, modified from reference [1] were used to produce GQDs. Filtration, centrifugation, concentration and dialysis were used to purify the obtained products. All GQDs were subsequently submitted to a hydrothermal (HT) process. Photoluminescence properties improved by HT, quantum yield percentage was the best for W-HT-GQDs (8.54%) followed by the E-GQDs, whose photo luminescent properties did not change by HT treatment (~1%). XPS and elemental analysis showed higher number of heteroatoms different from C and O (N, S, Mn) for WGQDs than for E-GQDs. Figure 1 shows the fluorescence spectra of samples before and after HT treatment and AFM image of sample E-GQD after ultrafiltration through a 20KD membrane. A preliminary electrochemical characterization of their applications as electrochemical sensors in combination with graphene nanoribbons, GNRs, showed that GQDs/GNR hybrid materials offered better current for ascorbic acid oxidation than GNRs alone. These hybrids nanomaterials reduced the capacitive current, thus decreasing the noise/signal ratio, allowing simultaneous detection of dopamine and uric acid, and so improving the intrinsically good properties of GNRs as electrochemical sensors [2]. 1/1 E-GQDs/GNR hybrid showed the best properties in this application.. References [1] Y. Sun, S. Wang, C. Li, P. Luo, L. Tao, Y. Wei, G. Shi, Physical Chemistry Chemical Physics 15 (2013) 9907. [2] A. Martin, J. Hernandez, L. Vazquez, M.T. Martinez, A. Escarpa, RSC Advances 4 (2014) 132.

70000

W-GQDs W-HT-GQDs E-GQDs E-HT-GQDs

60000

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50000

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40000 30000 20000 10000 0 300

350

400

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500

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650

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Figure 1.- Left, fluorescence spectra of the samples before and after hydrothermal process, right AFM image of sample E-GQD

Graphene | 163

Production of Nanostructured Carbon Materials and Hydrogen by Microwave Plasma at Atmospheric Pressure Rocío Rincóna, Cristóbal Meleroa, Margarita Jiméneza, José Muñoza and María Dolores Calzadaa,b. a Laboratorio

de Innovación en Plasmas, Edificio Einstein (C2), Campus de Rabanales, Universidad de Córdoba, 14071 b Plasmas Advances S.L Parque Científico-Tecnológico Rabanales 21, C/ Astrónoma Cecilia Payné Aldebarán Mod 4.7 fa2mejic@uco.es

During the last decade, arc discharge [1], laser ablation [2], chemical vapor deposition [3], plasmaenhanced CVD [4] and thermal decomposition on SiC techniques have widely been used for the synthesis of both graphene and CNTs. However, the techniques above mentioned require the use of harsh conditions and metals as substrates, thus increasing the production costs. In the present research, we would like to present a free-substrate synthesis of both nanostructured carbon materials and molecular hydrogen by surface microwave plasma at atmospheric pressure using alcohols as carbon and hydrogen sources. The system designed by our group is shown in Figure 1.With this new patent-protected technique neither other supplementary chemical process nor metallic catalyst are needed. The technique reported here, allow us to obtain two products with high added value. Hydrogen production was identified and quantified connecting a mass spectrometer to the gas exhaust stream coming from ethanol pyrolysis. High Resolution Transmission Electron Microscopy (HRTEM) and Raman Spectroscopy were used to characterize the carbon material obtained. Optical Emission Spectroscopy (OES) was used for on-line control of the radical formation processes from the alcohols decomposition into the plasma. Plasma emission spectrum showed the formation of C and C2 species which are considered as the precursors for formation of nanostructured carbon materials [5]. References [1] S. Iijima, T. Ichihashi, 363 (1993) 603. [2] A. Thess, R. Lee, P. Nikolaev, H. Dai, P. Petit, J. Robert, C. Xu, Y.H. Lee, S. G. Kim, D. T. Colbert, G. Scuseria, D. Tomanek, J.E. Fisher, R. E. Smalley, Science 273 (1996) 483. [3] A. Fonseca, K. Hernadi, P. Piedigrosso, J. F. Colomer, K. Mukhopadhyay, R. Doome, S. Lazarescu, L. P. Biro, Ph. Lambin, P.A. Thiry, D. Bernaerts, J.B. Nagy, Appl. Phys. A 67 (1998) 11. [4] T. Yamada, J. Kim, M. Ishihara, M. Hasegawa, J. Phys. D: Appl. Phys. 46 (2013) 63001 [5] M. Heintze, M. Magureann and M. Kettlitz, J. Appl. Phys. 92 (2002) 7022.

Monochomator

Gas mass flow controller MW power

Optic fiber Gaseous products

CEM Plasma SURFATRON

Ethanol

Liquid mass flow controller

Nanostructurated Materials Quartz tube

Figure 1. Experimental setup.

164 | Graphene

Filter

Determination of Shear Modulus and Out of Plane Young's Modulus of Layered Materials by Raman spectroscopy 1

S. Milana , D. Yoon , M. IjĂ¤s , W. P. Han , P. H. Tan , N. M. Pugno , T. Bjorkman , A. 4, 5 1 Krashenninnikov , A. C. Ferrari 1

Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China 3 Department of Structural Engineering and Geotechnics, Politecnico di Torino, 10129 Torino, Italy 4 COMP/Department of Applied Physics, Aalto University School of Science, Aalto, Finland 5 Department of Physics, University of Helsinki, P.O. Box 43, 00014 Helsinki, Finland

Contact: sm874@cam.ac.uk Abstract The set of elastic constants of a material describes its response to applied external forces [1]. The elastic constants relate such external forces, described by the stress tensor, to the resulting deformation, described by the strain tensor, and an in-depth knowledge of them is essential to gain insight on the nature of crystal structure and bonding forces [1]. In crystals with uniaxial hexagonal layered structure, the elasticity matrix describing mechanical properties contains five non-vanishing, independent terms: C11, C12, C13, C33, and C44 [1]. C44 represents the shear modulus of the layer-layer interface, accounting for displacement of the planes with respect to each other [1]. C33 determines the <RXQJÂśV PRGXOXV LQ WKH QRUPDO GLUHFWLRQ WKXV GHVFULELQg the out-of-plane compression or expansion of the layers [1]. Raman spectroscopy is the prime non-destructive characterization tool for graphene and related layered materials (LMs) [2]. The shear (C) [3] and layer breathing modes (LBMs) [4, 5, 6] are due to relative motions of the planes, either perpendicular or parallel to their normal. It is therefore possible to associate these Raman modes to their respective elastic constants accounting for such displacements. Here we consider three examples of LMs, namely NLG, NL-MoS2 and NL-hBN (N being the number of layers), which can be regarded as representative metallic, semiconducting and insulating templates, respectively. Similarly to the C mode of NLG and NL-hBN, the first-order C and LBMs of MoS2 are directly accessible at room temperature, whereas we gain insight on the LBM dynamics in NLG by measuring its combinations with the D' peak. We find that the positions of the observed C and LBMs in these materials depend strongly on N. A general linear-chain model, based on an interlayer force constant per unit area, can account for the observed trends, allowing a direct evaluation of C 44 and C33, with applicability to any layered materials. For NLG we find C44 ~4.3 GPa and C33 ~37GPa. The C44 and C33 of NL- MoS2 are found to be ~18.9 GPa and ~59.6 GPa, respectively, whereas the C44 of NLhBN is ~6.5 GPa.

References [1] G. Grimvall, North-Holland (1986). [2] A. C. Ferrari, D. M. Basko, Nat. Nanotechnol., 8 (2013) 235. [3] P. H. Tan, W. P. Han, W. J. Zhao, Z. H. Wu, K. Chang, H. Wang, T. F. Wang, N. Bonini, N. Marzari, N. Pugno, G. Savini, A. Lombardo, A. C. Ferrari, Nat. Mater. 11 (2012) 294. [4] X. Zhang, W. P. Han, J. B. Wu, S. Milana, Y. Lu, Q. Q. Li, A. C. Ferrari, P. H. Tan, Phys. Rev. B, 87 (2013) 115413. [5] F. Bonaccorso, P.H. Tan, A.C. Ferrari, ACS Nano, 7(3) (2013) 1838. [6] F. Herziger, P. May, J. Maultzsch, Phys. Rev. B, 85 (2012) 235447.

Figures

Figure 1: Schematic illustration of the atomic structure, rigid-layer displacement for the C (horizontal red arrows) and LB (vertical blue arrows) motion of (a) 2LG, (b) 2L-hBN, (c) 2L-MoS2 and (d) reduced linear chain model for MoS2.

Graphene | 165

Analyzing Thickness Dependent Electronic Properties of MoS2 1

Ryan J. Wu , Jong Seok. Jeong , K. Andre Mkhoyan 1

Department of Chemical Engineering and Material Science University of Minnesota, Minneapolis, MN, USA wuxx0642@umn.edu

Abstract Transition metal dichalcogenides (TMDs) with formula MX 2, where M is a group 4-6 transition metal and X is a chalcogen, have captured immense research interest as a unique class of 2D materials with 1

favorable electronic and optical properties . One notable aspect of this material is its tunable properties 2

with thickness as demonstrated by optical techniques . This work analyzes the changes in the electronic structure and properties of MoS2 with thickness using the analytical scanning transmission electron microscope (STEM). Annular dark field Âą STEM (ADF-STEM) provided atomic resolution images which, in conjunction with multislice simulations, allowed complete verification of layer thickness (Figure 1). Furthermore, electron energy loss spectroscopy (EELS) was used to acquire electronic information from 1 to 3 layer thick MoS2 (Figure 2). With each additional layer, the spectrum showed changes in the band gap, bulk and surface plasmon excitations, and other low energy transitions indicating a change in 3

the electronic properties with thickness as theoretically predicted . References 1. Wang, Q.H. et al., Nature Nanotechnology, 11, (2012) 699-712 2. Mak, K.F. et al., Physical Review Letters, 13, (2010) 136805 3. Johari, P., Shenoy, V.B., ACS Nano, 7, (2011) 5903-5908

Figure 1: (Top) Filtered STEM image showing step change in thickness from 1-3 layers. (Bottom) Comparison of experimental and simulated ADF-STEM images at each thickness.

166 | Graphene

Figure 2: Low-Loss EELS spectrum of a 3 layer MoS2. Notable peaks are highlighted.

Low-temperature photoluminescence of 2D Dichalcogenides and indirect excitons in their heterostructures 1

P. Nagler , G. Plechinger , P. Tonndorf , S. Michaelis de Vasconcellos , R. Bratschitsch , C. Schüller 1 and T. Korn

Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg, Germany 2 Physikalisches Institut, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany philipp.nagler@ur.de

Abstract Two-dimensional transition-metal dichalcogenides (TMD) have recently emerged as a promising class of novel ultrathin semiconductors. Once thinned down to the monolayer level, many of them like MoS2 or WSe2 exhibit a direct band gap, which renders them especially suitable for future optical devices. Here, we present low-temperature photoluminescence (PL) measurements and temperature series of the four most prominent TMDs, namely MoS2, MoSe2, WS2 and WSe2 (see Fig. 1). At 4K the diselenides and WS2 show a clear splitting of neutral exciton and trion which enables us to deduce the binding energy of the trion for these materials, in good agreement to recent literature (~ 30meV) [1]. Owing to the two-dimensional nature of the material and the resulting confinement effects, the observed binding energies of the trions are an order of magnitude larger than in well-known GaAs quantum well structures. For most of the materials we also observe additional peaks at low temperature which we attribute to surface-bound states [2]. Additional insight is gained by power-dependent measurements at low temperatures. Thereby, we can influence the relative intensities of excitons and trions and observe saturation effects for certain materials. Temperature series on all four materials allow us to deduce the temperature-induced shift of the bandgap which lies in the region of 70-80meV. Additionally, by using a recently developed deterministic all-dry transfer technique [3] we are able to fabricate large area van-der-Waals heterostructures consisting of different 2D-TMDs (Fig. 2a). In PLscanning measurements at room temperature we observe the emergence of indirect excitons at the interface (Fig. 2b,c,d). These quasi-particles stem from a spatial separation of electrons and holes which is caused by the type-II alignment of the two semiconductors [4,5,6]. Excitation-density dependent PL measurements on the heterostructures allow us to alter the excitonic regime where we observe saturation effects of the indirect exciton, which probably result from longer recombination times compared to the direct transitions. Financial support by the DFG via GRK 1570, SFB689 and KO3612/1-1 is gratefully acknowledged.

References [1] J. S. Ross, S. Wu, H. Yu, N. J. Ghimire, A. M. Jones, G. Aivazian, J. Yan, D. G. Madrus, D. Xiao, W. Yao and X. Xu, Nature Commun. 4, 1474 (2013). [2] T. Korn, S. Heydrich, M. Hirmer, J. Schmutzler and C. Schüller, Appl. Phys. Lett. 99 ,102109 (2011). [3] A. Castellanos-Gomez, M. Buscema, R. Molenaar, V. Singh, L. Janssen, H. S. J. van der Zant, G. A. Steele, 2D Materials 1, 011002 (2014). [4] J. Kang, S. Tongay, J. Zhou, J. Li and J. Wu, Appl. Phys. Lett. 102, 012111 (2013). [5] K. KoĞminder and J. Fernández-Rossier, Phys. Rev. B 87, 075451 (2013). [6] H. Fang, C. Battaglia, C. Carraro, S. Nemsak, B. Ozdol, J. S. Kang, H. A. Bechtel, S. B. Desai, F. Kronast, A. A. Unal, G. Conti, C. Conlon, G. K. Palsson, M. C. Matrin, A. M. Minor, C. S.Fadley, E. Yablonovitch, R. Maboudian and A. Javey, Proc. Natl. Acad. Sci. USA, 111, 6198-6202 (2014).

Graphene | 167

Figures

Fig. 1: Low-temperature (4K) PL spectra of monolayer MoSe2, WSe2, MoS2 and WS2. The diselenides and WS2 show a splitting of neutral exciton (A) and the trion (T). All materials except MoSe 2 show surface-bound states (S) at low temperatures.

Fig. 2: (a) Two-dimensional heterostructure consisting of a WSe2 monolayer on a MoS2 monolayer. The white square marks the area of the PL scan. Within the yellow triangle we observe the indirect exciton (b) False color map of the PL intensity (c) False color map of the PL peak energy (d) Representative PL spectra of the three different regions. The emission of the indirect exciton is weak and red-shifted compared to the emission of the isolated monolayers.

168 | Graphene

Evidence of the formation of a single layer of graphene and hexagonal boron nitride on Pt(111) from a single molecular precursor a

a,b

Silvia Nappini , Igor Ptã ,Tevfik Onur Mentes , Alessandro Sala , Mattia Cattelan , Stefano Agnoli , b b Federica Bondino , Elena Magnano . a

IOM CNR laboratorio TASC, Area Science Park-Basovizza (Ts), Elettra - Sincrotrone Trieste S.C.p.A. c S.S. 14 Km 163,5 in AREA Science Park, IT-34149 Basovizza (Ts), Italy, Department of Chemical Sciences, University of Padua, I-35131 Padova, Italy nappini@iom.cnr.it

Hexagonal boron nitride (h-BN) and graphene (G) are honeycomb atomic monolayer materials with similar atomic structure (lattice parameter mismatch less than 1.7%). Graphene has gained a clear prominence among materials thanks to its superb carrier mobility, high transparency, excellent thermal conductivity, chemical inertness. Hexagonal BN shares many of these properties with G, but, differently from it, h-BN is an insulator with a wide bandgap. One of the most attractive goals is the possibility to merge these two materials in stacked layers or inplane hybrid heterostructures for the realization of 2D atomic-layer circuits, and novel spintronic devices 1±3 tailoring the semiconducting properties of graphene . Up to now, h-BN-G in-plane hybrid structures have been obtained using chemical vapour deposition 4 5 (CVD) starting from two or more precursors , plasma-assisted deposition , by mechanical transfer or 2 hydrogen etching of G layers or by a two step process consisting in the growth of h-BN on existing 1,3,6 graphene patches We propose a novel bottom-up approach to grow continuous hybrid hexagonal heterostructures combining h-BN and G in 2 dimensional (2D) sheets on single crystals in ultra-high-vacuum (UHV) environment using only one molecular precursor, dimethylamine borane (DMAB). This novel growth route allows an easy and controlled preparation of perfectly merging domains of G and h-BN of different size and relative concentration or hybridized B-C-N materials on the clean surface of a crystal in UHV just adjusting the substrate temperature. In particular, G-BN layer grown on Pt(111) at 1000 K was investigated by high resolution X-ray spectroscopy (XPS and NEXAFS), scanning tunneling microscopy (STM), low energy electron microscopy (LEEM) combined with electron energy loss spectroscopy (EELS) and micro-low energy electron diffraction (P-LEED). The measurements have shown the formation of a continuous hybrid layer of h-BN and graphene that fully covers the Pt(111) surface. The layer has revealed a complete inertness towards molecular oxygen -6 up to 10 mbar partial pressure in the temperature range 300 K-600 K. Our findings have demonstrated that the dehydrogenation of a simple molecular precursor, such as DMAB, is an efficient and easy method for obtaining a continuous h-BN and graphene atomically thin lateral heterostructure on a metal substrate, such as Pt(111). References 1. Sutter, P., et al, Nano Lett. 12, 4869±4874 (2012). 2. Rajasekaran, S., et al. Phys. Rev. B 85, 045419 (2012). 3. Liu, L. et al. Science 343, 163±167 (2014). 4. Ci, L. et al. Nat. Mater. 9, 430±435 (2010). 5. Yang, W. et al. Nat. Mater. 12, 792±797 (2013). 6. Levendorf, M. P. et al. Nature 488, 627±632 (2012).

Graphene | 169

Environmental remediation of oxidised graphene nanocarbons: 2D sheets degrade faster than 1D tubular-shaped structures *

ŕ˛Ť

Newman LDD*, Lozano N , Zhang M , Yudasaka M , Bussy C , Kostarelos K

Nanomedicine Lab, Faculty of Medical & Human Sciences & National Graphene Institute, University of Manchester, AV Hill Building, Manchester M13 9PT, United Kingdom ŕ˛Ť Nanotube Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8565 Japan leon.newman@postgrad.manchester.ac.uk; cyrill.bussy@manchester.ac.uk; kostas.kostarelos@manchester.ac.uk

Graphene nanocarbons are currently fuelling a revolution in science and technology in areas ranging from aerospace engineering to electronics [1]. Unlike their pristine forms, the oxidised derivatives of those nanostructures are water dispersible that allows their application to areas such as biology and medicine [2]. There is a need for efficient and viable means of degrading these engineered structures that is relevant to their potential biological uses but also for environmental purposes [2, 3]. The aim of the present study was to assess the potential of the widely used sodium hypochlorite, NaClO, (1% by chlorine content) to degrade oxidised graphene nanocarbons within a week. NaClO was found by a risk assessment report completed by the European Union (EEC 793/93) to be safe for the environment with regards to its standard usage which includes domestic sanitation as well as municipal water and waste disinfection. We compared the morphological changes that occur during degradation of graphene oxide to two other oxidised graphene nanocarbons, namely oxidised multiwalled carbon nanotubes and oxidised carbon nanohorns. Degradation was monitored closely using a battery of techniques including UV-Vis, Raman spectroscopy, transmission electron microscopy and atomic force microscopy. The results demonstrate that graphene oxide was degraded into a dominantly amorphous structure lacking the characteristic Raman signature and microscopic (TEM/AFM) morphology. Oxidised carbon nanotubes underwent degradation via a wall exfoliation 2 mechanism, yet maintained a large fraction of the sp carbon backbone, while the degradation rate of oxidised carbon nanohorns was observed at a somewhat intermediate rate to that for the other two types of nanostructures. References [1] Geim, A. K. & Novoselov, K. S., Nat Mater, 6 (2007) 183-91. [2] Kostarelos, K. & Novoselov, K. S., Science, 344 (2014) 261-263. [3] Lalwani, G., Xing, W. & Sitharaman, B., J Mater Chem B Mater Biol Med, 2 (2014) 6354 6362. Figures

Figure 1: Schematic representation of the inferred progressive decay of structural integrity of graphene oxide, oxidised multiwalled carbon nanotubes and oxidised carbon Nanohorns over time when incubated in NaClO 1%.

170 | Graphene

Hybrid grapheneÂąquantum dot phototransistors for IR-imaging applications Ivan Nikitskiy1, A.M. Goossens1, G. Navickaite1, J. J. Piqueras1, G. Konstantatos1 and F.H. L. Koppens1 1ICFO

Âą The Institute of Photonic Sciences, Av. Carl Friedrich Gauss 3, 08860 Castelldefels (Barcelona), Spain ivan.nikitskiy@icfo.es

Abstract Graphene is an appealing material for optoelectronics and photodetection applications. It has various extraordinary properties, including ultrahigh mobility at room temperature, which enables fast response times. Colloidal quantum dots exhibit unique optical properties of spectral tunability and high absorption coefficients. We combine the favourable electronic properties of graphene with the optical characteristics of colloidal quantum dots to realize a novel hybrid graphene-quantum dot photodetector for visible and short-wave infrared frequencies. [1] The unique electronic properties of graphene offer a gate-tunable carrier density and polarity that enable us to tune the sensitivity and operating speed of the detector. Here, we exploit this to maximize the photoconductive gain or to fully reduce it to zero, which is useful for pixelated imaging applications, while the implementation of nanoscale local gates enables a locally tunable photoresponse. We also demonstrate our novel approach to fully suppress dark currents in graphene-based photodetectors and increase operation speed of our devices. At the current state our single- and multipixel photodetectors can operate at 30, 60 and up to 90 frames-per-second. The resulting technology is extremely promising for visible and, more importantly, short-wave infrared (SWIR) imaging applications. Sensing and imaging in SWIR range lies at the heart of safety and security applications in civil and military surveillance, night vision applications, automotive vision systems for driver safety, food and pharmaceutical inspection and environmental monitoring. Operation of a prototype device sensitive to visible and IR light in the auditorium will be demonstrated during the talk. References [1] Gerasimos Konstantatos, Michela Badioli, Louis Gaudreau, Johann Osmond, Maria Bernechea, F. Pelayo Garcia de Arquer, Fabio Gatti and Frank H. L. Koppens, Nature Nanotechnology, 7 (2012) 363Âą 368.

Graphene | 171

Contaminations and Doping in Defected Graphene by Raman Spectroscopy A. K. Ott, M. Barbone, M.Bruna, M.K. Ijäs, D. Yoon, U. Sassi and A. C. Ferrari Cambridge Graphene Centre, Cambridge CB3 0FA, UK ako24@cam.ac.uk The determination and control of defects, doping and contaminations in graphene is crucial to optimize fabrication processes and device performance. Raman spectroscopy is a fast, nondestructive technique and ideal to characterize graphene as it can probe not only its electronic properties but also its structural properties [1-4]. We first consider the effect of doping and defects. We combine polymer-electrolyte top gating [3] and in-situ Hall effect measurements to investigate the doping dependence of D and D¶ IRU D IL[HG DPRXQW RI GHIHFWV > @ , ' , * DQG , '¶ , * ERWK decrease significantly for increasing doping, Fig 1a). We attribute this dependence to the additional effect of electron-electron scattering for increasing doping [5]. We also present a general equation that relates the D peak intensity with the amount of doping and defects for any Raman excitation energy[5]. We then investigate contaminations arising from the fabrication process of graphene based hetero-structures. Hexagonal boron nitride (h-BN) is considered an ideal substrate to optimize graphene's mobility [6-8], but this requires a clean graphene/BN interface. Contaminants are mainly trapped at the interface between graphene and h-BN. We use Raman spectroscopy to map these contaminants and identify them as tape residuals. Fig. 1b) plots a Raman map of the intensity ratio of a contaminant peak and the G peak of graphene. This relates to the atomic force microscopy (AFM) o scan in Fig. 1c). We monitor the Raman peaks after successive steps of thermal annealing at 350 C and we find that the contamination Raman signal progressively decreases along with the height of trapped contaminants as confirmed by AFM scans. A systematic Raman and AFM study reveals that the contamination peaks only occur when acetone is used as an additional cleaning step after exfoliation. AFM scans confirm that avoiding this step enables us to produce atomically flat interfaces. Figures

Figure 1: a) I(D)/I(G) in dependence on charge carrier concentration and Fermi level. b) Raman map showing -1 intensity ratio of polymer peak at 1530cm and G peak. c) Corresponding AFM image; scale bar is 2µm.

References [1] A. C. Ferrari and D. M. Basko. Nature Nanotech. 8, 325 (2013). [2] A. C. Ferrari et al., Phys. Rev. Lett. 97, 187401 (2006). [3] A. Das et al., Nature Nanotech. 3, 210 (2008). [4] L. G. Cancado et al., Nano Lett. 11, 3190 (2011). [5] M. Bruna et al., ACS Nano 8, 7432 (2014). [6] C. R. Dean et al., Nature Nanotech. 5, 722 (2010). [7] A. S. Mayorov et al., Nano Lett. 11, 2396 (2011). [8] L. Wang et al., Science 342, 614 (2013).

172 | Graphene

Graphene field-effect transistor with a solution-processed gate dielectrics and UV-ozone-treated graphene/metal electrodes Goon-Ho Park, Hirokazu Fukidome, Tetsuya Suemitsu, Taiichi Otsuji, and Maki Suemitsu Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan ghpark@riec.tohoku.ac.jp 2

Theoretically, graphene has extremely high mobilities around 200,000 cm /Vs, which is more than 100 times higher than that of silicon. Thus, graphene-based field-effect transistors (GFETs) have been intensively investigated in recent years aiming at replacing silicon-based MOSFETs. The scaling down strategy of Si-MOSFETs is expected to reach physical, technical, and cost limits in the near future. There are however several challenges remaining in GFETs that impede their development. Among them are the carrier mobility degradation by gate dielectrics and the high contact resistance between graphene and metal electrodes. These two factors severely screen the excellent properties of pristine graphene in GFETs. In this work, we propose a solution process to form a qualified gate dielectrics. This novel method, together with a UV-ozone treatment to realize lower metal/graphene contact resistance, brings about substantial betterment of GFET performance. A CVD graphene layer was transferred onto a Si substrate covered with a 90 nm-thick SiO2 layer. To define the source/drain region, image reversal photolithography was conducted using AZ5214E. After a UV-ozone treatment to remove the photoresist residue, Ni was e-beam evaporated to form contact electrodes. Gate formation consists of three steps. First, an Al ultrathin layer (2 nm) was directly deposited onto graphene by e-beam evaporation, which turns into an ultrathin Al2O3 natural oxide layer in the atmospheric ambient. This first layer can be omitted, but it suppresses the unwanted doping to graphene. Second, an Al2O3 precursor solution was spin-coated onto this substrate, which was exposed to an oxygen plasma at room temperature and annealed in air at 250ºC for 2 hours. Finally, gate electrode of Al (150 nm) was deposited by e-beam evaporation. Doping, strain, and defects in graphene have been evaluated by Raman scattering measurements. Figure 1 shows the drain current as a function of the gate voltage. The Dirac point, i.e., the minimum conductivity point, is rarely shifted within ~0.1V, indicating that the graphene underneath the gate dielectrics is almost in its charge neutral states. To evaluate the intrinsic carrier mobility ȝ and the contact resistance Rc of the GFET, the total resistance RT as a function of the gate voltage has been fitted with the following formula [1] (figure 2): ௅ . (1) ்ܴ = 2ܴ஼ + ௐ௘ఓට௡బమ ା௡మ

Here n0 is the residual carrier concentration, n is gate-induced carrier density, and L and W are the 11 -2 channel length and width, respectively. By this fitting, we extract values of n0 =2.2 × 10 cm , ȝ=8600 2 cm /Vs and Rc=900 ȍāum. These high ȝ and low Rc values are one of the best to the authors knowledge. To summarize, we have successfully developed GFETs with solution-processed gate dielectric and UV-ozone treated contacts. As we confirm very high mobility and low contact resistance in the devices, the present combination of solution-processed gate dielectrics and UV-ozone treated contacts is quite promising for realizing high performance graphene FETs. References [1] S. Kim, J. Nah, I. Jo, D. Shahrjerdi, L. Colombo, Z. Yao, E. Tutuc, and S. K. Banerjee Appl. Phys. Lett., 94 (2009) 062107.

Fig. 1 Drain current as a function of the gate voltage.

Fig. 2 Measured RT (open squares) versus VTG fitted with equation (1) (solid line).

Graphene | 173

Bottom-gate graphene field-effect transistors with enhanced reliability based on passivation layer Hamin Park, Ick-Joon Park, Young-Wook Ha and Sung-Yool Choi

Department of Electrical Engineering and Graphene Research Center, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea parkhamin@kaist.ac.kr sungyool.choi@kaist.ac.kr

Abstract The reliability of graphene field-effect transistors (GFETs) is one of important issues for practical applications and has been widely reported[1]-[2]. We measured and analyzed negative bias-stressinduced instability of GFETs to investigate the reliability of GFETs. Several factors influence the reliability of GFETs including defects and residues. We investigated the effect of passivation layer to bias stress effect of GFETs by analyzing time-dependent Dirac voltage shift of transfer curves under the gate bias stress. We used H2O-based ALD-grown aluminum oxide (Al2O3) for passivation layer. Passivation layer has a significant effect to GFETs according to previous report which described mobility enhancement and the suppression of p-type doping from ambient air[3]. On the other hand, we investigated the effect of passivation layer to negative bias-stress-induced instability. The instability result revealed that GFET without passivation layer showed larger Dirac voltage shift than GFET with Al2O3 passivation layer under the equal stress level. The origin of the difference is considered as the dynamic process of adsorption±desorption characteristic at the graphene surface without passivation. Adsorbed molecules can act as charged trapping sites which induce large Dirac voltage shift. Furthermore, fitting parameters including characteristic equilibrium time constant (Ĳ) and stretchedexponential exponent (ȕ) from stretched-exponential model showed the clear tendency as trap density decreased using passivation layer. References [1] Lee, Jung-Kyu, et al. Applied Physics Letters 98.19 (2011): 193504. [2] Liu, Zihong, et al. Nano letters 11.2 (2010): 523-528. [3] Zheng, Li, et al. Applied Physics Letters 104.2 (2014): 023112. Figures

Figure 1 ± Transfer curves in (a) stress phase and (b) recovery phase of graphene field-effect transistor with Al2O3 passivation layer.

174 | Graphene

Investigation of Graphene N-type Doping Effects for S/D Electrodes via Cs2CO3 Doping in Amorphous InGaZnO Thin-Film Transistors Ick-Joon Park1, Chang-Woo Song2, Young-Wook Ha1, Hamin Park1 and Sung-Yool Choi1 1

Department of Electrical Engineering and Graphene Research Center, KAIST, Daejeon 305-701, Korea

School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 156-756, Korea ijpark@kaist.ac.kr, sungyool.choi@kaist.ac.kr

Abstract In this work, we investigate the doping effect of single-layer graphene (SLG) used as S/D electrodes on the devices performance of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). Control of work functions of S/D electrodes are highly demanded to improve the contact characteristics between the channel and S/D electrodes. In the a-IGZO TFTs, S/D electrodes with relatively low WF are needed because a-IGZO is an n-channel material while a p-doping of graphene is an unintentional and natural result in a transfer process via wet chemicals [1-2]. On the other hand, n-doping of graphene requires additional materials using evaporation or wet chemical doping method. The fabricated a-IGZO TFTs with SLG S/D electrodes are dipped in the 50mM Cs2CO3 aqueous solution for 30 minutes to decrease the work function of graphene electrodes. A UV photoelectron spectroscopy (UPS) analysis exhibits that the work function of SLG decreases from 4.8 eV to 4.1 eV. In the comparison of the measured transfer curves, the threshold voltage (V Th) decreases from 4.4 V to 2.9 V and the extracted field-effect mobility (Č&#x203A;FE) increases from 7.1 cm2/V-s to 10 cm2/V-s with increase of the drain current(IDS) because of the improved ohmic contact between the a-IGZO layer and Cs2CO3 doped SLG S/D electrodes.

References [1] X. Li, et al., Nano Lett., 9.12 (2009). [2] J. W. Suk, et al., ACS Nano, 5.9 (2011).

Figure

Fig 1. Representative transfer curves of the fabricated a-IGZO TFT with Cs2CO3 doped and nondoped SLG S/D electrodes.

Graphene | 175

Substrate-enhanced photocurrent in graphene Romain Parret, Achim Woessner, Michela Badioli, Klaas-Jan Tielrooij, Sebastien Nanot, Gabriele Navickaite, Tobias Stauber, F. Javier GarcĂa de Abajo and Frank H. L. Koppens ICFO-The Institute of Photonic Sciences, Mediterranean Technology Park, Av. Carl Friedrich Gauss, 3, 08860 Castelldefels (Barcelona), Barcelona frank.koppens@icfo.eu

The mid-infrared frequency range is extremely interesting for both fundamental studies and a variety of applications. It is the fingerprint region of many molecules and the frequency range of choice for thermal imaging for defense or medical purposes. Graphene opens new avenues in the field of infrared photo-detection due to its broadband absorption, tunability of optical properties and its flexibility [1, 2]. Furthermore, it is the energy scale that corresponds to the mid-infrared frequencies gives access WR JUDSKHQHÂśV (tunable) Fermi energy, as well as graphene optical phonons and substrate phonons. This recently led to the observation of several interesting phenomena such as tunable plasmon excitations [3] and plasmon-phonon hybridization [4, 5]. However, the role of substrate phonons on graphene photoresponse is not fully understood. Here, we measure spatially resolved photoresponse on a very broad spectral range of -1 illumination (1000-1600 cm ). We clearly observe a difference in the amplitude and spatial extent of the signal generated by light on and off resonance with the SiO2 transverse optical (TO) phonon band: on resonance the generated photocurrent is both larger in intensity and broader regarding its spatial extension from the contacts. Furthermore we also observe electrically tunable graphene transmission and photocurrent. By controlling the polarization we can excite the surface optical phonon (SO) of the substrate, associated to a strong concentration of the optical fields, leading to a strong photoresponse. From these observations we conclude that graphene photocurrent generation in the mid-infrared originates from two processes. The first comes from light absorption in the substrate: substrate phonons absorb light and heat up carriers in the graphene, leading to a temperature gradient over the device that results in a photo-thermoelectric voltage [6]. The other mechanism is due to hot carrier generation via direct absorption in the graphene, and can be strongly enhanced via electric field localization. Our results open new avenues for using graphene in compact and cheap room-temperature operating mid-infrared sensors.

[1] F. Bonaccorso et al., Nature Photonics 4,611-622 (2010) [2] T. Low and P. Avouris, ACS Nano 8, 1086-1101 ( 2014) [3] J. Chen et al. , Nature 487, 77-81 (2012) [4] V. W. Brar et al., Nano Letters 13, 2541-2547 (2013) [5] H. Yan et al., Nature Photonics 7, 394-399 (2013) [6] P. K. Herring et al., Nano Letters 14, 901-907 (2014)

176 | Graphene

Decomposing strain and doping in graphene J. Parthenios, C.Galiotis and K. Papagelis 1

Foundation of Research and Technology Hellas, Institute of Chemical Engineering and High Temperature Processes, P.O. Box 1414, GR-26504 Patras (Greece) 2 Department of Materials Science, University of Patras, GR-26504 Patras (Greece) 3 Department of Chemical Engineering, University of Patras (Greece) jparthen@iceht.forth.gr Abstract Following its first isolation in 2004, graphene has shown huge potential in both fundamental studies and industrial applications. Vast research efforts have revealed a great deal of the unique electronic, optical and mechanical properties of graphene. Typically, graphene is tested and characterized on graphene-coated substrates. These are made by either mechanically exfoliated of graphite crystals onto various substrates or synthesizing graphene in a furnace using chemical vapour deposition (CVD) on a copper foil, which acts as a catalyst, and then transferring the as- prepared graphene sheet to the target substrate using wet chemistry. Normally, biaxial strain and unintentional doping is imposed to the transferred graphene flake due to the substrate interaction, various adsorbents, and resist/process residuals. Raman spectroscopy has proven to be a versatile analytical tool in graphene metrology for measuring thickness, stacking, defect density, charge density, mechanical strain, temperature, etc. Such sensing functionality, however, turns into difficulty when more than a single parameter has to be determined [1]. For instance, upon uniaxial strain both G and 2D bands frequencies decrease [2,3]. On the other hand, G band frequency increases for either p or n doped graphene due to the modification of phonon dispersion close to the Kohn anomaly. On the contrary, for p doped graphene the 2D band upshifts in an almost linear fashion, while for n-doped is highly nonlinear. In this work, a methodology based on the correlation of Pos(2D) vs Pos(G) for decomposing strain and unintentional doping in supported single layer graphene is presented. It is found that for pure mechanically loaded and undoped single layer graphene the slope in the Pos(2D) ± Pos(G) correlation diagram is 2.2-2.5 independent of the substrate and the origin of the stress field (Fig. 1). It is, finally shown, that the methodology can be successfully applied even in supported graphene under uniaxial loading and strains higher than 0.2%, where G band splits. References [1] Lee J. E. et al., Nat Commun, 3, (2012) 1024 [2] Frank O., et al., Nat Commun, 2 (2011) 255 [3] Das A, et al, Nature Nanotech., 3, (2008) 210 [4] Filintoglou K., et al. Phys. Rev. B, 88 045418 (2013) Acknowledgements 7KLV UHVHDUFK LV SDUW RI WKH SURMHFW ³ '1DQR0HFKDQLFV´ ILQDQFHG E\ WKH *657 RI WKH 0LQLVWU\ RI Education and Religious Affairs in the frame of Greece - Israel Call for Joint R&D. 2620 2615

-1

Pos(2D) (cm )

2610

sample 1 slope = 2.51

sample 2 slope = 2.7

Diamond Anvil Cell Raman Laser

2605 2600 2595 2590 1580 1582 1584 1586 1588 1590 1592 1594 1596 1598 1600 -1

Pos(G) (cm )

Fig. 1 Pos(2D) vs Pos(G) for single layer graphene under (a) uniaxial compression and (b) hydrostatic pressure[4]

Graphene | 177

Capacitance compact modelling of four-terminal graphene FETs preserving charge conservation: A circuit-oriented device model benchmark 1,*

2,†

Francisco Pasadas , David Jiménez , Mario Iannazzo

and Eduard Alarcón

Department d’Enginyeria Electrònica, Escola d’Enginyeria, Universitat Autònoma de Barcelona, Campus UAB 08193 Bellaterra, Spain. 2 Department of Electronics Engineering, UPC BarcelonaTech, Campus Diagonal Nord, Building C4, 08034, Barcelona, Spain. *

francisco.pasadas@uab.cat, †mario.iannazzo@upc.edu

Abstract Experimental research into GFETs has rapidly increased in the past few years, mainly because of the potentially achievable extremely high-speed performance. However, there has been little exploration on the physical behavior of these devices under dynamic conditions. Previous examinations [1-2] have either been incomplete or have applied conventional (silicon based), and therefore inappropriate, assumptions regarding device behavior to the analysis. Such models, when applied to GFETs, may incorrectly interpret and predict the frequency performance of these devices. Most circuits operate under time-varying terminal voltage excitation of the constituting devices. The dynamic operation is affected by the capacitive effects of the device, rendering indeed essential for eventual circuit design to derive reliable compact models encompassing such capacitive effects. The most common approach to silicon-device capacitive modeling is the Meyer model, which is based upon non conservation of the charge and assumes the intrinsic capacitances as 2-terminal lumped capacitances [3]. Although it exhibits problems with some circuits (e.g. DRAMs and switched capacitor filters) this compact model is widely used because of its simplicity and fast computation. Most of the GFET compact models hitherto found in the literature are directly based upon such Meyer model. The question arises on whether Meyer capacitance model is also suitable for GFETs. In this framework, a compact capacitance-model for double-gate four-terminal GFETs derived from the Ward-Dutton’s linear charge partition scheme, which preserves the charge conservation, has been recently developed [4]. The model has been built from a field-effect model and drift-diffusion carrier transport. Using this novel model as a basis, explicit closed-form expressions for the 9 independent capacitances (16 capacitances in total: 4 self-capacitances and 12 intrinsic capacitances) are presented in this paper covering continuously all the operation regions (see Fig. 1, as an illustrative example). Additionally, they have been implemented in Verilog-A, a language suited to circuit simulators. To assess the impact of the new charge-conservation capacitive model of GFETs upon circuit performance, this capacitance-model [4] is benchmarked at the circuit level against an alternative Meyer-based capacitance-model [5] and the correspondent conclusions are drawn. References [1] Champlain JG, Solid-State Electronics, 67 (2012) 53-62. [2] Rakheja S, Wu Y, Wang S, Member S, and Avouris P, IEEE Tran. Nanot., 13(5) (2014) 1005-1013. [3] Arora N, MOSFET modeling for VLSI simulation, World Scientific Publishing (2007), 325-340. [4] Jiménez D, IEEE Tran. Elect. Dev., 58(12) (2011) 4377-4383. [5] Fregonese S, Magallo M, Maneux C, Happy H, Zimmer T, IEEE Tran. Nanot., 12(4) (2013) 539-546. [6] Meric I, Dean C and Young A, Int. Elect. Dev. Meeting (2010), pp. 23.2.1 – 23.2.4. Figures

FIG. 1.- GFET capacitances versus the gate bias for the device considered in Ref. [6] under Vds = 5V. Notice that capacitances Cgb, Cdb, Csb, Cbg, Cbd, Cbs, Cbb are almost negligible because the bottom oxide thickness is much larger than the top oxide. This work is supported by Ministerio de Economía y Competitividad (project TEC2012-31330) and the European Union (No. 604391, 7th FP Graphene Flagship).

178 | Graphene

Graphene double functionalization with xanthates and peroxides Florence Pennetreau, Olivier Riant, Sophie Hermans UniversitĂŠ catholique de Louvain, Place L. Pasteur, 1, Louvain-la-Neuve, Belgium florence.pennetreau@uclouvain.be Abstract

Carbon nanotubes and graphene have emerged as promising nanocarbon (nC) materials in various fields. However in order to benefit from their full potential, a functionalization step is usually required. For this reason, different covalent and non-covalent derivatization methods have been developed in the last few years. In this context, we have found a new functionalization method that consists in the grafting of xanthates at nanocarbon surfaces. This covalent grafting strategy implies the use of a peroxide as radical initiator and leads to the formation of new C-C and C-S bonds (Figure 1) [1,2] . The presence of xanthates at carbon nanotubes and reduced graphene oxide (rGO) surfaces has been highlighted by X-ray photoelectron spectroscopy, bulk elemental analysis and secondary ion 2 mass spectrometry. The covalent nature of the bond between the nanocarbon sp skeleton and the organic fragments has been shown by Raman spectroscopy and thermogravimetric analysis. After covalent anchoring, grafted fragments have been post-functionalized. Sulphured fragments were reduced in thiols as nucleation sites for gold or platinum species to prepare [3] 1 nanocarbon-supported nanoparticles . Moreover, different R fragments such as activated esters and phtalimides have been grafted and post-functionalized to create amide bonds with diverse organic ligands to immobilize homogeneous catalysts. Finally, experiments implying heteroatom-containing peroxides have been performed. These have highlighted the grafting of the peroxide at the nC surface along with the xanthate. The method proposed here is therefore an easy way to obtain doubly functionalized nC in one single step.

References [1] B. Vanhorenbeke, C. Vriamont, F. Pennetreau, M. Devillers, O. Riant, S. Hermans, Chem. Eur. J., 19 (2013) 852. [2] F. Pennetreau, O. Riant, S. Hermans, Chem. Eur. J, 20 (2014) 15009. [3] D. Marquardt, F. Beckert, F. Pennetreau, F. TĂślle, R. MĂźlhaupt, O. Riant, S. Hermans, J. Barthel, C. Janiak, Carbon, 66 (2014) 285. Figures

Figure 1 : Schematic representation of rGO double functionalization with R1 from a xanthate and R2 from a peroxide (minor S-containing functions omitted for clarity).

Graphene | 179

Thermal reduction of thin graphene films on different substrates monitored by AFM Ana M. PĂŠrez-Mas, Laura FernĂĄndez-GarcĂa, Patricia Ă lvarez, Patricia Blanco, Ricardo SantamarĂa, Marcos Granda, Clara Blanco, Rosa MenĂŠndez Instituto Nacional del CarbĂłn, CSIC, P.O.: 73, 33080 Oviedo, Spain rosmenen@incar.csic.es Abstract The morphology, size and height of graphene sheets are currently analysed by AFM without much difficulty. However, when dealing with graphenes obtained by thermal reduction of graphene oxides, the sheets cannot be easily visualized by this technique, mainly because of their shape, roughness and typical wrinkles, which difficult their AFM monitorization at the different temperatures. The aim of this work is to evaluate the effect of the thermal treatment on the graphene oxide (GO) sheet morfology in different substrates by means of AFM. For that, a GO obtained by D PRGLILHG +XPPHUÂśV method [1] and subsequently sonicated (exfoliated) for 8h [2], was initially drop casted into silicon and HOPG substrates. After that, the whole systems were heated in a horizontal furnace, at different temperatures, under a N2 atmosphere (rGO). All films were characterized by AFM and SEM microscopy. The lateral size of parent GO sheets, as determined by AFM, is about 1-2 Âľm and the height is 1.75 nm in both substrates, showing a homogeneous distribution of the sheets on each one. After the thermal treatment of the films at 700 ÂşC, it is observed that their thickness on HOPG decreases to a value below 1nm due to the loose of oxygen functional groups (about 8 wt % O content at 700ÂşC as compared with the 35 wt % of parent GO) (Fig.1a-c) +RZHYHU RQ 6L VXEVWUDWH WKH WKLFNQHVV GRHVQÂśW FKDQJH significantly at these temperatures (Fig. 1d-f). This is explained from the different type of interactions of the rGO sheets with the substrates during reduction (reconstruction of the sp2 carbon structure). Acknowledgements: This work has been supported by the Spanish MICINN (TECNIGRAF (IPT-20110951-390000) and Ramon y Cajal program of P. Alvarez). A. Perez-Mas acknowledges a fellowship from FICYT. References [1] D.R. Dreyer et al. Chem Soc Rev. 39 (2010) 228 [2] C. Botas et al. Carbon 63 (2013) 576 Figures a)

c) 4

Z[nm]

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0.5

X[Âľm]

1.5

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100

150 200 250 300

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Figure 1. (a, d) AFM 3D topography, (b,e) SEM image, and heigh profile average (c, f) of graphene oxide reduced at 700ÂşC on a silicon substrate (a, b, c) and HOPG (d,e,f).

180 | Graphene

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Graphene | 181

Patterning and tuning of electrical and optical properties of graphene by laser induced twophoton oxidation 1

Mika Pettersson, Jukka Aumanen, Andreas Johansson, Juha Koivistoinen, Pasi Myllyperkiö, 1

Nanoscience Center, Departments of Chemistry, and Physics, P.O. Box 35, FI-40014, University of Jyväskylä, Finland. mika.j.pettersson@jyu.fi Abstract Graphene has high potential for becoming the next generation material for electronics, 1,2 photonics and optoelectronics. However, spatially controlled modification of graphene is required for advanced applications. Electrical properties of graphene can be modified by tuning its shape or dimension. Narrow ribbons of graphene lead to opening of a band gap due to quantum confinement 3 effect. Graphene oxide (GO) has a band gap, which can be tuned by controlling the degree of 4 oxidation. Laser heating has been used for modification of electrical properties of GO. However, thermal reduction of GO does not fully recover the excellent electrical properties of graphene. So far, 5 laser patterning of graphene has been limited to ablation, which is of limited use. Here, we report patterning and controlled tuning of electrical and optical properties of graphene by 6 femtosecond laser induced non-linear oxidation. Patterning is achieved by focusing a pulsed laser beam to graphene in ambient air leading to photo-oxidation (See Fig. 1). We use four wave mixing (FWM) for imaging graphene and graphene oxide patterns. FWM produces a strong signal in monolayer graphene and the signal is very sensitive to oxidation providing good contrast between patterned and non-patterned areas. By adjusting the laser pulse parameters, we oxidize graphene without ablation or cutting. Patterning is performed for air suspended graphene as well as for graphene on silicon substrate. By tuning the level of oxidation, electrical (and optical) properties of oxidized regions can be continuously fine-tuned; however, the excellent electrical properties of the non-oxidized regions of graphene are preserved. We show via electrical measurements that gradual photo-oxidation leads to increase of resistance and finally opening of a band gap. We also demonstrate FET operation of photooxidized graphene with an ON-OFF ratio better than one order of magnitude, which can be improved in further studies (see Fig. 2). The presented concept allows development of all-graphene electronic and optoelectronic devices with an all-optical method. References [1] P. Pasanen, M. Voutilainen, M. Helle, X. Song and P. J. Hakonen, Phys. Scr., T146 (2012) 014025. [2] Q. Bao and K. P. Loh, ACS Nano, 6 (2012) 3677. [3] C. Berger, Z. Song, X. Li, X. Wu, N. Brown, C. Naud, D. Mayou, T. Li, J. Hass, A. N. Marchenkov, E. H. Conrad, P. N. First and W. A. de Heer, W. A., Science, 312 (2006) 1191. [4] Y. Zhou, Q. Bao, B. Varghese, L. A. I. Tang, C. K. Tan, C.-H. Sow and K. P. Loh, Adv. Mater., 22 (2010) 67. [5] R. J. Stöhr, R. Kolesov, K. Xia and J. Wrachtrup, ACS Nano, 6 (2011) 5141. [6] J. Aumanen, A. Johansson, J. Koivistoinen, P. Myllyperkiö, M. Pettersson, Nanoscale, 2015, DOI: 10.1039/C4NR05207B. Figures

Figure 1.

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Figure 2.

Electronic Interaction between Nitrogen-Doped Graphene and Porphyrin Molecules V. D. PHAM1, J. Lagoute1, O. Mouhoub1, Y. Tison1, V. Repain1, C. Chacon1, A. Bellec1, Y. Girard1, F. Joucken2, S. Rousset 1Matériaux

et phénomènes quantiques CNRS-Université Paris Diderot, 10, rue Alice Domon et Léonie Duquet 75205 Paris Cedex 13, France 2Research center in Physics of Matter and radiation Université de Namur, 61, rue de Bruxelles, Namur, Belgium van-dong.pham@univ-paris-diderot.fr Abstract Controlling the properties of graphene and mastering its interaction with molecules is a cornerstone for the realization of graphene-based devices. One of the promising routes explored to tune the properties of graphene is the doping by nitrogen atoms inserted in the carbon lattice. Here, we present an extensive study of the interaction of porphyrin molecules (H2TPP) with nitrogen doped graphene. Using scanning tunneling microscopy and spectroscopy (STM and STS) we evidenced the decoupling effect by the opening of the HOMO-LUMO gap of the porphyrin molecules adsorbed on graphene (3.3 eV) as compared to Au (111) (2.4 eV). The comparison of the spectroscopy of molecules on carbon and nitrogen sites reveals a downshift of the molecular levels typical of a charge transfer towards the molecule at the nitrogen sites. This shift induces a clear topographic contrast in the STM images that allows us to discriminate the molecules above the nitrogen sites (that appear bright) compared to those on the carbon sites at +2V (see Figure), which is attributed to the purely electronic effect. These results show a fascinating understanding at the atomic scale of the porphyrin molecules on graphene, in which the electronic interaction of molecules with graphene, particularly, on doped graphene, the sensitive charge transfer at nitrogen sites provide new strategic study for the further investigation of graphene as well as graphene-based devices. References [1] Georgiou et al., Nature Nanotechnology, 8 (2013), 100. [2] F. Schedin et al., Nature Materials 6 (2007), 652. [3] Bruno F. Machado et al., Catal. Sci. Technol. 2 (2012) 54. [4] Yan et al., ACS Nano, 8 (2014) 4720. Figures

Topography image reveals the molecule island on N doped graphene in which the red molecules correspond to those adsorbed on N sites. Comparative dI/dV spectra recorded on H2TPP molecules on carbon (blue) and nitrogen (red) sites showing the energy shifts of the HOMO and LUMO states measured on the molecular island.

Graphene | 183

Influence of substrate temperature and SiC buffer layer on the quality of graphene formation directly on Si(111) Trung T. Pham1, Cristiane N. Santos2, Frédéric Joucken1, Benoît Hackens2, Jean-Pierre Raskin3 and Robert Sporken1 1

Research Center in Physics of Matter and Radiation (PMR), University of Namur (FUNDP), 61 Rue de Bruxelles, 5000 Namur, Belgium. 2 Nanoscopic physics (NAPS), Institute of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain (UCL), 2 chemin du Cyclotron, Louvain-la-Neuve, Belgium. 3 Electrical Engineering (ELEN), Institute of Information and Communication Technologies, Electronics and Applied Mathematics (ICTEAM), Université catholique de Louvain (UCL), 3 place du Levant, Louvain-la-Neuve, Belgium. E-mail contact: phamtha@fundp.ac.be

Abstract: Evidence for the epitaxial growth of graphene films directly on Si(111) 7×7 surface reconstruction was demonstrated (Fig. 1), however the production of low surface roughness and large area graphene on Si wafer is still a challenge in the context of direct deposition of carbon atoms using an electron beam evaporator [1, 2]. Therefore, in order to optimize this film for approaching industrial applications, in this paper we continue investigating the structural and electronic properties of our material at various substrate temperatures using covered SiC buffer layers with different thicknesses under appropriate preparation by Auger electron spectroscopy, X-ray photoemission spectroscopy, Raman spectroscopy, scanning electron microscopy and scanning tunneling microscopy. Recorded experimental results confirm this significant influence on the quality of graphene formation. This method might be very promising for graphene-based electronics and its integration into the silicon technology. References: [1] Pham Thanh Trung, Frederic Joucken, Jessica Campos-Delgado, Jean-Pierre Raskin, Benoit Hackens, and Robert Sporken, Appl. Phys. Lett. 102, 013118 (2013). [2] Pham Thanh Trung, Jessica Campos-Delgado, Frédéric Joucken, Jean-François Colomer, Benoıt Hackens, Jean-Pierre Raskin, Cristiane N. Santos, and Sporken Robert, J. Appl. Phys. 115, 223704 (2014); Figure:

Fig. 1: An atomic resolution STM image of 30×30Å2 (VSample = -0.12V, IT = 10nA) from graphene films on Si(111) 7x7 surface reconstruction showing the AB (Bernal) stacking order of a typical graphene lattice [2].

184 | Graphene

Biodegradation influence on PLA/graphene-nanoplatelets composite biomaterials mechanical properties and biocompatibility Artur M. Pinto1,2, Carolina Gonçalves1, Inês C. Gonçalves2, Fernão D. Magalhães 1 1

LEPABE, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal 2

INEB, Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal arturp@fe.up.pt

Abstract Two types of graphene-nanoplatelets (GNPs) were incorporated in PLA (poly(lactic acid)) by melt blending. Materials were biodegraded during 6 months and characterized by XRD, tensile tests, DMA and biocompatibility assays. For both fillers, low loadings (0.25 wt.%) improved mechanical properties and decreased decay until 6 months biodegradation. PLA degradation decreased its toughness (AUC) by 10 fold, while for PLA/GNP-M and C, toughness was only reduced by 3.3 and 1.7 fold, respectively. Comparing with PLA, PLA/GNP-M and C composites presented similar (HFF-1) fibroblasts adhesion and proliferation at the surface and did not released toxic products (6 months). Introduction A commercial available product, with reduced cost comparing with single layer graphene, GNPs, are constituted by few stacked graphene layers. These materials present high aspect ratio and possess oxygen-containing functional groups in the platelet edges, which may facilitate extensive interfacial interaction with polymer matrices. [1] Some typical composite production techniques like solvent mixing and electrostatic deposition lead to obtainment of toxic materials. [1,2] Thus, melt blending, which assures complete embedding of GNPs in polymer matrix preventing filler leaching, is studied in this work as a green method for production of PLA/GNPs composites. Materials and Methods PLA 2003D (Natureworks), GNPs (XG Sciences). Composites were prepared by melt blending and moulded in a hot press into thin sheets (0.3-0.5 mm). Samples were immersed in PBS and incubated for 6 months (37 °C, 100 rpm). Tensile properties were measured (Mecmesin Multitest-1d, Mecmesin BF 1000N) using a strain rate of 10 mm min-1. Creep/recovery assays were performed using a DMA 242 E Artemis (Netzsch). Biocompatibility of materials was evaluated using HFF-1 cells cultured at the surface of composite films and in direct contact with materials extracts obtained after 6 months degradation. Metabolic activity was determined using resazurin assay. Results and discussion XRD GNP-M and C powders present similar XRD spectra, typical of carbon materials. PLA, before (0M) and after 6 months (6M) biodegradation, presents similar spectra, also typical for this polymer. In composites PLA and GNPs peaks were observed. Degradation did not affected spectra. Tensile tests Incorporation of GNP-C and M in PLA increased its Young´s modulus by 14 %. Also, tensile strength is increased by 20% for GNP-C and by 6% for GNP-M. After 6 months biodegradation, decreases in tensile strength, elongation at break, and toughness are respectively, for PLA of 2.6, 2.5, and 10 fold, for PLA/GNP-M of 1.6, 1.8 and 3.3 fold, and for GNP-C of 1.4, 1.4 and 1.7 fold. Creep/recovery Figure 1 shows that for undegraded PLA, dLf (final, at 6N) after 10 creep/recovery cycles was of 14.2 µm, being of 13.7 and 13.2 µm for PLA/GNPM and C 0.25 wt.%, respectively. After 6 months degradation, PLA sample ruptured after 4 cycles (1.A) reaching a dLf of 56.3 µm. PLA/GNP-M and C 0.25 wt.% did not rupture (1.B,C) and presented only a slight increase in dLf, of 16.8 and 16.7 µm, respectively. Materials degradation was confirmed in terms of molecular weight decrease and changes in surface morphology (results not shown). Biocompatibility evaluation PLA/GNP-M and C 0.25 wt.%, metabolic activity never decreased below 90%, for both composites in comparison with PLA. Composites degradation products are not toxic (24, 48, 72h), comparing with PLA 6M. Also, cell morphology is normal and similar for all conditions tested (images not shown). Conclusions GNP-M and GNP-C incorporation in PLA (0.25 wt.%) improved mechanical properties and decreased their decay after 6 months biodegradation. GNPs can be used to tune PLA mechanical performance during biodegradation in biomedical applications, since they did not decrease cell proliferation or cause toxicity. References [1] Lahiri D, Rupak D, Cheng Z, Socarraz-Novoa I, Bhat A, Ramaswamy S, Agarwal A, ACS Appl. Mater. Interfaces, 4 (2012) 2234. [2] Pinto AM, Gonçalves IC, Magalhães FD, Colloids and Surf B Biointerfaces, 111 (2013) 188.

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Ultrafast broadband study of photocarrier dynamics in MoS2 single layer E.A.A. Pogna1, S. Dal Conte1, M. Marsili2, D. Prezzi2, D. Sangalli3, C.Manzoni1, A. Marini3, D. De Fazio4, M. Bruna4, I. Goykhman4, A. C. Ferrari4, G. Cerullo1 1. Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133, Milano, Italy 2. CNR-Istituto Nanoscienze, 41125 Modena, Italy 3. CNR-Istituto di Struttura della Materia, Montelibretti, Italy 4. Cambridge Graphene Centre, Cambridge, CB3 OFA, UK eva.a.pogna@gmail.com We present a time-resolved study of charge carrier dynamics in single-layer MoS2 (1L-MoS2) by ultrafast transient absorption spectroscopy. Using tunable pump pulses and broadband probing, we monitor the relaxation dynamics of the photo-excited states with unprecedented spectral coverage (the entire visible range). The sample is a 10 x 30 Pm2 1L-MoS2 prepared by micromechanical exfoliation and transferred onto a transparent fused silica substrate [1]. The transient absorption spectrum has three prominent features, each consisting of a bleaching at the energies of the excitonic transitions A, B C (at 1.9, 2.1 and 2.9 eV) and a red-shifted photoinduced absorption, Fig. 1. These features do not depend on the excitation energy, which is tuned to be resonant and non-resonant with the excitonic transitions. Pauli blocking cannot explain, alone, the simultaneous bleaching of the three excitonic transitions and the corresponding photoinduced absorption. Instead, we believe that a transient band gap renormalization caused by the presence of photo-excited carriers should be also considered. A static strong renormalization of both electronic band gap and exciton binding energy was previously reported in MoSe2 due to the interaction with the substrate [2]. Here we compare our data with simulations combining non-equilibrium Green's functions with ab-initio methods [3,4]. The comparison of experimental data with simulations allows us to shed light on the delicate interplay among Pauli blocking, band gap renormalization and electron-phonon relaxation, which are the key phenomena governing the carrier dynamics after photo-excitation. [1] Bonaccorso et al.Materials Today, 15 (2012) 564-589; [2] M. M. Ugeda et al., Nat. Mat., 13 (2014) 1091-1095; [3] A. Marini, J. Phys.: Conf. Ser. 427 (2013) 012003; D. Sangalli and A. Marini, arXiv:1409.1706 (2014) [4] A. Marini, C. Hogan, M Gr端ning, and D. Varsano, Comp. Phys. Comm., 180 (2009) 1392 Figure.1 Transient Absorption of 1L-MoS2. 100 fs-pulse excitation in the visible range determines simultaneous bleaching of the A, B, C excitons, with the absorption surviving up to hundreds ps. a) Transient absorption map with Opump= 400nm; b) Transient absorption spectrum at fixed delays; c) Relaxation dynamics of C-exciton bleaching with Opump= 400, 600 and 650 nm. 0.03

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Ioannis Polyzos , Massimiliano Bianchi , Laura Rizzi , John Parthenios , Konstantinos Papagelis , 2 1,5 Roman Sordan and Costas Galiotis 1

Institute of Chemical Engineering Sciences, Foundation of Research and Technology-Hellas (FORTH/ICE-HT), Patras, Greece 2 L-NESS, Department of Physics, Politecnico di Milano, Polo di Como, Via Anzani 42, 22100, Italy 3 DIRECTA PLUS S.p.A., c/o Parco Scientifico di ComoNExT, Via Cavour 2, 22074 Lomazzo (Co), Italy 4 Department of Materials Science, University of Patras, Greece 5 Department of Chemical Engineering, University of Patras, Greece ipolyzos@iceht.forth.gr

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Abstract 1 Graphene is a perfect 2D covalent crystal, which forms the basis of all graphitic structures . It can be stacked into three-dimensional graphite, rolled into one-dimensional nanotubes, or wrapped into zerodimensional fullerenes. Due to its inherent properties and the great variety of possible applications graphene has stimulated a lot of theoretical and experimental research over the last decade. The mechanical properties of graphene make it an ideal candidate for micro and nano-mechanical applications. Graphene has intrinsic tensile strength higher than any other known material and tensile 2 stiffness similar to values measured for graphite . Furthermore, mechanical deformation (strain) can be 3 used to tailor its electronic properties allowing the fabrication of all-graphene circuits. In addition, 4 certain strain configurations are equivalent to high pseudo-magnetic fields . Therefore, the understanding of graphene properties under strain is of great importance. In this work, a graphene flake was sandwiched between two PMMA layers and was suspended in air by removing a section of the polymer with e-beam lithography. This procedure resulted in the imposition of true uniaxial tension to graphene of up to 0.8% strain (fig.1), as confirmed by laser Raman mapping at steps as small as 100 nm along and across the flake. Splitting of the Raman G line as well as of the 2D line was observed. The strain estimated directly from the well-known peak shifts of the + 1 2 Raman G sub-peaks. The dependence of Raman shift of G , G , 2D , 2D and 2DÂś PRGHV RQ strain are presented. Our results are in excellent agreement with the previously reported results for supported graphene and the theoretical predictions for graphene in air.

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Figure 1 (a) Initial (zero strain) and final (with strain distribution) window (b) Representative Raman spectra of the G-peak at various strain levels (c) G sub-peaks position as a function of strain for suspended SLG References 1 A. K. Geim and K. S. Novoselov, Nat Mater 6 (3), 183 (2007). 2 Changgu Lee, Xiaoding Wei, Jeffrey W. Kysar, and James Hone, Science 321 (5887), 385 (2008). 3 Vitor Pereira and A. Castro Neto, Physical Review Letters 103 (4), 046801 (2009). 4 F. Guinea, M. I. Katsnelson, and A. K. Geim, Nat Phys 6 (1), 30 (2010).

Graphene | 187

Electrically tunable terahertz magneto-absorption and Faraday rotation in graphene 1

J. M. Poumirol , P. Q. Liu , M. Tamagnone ,! Clara Moldovan 1 Kuzmenko

"J. Perruiseau-Carrier3, J. Faist2, A. B.

1 2

Department of Quantum Matter Physics, University of Geneva,1211 Geneva, Switzerland Institute of Quantum Electronics, Department of Physics, ETHZ, 8093 Zurich, Switzerland 3 Adaptative MicroNano Wave Systems, EPFL, 1015 Lausanne, Switzerland 4 Nanoelectronic Devices Laboratory (NANOLAB), EPFL, Lausanne, Switzerland. jean-marie.poumirol@unige.ch

Abstract Recent publications have revealed a great potential of graphene for photonic applications, due to a possibility of efficient control of its optical properties by electrostatic gating and plasmonic patterning. Interestingly, the optical absorption of graphene is also highly sensitive to the magnetic field, owing to the extremely small cyclotron mass of charge carriers. Moreover, the magnetically broken time reversal symmetry results in a giant Faraday rotation [1] opening avenues towards realization of graphene-based non-reciprocal devices, such as Faraday rotators and isolators, which would be fundamentally impossible in zero field. As a first step towards applications, we studied systematically the effect of the key graphene electrical characteristics, namely the carrier concentration and mobility, on its magneto-optical properties, by using a large number of CVD graphene samples. Furthermore, we measured terahertz magnetoabsorption and Faraday rotation in large-area CVD graphene field effect transistors, where we combined the magnetic biasing (up to 7 T) with electrostatic gating and plasmonic antidot patterning [2] in order to exploit a complete set of tuning parameters in a same device. This allowed us to achieve a rather deep (up to 50%) magneto- and electro-modulation of graphene properties in a broad range of frequencies. Most significantly, we demonstrate the sign inversion of the Faraday rotation in ambipolar graphene transistors by using the electric field rather than the magnetic field as it is done conventionally. Last but not least, the patterning gives rise to strong magnetoplasmonic modes, which can be used to enhance magneto-optical effects at desired frequencies. Overall, our results show a feasibility of fast-tunable graphene-based terahertz magneto-optical modulators and non-reciprocal devices. References [1] I. Crassee, J. Levallois, A. L. Walter, M. Ostler, A. Bostwick, E. Rotenberg, T. Seyller, D. van der Marel, A. B. Kuzmenko, Nature Physics, 7, (2011) 48. [2] P. Q. Liu F. Valmorra, C. Maissen and J. Faist. Submitted to Optica.

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(a) Gate-voltage dependent magneto-resistance of a 3x3 2 mm ambipolar CVDgraphene transistor with an antidot patterning. The inset shows schematically the device and the magnetooptical experiment. The Faraday rotation (b) and absorption (c) at 7 T at selected gate voltages, indicated by circles in (a).

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Graphene | 189

PROPERTIES OF THE CARBON FOUND IN THE ATOMIC STATE AND NANOPARTICLES USED TO GENERATE HYDROGEN FROM WATER WITH APPLICATIONS TO THERMAL PLANTS Marin RADU, Florica RADU, Valentin RADU, Daniela RADU, Florian CIOROIANU, Mariana CIOROIANU Research Center for Macromolecular Materials and Membranes, 202B Splaiul Independentei, Bucharest, Romania, e-mail: marin.radu@ccmmm.ro Summary: This paper highlights several important properties of the carbon found in the atomic state and nanoparticles. They were observed during experiments made with a membrane electro-catalytic system for obtaining a hydrogen-based fuel gas from water covered by a patent (International Application No. PCT/RO2011/000015 published under No. WO 2012/011 829 on 26/01/2012). The hydrogen generator built in accordance with the international application mentioned above works under normal pressure and temperature conditions, being comprised of a high frequency source, a programmable control system, a membrane electro-catalytic module with cylindrical metal electrodes in concentric arrangement and a module for processing of the generated fuel gas. The space between electrodes comprises granular carbon in the atomic state and nanoparticles which acts as a catalyst for the water decomposition reaction, with a small proportion of other metal particles.The final module for fuel gas processing comprises a composite membrane and a Mg charge as catalyst, which ensure the reduction of the CO2 at pure carbon, reusable in the mentioned electro-catalytic process. This component of the system was developed in another patent (International Application No. PCT/RO2012/000019 published under No. WO 2013/157974 on 24/10/2013), to eliminate harmful gaseous emissions by burning them together with the hydrogen in the presence of the magnesium catalyst. The properties highlighted by the development of the membrane electro-catalytic process above presented are the following: - the carbon, in atomic state, have very high values of electrical conductivity and thermal conductivity - the carbon, in atomic state and in combination with water, form a very good electrolyte; - the carbon, in atomic state, is a stabilizer for hydrogen; - the carbon, in atomic state, is an excellent catalyst.

190 | Graphene

Low Temperature Growth of Graphene by Hot Wire Chemical Vapour Deposition

Shilpa Ramakrishna, Vivek Pandey, Rajeev O Dusane Indian Institute of Technology Bombay, Powai, Mumbai, India shilpark@iitb.ac.in Abstract With the isolation of graphene in the year 2004 by A.K. Giem and K.S. Novoselov it has been explored to have vast scope in various applications as it exhibits exceptional electrical, mechanical, optical and thermal properties [1]. Till date, large area graphene of device quality has been grown by chemical vapor deposition successfully, however it is grown at very high temperatures around 800 oC -1000 oC by this technique [2]. There is a need for alternative synthesis route to obtain cost effective growth of graphene films for industrial scale production at low thermal budget. We have successfully grown for the first time, few layer graphene by hot wire chemical vapor deposition (HWCVD) at relatively low temperature around 500 oC Âą 600 oC on copper. Utilizing the decoupled nature of this deposition technique, wherein the dissociation of the precursor gas (methane and hydrogen) takes place away from the substrate and subsequent transportation of film forming species to the substrate enables the film growth at lower substrate temperature. We have characterized the as deposited films by Raman spectroscopy and transmission electron microscopy, which confirms the growth of few layer graphene. The film grown shows non uniformity across, the substrate surface (Cu) which could be due to surface morphology of Cu, as observed through scanning electron microscopy. Initially we have grown few layer graphene film grown at 500 oC with high defect density as analysed from the Raman spectrum, shown in figure 1, and the defect has been reduced further by controlling the process parameters namely precursor flow rate and chamber pressure as well as by engineering the copper surface.

References [1] K. Geim and K. S. Novoselov, Nature materials, 6 (2007) 183 Âą 191. [2] X. Li, C. W. Magnuson, Venugopal, Archana, Tromp, M. Rudolf, Hannon, B. James, Vogel, Eric, Colombo, Luigi, Ruoff, Rodney S Âľ/DUJH- area graphene single crystals grown by low-pressure chemical YDSRXU GHSRVLWLRQ RI PHWKDQH RQ FRSSHUÂś Nano Letters, 10 (2010) 4328Âą4334. Figure 1: Raman Spectrum of graphene grown by HWCVD

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Graphene | 191

Epitaxial synthesis of WS2 Francesco Reale, Chiara Grotta, Cecilia Mattevi Materials Department, Imperial College London, SW7 2AZ, UK f.reale13@imperial.ac.uk The chemical vapour deposition (CVD) of layered transition metal dichalcogenides (TMDs) holds promise for the synthesis of monolayered material over large areas with high structural quality for integration in optoelectronic devices. However, the synthesis of TMDs, and especially of WX2 materials is still challenging since film continuity and thickness uniformity are often limited to tens of micron-sized areas. We have studied the CVD synthesis mechanism in low vacuum demonstrating formation of single layered WS2 over hundred of micron-sized areas. We investigated the synthesis form the early stages of nucleation up to formation of a continuous films onto different substrates: epitaxial and amorphous. Single layered films extended over large areas were obtained by optimizing the amount of metal oxide precursors, carrier gas flow rate and deposition temperature. Using a ³ERXQGDU\ OD\HU´ PRGHO DQG WDNLng into account the TX2-substrate interaction, we have been able to provide a unified description of how different growth conditions can lead to different layer numbers and size and density of the nuclei. We show that different substrate interactions play a very important DQG FRXQWHULQWXLWLYH UROH DQG ZH SUHVHQW D ³SKDVH GLDJUDP´ RI QXFOHL VL]H and density as a function of the substrates properties. Optical and electrical properties are also presented and correlated with different interface characteristics.

192 | Graphene

Spectral Sensitivity of pn-junction Photodetectors based on 2D materials Sarah Riazimehr1, Daniel Schneider1, Chanyoung Yim2, Satender Kataria1, Vikram Passi1, Andreas Bablich1, Georg S. Duesberg2 and Max C. Lemme1* 1University of Siegen, Hölderlinstrasse 3, 57076 Siegen, Germany 2School of Chemistry, Trinity College Dublin, Dublin 2, Ireland max.lemme@uni-siegen.de Broad spectral range detection is interesting for several technological applications such as imaging, sensing, communication and spectroscopy. Two-dimensional (2D) materials are very promising for such applications. Graphene is a suitable material for broadband detection due to its absorbance covering the entire spectrum from ultraviolet to terahertz, which is a consequence of its linear dispersion and zero bandgap characteristic [1], [2]. In contrast to graphene, molybdenum disulfide (MoS 2) is an ntype semiconducting 2D material. MoS2 shows a more limited spectral response due to its band structure. Monolayer MoS2 has a direct band gap of ~1.8 eV, whereas bulk MoS2 has an additional indirect band gap of ~1.3 eV [3]. In this work, we investigate graphene ± silicon Schottky barrier diodes composed of chemical vapor deposited (CVD) graphene on n-type Si substrates. A device schematic along with its cross-section is shown in Fig. 1a and 1b, respectively. The effects of incident light intensity and wavelength are investigated. Fig. 1c shows the band diagram of the device in reverse bias under illumination. The diodes exhibit good rectifying behavior and high sensitivity to changes of incident light, as shown in Fig. 1d. A broad spectral response (SR) of 60 - 407 mAW -1 at reverse dc bias of 2V is measured from ultraviolet (UV) to near infrared (NIR) light (Fig. 2a). In our previous work on MoS2/Si diodes, we reported a maximum SR of 8.6 mA/W (Fig. 2b, [4]). This is 47 times less than the Si-graphene diode value presented in this work, even though multilayer MoS2 should have higher absorbance than graphene. We attribute the greatly enhanced SR to an optimized design, with larger contact electrodes that were also placed closer to the active device area. This results in an increased external electrical field. Therefore, more photogenerated electron-hole pairs can be captured before recombination and consequently, the overall photodetection efficiency is improved. References [1] R. R. Nair, et al., Science, vol. 320, no. 5881, (2008) 1308±1308. [2] K. F. Mak, et al., Solid State Commun., vol. 152, no. 15,( 2012) 1341±1349. [3] K. F. Mak, et al., Phys. Rev. Lett., vol. 105, no. 13, (2010). 136805 [4] C. Yim, et al., Sci. Rep., vol. 4, (2014). 1-7 Figures

Figure 1: a) Schematic, (b) Cross-section of the graphene/nSi heterojunction diode and (c) its band diagram in reverse bias under illumination. (d) J-V plot of the diode on a semilogarithmic scale under various light intensities of 20%, 60% and 100% compared to the dark-state.

Figure 2: Absolute spectral response (Abs. SR) vs. wavelength (lower x-axis) and energy (upper x-axis) of the (a) graphene/ n-Si photodiode and for comparison (b) MoS2 /p-Si photodiode at zero bias and reverse bias of 1 and 2 V taken from [our previous paper].

Graphene | 193

Synthesis of GO/TiO 2 composite through hydrothermal method for photocatalytic application Paula Ribao1, F. Ramirez1, M. Gonzalez-Barriuso2, Maria J. Rivero1, A. Yedra2 and Inmaculada Ortiz1 1

Department of Chemical and Biomolecular Engineering, ETSIIT, University of Cantabria, Avda. de los Castros, s/n, 39005 Santander, Spain, +34 942201585 2 Centro Tecnol贸gico de Componentes (CTC), Parque Cient铆fico y Tecnol贸gico de Cantabria, C/Isabel Torres, 1, 39011 Santander, Spain ribaop@unican.es

Abstract Heterogeneous photocatalysis is a technology that combines a source of appropriate light and a solid semiconductor material as catalyst in order to promote chemical reactions by means of the generation of electron-hole pairs. TiO 2 is the most popular catalyst; however, the photocatalytic activity of this compound is limited because i) energy is absorbed mainly in the UV region of the solar spectrum, ii) the rapid recombination of photogenerated electron-hole pairs in TiO 2 nanoparticles and iii) the difficult contact between the catalyst and the contaminant [1]. Therefore research on new materials that overcome these drawbacks, among them graphene oxide (GO), is a scientific and technical challenge nowadays [2]. In this work, GO/TiO 2 nanocomposites were prepared and used as photocatalyst for water treatment by blending TiO 2 with graphene oxide (GO/TiO 2 ) through hydrothermal synthesis. Nanocomposites were characterized by atomic force microscope (AFM), thermogravimetric analysis (TGA), Brunauer-EmmetTeller (BET) surface area and Fourier-transformed infrared spectroscopy (FT-IR). Dichloroacetic acid (DCA) was used as probe in order to assess the photocatalytic activity through its mineralization. AFM image illustrates that the height profiles showed 2nm thickness GO nanoplatelets decorated with TiO 2 nanoparticles of an average diameter of 16nm (Figure 1). The TGA results show that the composite is more stable than the GO due to the embedded TiO 2 , which delays the weight loss. The BET analysis demonstrates that the synthesized composite has greater surface area than commercial TiO 2 and finally, FT-IR spectroscopy showed that GO is significantly reduced during the synthesis process. Furthermore, the results highlight that GO is not active as independent catalyst and using the composite the photocatalytic activity is improved because 31.6% mineralization was achieved after three hours of experiment while only 15% mineralization was obtained with titanium dioxide as catalyst. References [1] [2]

Kumar,J., Bansal, A. Materials Science Forum, 764 (2013) 130-150. Liang, D., Cui, C., Hu, H., Wang, Y., Xu, S., Ying, B., Li, P., Lu, B., Shen, H. Journal of Alloys and Compounds, 582 (2014) 236-240.

Figures

Figure 1. Non contact mode AFM images of GO/TiO2 composite synthetized by hydrothermal method

194 | Graphene

Use of the tight-binding approach to investigate the Wannier functions of graphene

Allan Victor Ribeiro

(1,2)

and Alexys Bruno-Alfonso

(3)

(1) Instituto Federal de Educação, Ciência e Tecnologia de São Paulo, Birigui, SP, Brazil (2) Programa de Pós-graduação em Ciência e Tecnologia de Materiais, Unesp, Brazil (3) Departamento de Matemática, Faculdade de Ciências, Unesp, Bauru, SP, Brazil allanvrb@ifsp.edu.br Abstract At the very frontier of science for several years [1], graphene has been studied because of its unique transport properties and relative ease of manufacturing. It is one of the most promising materials for a wide range of applications in nano-electronics, opto-electronics and photodetectors [2, 3]. Recent work has shown that a tight-binding approximation [4] associated with generalized Wannier functions provides a physically intuitive picture of the electronic bands of graphene [5-7]. The crystalline structure 2 of graphene is a planar honeycomb atomic array with covalent bonds between sp hybrid orbitals. In the present work, the symmetry and the localization properties of the Wannier functions of graphene are investigated. The Bloch functions, which depend on the three spatial coordinates and on the twodimensional wave vector, are obtained through the tight-binding method. Only the on-site and the nearest-neighbor matrix elements of the Hamiltonian are taken into account. Due to symmetry, the band structure is split into six s-px-py bands and two pz bands. The phase of the Bloch functions of each band is appropriately chosen, in order to produce Wannier functions of maximal localization. The calculated Wannier functions are shown to resemble either bonding or anti-bonding molecular orbitals, whose 2 relation with the sp hybrid orbitals is discussed. The numerical code gives Bloch functions that depend smoothly on the wave vector, and this leads to well localized Wannier functions. They also show rotational and mirror symmetries. Nevertheless, the phase of the Bloch functions is further improved in order to minimize the spread of the Wannier functions. Such functions are compared with the available multi-band Wannier functions [7]. The present approach sheds further light on the physical properties of graphene and provides a simple mathematical treatment of Wannier functions in two-dimensional materials. Acknowledgements: The authors thank the Brazilian Institutions IFSP and UNESP and the Brazilian Agency CAPES for financial support. References [1] K. S. Novoselov et al. Science 306, 666, (2004). [2] A. H. Castro Neto et al., Rev. Mod. Phys. 81, 109 (2009). [3] C. H. Liu et al. Nature Nanotechnology 9, 273 (2014). [4] R. Kundu, Modern Physics Letters B 25 (3), 163 (2011). [5] J. Jung and A. H. MacDonald, Phys. Rev. B, 87, 195450 (2013). [6] J. Jung and A. H. MacDonald, Phys. Rev. B 89, 035405 (2014) [7] N. Marzari et al, Rev. Mod. Phys. 84, 1419 (2012).

Graphene | 195

Electron optics in graphene 2

P. Rickhaus , M.-H. Liu , P. Makk , S. Hess , R. Maurand E. Tovari , M. Weiss , 2 1 K. Richter and C. SchĂśnenberger 1 Dept. of Physics, University of Basel, Switzerland 2 Institute of Theoretical Physics, University of Regensburg, Germany 3 Dept. of Physics, Budapest University of Technology and Economics, Hungary peter.rickhaus@unibas.ch In ballistic graphene, electrons behave in many ways similar to photons. By changing the electrostatic potential locally, we realized elements in graphene that are known from optics. But in contrast to conventional optics, gapless p-n interfaces can be formed showing a negative index of refraction and the effect of Klein tunneling. Even more, electron trajectories can be bent by applying a magnetic field. The electron-optics devices that we will show were fabricated using high-mobility suspended monolayer graphene on organic lift-off resists. We extended the technology introduced by N. Tombros et al. [1] allowing to add a multitude of bottom and top gates [2]. Recently we have demonstrated that with this technique a ballistic p-n junction can be created forming a Fabry-PĂŠrot etalon. We will go beyond our recent publication [3] and discuss the observed transition from the Fabry-PĂŠrot to the Quantum Hall regime that is observed once a magnetic field is applied. We will show striking features that can be traced to the formation of snake state trajectories along a pn interface. By this we can guide electrons along arbitrary interfaces already at very small magnetic fields of 100 mT. Beyond that we will demonstrate that electrons in ballistic graphene can be guided by gate potentials (Fig.1a) the same way as photons in an optical fiber, and that the formation of a p-n interface increases the guiding efficiency due to Klein filtering. We will show that we can fill the electrostatic guiding channel mode by mode. A further electron-optics element that we will present is a four terminal device that involves a tilted gate structure (Fig.1b) which acts as a mirror. Theoretical calculations [4] clearly reproduce the measured features of the different electron-optics devices, and the simulated current density plots give further insight to the nature of the discussed effects. References [1] N. Tombros et al. Journal of Applied Physics 109, 093702 (2011). [2] R. Maurand, P.Rickhaus, P.Makk et. al. Carbon 79, 486 (2014) [3] P. Rickhaus, P.Makk, M.-H. Liu et al., Nature Communications 4, 2342 (2013) [4] M.-H.Liu, P.Rickhaus, P.Makk et.al., arXiv:1407.5620 (2014)

Fig. 1. a) False color image of a suspended graphene flake (blue) with side contacts (gray) and bottomgates (yellow) that can be used for electron guiding. b) Another four-terminal device with a tilted gate structure allows studying the reflection at the pn-interface and acts as a mirror.

196 | Graphene

The graphene oxide-based inkjet technology for flexible electronics 1

M. Rogala , I. Wlasny , P. Dabrowski , P. J. Kowalczyk , A. Busiakiewicz , W. Kozlowski , L. Lipinska , 2 2 2 2 3 4 4 J. Jagiello , M. Aksienionek , W. Strupinski , A. Krajewska , Z. Sieradzki , I. Krucinska , M. Puchalski , 4 1 E. Skrzetuska , Z. Klusek 1

Department of Solid State Physics, Faculty of Physics and Applied Informatics, University of Lodz, Pomorska 149/153, 90-236 Lodz, Poland 2 Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw, Poland 3 Electrotechnological Company QWERTY Ltd., Siewna 21, 94-250 Lodz, Poland 4 Faculty of Material Technologies and Textile Design, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland rogala@uni.lodz.pl Abstract Flexible electronics is recently attracting increasing interest due to its large potential for application. Among the methods used in the production of flexible electronic devices the inkjet and screen printing are popular as they allow for fast production of thin, conductive tracks on elastic polymer foil and textile surfaces. Recent research shows that it is possible to produce graphene coatings with the inkjet method. However, currently developed inks and printing techniques, which employ various forms of graphene, are still in research phase and do not allow for commercial production of electrodes and devices. To fully exploit the potential of the graphene for printed, flexible electronics new printing compositions and new overprinting methods need to be developed. The abovementioned challenges are the subject of our current research. We present the overprints produced in the inkjet technology with graphene oxide dispersion. The graphene oxide ink that we used was developed to be fully compatible with standard industrial printers and polyester (PET) substrates. We describe the post-printing chemical reduction procedure which leads to the restoration of electrical conductivity without destroying the substrate. Our results prove that the proposed method allows to obtain graphene overprints of high optical transparency and low electrical resistivity (from few to hundreds kOhm/sq). The presented results show the outstanding potential of graphene oxide for rapid and cost efficient commercial implementation to production of flexible electronics. Properties of graphene-based electrodes are discussed basing on the macro- and nano-scale characterizations. The observed nano-scale inhomogeneity of the conductivity of the overprints is found to be essential in the field of future industrial applications. This work is supported by the National Centre for Research and Development under the project GRAFTECH/NCBR/15/25/2013. Figures

1. The photo of graphene oxide overprint on PET foil after chemical reduction.

2. The atomic force microscopy (a) topography and (b) conductivity images recorded on the surface of the reduced graphene oxide overprints.

Graphene | 197

Covalent modification of large area monolayer graphene towards biosensing.

Felix Rösicke1,2, Marc Gluba1, Guoguang Sun3, Karsten Hinrichs3, Norbert Nickel1, and Jörg Rappich1 1Helmholtz-Zentrum

2School

Berlin für Materialien und Energie GmbH, Insitut für Si-Photovoltaik, Kekuléstr. 5, 12489 Berlin, Germany

of Analytical Sciences Adlerhof (SALSA), Humboldt University of Berlin, Sitz: IRIS-Building, Adlershof, Unter den Linden 6, 10099 Berlin, Germany

3Leibniz-Institut

für Analytische Wissenschaften - ISAS - e.V., Department Berlin, Schwarzschildstr. 8, 12489 Berlin, Germany Felix.Roesicke@helmholtz-berlin.de

Abstract We investigated the electrochemical grafting of para-N-maleimidophenyl (p-MP) onto graphene from the respective diazonium salt (p-(N-Maleimido) benzenediazonium tetrafluoroborate, p-MBDT) by electrochemical quartz crystal microbalance (EQCM), Raman- and infrared spectroscopies. The p-MP residue is well known to react with any SH-group present in solution and is therefore a possible candidate to build up bio-sensing devices. In combination with graphene, this forms a very stable and conductive system that can be transferred to any substrate. The sample preparation was performed by transfer of CVD grown large area graphene [1] to an isolating layer of SiNx on Au-coated QCM chips. Using graphene as working electrode, the current transfer behaviour and the change in the resonance frequency of the QCM chip reflect the electrochemical reduction of the diazonium compound and binding to the graphene layer surface that was additionally supported by Raman and infrared spectroscopies. The charge used for the reduction of p-MPDT correlates well to the amount of grafted p-MP and the observed defect density of graphene. The calculated faradaic efficiencies resemble the deposition of p-MP on bare Au-QCM chips [2]. Finally the p-MP functionalized graphene surface was tested by reaction with 4-nitrobenzenethiol. This was the first time EQCM experiment using graphene as working electrode

References

1. M. A. Gluba, D. Amkreutz, G. V. Troppenz, J. Rappich, and N. H. Nickel, Appl. Phys. Lett. 103, 073102 (2013). 2. X. Zhang, F. Rösicke, V. Syritski, G. Sun, J. Reut, K. Hinrichs, S. Janietz, and J. Rappich, Z. Phys. Chem. 228, 557 (2014).

198 | Graphene

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Graphene | 199

High thermoelectric figure of merit in graphene nanorings M. Saiz-Bretín, A. V. Malyshev, and F. Domínguez-Adame Departamento de Física de Materiales, Universidad Complutense, E-28040 Madrid, Spain marta.saiz.bretin@ucm.es Abstract Nanostructured materials have proven to be very promising to achieve high thermoelectric figure of merit [1,2]. The enhancement of the figure of merit in these systems can be caused by different mechanisms. In particular, quantum effects were predicted to have strong impact on the thermoelectric efficiency [3]. Therefore, graphene is an ideal material for designing nanodevices with enhanced figure of merit due to its long coherence lengths [4]. In this work, we consider a square graphene ring connected symmetrically or asymmetrically to two leads. A side-gate voltage allows us to control the current in the device [5]. The transmission coefficient of the non-gated ring manifests Breit-Wigner resonances or Fano anti-resonances, depending on the connection geometry and the width of nanoribbons forming the ring. While Breit-Wigner resonances lead to a moderate thermoelectric response, the occurrence of Fano anti-resonances causes a dramatic enhancement of the figure of merit. However, even if a ring does not support Fano anti-resonaces, the application of a side-gate voltage can induced such features in the transmission spectrum which, consequently, leads to an enhancement of the thermoelectric response. This opens a possibility to use the proposed device as a tunable thermoelectric generator. References [1] G. Joshi, H. Lee, Y. Lan, X. Wang, G. Zhu, D. Wang, R. W. Gould, D. C. Cuff, M. Y. Tang, M. S. Dresselhaus, G. Chen, and Z. Ren, Nano Lett. 8, 4670 (2008). [2] W. Zi-Hua Wu, X. Hua-Qing, and Z. Yong-Biao, Appl. Phys. Lett. 103, 243901 (2013). [3] V. M. García-Suárez, R. Ferradás, and J. Ferrer, Phys. Rev. B 88, 235417 (2013). [4] F. Mazzamuto V. Hung Nguyen, Y. Apertet, C. Caër, C. Chassat, J. Saint-Martin, and P. Dollfus, Phys. Rev. B 83, 235426 (2011). [5] J. Munárriz, F. Domínguez-Adame, and A. V. Malyshev, Nanotech. 22, 365201 (2011).

Figures

Figure 1. Schematic view of graphene nanorings connected symmetrically or asymmetrically to two armchair nanoribbons. A side-gate voltage, VG, can be applied across the ring.

200 | Graphene

Disorder and Screening in Decoupled Graphene on a Metallic Substrate S. Samaddar1, S. C. Martin1, B. Sacépé1, A. Kimouche1, J. Coraux1, F. Fuchs2, B. Grévin2, H. Courtois1 and C. B. Winkelmann1 1

Université Grenoble Alpes and CNRS, Institut NÉEL, F-38042 Grenoble, France, 2UMR 5819 (CEACNRS-UJF) INAC/SPrAM, CEA-Grenoble, 38054 Grenoble Cedex 9, France sayanti.samaddar@neel.cnrs.fr Abstract We report the coexistence of charge puddles and topographic ripples in graphene decoupled from the Ir(111) substrate it was grown on. We show the topographic and the charge disorder to be locally correlated as a result of the intercalation of molecular species. These result in an overall positive doping of the graphene. The doping gradually decreases and becomes non-existent on graphene wrinkles where the graphene surface is far away from the influence of the substrate. From the analysis of quasi-particle scattering interferences, we find a linear dispersion relation, demonstrating that graphene on a metal can recover its intrinsic electronic properties. The measured 6 Fermi velocity vF = (0.9 ± 0.04) x 10 m/s is lower than in graphene on dielectric substrates, pointing to a strong screening of electron-electron interactions in graphene by the nearby metallic substrate.

References [1] S. C. Martin, S. Samaddar, B. Sacépé, A. Kimouche, J. Coraux, F. Fuchs, B. Grévin, H. Courtois and C. B. Winkelmann, arXiv:1304.1183, accepted in PRB Rapid Comm. [2] A. Kimouche, O. Renault, S. Samaddar, C. B. Winkelmann, H. Courtois, O. Fruchart and J. Coraux, Carbon 68, 73 (2014). Figures

Topography positively correlated with Doping. Dirac point map (color code) superimposed with a 3D plot of the long-wavelength topography. Image of 250 x 250 nm2.

Graphene | 201

Magnetotransport in high-mobility graphene antidot arrays A. Sandner1, T. Preis1, C. Schell1, P. Giudici1, K. Watanabe2, T. Taniguchi2, D. Weiss1 and J. Eroms1 1Institut

fĂźr Experimentelle und Angewandte Physik, UniversitĂ¤t Regensburg, 93040 Regensburg, Germany 2National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan andreas.sandner@ur.de

We report on the observation of antidot peaks in ßŠâ&#x20AC;Ť Ý&#x201D;Ý&#x201D;â&#x20AC;Źin monolayer-graphene (MLG), encapsulated between hexagonal boron nitride (hBN). The hBN-MLG-hBN heterostructures were fabricated with a dry transfer pick-up technique; subsequently mesas were etched in Hall bar geometry and contacted with 1dimensional side contacts [1]. The periodic antidot lattice was defined in a following step by additional electron-beam lithography and reactive ion etching (see fig. 1). We performed measurements on stacks with different antidot lattice periods down to 100 nm. Several peaks in magnetoresistance can be identified and assigned to orbits around one and several antidots (see fig. 2) [2]. This proves ballistic transport in our graphene heterostructures, in spite of the critical etching step for small lattice periods. We show measurements at different temperatures and can study antidot peaks down to very low carrier densities (n = 2ŕŁ1011 cmĂ2) and magnetic fields (B = 0.5 T). At higher magnetic fields, well defined quantum Hall plateaus with filling factors down to ßĽ = 1 are observed, even at an antidot period of 100 nm.

[1] L. Wang et al., Science 342, 614 (2013) [2] D. Weiss et al., Phys. Rev. Lett. 66, 2790 (1991)

Fig. 1: SEM image of a hBN/MLG/hBN heterostructure with a patterned antidot array (lattice constant d = 100 nm). The stack is contacted by Cr/Au leads.

202 | Graphene

Fig. 2: Magnetoresistance (black) and Hall resistance (red) of a patterned sample (antidot lattice period d = 100 nm) as a function of magnetic field at 1.4 K. For small perpendicular magnetic fields, additional peaks rise in ßŠâ&#x20AC;ŤÝ&#x201D;Ý&#x201D;â&#x20AC;Ź, which can be assigned to orbits around 1, 2 DQG DQWLGRWV $W KLJKHU ILHOGV % Â&#x2022; 7 ZH FDQ VHH pronounced plateaus from the QHE. The inset shows a sketch of electron orbits around a different number of antidots.

Charge carrier extraction in a graphene-WSe2-graphene heterostructure Peter Schmidt, Mathieu Massicotte, Fabien Vialla, and Frank H. L. Koppens

ICFO-Institut de CiĂŠncies Fotoniques, Mediterranean Technology Park, 08860 Casteldefells, Barcelona, Spain

Peter.Schmidt@icfo.es

Abstract Two-dimensional (2D) crystals, such as graphene, hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs), have aroused a lot of interest in both fundamental and applied physics during the past decade. Combining the complementary properties of these crystals in a single heterogeneous material is a promising approach to creating multi-functional, high performance optoelectronics [1]. This can be achieved by stacking them on top of each another, thus forming atomically sharp van der Waals heterostructures with clean interfaces. Recently, photodetectors using TMDs as light absorber and graphene as a gate-tunable electrode have been shown to be highly efficient [2-3]. Optical pump-probe experiments also found the charge transfer between TMDs and graphene to be very fast (~1 ps) [4]. Here we present a spectrally resolved study of the transport properties and photoresponse of grapheneWSe2-graphene heterostructures, encapsulated in hexagonal boron nitride. First, we find that the device exhibits a gate-tunable Schottky barrier, confirming a nearly defect and trap-free interface. We show that visible light is absorbed in WSe2, creating excitons that can be efficiently dissociated and extracted via the graphene layers at the top and bottom of WSe2. The excitonic absorption peaks are directly revealed in the photocurrent spectrum. We study the charge separation efficiency inside WSe2 and the charge carrier transfer from WSe2 to graphene. The underlying physics depends strongly on the thickness of WSe2 and the applied electric field. Our results pave the way to ultra-fast, high-efficiency and gate-tunable photodetectors.

References [1] Geim et al., Van der Waals heterostructures, Nature 499, 419-425 (2013) [2] Yu et al., Highly efficient gate-tunable photocurrent generation in vertical heterostructures of layered materials, Nature nanotechnology 8, 952-958 (2013) [3] Britnell et al., Strong light-matter interactions in heterostructures of atomically thin films, Science 340, 1311-1314 (2013) [4] He J. et al., Electron transfer and coupling in grapheneâ&#x20AC;&#x201C;tungsten disulfide van der Waals heterostructures, Nature Communications 5 (5622), 2014

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Structural and optical characterisation of h-BN layers L. Schue1,2, A. Pierret1, F. Fossard1, F. Ducastelle1, J. Barjon2 and A. Loiseau1 1LEM,

2GEMAC,

ONERA-CNRS, 29 avenue de la Division Leclerc, Châtillon, France Université Versailles St Quentin – CNRS, 45 avenue des Etats Unis, Versailles, France leonard.schue@onera.fr

Abstract Hexagonal boron nitride is a wide band gap semiconductor (~ 6.5 eV), which meets a growing interest for graphene engineering [1]. In particular electron mobility of graphene is shown to be preserved when graphene is supported by a h-BN film. We attempt to have a better comprehension of the optical and electronic properties of thin BN layers, in correlation with their structural properties and to better know how electronic properties of graphene can be impacted by underlying BN layers. Until recently, these properties were poorly known due to both the scarcity of crystals and suitable investigation tools. This situation has changed thanks, first, to the development of dedicated cathodoluminescence (CL) experiments running at 5K and adapted to the detection in the far UV range [2], and second to the avaibility of high quality single crystals [3]. H-BN has been shown to display original optical properties, governed, in the energy range 5.2 – 6 eV, by strong Frenkel-type excitonic effects [2, 4]. In this work, we first investigate by CL the luminescence properties of hBN samples synthesized by three different processes (HPHT, PDCs and a commercial powder). We observe in CL spectra the same features of the S series, in the energy range 5.7 – 6 eV. This reveals the intrinsic origin of these excitonic recombinations unlike the D series previously attributed to excitons trapped on defects such as dislocations or grain boundaries and observed at lower energy (5.2 – 5.7 eV) [5]. Besides, thin hBN layers have been obtained by mechanical exfoliation from small crystallites of a commercial powder and single crystal. We performed CL measurements on several flakes with various thicknesses from 100L to 6L and observed a significant effect of the confinement on the luminescence of hBN, especially in the energy range 5.7 – 6 eV previously mentioned. Indeed, CL spectra exhibit S series with different features depending on the hBN thickness. This strongly suggests that this signal (S series) could arise from distinct contributions that we will discuss.

References [1] C.R. Dean et al. Nature Nanotechnology, 5 (2010) 722. [2] P. Jaffrennou el al., Phys. Rev. B, 77 (2008) 235422. [3] Y. Kubota et al., Science, 317 (2007) 932. [4] L. Museur et al., Phys. Stat. Sol. RRL, 5 (2011) 414. [5] A. Pierret et al., Phys. Rev. B, 89 (2014) 035214.

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Local Optical Probe for Motion and Strain Detection of Resonances in Graphene Membrane Drums C. Schwarz, B. Pigeau, A. Kuhn, D. Kalita, Z. Han, L. Marty, O. Arcizet, N. Bendiab, V. Bouchiat Univ. Grenoble Alpes, F-38000 Grenoble, FRANCE CNRS, Inst Néel, F-38000 Grenoble, FRANCE cornelia.schwarz@neel.cnrs.fr Nanoelectromechanical systems (NEMSs) are emerging nanoscale elements at the crossroads between mechanics, optics and electronics, with significant potential for actuation and sensing applications. The reduction of dimensions compared to their micronic counterparts brings new effects including sensitivity to very low mass, resonant frequencies in the radiofrequency range, mechanical non-linearities and observation of quantum mechanical effects. An important issue of NEMS is the understanding of fundamental physical properties conditioning dissipation mechanisms, known to limit mechanical quality factors and to induce aging due to material degradation. There is a need for detection methods tailored for these systems which allow probing material parameters, motion and stress at the nanometer scale. Graphene, as a one-atom-thick layer, provides an ultimate membrane with a very low mass along with high Young modulus. Moreover its vibrational properties make it a new playground to probe strain in an actuated NEMS. Here, we show a non-invasive local optical probe for the measurement of motion and stress within a monolayer graphene NEMS with a well-defined geometry provided by a combination of reflection measurements and Raman spectroscopy. The system studied consists of a monolayer graphene sheet grown by chemical vapour deposition (CVD) that is suspended over prepatterned holes in a silicon dioxide substrate. Thus the geometry of the resonators is well- controlled and diameters up to 10 µm are reached. The graphene membrane is actuated electrically by applying a voltage to the silicon backgate or mechanically with a piezo crystal. The actuation ranges from a quasi-static load up to the mechanical resonance at some MHz. With reflection measurements of the actuated membrane the resonance frequencies of up to the first eight vibrational membrane modes can be determined. Furthermore mechanical non-linearities of the graphene are revealed by reflection measurements at high excitation powers. Raman measurements comparing the static and actuated state allow to determine the strain induced in the driven graphene membrane. In summary, a geometrically well-defined monolayer graphene resonator is presented which allows to study graphene material properties by reflection measurements. The latter are complemented by Raman spectroscopy measurements which open the route towards the nanoscale spatial detection of strain induced in a mechanical resonance mode of the graphene. Such spectroscopic detection reveals the coupling between a strained nano-resonator and the energy of an inelastically scattered photon, and thus offers a new approach to optomechanics. References [1] A. Reserbat-Plantey et al., Nat Nano, 7 (2012), 151-155 [2] A. Reserbat-Plantey et al., J. Opt., 15 (2013), 114010 [3] O. Frank et al ACS Nano, 5 (2011), 2231±2239

2 µm Figure 1: SEM micrograph of a suspended monolayer graphene drum

Figure 2: Mechanical resonance modes of suspended monolayer graphene drum

Graphene | 205

Contact Resistance of Molybdenum Disulfide Field Effect Transistor with Doped-Graphene Electrodes Seung-Bum Seo, Gi Woong Shim, Sang Yoon Yang, Dae Yool Jung, Gwang Hyuk Shin and Sung-Yool Choi Department of Electrical Engineering and Graphene Research Center, 291 Daehak-ro Yuseong-gu, Daejeon, Republic of Korea seosb@kaist.ac.kr Abstract Recently, the interest in layered tow-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) field effect transistor (FET) has been increased for the next generation electronic device. Especially, molybdenum disulfide (MoS 2 ) has attracted worldwide attention using channel material of the FET, showing high on/off ratio and high mobility.[1] However, most reports on the high performance of the MoS 2 FET have dealt with single crystalline bulk MoS 2 using scotch tape method. There are few reports on contact properties of the chemically synthesized MoS 2 compared with mechanical exfoliated MoS 2 . Thus, there are need for systematic investigation of contact characteristic with synthesized MoS 2 . The nature of MoS 2 FET is Schottky barrier transistor, which is switched by the tuning of the Schottky barriers at the metal-semiconductor interface. Many study commonly reported that this Schottky barrier can be attributed to the presence of sulfur vacancies, which is related to Fermi level pinning at contact and resulted in contact resistance increase. In order to reduce contact resistance, widely research efforts have been made recent years such as chemically doped contacts, low work function metal contacts. Another approach of reducing contact resistance has reported using high conductivity of the graphene, which is inserted between the metal and semiconductor [2]. The purpose of our work is to investigate the effect of the doped-graphene electrode on the contact characteristic of the chemically synthesized MoS 2 FET. We synthesized mono layer graphene and 1~3 layer MoS 2 by using chemical vapor deposition. Doped-graphene is transferred on the MoS 2 /SiO 2 substrate and then back-gate MoS 2 FET is fabricated by using photo-lithography and etching process. Applying doped-graphene electrode, the threshold voltage was slightly shifted in the negative direction and the drain current in the above threshold region was significantly increased. There are two kinds of mechanism which can be summarized as the occupation of sulfur vacancies by dopants at the graphene-MoS 2 interface and the enhancement of carrier injection at metal-graphene interface. Both mechanism are pretty similar assuming that the doping effect is accomplish by the extra carrier. More detailed discussions will be presented. References [1] B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, A. Kis, Nat. Nanotechnol., 6 (2011) 147 [2] Y. Du, L. Yang, J. Zhang, H. Liu, K. Majumdar, P. D. Kirsch, P. D. Ye, IEEE Electron Device Lett. 35, (2014) 599

Figures

Figure 1 Schematic of the atomic layer MoS 2 back-gate FET with doped-graphene electrode

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Superconductive-graphene hybrid devices I. Serrano-Esparza1,2, J.Michalik3, J. Rodríguez-Fernández4, L. Fernández-Barquín4, M.R. Ibarra2,3, J.M. de Teresa1,2,3 1

Instituto de Ciencia de Materiales de Aragón, Fac. Ciencias , 50009, Zaragoza, Spain 2 Dept. Física de la Materia Condensa, Fac. Ciencias, 50009, Zaragoza, Spain 3 Laboratorio de Microscopias Avanzadas, INA, 50018, Zaragoza, Spain 4 Dept. CITIMAC, Fac. Ciencias, Av/ Los Castros s/n, 39005, Santander, Spain iserranoe@unizar.es

Abstract In a superconductor-insulator-superconductor (SIS) junction we can have both tunnelling of quasiparticles (above the superconductor gap 2¨) or tunnelling of Cooper pairs at zero voltage, called Josepshon supercurrent. The width of the insulator layer must be very thin so that we can have a tunnelling current. We can also change the insulator layer by a normal metal of a given width. In this case, the Cooper pairs can survive inside the normal metal over a large length scale – what is called proximity effect – provided that the normal metal shows several properties like phase coherence and time reversal symmetry [1][2]. Although these properties were not clearly present in graphene [3], recent studies showed that the Cooper pairs could survive over distances up to 500nm [2]. Our purpose was to induce superconductivity in graphene by proximity effect. We used a SiO2 substrate and, as superconductor contacts, we prepared W-based deposits by Focused Ion Beam Induced Deposition (FIBID) using Ga+ ions, whose critical temperature is around 5K [4]. The ion beam can damage the graphene in an unrepairable way and the only solution is to prepare the device in a first step and deposit the graphene over it. We have used both CVD graphene and exfoliated graphene. The former must be grown on top of a copper substrate and then transferred to the device; whereas the latter can be deposited directly on top of the device using PDMS gel [5]. References [1] B. Pannetier and H. Courtois, J. Low Temp. Phys.118 (2000) 599 [2] H.B. Heersche et al., Nature 446 (2007) 56 [3] S.V. Morozov et al., Phys. Rev. Lett. 97 (2006) 016801 [4] E.S. Sadki, S.Ooi, and K. Hirata, Appl. Phys. Lett. 85 (2004) 6206 [5] A. Castellanos-Gomez et al., 2D Mater. 1 (2014) 011002 Figures 16

R (:)

TC1

TC2

11 2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

T(K)

Left. Device ready for graphene transfer. The separation between the superconductor contacts is around 500nm. Right. Resistance versus temperature in a sample with CVD graphene. We can observe two critical temperatures: TC1 at 4.5K, which corresponds to the critical temperature of the W deposits; and TC2 at 3.75K, which corresponds to the superconducting transition induced on the graphene layer.

Graphene | 207

Bubbles and perforations in graphene using a patched Green’s function technique Mikkel Settnes, Stephen R. Power, Dirch H. Petersen, and Antti-Pekka Jauho Center for Nanostructured Graphene (CNG), DTU Nanotech, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark mikse@nanotech.dtu.dk We present a new approach to the widely used recursive Green’s function technique and its application to local electronic and transport calculations of graphene nanostructures such as bubbles and perforations. First, we consider strained graphene bubbles and calculate the local density of states (LDOS) directly from tight binding thus going beyond the effective Dirac model. We demonstrate how the LDOS in nanobubbles with clamped edges contains strong signatures of this edge. In particular, we show how the clamped edge gives rise to significant Friedel type oscillations and spatial variations in the LDOS, as shown in Fig. 1a. The Friedel effects mix with any pseudomagnetic effects arising from the strain field. As many attempts to reliably produce nanobubbles result in significant edge effects, it is important to note that, when looking at the LDOS, simple size dependent features can become comparable to the effect of the strain induced pseudomagnetic field. Secondly, we consider the transmission between two point probes connected to an extended graphene sample. This demonstrates how the patched Green’s function technique efficiently calculates transport properties for widely separated features while still allowing for local mapping of bond currents and LDOS. Specifically, we show the current flow around perforations of the graphene lattice. Here localised states around zigzag edge segments of the perforation give rise to distinct signatures in the transmission spectrum. Furthermore, local mapping of the bond currents show how the transmission signatures are connected to vortex like current paths formed near these edges, see Fig. 1b. The developed method is based on Green’s functions and considers several device patches described by the Hamiltonian, HD , and connected through a self energy, ΣB , describing the extended part of the system as shown schematically on Fig. 1c. The patched Green’s function technique thus allows for calculations of non-periodic structures embedded within extended samples. The calculation scheme relies on a combination of analytic expressions for infinite pristine systems and an adaptive recursive Green’s function scheme. The combination allows us to efficiently calculate both local electronic and transport properties while including multiple leads on arbitrary geometries within extended samples.

Fig. 1: a) Shows deformation profile of a graphene bubble. The colormap indicates the difference in LDOS between the situation with and without the bubble. Yellow indicates high LDOS difference and black denote zero difference. The scalebar is 5 nm. b) The arrows indicate the bond currents emitted from the top probe and passing a perforation with zigzag edges (region without arrows). The color of the arrows correspond to the size of the current. c) Schematic of the patched Green’s function calculation setup. Where the device is indicated in dark gray and the extended part, described efficiently by the self energy ΣB , is indicated by light gray.

208 | Graphene

Negative Differential Resistance in Top-Gated Chemical Vapor Deposition Grown Graphene Transistors Pankaj Sharma, Laurent Syavoch Bernard, Antonios Bazigos, Arnaud Magrez and Adrian M. Ionescu École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland adrian.ionescu@epfl.ch Abstract Negative differential resistance (NDR) is a phenomenon in which an increase in voltage across the device's terminals results in a decrease in electric current through it. This is in contrast to a resistor in which an increase of applied voltage causes an increase in current due to Ohm's law. This unique phenomena can be exploited in numerous interesting applications, including high frequency oscillators, amplifiers, logic, memories and analog-to-digital converters. The NDR behavior can be realized with graphene transistors at high fields, thanks to its field-dependent carrier density and carrier-dependent saturation velocity, and has been demonstrated experimentally by few groups. [1]±[3] In this work, we report the observation of NDR in the output characteristics of graphene transistors fabricated using monolayer graphene grown by large-scale chemical vapor deposition process. The NDR here was demonstrated for various channel lengths ranging from 200 nm to 5 µm by employing wide channels, small un-gated regions, dual gating and thin top-gate dielectric. [4] Figure 1 shows the schematic view of the fabricated graphene transistor. Figure 2 shows the transfer characteristics of graphene transistor for 500 nm long and 30 µm wide channel having an equivalent oxide thickness of 2.5 nm. [4] Figure 3 shows the output characteristics for the same device. At the bias ܸ஻ீ ൌ െ 40 V, we see the decrease in the drain current (ISD) as drain voltage (VSD) is increased beyond ܸௌ஽ > 1.5 V, resulting in NDR. This effect is also reflected in the corresponding differential conductance ௗூೄವ ) showing negative values between ܸௌ஽ = 1.5 V and ܸௌ஽ = 1.98 V. (݃஽ௌ ൌ ௗ௏ೄವ

We have proposed a novel explanation for the mechanism behind this unusual feature of graphene, relating NDR with the interplay between the field dependent carrier modulation and the drift velocity in graphene transistors. [4] In addition, we have also shown that the NDR phenomenon in graphene can be realized in transistors with relatively thicker oxide, however, the NDR in this case is achieved at relatively higher gate voltages and has a lower maximum negative differential conductance value. [4] Our demonstration of NDR using graphene grown by production-worthy CVD process opens up a new route IRU JUDSKHQH¶V DSSOLFDWLRQ in oscillators, amplifiers, switches, memories etc. References

[1] Y. Wu, D. B. Farmer, W. Zhu, S.-J. Han, C. D. Dimitrakopoulos, A. A. Bol, P. Avouris, and Y.-M. Lin, ACS Nano, vol. 6, no. 3, pp. 2610±2616, 2012. [2] G. Liu, S. Ahsan, A. G. Khitun, R. K. Lake, and A. A. Balandin, J. Appl. Phys., vol. 114, no. 15, p. 154310, 2013. [3] S.-J. Han, D. Reddy, G. D. Carpenter, A. D. Franklin, and K. A. Jenkins, ACS Nano, vol. 6, no. 6, pp. 5220±5226, 2012. [4] P. Sharma, L. S. Bernard, A. Bazigos, A. Magrez, and A. M. Ionescu, ACS Nano, Article ASAP, http://dx.doi.org/10.1021/nn5059437

Figures

Figure 1 Schematic view of graphene transistor on Si/SiO2 substrate.

Figure 2 Transfer characteristics of 500 nm long and 30 µm wide channel at VBG = 0 and VDS = 0.01 V.

Figure 3 Drain current as a function of source-drain voltage for the same transistor as in Figure 2. Inset shows the corresponding differential conductance (gDS) as a function of source-drain voltage. NDR was not observed for VBG = 0 V because of higher series resistance as compared to the VBG = െ40 V.

Graphene | 209

Controllable Growth and On-Site Domain Boundary Imaging of Monolayer MoS2 on Au foils and Its Potential Application in Hydrogen Evolution Reaction Jianping Shi, Yanfengzhang Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 3HRSOHÂśV 5HSXEOLF RI &KLQD Center for Nanochemistry (CNC), Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular EQJLQHHULQJ 3HNLQJ 8QLYHUVLW\ %HLMLQJ 3HRSOHÂśV 5HSXEOLF RI China yanfengzhang@pku.edu.cn Abstract Controllable synthesis of monolayer MoS2 is the basic premise both for exploring some fundamental physical issues, and for engineering its applications in nanoelectronics, optoelectronics, etc. Herein, we report the scalable growth of domain size tunable (edge length from~ 200 nm to 80 Âľm), strictly monolayer MoS2 flakes or even complete films on commercially available Au foils, via low pressure chemical vapor deposition (LPCVD) method. By introducing H2 as carrier gas, we report the successful synthesis of large domain monolayer MoS2 triangular flakes on Au foils, with the edge length approaching to 80 Č?m. The growth process is proposed to be mediated by two competitive effects with H2 acting as both a reduction promoter for efficient sulfurization of MoO 3 and an etching reagent of resulting MoS2 flakes. By using low-energy electron microscopy/diffraction, we have further identified the crystal orientations and domain boundaries of MoS2 flakes directly on Au foils for the first time. Of particular interesting, the nanosized triangular MoS2 flakes on Au foils are proved to be excellent electrocatalysts for hydrogen evolution reaction (HER), featured by a rather low Tafel slope 2 (61mV/decade) and a relative high exchange current density (38.1ÂľA/cm ). The excellent electron coupling between MoS2 and Au foils is considered to account for the extraordinary hydrogen evolution reaction activity. These on-site and transfer-free characterizations should shed light on the initial growth and the aggregation of MoS2 on arbitrary substrates, further guiding the growth towards large domain flakes or monolayer films. And the synthesis of monolayer MoS2 with introducing metal foils as substrates presents a sound proof that monolayer MoS2 assembled on a well selected electrode can manifest comparable HER property with that of nanoparticles or few-layer MoS2 electrocatalysts. References [1] J.P. Shi, Y.F. Zhang, et al. ACS Nano, 8 (2014) 10196-10204. [2] J.P. Shi, Y.F. Zhang, et al Adv. Funct. Mater, (2014) In press. [3] T.F. Jaramillo, et al Science, 317 (2007) 100-102. [4] Y.Li, et al J. Am. Chem. Soc, 133 (2011) 7296-7299.

210 | Graphene

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Graphene | 211

NEW ALTERNATIVES TO GRAPHITE FOR GRAPHENE PRODUCTION BY SOLVENT EXFOLIATION Uriel Sierra, Patricia Álvarez, Clara Blanco, Marcos Granda, Ricardo Santamaría and Rosa Menéndez* Instituto Nacional del Carbón INCAR-CSIC, P.O. Box 73, 33080, Oviedo, Spain rosmenen@incar.csic.es The preparation of graphene by chemical methods, such as the graphite oxide or the solvent exfoliatin routes, offers the possibility of producing it on a large scale and, at the same time, of controlling its quality, depending on: a) the characteristics of the parent graphite[1] or the experimental conditions used [2, 3]. We recently reported that graphene oxides with standard characteristics can be obtained from pregraphitic materials (cokes) without the graphitization step.[4] Following with these investigations we studied herein the preparation of solvent exfoliated graphene materials directly from the pregraphitic precursor. The characteristics of the graphene materials obtained from coke and the correspondent graphite were determined. Sonication of the raw coke in N-Methyl-pyrrolidinone for 8h led to the formation of exfoliated graphene (EG-C and EG-CG from coke and graphite respectively) in the form of monolayers and more preferment few layers graphenes, as determined by AFM measurements (Figure 1), results being similar to those obtained from graphite. TEM images also confirm the exfoliation of coke and graphite (Figure 1) The different structure of the coke when compared to that of graphite is reflected in the composition of the exfoliated graphenes obtained from both materials. Thus, as determined by XPS, the carbon content in sp2 hybridization in EG-C is lower than that of EG-CG (67.0 % compared to 78.6 %), while there is a significant increment of the C-N bonding (12.3% compared to 7.3%) in this sample (Figure 1) from the NMP. Acknowledgments: Authors thank MICINN (CONSOLIDER INGENIO 2010 CSD2009-00050, U.Sierra fellowship, Ramón y Cajal contract of P. Alvarez) for financial support. References [1] Botas C, Álvarez P, Blanco C, Santamaría R, Granda M, Ares P, et al. Carbon 50 (2012) 275. [2] Dreyer DR, Park S, Bielawski CW, Ruoff RS. Chem. Soc. Rev.39 (2010) 228. [3] Keith R. Paton, Eswaraiah Varrla, Claudia Backes et al. Nature Materials 13 (2014) 624 [4] Patent PCT/ES2014/070178. Figures

Figure 1: AFM, TEM and XPS characterization of solvent exfoliated graphenes from coke (EG-C) and graphite (EG-CG)

212 | Graphene

Fig. 1 - Densely packed FLG sheet after deposition.

Graphene | 213

Spin±orbit interaction in the graphitic nanocone Jan Smotlacha, Richard Pincak Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Russia smota@centrum.cz Abstract The spin±orbit interaction in graphene is supposed to be weak, due to the low atomic number of carbon. In a curved graphene sheet where the symmetry of honeycomb lattice is broken there is a possibility of curvature± induced spin±orbit coupling. A consistent approach to introduce this kind of SOC has been developed by Ando [1]. The experimental evidence for this kind of spin±orbit coupling was reported by Kuemmeth et al. [2], where the authors measured the values of spin±orbit coupling in carbon nanotubes at various values of the magnetic field strength. It was revealed that the symmetry in electron±hole spectrum is broken. This can be caused by spin±orbit coupling. Energy spectra and transport properties of armchair nanotubes with curvature±induced spin±orbit interactions were investigated by Pichugin et al [3]. In [4] we derived the effective Hamiltonian for the graphitic nanocone with spin±orbit coupling induced by curvature and with the help of the Dirac-like equation, we introduced an explicit formula for the eigenspectrum of this Hamiltonian and found the solution numerically. Then we calculated the local density of states for different numbers of the pentagonal defects in the tip of the nanocone which influence the vortex angle. References [1] T. Ando, J. Phys. Soc. Jpn. 69 (2000) 1757. [2] F. Kuemmeth, S. Ilani, D. C. Ralph, P. L. McEuen, Nature 452 (2008) 448. [3] K. N. Pichugin, M.Pudlak and R.G. Nazmitdinov, Eur. Phys. J. B 87 (2014) 124. [4] R. Pincak, J. Smotlacha and M. Pudlak, EPJB (2014).

2D and 3D (bottom) graphs of the local density of states with and without (turned off) spin±orbital interaction for different distances r from the tip for different number of the defects: Nd = 1 (left), Nd = 2 (middle) and Nd = 3 (right).

214 | Graphene

Exciton-exciton annihilation and Stimulated Emission in Graphene Nanoribbons Giancarlo Soavi1, Stefano Dal Conte1, Cristian Manzoni2, Francesco Scotognella1, Akimitsu Narita3, Xinliang Feng3, Klaus Müllen3, Giulio Cerullo1,2 1. Dipartimento di Fisica, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano, Italy 2. IFN-CNR, Piazza L. Da Vinci 32, 20133 Milano, Italy 3. Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany giancarlo.soavi@polimi.it Although graphene displays extraordinary electronic properties, with its massless electrons (Dirac fermions) propagating for sub-micrometer distances in a ballistic regime without scattering, the absence of an energy-gap between valence and conduction bands is a severe limitation to its applications in electronics and optoelectronics. A possible solution to this problem is to induce a bandgap opening via quantum confinement, as for the one-dimensional Carbon Nanotubes (CNTs) and Graphene Nanoribbons (GNRs). Both systems attract great interest since they maintain the outstanding transport properties of graphene with the advantage of a sizable diameter or width-dependent bandgap. While CNTs have been intensely investigated over more than 20 years, studies on GNRs are still at their early stage and only little is known about their photophysical properties. Recent works demonstrate that, in analogy with CNTs, also in GNRs the optical absorption is dominated by excitons with high binding energy [1]. Here we apply femtosecond pump-probe spectroscopy to study the ultrafast temporal evolution of excitons in narrow (~1 nm) GNRs with cove-type edge structures, which were bottom-up synthesized in solution (THF). In particular, fluence dependent measurements for excitation at 570 nm, i.e. resonant with the first excitonic transition (inset fig. 1b), clearly highlight the appearance of a fast decay component of the ground-state bleaching (GSB) signal for increasing fluences (inset fig.1a). As for CNTs [2], this fluence-dependent ultrafast dynamics can be assigned to exciton-exciton annihilation, a mechanism that is greatly enhanced in quantum-confined systems due to relaxation of the momentum conservation and spatial confinement. Interestingly, the spectroscopic signature of this recombination process comes along with the formation of a positive differential transmission (ȴT/T) signal red-shifted with respect to the exciton GSB, at approximately 650 nm. This is evidenced by the change in sign of the dynamics at 650 nm (fig 1a) and the ȴT/T spectra at 100 ps pump-probe delay (fig. 1b). Since this delayed feature is energetically far from the exciton absorption and it does not appear in the groundstate absorption spectrum, we assign it to Stimulated Emission (SE). Similar results have been obtained for nanocrystal quantum dots [3], where the optical gain has been assigned to SE of bi-excitons [4]. Extending this result to our experimental data we find that bi-excitons in GNRs should have extremely high binding energy, in the order of 240 meV, even larger than the values obtained for CNTs [5]. These results provide new fundamental insights into the photophysics of GNRs and confirm their great potential for optoelectronics and laser applications. References [1] R. Denk et al., Nat. Comm. 5 (2014) 4253. [2] L. Huang et al., Phys. Rev. Lett. 96 (2006) 057407. [3] V. I. Klimov et al., Science 290 (2000) 314. [4] F. Kreller et al., Phys. Rev. Lett. 75 (1995) 2420. [5] T. G. Pedersen et al., Nano Lett. 5 (2005) 291. Figure 1. (a) Pump-probe dynamics of GNRs for different pump fluences at 650 nm and (inset) QRUPDOL]HG G\QDPLFV DW QP E ǻ7 7 VSHFWUD DW GLIIHUHQW SXPS IOXHQFHV IRU D IL[HG SXPS-probe delay of 100 ps and (inset) ground-state absorption spectrum of the sample.

Graphene | 215

Single and multilayer 2D-coatings for corrosion protection Adam C. Stoot, Luca Camilli, Susie-Ann Spiegelhauer*, Line E. Bergmann°, Peter Bøggild DTU Nanotech, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark *Accoat, Munkegårdsvej 16, 3490 Kvistgård, Denmark °Welltec A/S, Gydevang 25, 3450 Alleroed, Denmark adam.stoot@nanotech.dtu.dk Abstract Graphene’s [1,2] chemical stability and impermeability makes it a promising membrane for protection of various forms of corrosion [3]. However, recent investigations suggested that single layer graphene cannot be used as an anti-corrosion coating in the long run, due to galvanic corrosion phenomena arising when oxygen or water penetrate through graphene cracks or domain boundaries [4]. Here, we consider two approaches to overcome this issue; a multilayered (ML) graphene/graphite film or an insulating 2D material. A thicker graphene coating increases the diffusion path and thus limits the corrosion rate. This approach is shown to be effective in very aggressive industrial testing with real, rough samples. When it comes to thinner coatings, we choose to use hexagonal Boron Nitride, the 2D counterpart to graphene. It offers an alternative to graphene with comparable physical properties in terms of strength, stability and permeability, and which due to the sizeable bandgap is highly insulating, and thus cannot give rise to galvanic corrosion [5,6,7]. In this work we compare the two approaches in terms of not only galvanic corrosion, but also scalability, tendency of delamination (with and without mechanical stress), temperature and chemical environment. References [1] A.K. Geim, Nat Materials, 5 (3) (2007), page 183-191 [2] A.K. Geim, Science, 306 (2004), page 666-669 [3] D. Prasai, ACS Nano, 6 (2) (2012), page 1102-1108 [4] M. Schriver. ACS Nano, 7 (7) (2013), page 5763-5768 [5] X. Li, Nanotechnology 25 (10) (2014) [6] L.H. Li, Advance Materials and Interfaces, 1 (8) (2014) [7] Z. Liu, Nature Communications, 4 (2013) Figures

216 | Graphene

&9' JUDSKHQHÂśV GRSLQJ with Au nanoparticles

Aleksandra Krajewska1,2, Iwona Pasternak1, Alejandro Gutierrez3, Carmen Munuera 4, Mar Garcia Hernandez4, J.A. Martin-Gago4 and Wlodek Strupinski1 1) Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw, Poland, 2) Institute of Optoelectronics, Military University of Technology, Gen. S. Kaliskiego 2, 00-908 Warsaw, Poland 3) 'HSDUWDPHQWR GH )tVLFD $SOLFDGD ,QVWLWXWR GH &LHQFLD GH 0DWHULDOHV 1LFROiV &DEUHUD 8QLYHUVLGDG $XWyQRPD GH 0DGULG Cantoblanco, E-28049 Madrid, Spain 4) ,QVWLWXWR GH &LHQFLD GH 0DWHULDOHV GH 0DGULG &RQVHMR 6XSHULRU GH ,QYHVWLJDFLRQHV &LHQWtILFDV Cantoblanco, ES-28049 Madrid, Spain aleksandra.krajewska@itme.edu.pl Abstract Graphene appears to be a promising candidate for many applications that require the use of conductive, transparent and flexible material. Nevertheless, the characteristics of graphene and especially its sheet resistance remain inadequate to meet industrial demands. Chemical doping is used to solve this problem and enable obtaining top quality material. In this work we present the results of the studies of the influence of CVD grapheneÂśV chemical doping with tetrachloroauric acid on transport parameters. CVD graphene was grown on copper foil and subsequently transferred onto high-resistive Si/SiO2 and PET substrates. The transfer method was based on electrochemical delamination [1]. HAuCl4 solution of different concentrations was poured over graphene and spin-coated. It was observed WKDW JUDSKHQHÂśV Fhemical doping with HAuCl4 enables to reduce the sheet resistance even below 80 Â&#x; Ć&#x2018; The morphology of graphene before and after chemical doping was analyzed using AFM and SEM imaging. Raman spectroscopy was employed to characterize the optical properties of graphene films on Si/SiO2 and PET substrates. XPS spectroscopy was used to study the ratio of the reduction level of Au3+ ions to Au0 nanoparticles. The electrical properties of graphene samples were measured by the Hall method in van der Pauw geometry. This work was partially supported by the National Science Centre under the PRELUDIUM 2013/09/N/ST5/02481 grant.

References: [1] T. Ciuk, I. Pasternak, A. Krajewska, J. Sobieski, P. Caban, J. Szmidt, and W. Strupinski, J. Phys. Chem. C, 117, (2013) 20833Âą20837.

Graphene | 217

Binder-free graphene film via solvent exchange process as anode in Li-ion battery Haiyan Sun, Antonio Esau Del Rio Castillo, Andrea Capasso, Vittorio Pellegrini, Bruno Scrosati, and Francesco Bonaccorso Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, 16163 Genova, Italy haiyan.sun@iit.it Abstract Graphene showcases several key properties that can address emerging technological needs, in particular for the conversion and storage of energy in the ever-growing market of portable and wearable electronic devices [1]. The challenge lying ahead is to develop high-quality graphene in large volumes to ultimately suit the needs of an industrial-scale production [2]. Liquid-phase exfoliation (LPE) of graphite [3] is a promising tool for mass production of single and multi-layer graphene flakes, which can be prepared in the form of inks [4], thin films [3], and composites [5]. In particular, LPE graphene has been considered an ideal yet not fully explored material for anode in Li-ion battery [6] thanks to its chemical stability, large surface area and excellent electrical conductivity [7,8]. Here we report the fabrication of graphene-based anodes by LPE of graphite in N-Methyl-2pyrrolidone (NMP). By using a combination of sono-chemical exfoliation and ultracentrifugation we were able to obtain graphene flakes with controlled morphological properties (single and few-layer graphene flakes with lateral size of ~100nm (Fig.a)) [6,9]. A solvent exchange process is used to remove the NMP and re-disperse the flakes in ethanol [10], which has a lower boiling point. This procedure promotes the sedimentation of the graphene flakes in solution (concentration ~10mg/ml) due to the low surface tension of ethanol (~22 mN/m)[3]. By drop-casting the sediment flakes at ambient conditions (pressure and temperature) on a copper foil we are able to form a graphene film (Fig. b), avoiding high temperature deposition that can cause a partial oxidation of the flakes. Our electrodes have a significant advantage with respect to traditional Li-ion battery anodes requiring a binder (e.g., polyvinylidene fluoride) to draw the material together [2]. In fact, a binder-free anode film can avoid numerous drawbacks, such as time-consuming treatments to dissolve and dry the binders, additional mass loading, and possible performance degradation during charge-discharge cycles [11]. We tested our graphene film as anode against Li foil and the battery provided a specific capacity of 443 mAh/g after 50 cycles at a current density of 100 mA/g (higher than the specific capacity -185 mAh/g- of NMP-based graphene electrode tested in the same experimental conditions), with a Coloumbic efficiency approaching 100% (Fig.c). This in turn opens the way to the optimization of energy/power densities, lifetime, safety, while minimizing the cost and the environmental impact of this energy-storage technology. References [1] F. Bonaccorso et al., Science, 1246501 (2015) [2] B. Scrosati, et al., Journal of Power Sources, 9 (2010) 2419-2430. [3] Y. Hernandez, et al., Nature Nanotechnology, 9 (2008) 563-568. [4] F. Torrisi, et al., ACS Nano, 4 (2012) 2992-3006. [5] F. Bonaccorso, Z. Sun, Optical Materials Express, 1 (2014) 63-78. [6] J. Hassoun, et al., Nano Lett. 14 (2014), 4901í4906. [7] A. K. Geim, K. S. Novoselov, Nature Materials, 3 (2007) 183-191. [8] F. Bonaccorso, et al., Nature Photonics, 9 (2010) 611-622. [9] O. M. Maragó, et al., ACS Nano, 12 (2010) 7515-7523. [10] X. Zhang, et al., Chemical Communications, 40 (2010) 7539-7541. [11] I. Lahiri, et al., ACS Nano, 6 (2010) 3440-3446. Figures

Figure: a) Bright-field TEM image of graphene flakes at high magnification. Inset: Electron diffraction pattern collected on an area of 2 ȝP LQ GLDPHWHU 7KH ࡄ DQG ࡄ0 polycrystalline diffraction rings of graphene are clearly visible. b) SEM image of graphene film on Cu foil. Inset: optical image of the graphene-Cu supported electrode. c) Prolonged cycling (black NMP film; red ethanol film) and corresponding Coulombic efficiency (purple dots NMP film; orange dots ethanol film). Rate: 100 mAgí1.

218 | Graphene

Structural Characterization of 2D materials in the SEM using EDS and EBSD Christian Lang, Matthew Hiscock, Jonathan Moffat, Kim Larsen, Ravi S. Sundaram Oxford Instruments, Halifax Road, High Wycombe, United Kingdom christian.lang@oxinst.com 2D Materials enable exciting new applications in electronic devices and show great promise to replace traditional silicon technology as functional building blocks. However, in order to realise this potential there is a range of fabrication and integration challenges that have to be overcome and suitable characterisation techniques are needed. Due to their high resolution, electron optical characterisation in scanning electron microscopes (SEMs) and transmission electron microscopes (TEMs) is ideally suited for the structural characterisation of devices incorporating 2D materials. However, while electron imaging can give important insights into the device structure, for a full structural characterisation additional compositional data obtained from EDS analysis and crystallographic data from EBSD analysis can be added. Here we show how by processing EDS data obtained using highly sensitive, new generation EDS detectors in specially adapted software we can obtain data of sufficiently high quality to nondestructively measure the number of layers in 2D MoS2 (fig. 1) and thereby enable the characterisation of working devices based on 2D materials. We also show how we can use EBSD to address fabrication challenges of 2D materials. Results from EBSD analysis of individual flakes of exfoliated MoS2 obtained using the are shown to aid a better understanding of the exfoliation process which is widely used to produce 2D materials for research purposes. We show how EBSD can be used to detect the misorientation between flakes originating from different transfers (fig. 2).

Figures

Fig. 1: Shows the ability to clearly distinguish between one and two layers of MoS 2 from EDS spectra

Fig. 2 Shows the electron image and corresponding EBSD orientation map of an assembly of MoS2 flakes

Graphene | 219

Cooper Pair Splitting by means of Graphene Quantum Dots Zhenbing Tan,1 D. Cox,1 T. Nieminen,1 P. Lähteenmäki,1 D. Golubev,1 G. B. Lesovik,2 and P. J. Hakonen1 1

O.V. Lounasmaa Laboratory, Aalto University, Puumiehenkuja 2B, Espoo, Finland L.D. Landau Institute for Theoretical Physics RAS, Chernogolovka, 142432, Moscow Region, Russia

zhenbing.tan@aalto.fi Abstract Quantum entanglement is at the heart of Einstein–Podolsky–Rosen (EPR) paradox, which is fundamental for quantum information. Quantum entanglement has been successfully realized in optics, where the experiment benefit from the easy generation of entangled photons. In solid state, however, the progress has been modest. One natural source for quantum entanglement in solid state is split Cooper pairs. A Cooper pair, split out from a superconductor into two different terminals, will form a nonlocal entangled spin pair [1,2]. We report an experiment on a superconductor-graphene double quantum dot (QD) system, in which we observe Cooper pair splitting (CPS) up to a CPS efficiency of ~ 10% [3]. Comparing to the previous Cooper pair splitters [4-6], we were able to independently tune the bias and the energy levels of the two graphene QDs. Benefit from that, for the first time, the energy levels of the two QDs were tuned to be asymmetric or symmetric with respect to Fermi level in the superconductor. And we observed CPS or elastic co-tunneling favored as theories predicted [7,8]. The realization of CPS in graphene makes it feasible for graphene to be used for quantum information processing.

References [1] G. B. Lesovik, T. Martin, and G. Blatter, Eur. Phys. J. B 24 (2001) 287. [2] P. Recher, E. V. Sukhorukov, and D. Loss, Phys. Rev. B 63 (2001) 165314. [3] Z. B. Tan, D. Cox, T. Nieminen, P. Lähteenmäki, D. Golubev, G. B. Lesovik, P. J. Hakonen, http://arxiv.org/abs/1412.8451. [4] S. Russo, M. Kroug, T. M. Klapwijk, and A. F. Morpurgo, Phys. Rev. Lett. 95 (2005) 027002. [5] L. Hofstetter, S. Csonka, J. Nygard and C. Schonenberger, Nature 461 (2009) 960. [6] L. G. Herrmann, F. Portier, P. Roche, A. Levy Yeyati, T. Kontos, and C. Strunk, Phys. Rev. Lett. 104 (2010) 026801. [7] D. Feinberg, Eur. Phys. J. B 36 (2003) 419. [8] D. Chevallier, J. Rech, T. Jonckheere, and T. Martin, Phys. Rev. B 83 (2011) 125421. Figures

220 | Graphene

Tuning work function values in graphene oxide 卤 derived films Dimitrios Tasis

1,2

Lamprini Sygellou , Georgios Paterakis , and Costas Galiotis

1,3

Foundation of Research and Technology Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes (FORTH/ICE-HT), P.O. Box 1414, Gr-26504, Rion Patras, Greece. 2 Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece 3 Department of Chemical Engineering, University of Patras, 26504 Patras, Greece dtassis@cc.uoi.gr Abstract Work function (WF) is a fundamental electronic property of any material and provides understanding of the relative position of the Fermi surface level. WF tuning of the contact electrodes is a key requirement in several device technologies, including organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs), and complementary metal oxide semiconductor (CMOS) transistors [1]. Work function of graphene and its derivatives and the ability to control its value is a very important factor in applying these as an electrode material. Very recently, interest in a thin film of graphene oxide (GO) and reduced GO as an efficient hole transporting layer (HTL) for high-performance polymer solar cells (PSCs) has been emerged [2]. The aim of this work is to correlate the absolute WF value with the oxygen functionalities in a thin GO and rGO films. The GO film was deposited on ITO substrate, reduced with thermal treatment (heating in ultra high vacuum), chemical treatment or a combination of chemical and thermal process in vacuum. 强n order to investigate the effect of GO synthetic strategy , two different GO synthetic protocols which lead to differences in flake size and oxygen content were investigated. Additionally, the effect of GO thickness was also investigated. In order to correlate the WF with oxygen content and oxygen functionalities, X-ray and Ultraviolet Photoelectron Spectroscopies (XPS/UPS) used in each reduction step. The results showed that, as the oxygen content decreases upon thermal reduction of GO/ITO films, the work function decreases up to ~1eV. The combination of both chemical and subsequent thermal reduction leads to reduction of WF at even lower values depending on the presence of heteroatoms on the surface.

References [1] Abhishek Misra , Hemen Kalita , and Anil Kottantharayil, ACS Appl. Mater. Interf., 6 (2014) 786. [2] S.-S. Li, K.-H. Tu, C.-C. Lin, C.-W. Chen, M. Chhowalla, ACS Nano, 4 (2010) 3169.

Graphene | 221

Size quantization effects in quasiparticle interference on epitaxial graphene nanoflakes 1

Julia Tesch , Philipp Leicht , Felix Blumenschein , Anders Bergvall , Tomas Löfwander , Luca 1 1 Gragnaniello , Mikhail Fonin 1

Universität Konstanz, Konstanz, Germany Chalmers University of Technology, Göteborg, Sweden Julia.Tesch@uni-konstanz.de

Abstract Graphene nanostructures represent an exciting topic for research, as a strong spatial confinement together with the edge structure impose new electronic properties, making them promising candidates for future nanoscale electronic units. By means of low-temperature scanning tunnelling microscopy and spectroscopy we investigate the electronic properties of elongated quasi-freestanding epitaxial graphene nanoflakes (GNFs) on Ag(111) and Au(111). Samples are prepared by temperature programmed growth of graphene flakes on Ir(111) and subsequent intercalation of noble metals. This procedure allows us to produce GNFs of different shapes and sizes exhibiting no substantial edge bonding towards the substrate [1]. The edges display an edge configuration with long-range zigzag or rougher zigzag sections with single hydrogen termination. We implement local density of states (LDOS) mapping to analyze standing wave patterns arising from elastic scattering processes within single nanoflakes [2,3]. The Fourier analysis of the obtained LDOS maps shows that characteristic ringlike features due to the intervalley and intravalley scattering observed for large graphene sheets are also visible on the GNFs with lateral sizes down to 20nm. For GNFs, additional features appear inside the ringlike structures, which can be related to the transverse confinement in a nanoflake [4]. The scattering processes between the confinement-induced discrete bands in the nanoribbon electronic structure observed in flakes with a width of 100 nm indicate a large electron coherence length, though these features appeared less prominent within the Fourier transform for larger flakes. Our experimental results are supported by tight-binding calculations of realistic flakes, which very well reproduce the experimentally observed fingerprints of confinement in the Fourier transform of the standing wave patterns and confirm the strong influence of edge type as well as confinement direction and dimensions on the scattering in GNFs. References [1] P. Leicht et al., ACS Nano, 8 (2014) 3735 [2] G.M. Rutter et al., Science, 317 (2007) 219 [3] L. Simon et al., J. Phys. D: Appl. Phys., 44 (2011) 464010 [4] A. Bergvall et al., Phys. Rev. B, 87 (2013) 205431 Figures

Figure 1 (a) Topography of an investigated graphene flake on Ag(111). (b) QPI mapping with atomic 2 resolution (scanning parameters: 54x54 nm , V = -10mV, I = 0.8 nA, Vmod = 3 mV), the inset indicates the mapping position on the flake. (c) FFT of the obtained mapping. The inset shows a magnification of the intervalley scattering rings with clearly visible confinement features inside the characteristic trigonally warped circles. All measurements were carried out at 10 K.

222 | Graphene

Imaging and analysis of liquid-phase-processable graphene nanoribbons Joan Teyssandier,1 Wout Frederickx,1 Oleksandr Ivasenko,1 Tatyana Balandina,1 Kunal S. Mali,1 Akimitsu Narita,2 SĂ¸ren A. Jensen,2 Michael R. Hansen,2 Xinliang Feng,2 Klaus MĂźllen2 and Steven De Feyter1 1Division

of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven-University of Leuven, Celestijnenlaan, 200 F, B-3001 Leuven, Belgium 2Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany joan.teyssandier@chem.kuleuven.be

Abstract One of the major hurdles in the implementation of graphene in present day electronics is its lack of bandgap. One way to overcome this challenge is the creation of graphene nanoribbons (GNRs). Since the magnitude of the bandgap strongly depends on the width and the edge structure of such ribbons, the ÂľERWWRP-XSÂś V\QWKHVLV RI VWUXFWXUDOO\ ZHOO-defined GNRs is being actively pursued [1]. In this contribution, we present structural characterization of monolayer thick films of bottom-up synthesized GNRs on solid substrates using scanning probe methods, namely AFM and STM. We show that STM and AFM can be efficiently employed as complementary analytical tools for characterization of GNR together with conventional spectroscopic tools [1,2]. The highly controlled synthesis and liquid phase processability opens the way to GNR-based devices.

References [1] Narita, A., Feng, X., Hernandez, Y., Jensen, S. A., Bonn, M., Yang, H., Verzhbitskiy, I. A., Casiraghi, C., Hansen, M. R., Koch, A. H. R., Fytas, G., Ivasenko, O., Li, B., Mali, K. S., Balandina, T., Mahesh, S., De Feyter S. and MĂźllen, K., Nature chemistry, 6 (2014) 126-132. [2] Narita, A., Verzhbitskiy, I. A., Frederickx, W., Mali, K. S., Jensen, S. A., Hansen, M. R., Bonn, M., De Feyter, S., Casiraghi, C., Feng, X. and 0Â OOHQ . ACS Nano, 8 (2014) 11622-11630. Figure

Figure 1: (a) AFM phase image of a self-assembled monolayer of GNRs on HOPG (dry film), showing a small isolated domain. (b) Representative line profile, which was measured along the white line in the phase image shown in panel a. (c) Molecular model of this GNR displaying the packing of the GNRs in the self-assembled monolayer.

Graphene | 223

Imaging Spectroscopic Ellipsometry and Spectral Reflectometry with Ellipsometric Contrast (SREC), Two Methods for Optical Characterization of 2D-Material Peter H. Thiesen, Niklas Reineking, Dirk HĂśnig Accurion GmbH, Stresemannstr. 30, GĂśttingen, Germany pt@accurion.com Abstract Ellipsometry is a well-known non-destructive optical method for determining film thickness and optical properties. It measures the change in the state of polarization of the light reflected off the filmÂśs surface. Ellipsometry remains a macroanalysis technique, i.e., the sample size cannot be any smaller than about 20 Âľm. The development of imaging ellipsometry, which combines the power of ellipsometry with microscopy, has overcome this limitation. The enhanced spatial resolution of imaging ellipsometers in the range of 1 Âľm potentially expands ellipsometry into new areas of microanalysis, microelectronics, and especially exfoliated 2D materials. In a number of papers, Imaging ellipsometry has been applied to characterize graphene flakes of few micrometer size. Ellipsometric contrast micrographs, delta and Psi maps as well as wavelength spectra [1],[2] and single layer steps in multilayer graphene/graphite stacks [3] have been reported. Also Molybdenum disulfide, a layered transition metal dichalcogenide have been reported [4]. As an example, Delta- and Psi maps of a MoS2 flake at different wavelength are displayed (figure 1). Additional to microscopic characterization of tiny flakes, there is an increasing need of fast methods for quality control of large area graphene samples. This becomes possible by comparing the sample with a similar reference sample. Due to the orientation of the reference (see Fig. 1) it acts as an ideal compensator for all wavelengths. Hence no compensator is required. If the sample is equal to the UHIHUHQFH WKH RXWJRLQJ OLJKW LV OLQHDU SRODUL]HG DQG FDQ H[WLQJXLVKHG ZLWK D FURVVHG DQDO\]HU ,I WKHUHÂśV any difference between sample and reference, the light becomes elliptic polarized and the detected light flux increases. In order to maximize the rate of data acquisition, the analyzer is set to an off-nullposition. During the measurement neither the polarizer- nor the analyzer-angle are changed, so the measurement speed is only limited by the intensity of the light source and the processing speed of the spectrometer. References [1] Wurstbauer et al. (2010) Appl. Phys. Lett. 97, 231901 [2] Matkovic et al. (2012) J. Appl. Phys. 112, 123523 (2012) [3] Albrektsen O. J. et al. (2012) Appl. Phys. 111, 064305 (2012) [4] Thiesen et al. (2014) AVS AVS 61st International Symposium and Exhibition on November 11-13, 2014, in Baltimore, Maryland (USA) Figures

Figure 1. Delta- and Psi maps of a MoS2 flake at different wavelength.

224 | Graphene

CVD Graphene Electrical Quantum Metrology Kishan Thodkar, Christian SchĂśnenberger, Michel Calame Â&#x201A; Â&#x201A; Â&#x201A; Â&#x201A; F. LĂźĂśnd , Frederic Overney , Beat Jeckelmann , Blaise Jeanneret Department of Physics, University of Basel, Klingelbergstrasse 82 , 4056 Basel, Switzerland Â&#x201A; Federal Institute of Metrology, Lindenweg 50, 3003 Bern-Wabern, Switzerland kishan.thodkar@unibas.ch Abstract 2

Graphene, a two dimensional material with sp hybridized carbon atoms arranged in honey comb lattice, is known for its unique electronic and mechanical properties [1]. Quantum Hall Effect (QHE) in graphene is of particular interest for metrology. Due to its relatively large spacing between Landau levels in comparison to other 2DEGs; it is possible to observe QHE at lower magnetic fields and higher temperatures than in conventional two-dimensional electron gases (2DEGs). This makes graphene an ideal material to define a quantum resistance standard in terms of electron charge and Planck's constant [2]. QHE in graphene is so robust that it has been observed at room temperature (RT) [3]. We will present results for graphene grown via Chemical Vapor Deposition (CVD) and transferred to SiO 2/Si using different techniques. The transferred graphene films were patterned into millimeter scale Hall bar geometry and characterized using confocal Raman spectroscopy. Room and low temperature electrical transport measurements will be presented [4]. References [1] S.Das Sarma et. al, "Electronic transport in two-dimensional graphene", Rev.Mod.Phys. 83, 407-470 (2011). [2] 7 - % 0 -DQVVHQ HW DO Âł*UDSKHQH XQLYHUVDOLW\ RI WKH TXDQWXP +DOO HIIHFW DQG UHGHILQLWLRQ RI WKH 6, V\VWHP Â´ 1HZ - 3K\V YRO QR SS Âą6, Sep. 2011. [3] . 6 1RYRVHORY HW DO Âł5RRP-7HPSHUDWXUH 4XDQWXP +DOO (IIHFW LQ *UDSKHQH Â´ 6FLHQFH YRO March, p. 1379, 2007. [4] K.Thodkar et. al, "CVD Graphene for Electrical Quantum Metrology", CPEM 2014, 540-541 (2014). Figures 1 b) 1 a)

1 c)

1 d)

Figure 1 a) Optical image of CVD graphene on SI/SiO2 substrate. 1 b) Hall Voltage vs Magnetic & Gate Voltage sweep (RT). 1 c) Resistance vs Gate Voltage plot of a typical sample. 1 d) Rxx and Rxy vs Magnetic field sweep of a typical CVD graphene sample

Graphene | 225

Graphene Coating for Corrosion Resistance of Metals Abhishek Tiwari and R.K. Singh Raman Department of Mechanical and Aerospace Engineering Monash University (Melbourne), Vic 3800, Australia abhishek.tiwari@monash.edu Abstract: We demonstrate great potential of graphene coating as an exciting and durable protective coating against corrosion. The potential of an ultra-thin graphene layer as a corrosion resistant coating for copper, nickel and their alloys is a topic of very recent and exciting research interest (2011-2014). Large area graphene coating is generally synthesized by chemical vapour deposition (CVD). We have employed a low vacuum CVD process for synthesis of multilayer graphene on copper and Cu-Ni (75/25) alloy using n-hexane as hydrocarbon source. The characterization of graphene was done using Raman spectroscopy. The performance of graphene coating on corrosion resistance of Cu and Cu-Ni (75/25) alloy in 0.1M sodium chloride was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion protection shown by multilayer graphene coating on Cu and Cu-Ni (75/25) alloy was found to be nearly 5 times and 10 times respectively as compared to bare metal. The graphene coated Copper also continues to show corrosion resistance for longer durations of immersion in 0.1 M NaCl (upto 386 h). The level of corrosion protection due to this ultra-thin graphene coating can be further improved by circumventing the challenges in producing defect-free graphene layers. References [1] R.K. Singh Raman and A. Tiwari, Graphene: The Thinnest Known Coating for Corrosion Protection, J The Minerals, Metals & Materials Society (JOM),2014;66(4):637-42.DOI: 10.1007/s11837-014-0921-3 Figures

Fig.1: Evolution of Nyquist plots for the graphene coated copper in 0.1 M NaCl for different durations[1] ( The corrosion resistance is determined by diameter of semicircular loop in Nyquist Loop.)

226 | Graphene

Flexible, graphene-integrated, 122,880 pixels, electrophoretic display ‡

‡

F.Tomarchio , L.Lombardi , R. Agaiby , M.Banach , F.Torrisi , A.C. Ferrari ‡ §

‡

Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 OFA, UK Plastic logic Ltd, Cambridge, UK ft272@cam.ac.uk

Abstract Flexible displays are essential components in wearable screens, electronic newspapers, and smart identity cards [1]. Flexibility is usually limited by the weakest interface or by the most brittle layer in the stack, which is often a conducting oxide or metal [1]. Widespread use of flexible displays faces challenges due to processing limitations, such as high temperature (>200°C) [2] and fabrication costs of the active-matrix backplane[3,4,5]. Here, we present an active-matrix, flexible electrophoretic display that includes in its pixel electronics films of solution processed graphene combined with Single Wall Carbon Nanotubes (SWNTs). Graphene is produced by liquid phase exfoliation of graphite [6,7,8]. SWNTs are produced by arc discharge[9]. These are also functionalized with 3% carboxyl groups [9] to enhance dispersibility in water[10]. The SWNTs are individualized and stabilized in solution using tip sonication [11]. The de-bundling is performed employing linear chains surfactants [11], followed by ultracentrifugation to remove residual bundles [11].Coating by Meyer bar is used to deposit first the SWNTs dispersion and subsequently the graphene-ink, directly on the backplane of the display. The SWNTs-graphene ratio is 40:60% in mass, that assures the uniformity of the film on the backplane without aggregates. The SWNTs role is fourfold: 1) decreasing the contact angle of the ink on the backplane from 27.5° to 9.75°, 2) increasing the interfacial adhesion of the graphene ink with the substrate, 3) formation of a conductive network on the backplane for the subsequent graphene coating [12, 13], 4) promoting the charge transfer between graphene flakes, improving the conductivity of the graphene film [14]. The graphene coating improves the adhesion of the graphene/SWNTs film on the backplane during the processing of the display. The display contains 122880 pixels (320x384) (Fig.1a), driven by the same number of Thin Film transistors (TFTs). Graphene and SWNTs conformally cover 3µm deep vias (Fig.1b) and create the contact with the gold electrodes underneath. The graphene/SWNTs layer has strong adhesion on the backplane, with a peel force of 2.68 N. No delamination or cracking occurs up to a radius of curvature of 0.5mm, assuring the full flexibility of the display. References [1] PCP Bouten, Wiley (2005) [2] J.Lewis et al. Mat. Today 4 (2006) 38 [3] S.R.Forrest. et al. Nature 428 (2004) 911 [4] Y. Chen. et al. Nature 423 (2003) 136 [5] M. A. McCarthy et al. Science 6029 (2011) 570 [6] Y.Hernandez et al. Nat. Nanotech. 3 (2008) 563 [7] F. Torrisi et al. ACS Nano 6 (2012) 2992 [8] M.Lotya et al. J. Am. Chem. Soc. 131 (2009) 3611 [9] M. E. Itkis et al. Nano Lett., 3, (2003), 309 [10] B.White et al. J. Phys. Chem. C, 111, (2007), 13684 [11] T.Hasan et al. J. Phys. Chem. C 111 (2007) 12594 [12] L. Hu et al. Nano Lett. 4 (2004) 2513 [13] D. Zhang et al. Nano Lett. 6 (2006) 1880 [14] D. S. Hecht et al. Adv. Mater. 23 (2011) 1482 Figures

Fig 1. a) picture of the final flexible display, b) SEM image of one of the “via” of the backplane coated with graphene/SWNTs.

Graphene | 227

Structural differences between few-layer graphene oxide suspensions obtained from carbon nanotubes and fishbone nanofibers D. Torres, J.L. Pinilla, R. Moliner, I. Suelves Instituto de Carboquímica, CSIC. Miguel Luesma Castán 4, 50018 Zaragoza, Spain dtorres@icb.csic.es Abstract Graphene-based materials combine extreme mechanical strength with exceptional thermal and electronic conductivities and total impermeability to gases. These characteristics make them very attractive for numerous applications such as electronics, sensors, energy-storage materials, composites or catalytic supports. Synthesis of graphene oxide from graphitic carbon using chemical routes followed by ultrasonic exfoliation allows processing in liquid suspension. This opens the possibility of its industrial production where reduced graphene can be obtained in a final reduction step. Carbon nanofilaments (CN) can be used for graphene obtention as an alternative to the use of synthetic graphite, whose environmental sustainability and cost are penalized by the use of coke from petroleum processing and graphitization treatment at high temperature (> 2500 ° C), respectively. In this work, multi-wall carbon nanotubes (MWCNT), and fishbone carbon nanofibers (CNF) (structures shown in Figure 1) generated by catalytic decomposition of methane in a rotating bed reactor using a Fe-Mo/MgO and Ni/Al2O3 catalyst, respectively, were subjected to oxidation and exfoliation to obtain few-layer graphene oxides (FLGO, Figure 1). FLGO were obtained using a modified Hummers method [1], under a ratio of oxidation of KMnO4/CN = 6 (wt.) [2], followed by ultrasonic exfoliation. Homogeneous FLGO suspensions from expanded nanofilaments were separated by centrifugation at 2000 rpm in supernatant and precipitate, respectively. The products obtained were characterized by Raman spectroscopy, XRD, SEM and TEM. This synthesis strategy resulted in different exfoliation mechanisms depending on the starting CN: MWCNT showed an easier exfoliation, resulting in FLGO flakes, while fishbone CNF resulted in expanded CNF and small FLGO sheets after separation at 2000 rpm. The exfoliation degree is attributed to the different plane arrangement and lateral dimension of the graphene layers in the nanofilaments. References [1] W.S. Hummers, R.E. Offeman, JACS, 80 (1958) 1339. [2] D. Torres, J.L. Pinilla, R. Moliner, I. Suelves, Carbon, 81 (2015) 405.

Fishbone CNF

MWCNT

After centrifugation FLGO

Carbon Nanofilaments

Figures Pre 2000 rpm

Sup 2000 rpm

Pre 2000 rpm

Sup 2000 rpm

Figure 1. FLGO products obtained at 2000 rpm from fishbone CNF and MWCNT.

228 | Graphene

Hybrid states at interfaces of zigzag Graphene/BN heterostructures Van-Truong Tran, Jérôme Saint-Martin and Philippe Dollfus IEF, Université Paris-sud, CNRS, UMR 8622, Bât 220, 91405 Orsay, France van-truong.tran@u-psud.fr and philippe.dollfus@u-psud.fr Abstract It is well known that in zigzag graphene nanoribbons (ZGNRs), the top of the valence band and the bottom of the conduction band are always degenerate at k = ±S/a, forming states localized in the vicinity of the zigzag edges. These edge states appear in the band structure as nearly flat bands, i.e. with nearly zero group velocity (Fig. 1), i.e. they cannot contribute significantly to the conduction [1,2]. Recently, studies of topological insulators (TIs) have revealed the existence of states with very high group velocity localized at the surface or edge of samples, while bulk states have the usual properties of states in conventional insulators [3]. Taking advantage of the fact that it is now possible to grow in-plane heterostructures of hexagonal BN (h-BN) and graphene on the same monolayer [4], by means of atomistic simulation we have evidenced the emergence of interface states that look like edge states in ZGNRs but with high group velocity, as can be observed in TIs (Fig. 2). These interface states are localized in the graphene side of G/BN structures. Their maximum group velocity reaches 4.3×105 m/s at B-C interfaces and even 7.4×105 m/s at N-C interfaces. Additionally, in the case of asymmetric structure BN/Graphene/BN (with both B-C and N-C interfaces), a bandgap of 207 meV has been shown to be open for BN and graphene sub-ribbon widths of 5 nm. These specific properties suggest new ways to engineer and control the transport properties of graphene nanostructures. References [1] K. Nakada, M. Fujita, G. Dresselhaus, and M. Dresselhaus, Phys. Rev. B 54 (1996) 17954-17961. [2] A. Cresti, G. Grosso, and G. Parravicini, Phys. Rev. B 77 (2008) 115408. [3] B. A. Bernevig, T. L. Hughes and S.-C. Zhang, Science 314 (2006) 1757-1761. [4] Y. Gao, Y. Zhang, P. Chen, Y. Li, M. Liu, T. Gao, D. Ma, Y. Chen, Z. Cheng, X. Qiu, W. Duan and Z. Liu, Nano Lett. 13 (2013) 10-14. Figures (a)

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BN2 graphene BN1 BN2 graphene

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-1

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(b)

B-C

BN1 -0.5

0 k a /S

0.5

x x

Fig. 2. (a) zigzag BN/G/BN heterostructure with B-C-C-N interface bondings. (b) band structure of B-C-C-N for MBN1 = MCC = MBN2 = 50 with bandgap and high group velocity hybrid states (red color).

Graphene | 229

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Graphene Transistors for Detection of Neuronal Activity 1

Farida Veliev , A. Briancon-Marjollet , A. Bourrier , D. Kalita , V. Bouchiat and C. Delacour

Institut Néel, CNRS, 25 Rue des Martyrs, 38042 Grenoble, France Université Grenobel Alpes, HP2 & INSERM U1042, 38041 Grenoble, France vincent.bouchiat@greboble.cnrs.fr and cecile.delacour@greboble.cnrs.fr

Abstract: Due to its outstanding properties graphene offers an ideal platform for sensing and culturing neural networks. Its biocompatible, soft, and chemically inert nature associated to the lack of dangling bonds offers novel perspectives for direct integration in bioelectric probes. The presence of readily accessible surface charges gives the unprecedented possibility to realize a strong electrical coupling with cells. Moreover, the possibility to transfer it on transparent and flexible substrates opens the way to a variety of applications for in-vitro studies and in-vivo implants with reduced inflammatory response [1]. Here we present a study of our CVD grown SL graphene [2] with regard to its biocompatibility and bioelectrical interfacing. We found, that while on any other substrate an adhesive coating (such as polyL-lysine) is needed to assure neuronal growth in culture, graphene actively promotes the growth even without a coating. Moreover, in comparison to other frequently used substrates the neuron density and the neurite length are significantly higher for neurons cultured on uncoated graphene as shown in Fig. 1. Further, in order to prove the ability of graphene based devices to detect neuronal signals, we realized graphene FET arrays on Si/SiO2, glass and polyimide substrates and performed characterization measurements in cell culture medium with a Pt gate electrode. To mimic the neuronal spiking we superimposed 1ms long Gaussian pulses on the DC offset of the Pt-electrode. All graphene FETs 2 -1 -1 showed reproducible electrical properties with a mobility around 6000 cm V s and a sensitivity to potential changes up to 2 mS/V allowing a rapid detection of very small (around 200µV) potential spikes comparable with neuronal signaling [3]. Also, neurons were shown to survive on graphene FETs for periods up to 19-21 days achieving the regular maturation stage. In conclusion, our studies show the enormous potential of graphene based devices as neuronal growth support and bioelectrical sensors. References: [1] V.S. Polikov, P.A. Tresco, W.M. Reichert, Journal of Neuroscience Methods 148 (2005) 1±18 [2] Z. Han, A. Kimoche, D. Kalita, A. Allain, H. Arjmandi-Tash, A. Reserbat-Plantey, L. Marty, S. Pairis, N. Bendiab, J. Coraux, V. Bouchiat, Adv. Func. Mat., 24 (2014) 964-970. [3] J.J. Pancrazio, J.C. Keefer, W. Ma, D.A. Stenger, G.W. Gross, NeuroToxicology, 22 (2001) 393-400. Figures:

Fig. 1: Coating-free graphene promotes neuronal growth. a) Coating-free glass and graphene with neurons after 4 days in culture. The neurons survive only on graphene. b) Neuron density on day 1 and day 2 of and c) the average neurite length on day 2 of culture on different substrates: Ctrl - glass control sample, Gr graphene, Gr-noPLL ± coating-free graphene, Par-C ± parylene-C and PI ± polyimide.

Fig. 2: Graphene FET characteristics. a) Optical micrograph of a typical device. b) Conductance variation (black line) and device sensitivity (red line) as function of front liquid gate potential measured in cell culture medium. c) Detection of 1 ms long 250 µV Gaussian potential spike applied to the medium through a Pt-electrode using graphene FET.

Graphene | 231

Optical properties of highly transparent conductive uniaxial carbon films C. Villringer1, H. Lux1,2, P. Steglich1,2, J. Bauer1, S. D端mecke1, M. A. Schubert3, and S. Schrader1 1University

of Applied Sciences Wildau, Hochschulring 1, 15745 Wildau, Germany of Industrial Engineering, University of Rome 'Tor Vergata' Via della Ricerca Scientifica 1, 001333 Rome, Italy 3IHP Innovations for High Performance Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany claus.villringer@th-wildau.de

2Department

Abstract We present the fabrication and optical characterisation of highly transparent and conductive carbon films. A modified filtered high current arc (HCA) evaporation process was used for the deposition. The largearea carbon films with thickness of few nanometres were deposited directly on a silicon wafer coated with 300 nm silicon dioxide and on quartz substrate. The orientation of the polycrystalline carbon layers can be adjusted. Introducing a hydrogen flow, the carbon layers are mainly parallel to the interface, whereas without hydrogen the orientation are predominantly perpendicular to the interface. Variable angle spectroscopic ellipsometry measurements and transmission measurements were performed using SENresearch SE 800 DUV 2C 16M and Perkin Elmer LAMBDA 1050 UV/Vis/NIR devices in the spectral range from 190 nm to 980 nm and from 200 nm to 2500 nm, respectively. We used a uniaxial anisotropic layer model, where the optical axis is perpendicular to the sample surface, to determine the dispersions of the complex refractive index of ordinary and extraordinary rays. The optical model was supported by transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements. Finally, we present a comparison of ordinary and extraordinary optical constants of the samples as well as the isotropic dispersion of graphene and few-layer graphene (FLG) prepared by different technological processes [1-3]. References [1] J. W. Weber, V. E. Calado, and M. C. M. van de Sanden, Appl. Phys. Lett., 97 (2010) 091904. [2] A. Boosalis, R. Elmquist, M. Real, N. Nguyen, M. Schubert, and T. Hofmann, MRS Proceedings, 1505 (2013). [3] F. J. Nelson, V. K. Kamineni, T. Zhang, E. S. Comfort, J. U. Lee, and A. C. Diebold, Appl. Phys. Lett., 97 (2010) 253110.

232 | Graphene

High performance photodetectors based on graphene a and nd other 2D materials 1

1,2

Xuechao Yu , Qi Jie Wang , 1. OPTIMUS, Photonics Centre of Excellence, School of Electrical and Electronic Eng Engineering ineering , Nanyang Technological University, 50 Nanyang Avenue, 639798 639798, Singapore 2. Centre for Disruptive Photonic Technologies, Nanyan Nanyang g Technological University, 21 Nanyang Link, 63737, Singapore

qjwang@ntu.edu.sg Abstract Graphene and other 2D materials have attracted trem tremendous endous attention thanks to their extraordinary electronic and optical properties, ac accommodating commodating a large potential in modern optoelectronic optoelectro applications such as photodetection. Graphene is co considered as a suitable candidate for ultrafast and broadband photodetector, however, suffering from low light absorption and photoresponsivity. In our group, nanostructured graphene (graphene quantum do dots ts and nanoribbons) were employed to enhance the photoresponsivity off graphene based photodetector. The low detectivity of graphene photodetector based on photoconductive mode operation remains big challenges in further applications. Here, we demonstrated the photovoltaic mode operation in gra graphene p-n junctions fabricated by a simple but effective electron irradiation method that induces n-type doping in the intrinsic p-type type graphene and 10 exhibit a high detectivity of ~ 3Ă&#x2014;10 Jones. On the other hand, metal dichalcogenides and black phosphorene with strong in-plane in and weak out-of-plane plane interactions open up new opportunities for 2D materials for optoelectronic applications. Single crystal 1T phase Tin Diselenide (SnSe2) was synthesized and exfoliated into single and few fe layers. Atomically layered SnSe2 field-effect ect transistors displayed a high responsivity (0.5 A/W) and response time (~2 ms) in the visible range. Few layer black phosphorene p-n n junction formed by chemical doping was also demonstrated as a promising material for IR photodetector and filled the gap between graphene and metal dichalcogenides.

hotodetector based on graphene nanoribbon (a), grap graphene p-n n junction, bilayer SnSes Figure 1. Photodetector (c) and few layer black phosphorene (d).

Graphene | 233

Energy transfer in graphene-based nanostructures 1

Kamil Wiwatowski , Magdalena Twardowska , Aneta Prymaczek , Johannes Sommerkamp , Piotr 3 1 1 Nyga , Izabela KamiĔska , Sebastian Maükowski 1

Institute of Physics, Nicolaus Copernicus University, ToruĔ, 87-100, Poland Department of Biology and Biotechnology, Ruhr-University Bochum, Bochum, 44801, Germany 3 Institute of Optoelectronics, Military University of Technology, Warsaw, 00-908, Poland kamilw@doktorant.umk.pl

Among two-dimensional materials one of the best-known is graphene, which exhibits 1 extraordinary electronic and optical properties. For that reason, it has found a number of potential applications in photonics and optoelectronic. Fluorescence resonance energy transfer (FRET) can occur when the emission spectrum of a donor overlaps with the absorption spectrum of an acceptor. One of the factors that strongly influences this process is a distance between the two. It might result in quenching of donor emission in the 2,3 presence of an acceptor that is accompanied by shortening of donor fluorescence lifetime. In this work we exploit graphene as an energy acceptor. The spectral overlap required to observe FRET can be easily achieved as graphene exhibits 2,3% absorbance over the whole visible 4 range up to the infrared. As an energy donors we applied natural photosynthetic complexes and semiconductor nanocrystals. We study both a distance dependence of FRET, as well as an influence of excitation energy on the efficiency of the process. To achieve distance variations between emitters and graphene, we covered CVD graphene with silica layers of thickness up to 15 nm. Fluorescence intensities and lifetimes were measured using confocal microscopy and time-resolved fluorescence spectroscopy. The observed energy transfer from emitters to graphene results in shortening of fluorescence lifetime. The efficiency of the energy transfer shows strong distance dependence. The efficiency may also vary with wavelength of excitation or emission of energy donor. The results indicate a great potential for using graphene as a component of biologically functional hybrid nanostructures.

References [1] Geim A. K.; Novoselov K. S., Nature Materials, 6 ( 2007) 183-191. [2] Lakowicz J. R., Principles of fluorescence spectroscopy, Springer (2007). [3] Chen Z.; Berciaud S.; Nuckolls C.; Heinz T. F.; Brus L. E., ACS Nano, 4 (2010) 2964-2968. [4] Nair R. R.; Blake P.; Grigorenko A. N.; Novoselov K. S.; Booth T. J.; Stauber T.; Peres N. M. R.; Geim A. K., Science, 320 (2008) 1308.

Figures

234 | Graphene

High resolution near-field photocurrent measurements reveal optoelectronic properties of graphene Achim Woessner,1 Pablo Alonso-Gonzalez,2 Mark B. Lundeberg,1 Gabriele Navickaite,1 Yuanda Gao,3 Qiong Ma,4 Davide Janner,1 Kenji Watanabe,5 Takashi Taniguchi,5 Valerio Pruneri,1 Pablo Jarillo-Herrero,4 James Hone,3 Rainer Hillenbrand,6,7 and Frank H.L. Koppens1 1ICFO

- Institut de Ciencies Fotoniques, 08860 Castelldefels (Barcelona), Spain 2CIC nanoGUNE, 20018 Donostia-San Sebastian, Spain 3Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA 4Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 5National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan 6CIC nanoGUNE and UPV/EHU, 20018 Donostia-San Sebastian, Spain 7IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain achim.woessner@icfo.eu, frank.koppens@icfo.es Abstract Graphene is a promising material for optoelectronic applications as its lack of a bandgap leads to a broad band absorption that spans the visible, near-infrared, mid-infrared and THz regime.[1,2] For applications it is of great importance to know the exact optoelectronic properties of the devices used. With common far-field methods the large size of the laser spot after focusing prevents a spatial resolution below the diffraction limit. This leads to smearing of the spatial photocurrent maps, which can mask important details. Here we introduce a photocurrent measurement technique which is not limited by the diffraction limit. Using a scattering-type scanning near-field optical microscope (s-SNOM) [3,4] with a mid-infared laser source we excite a strong near-field at the apex of a metallized atomic force microscope probe tip, which acts as a local heat source, generating a temperature gradient in the graphene. This temperature gradient together with a change in Seebeck coefficient leads to a photothermoelectric photocurrent that can be measured spatially. [5] Here we show how near-field photocurrent measurements with extremely high spatial resolution can be used for characterizing optoelectronic devices made of graphene and graphene heterostructures.[6] We show photocurrent measurements at grain boundaries intrinsic to graphene grown by chemical vapor deposition [7] and extract their polarity. Furthermore we use this unique tool to measure photocurrent from charge puddles [8] of exfoliated graphene on silicon dioxide and show a photocurrent resolution of sub-30 nm. This proofs the extremely high spatial resolution which can be obtained, which ultimately is only limited by the radius of the tip apex. Finally we use the near-field photocurrent technique to confirm the spatial uniformity of the charge neutrality point of graphene encapsulated in hexagon boron nitride.[9] In summary, in this talk we introduce the novel near-field photocurrent mapping technique and show its potential applications in device characterization and quality control. References [1] F.H.L. Koppens et al., Nature Nanotechnology, 9 (2014) 780-793. [2] M. Badioli et al., Nano Letters, 14 (2014) 6374-6381. [3] J. Chen et al., Nature, 487 (2012) 77Âą81. [4] Z. Fei et al., Nature, 487 (2012) 82-85. [5] N. Gabor et al., Science, 334 (2011) 648-652. [6] A.K. Geim et al., Nature, 499 (2013) 419-425. [7] A.W. Cummings et al., Advanced Materials, 30 (2014) 5079-5094. [8] J. Martin et al., Nature Physics, 4 (2008) 144-148. [9] L. Wang et al., Science, 342 (2013) 614-617.

Graphene | 235

The Atomic and Electronic Structure of Phosphorene 1

Ryan J. Wu , Jong Seok. Jeong , Matt Robbins , Nazila Haratipour , Mehmet Topsakal , 1 2 1 Renata M. M. Wentzcovich , Steven J. Koester , K. Andre Mkhoyan 1

Department of Chemical Engineering and Material Science 2 Department of Electrical and Computer Engineering University of Minnesota, Minneapolis, MN, USA Email:Wuxx0642@umn.edu

Abstract Black phosphorus or phosphorene received considerable scientific interest over half a century ago due to its unusual stability compared to other phosphorus allotropes as a result of its unique crystal and 1

electronic structure . The recent emergence in 2-dimensional materials, however, has led to a 2

rediscovery of phosphorene as a layered 2D material with considerable applicability . While first principle studies have predicted both the atomic and electronic structure of phosphorene, atomic resolution experimental evidence to support the theoretical predictions would verify and further our understanding of this material. In this work, scanning transmission electron microscopy (STEM) was used to image few-layer phosphorene with atomic resolution to provide directly interpretable images of its crystal structure in three different zone axes models of which are shown in Figure 1. The 4

experimentally measured lattice parameters match those predicted by simulation . In addition, low-loss and core-loss electron energy loss spectroscopy (EELS) were used to analyze the electronic structure of this material. The resulting conduction band density of states measurements closely resembled those from DFT calculations. The effects of oxidation of phosphorene were also explored using a STEMEELS approach which explained the degradation observed in devices. References 1. Keyes, R. W, Physical Review, 92 (1953). 580-584 2. Xia, F., Wang, H. & Jia, Y., Nat Commun 5 (2014). 4458 3. Rudenko, A. N. & Katsnelson, M. I., Physical Review B 89 (2014). 201408 4. Dai, J. & Zeng, X. C. The Journal of Physical Chemistry Letters 5, (2014) 1289-1293

Figure 1: Structure of Black Phosphorus. a) top down view or [001] zone axis. b) 17.5 degrees off of [001] or [101] zone axis. c) cross sectional view or [100] zone axis.

236 | Graphene

Adsorption of emerging organic pollutants on graphene-based materials in the aqueous phase Nikolaos P. Xekoukoulotakis1, Catherine Drosou1, Konstantina Tyrovola1, Dimitris Christofilos2, Jiannis Arvanitidis3, Gerasimos S. Armatas4, Labrini Sygellou5, Despo Fata-Kassinos6 1

Department of Environmental Engineering, Technical University of Crete, Polytechneioupolis, GR73100 Chania, Greece, nikos.xekoukoulotaki@enveng.tuc.gr 2 Chemical Engineering Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 3 Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 4 Department of Materials Science and Technology, University of Crete, 71003 Heraklion, Greece 5 Foundation of Research and Technology Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes (FORTH/ICE-HT), P.O. Box 1414, Gr-26504, Rion, Patras, Greece 6 Department of Civil and Environmental Engineering and Nireas-International Water Research Centre, School of Engineering, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus Abstract In recent years, graphene and graphene oxide based materials have attracted considerable attention as adsorbents for water and wastewater purification, due to their outstanding adsorption properties [1-6]. More specifically, graphene and graphene oxide offer large surface area, significant pore volume, high conductivity, reach surface chemistry and low cost production [1-6]. In the case of graphene, the extended, delocalized, polyaromatic ʌ-system plays an important role for the formation of ʌ-ʌ stacking interactions with aromatic rings of several organic pollutants in the aqueous phase [1-6]. On the other hand, graphene oxide has lower ʌ-electron density, and more oxygen containing functional groups (such as carboxyl (-COOH), carbonyl (-C=O), epoxy (C-O-C-) and hydroxyl (-OH) functional groups) for the formation of hydrogen bonds and/or electrostatic interactions with dissolved organic pollutants in the aqueous phase [1-6]. Therefore, in the last few years graphene and graphene oxide have been successfully employed as novel adsorbent materials for the adsorption of inorganic pollutants, such as heavy metals and non metals such as fluoride, as well as for the adsorption of organic pollutants, including pharmaceutical compounds, from water and wastewater [1-6]. The aim of the present work was to study the adsorption of various emerging organic pollutants using graphite oxide and reduced graphene oxide as adsorbent materials in the aqueous phase. Graphite oxide was synthesized by the Hummers and Offeman oxidation method [7], while reduced graphite oxide was synthesized photochemically by the exposure of an aqueous suspension of graphene oxide to ultraviolet irradiation [8]. Graphite oxide and reduced graphite oxide were characterized in detail by various spectroscopic and microscopic techniques, such as XRD, FT-IR, Raman, XPS, and SEM. Moreover, the kinetics and the thermodynamics of the adsorption process of various pharmaceutical compounds, including antibiotics, onto graphite oxide and reduced graphene oxide in aqueous solutions was studied. Several experimental conditions were investigated, such as the contact time, the concentration of the organic pollutants, the temperature, the pH of the solution, and the effect of water matrix. Our results show that graphite oxide and reduced graphite oxide are very promising adsorbent materials for the decontamination of emerging organic pollutants from the aqueous phase. References [1] Yu J-G, Yu L-Y, Yang H, Liu Q, Chen X-H, Jiang X-Y, Chen X-Q, Jiao F-P, Science of the Total Environment, 502 (2015) 70–79. [2] Chowdhury S, Balasubramanian R, Advances in Colloid and Interface Science, 204 (2014) 35–56. [3] Upadhyay RK, Soin N, Roy SS, RSC Advances, 4 (2014) 3823–3851. [4] Kyzas GZ, Deliyanni EA, Matis KA, Journal of Chemical Technology and Biotechnology, 89 (2014) 196–205. [5] Wang S, Sun H, Ang HM, Tadé MO, Chemical Engineering Journal, 226 (2013) 336–347. [6] Kemp KC, Seema H, Saleh M, Le NH, Mahesh K, Chandra V, Kim KS, Nanoscale, 5 (2013) 3149– 3171. [7] Hummers Jr. WS, Offeman RE, Journal of the American Chemical Society 80 (1958) 1339. [8] Gengler RYN, Badali DS, Zhang D, Dimos K, Spyrou K, Gournis D, Miller RJD, Nature Communications, 4 (2013) 2560.

Graphene | 237

Molecular Beam Epitaxy of atomically thin 2D dichalcogenide Van der Waals semiconductor heterostructures K. E. Aretouli, P. Tsipas, E. Xenogiannopoulou, D. Tsoutsou, J. Marquez-Velasco, S.A. Giamini, E. Vassalou and A. Dimoulas Institute of Nanoscience and Nanotechnology, National Center for Scientific 5HVHDUFK Âł'EMOKRITOSÂ´ 15310, Athens, Greece Contact@E-mail:dimoulas@ims.demokritos.gr Abstract Atomically thin 2D semiconductors offer solutions for nanoelectronic device scaling and a number of low power versatile applications. There are a number of other 2D semiconductors such as the group IVdichalcogenides (e.g. HfSe2, ZrSe2) which remain unexplored. Due to Van der Waals heteroepitaxy [1] and the variety of energy gaps and electron affinities, VIB/IVB dichalcogenide heterostructures offer the possibility of sharp, defectÂąfree heterointerfaces and type-II band alignments [2] with potential applications in vertical broken gap 2D-2D TFETs. In this work, we show that using molecular beam epitaxy (MBE) of selenides [3] it is possible to grow good crystalline quality MoSe 2/HfSe2 (ZrSe2) heterostructures on large area (up to 2 inch) w-AlN(0001)/Si(111) substrates. The availability of 200 and 300 mm AlN/Si substrates creates the prospect for Si compatible processing in compliance with the semiconductor industry standards. All materials require a low temperature deposition step, followed by in-situ UHV annealing at high temperature. Epitaxy can start either with MoSe 2 in direct contact with AlN substrate followed by HfSe2 or with the reverse order without jeopardizing the quality of heterostructure bilayer. In situ RHEED (Fig. 1) and HRTEM (not shown here) reveal that the 2D heterostructures, despite the relatively large lattice mismatch, are epitaxially grown on AlN such that the [11-20] in-plane crystallographic direction of all materials are aligned. Films of a few layers of MoSe2 and HfSe2 are continuous with smooth surfaces over substrate area of at least 2 inches as seen by in-situ UHV-STM and SEM characterization (Fig. 2). Using in-situ XPS, the films are found to be very close to the ideal stoiFKLRPHWU\ 8VLQJ .UDXWÂśV PHWKRG, the valence band offsets are calculated to be (VBO~0.45 eV and CBO~0.9 eV) which deviate from the ideal band alignment as estimated by DFT [2]. The electronic valence band structure of 4 ML ZrSe2 (Fig. 3) and HfSe2 was imaged by in-situ HeI-ARPES and found to be in good agreement with our DFT calculations using GGA / v.der Waals potentials and spin orbit coupling in the scalar approximation. Acknowledgements: ERC AdG SMARTGATE (Grant No 291260)/ Greek Program for Excellence ARISTEIA-TOP-ELECTRONICS (Grant No. 745). We thank IMEC for providing us with AlN/Si wafers. References [1] A. Koma and K. Yoshimura, Surf, Sci. 174 (1986) 556. [2] C. Gong, H. Zhang, W. Wang, L. Colombo, R. M. Wallace, and K. Cho, Appl. Phys. Lett., 103, (2013) 053513. [3] P. Tsipas, E. Xenogiannopoulou, S. Kassavetis, D. Tsoutsou, E. Golias, C. Bazioti, G. P. Dimitrakopulos, P. Komnimou, H. Liang, M. Caymax and A. Dimoulas, ACS Nano. 8, (2014) 6614.

AlN

2L MoSe2 Tg = 350C + Tann=690 C

4L HfSe2 Tg = 350C + Tann=690 C

Fig. 1: RHEED of the HfSe2/MoSe2/AlN structure along the [11-20] azimuth

238 | Graphene

Fig. 2: UHV-STM of the HfSe2/MoSe2/AlN structure over an 2 area 1x1 Pm , with an RMS surface roughness of ~0.3 nm

Fig. 3: ARPES of the valence band structure of ZrSe2/MoSe2/AlN

Secondary Layer Evolution of Bilayer Graphene on Copper Ning Yang and Hyung Gyu Park*

Nanoscience for Energy Technology and Sustainability Department of Mechanical and Process Engineering ETH Z端rich Z端rich CH-8092, Switzerland * parkh@ethz.ch

Abstract The synthesis of bilayer graphene by chemical vapor deposition (CVD) on copper has been challenged by its self-limiting nature. The formation of continuous graphene layer prevents carbon supply from arriving at the underneath second layer, thus limiting the second-to-first-layer yield of the bilayer graphene. Here, we report a simple regrowth method capable of synthesizing the second layer graphene selectively with minimal change in size of the first layer. This regrowth method consists of two sequencing CVD processes with different hydrogen partial pressures and/or temperatures. We allocate the edge termination state of top layer graphene as the key parameter for this layer selective growth. A reaction mechanism based on hydrogen and carbon adatoms diffusion as well as carbon incorporation is applied to describe the saturation behaviour of the second layer graphene growth. The growth limiting step is found to be time dependent, transitioning from diffusion-limited to reaction-limited regimes.

Figures Hydrogen Terminated

Copper Passivated

Breaking graphene C-H bond

C diffusion

from free Cu to graphene+Cu

graphene+H graphene-H

Scale bar: 200 nm

Graphene | 239

High-Surface-Area Nitrogen-doped Reduced Graphene Oxide for Electric Double Layer Capacitors Hee-Chang Youn and Kwang-Bum Kim* Department of Material Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemoon-gu, Seoul 120-749, Republic of Korea ppopssong@yonsei.ac.kr Abstract Graphene has garnered tremendous research attention in the fields of sensors, energy storage, and energy conversion devices owing to the unique physical and chemical properties associated with its single-atomic-layered sp2 carbon network.[1] In particular, considerable research in the field of energy storage devices has focused on graphene as an electrode material for EDLCs because of its beneficial characteristics: superior high surface area and electrical conductivity.[2, 3] However, most of graphenebased electrode materials reported in the literature showed relatively low specific capacitance compared to the theoretical value (ca. 550 F/g) of a single layer graphene supported by an intrinsic EDL 2 FDSDFLWDQFH RI Č?)/cm and a specific surface area of 2650 m /g.[2, 4] As an electrode material for EDLCs, reduced graphene oxide (denoted as RGO) prepared by exfoliation and reduction of graphene oxide is extensively investigated due to its advantages of bulk-scale productivity and versatility in chemical functionalization.[5] However, oxidation treatment of graphite involved in the preparation of graphite oxide (denoted as GO) induces a variety of defects and oxygen functional groups, which break XS WKH Ę&#x152;-conjugated electronic structure of graphene and thereby degrade the electrical conductivity. The thermal/chemical reduction processes employed to reduce GO to RGO cannot completely restore WKLV Ę&#x152;-FRQMXJDWHG VWUXFWXUH )XUWKHUPRUH WKH 5*2 VKHHW WHQGV WR DJJORPHUDWH GXH WR VWURQJ Ę&#x152;-Ę&#x152; interaction between them during the reduction process, and thereby loses the specific surface area. Therefore, key issues in preparing RGO as an electrode material for EDLCs are an efficient exfoliation IRU KLJK VSHFLILF VXUIDFH DUHD DQG DQ H[WHQGHG UHFRYHU\ RI WKH Ę&#x152;-conjugated structure of RGO for high electrical conductivity. The heteroatom doping is another consideration for improving the electrochemical properties by manipulating local electronic structure of the RGO and hence increase in the EDL capacitance and electronic conductivity.[6] Since the quantum capacitance of RGO is thought to be in series with its EDL capacitance, the specific capacitance of RGO, which is the equivalent capacitance for the two capacitances in series, is expected to increase with an increase of the quantum capacitance. A nanoscale EDL is between a carbonaceous active material and an electrolytic solution and contribute to the specific capacitance of RGO, therefore, care should be taken not to decrease the specific surface area of RGO during heteroatom doping.[7] In this study, a nitrogen-doped RGO (denoted as N-RGO) with high specific surface area, electrical conductivity and low oxygen contents was synthesized using a time-efficient and scalable process composed of microwave irradiation and heat-treatment under NH3 gas. The near-edge X-ray absorption fine structure (NEXAFS) spectroscopy was emSOR\HG WR LQYHVWLJDWH WKH VHTXHQWLDO UHFRYHU\ RI WKH Ę&#x152;conjugated structure with removal of oxygen functional groups as well as the chemical bonding environments of incorporated nitrogen atoms in N-RGO. More detailed on the synthetic procedure, morphology, electrochemical and structural properties of encapsulated selenium in graphene micro-ball hybrid materials will be discussed at the meeting. References [1] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, A. A. Firsov. Science, 306 (2004) 666 [2] M. D. Stoller, S. Park, Y. Zhu, J. An, R. S. Ruoff. Nano Letters., 8 (2008) 3498 [3] X. Huang, Z. Zeng, Z. Fan, J. Liu, H. Zhang. Advanced Materials, 24 (2012) 5979 [4] J. Xia, F. Chen, J. Li, N. Tao. Nature Nanotechnology, 4 (2009) 505 [5] M. Choucair, P. Thordarson, J. A. Stride. Nature Nanotechnology 4 (2009) 30 [6] L. L. Zhang, X. Zhao, H. Ji, M. D. Stoller, L. Lai, S. Murali, S. McDonnell, B. Cleveger, R. M. Wallace, R. S. Ruoff. Energy & Environmental Science, 5 (2012) 9618. [7] Y. Qiu, X. Zhang, S. Yang. Physical Chemistry Chemical Physics, 13 (2011) 12554

240 | Graphene

Visible Light Modulation with Graphene R. Yu1, and F. Javier GarcĂa de Abajo1,2

ICFO Institut de CiĂ¨ncies FotĂ˛niques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain 2 ICREA-InstituciĂł Catalana de Recerca i Estudis AvanĂ§ats, Passeig LluĂs Companys 23, 08010 Barcelona, Spain renwen.yu@icfo.es , javier.garciadeabajo@icfo.es Abstract Fast modulation and switching of light at visible and near-infrared (vis-NIR) frequencies is of utmost importance for optical signal processing and sensing technologies. No fundamental limit appears to prevent us from designing wavelength-sized devices capable of controlling the light phase and intensity at terahertz speeds in those spectral ranges. However, this problem remains largely unsolved, despite recent advances in the use of quantum wells and phase-change materials for that purpose. Here, we explore an alternative solution based upon the remarkable electro-optical properties of graphene. In particular, we predict unity-order changes in the transmission and absorption of vis-NIR light produced upon electrical doping of graphene sheets coupled to realistically engineered optical cavities. The light intensity is enhanced at the graphene plane, and so is its absorption, which can be switched and modulated via Pauli blocking through varying the level of doping. Specifically, we explore dielectric planar cavities operated under resonant tunneling transmission conditions, as well as Mie modes in silicon nanospheres and lattice resonances in metal particle arrays. Our simulations reveal absolute variations in transmission â&#x2C6;ź 90% using feasible material parameters, thus supporting the use of graphene for fast electro-optics at visNIR frequencies.

References [1] R. Sainidou, et al., Nano Lett 10, 4450 (2010). [2] F. J. GarcĂa de Abajo, Acs Photon. 1, 135 (2014).

Figures !"#

graphene

k BF11

SiO2

n= 1.61

1.457

2.1

SiO2

BF11

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We present a planar multilayer structure considered for resonant tunneling light transmission, including a central BN planar waveguide (not to scale) and two single-layer graphene films intercalated at the BN/SiO2 interfaces. We show that transmission spectra of the multilayer structure at 71â&#x2014;Ś incidence for different levels of doping. At a wavelength of 689 nm, transmittance can be tuned from 95% to almost 0.

Graphene | 241

Growth Mechanism of Multi-Layer Graphene at Low-Temperature by Plasma Enhanced Chemical Vapor Deposition Kayoung Yun1, Dasol Cheang1, Jiyeon Hyun1, Aeran Roh1, Sun Heo1, Lanxia Cheng2, Jiyoung Kim 2, Pil-Ryung Cha1, Jagab Lee1, Ho-Seok Nam1,* 1School 2Department

of Advanced Materials Engineering, Kookmin University, Seoul, 136-702 Korea

of Materials Science & Engineering, University of Texas at Dallas, Richardson, Texas, 75080 USA kaysoars@kookmin.ac.kr hsnam@kookmin.ac.kr

Abstract

Graphene has received a lot of attention in many applications due to its unique and outstanding properties. Especially, multi-layer graphene has been considered as a replacement of copper wiring on LSI (largescale integration). Synthesis techniques for high-quality and large-scale graphene at low-temperature are required to apply for LSI semiconductor area. PECVD (plasma enhanced chemical vapor deposition) is one of the most expected methods for the industrial demands. Compared with thermal CVD graphene, the relatively lower quality of PECVD graphene is main drawback. In order to suggest a solution for the problem, we studied growth mechanism of multi-layer graphene on nickel by PECVD at 400Č&#x201D;. This study would be useful to optimize graphene growth conditions in many applications.

242 | Graphene

Solvent co-exfoliated graphene/MoS2 nanocomposite for photoactivated VOCs gas detection Shaolin Zhang, Woochul Yang* Department of Physics, Dongguk University, Seoul 100-715, Korea *wyang@dongguk.edu Abstract Graphene has been demonstrated as a potential gas sensor material by many researches [1,2]. However, the strong binding energy between graphene and analyte molecules leads to an inefficient desorption and subsequently a poor reliability on sensing performance. Besides, the lack of semiconducting property of graphene also disables the modulation of the transport characteristics through light irradiation or gate bias tuning to enhance the sensing performance. Compositing graphene with other two-dimensional (2D) layered materials brings in new or tailored properties, and offers the possibility to overcome the abovementioned shortcomings of graphene as sensor material. It is reported that compositing graphene with MoS2 provides ultrahigh photogain and excellent photoresponsivity [3,4]. The light induced electron-hole pairs would be greatly helpful for gas adsorption and desorption since the separation of electron-hole pairs increases the carrier concentration on the surface of sensor material. However, up to now, there is no report concerning this photoactivated gas sensing performance of graphene-MoS2 nanocomposite yet. In this study, we developed a cost-economical, time-saving and efficient ultrasound-assisted solvent method to exfoliate graphene and MoS2 simultaneously in a proper solvents mixture. The Hansen Solubility Parameter strategy basing on the theory of surface energy equilibration was applied to predict and optimize the composition of solvents mixture. A ternary-solvent system was used to minimize the difference of surface energy between solvents mixture and solutes. We demonstrated that the addition of solvent species provided an extra dimension to tune the surface energy of solvents mixture, and enabled us to brew the best solvents mixture for exfoliation process. Impressively, graphene-MoS2 hybrid structure was observed after heat treating co-exfoliated graphene-MoS2 solution, which was due to the restacking effect. The graphene-MoS2 nanocomposite was drop-casted on the sensor substrates, as shown in Fig.1 (a), and tested with various volatile organic compounds (VOCs) gases, including ethanol, methanol, benzene, and toluene, at room temperature with visible light irradiation. The experimental results revealed that the nanocomposite sensor exhibited n-type sensing response towards reducing VOCs gases, as shown in Fig. 1 (b). The sensing performance of nanocomposite sensor surpassed both graphene-based and MoS2-based sensor owing to the synergetic effect. Remarkably, the sensing property of nanocomposite sensor underwent degradation when the visible light irradiation was removed. References [1] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, M. I. Katsnelson, I. V. Grigorieva, S. V. Dubonos and A. A. Firsov, Nature, 438 (2005) 197. [2] A. K. Geim and K. S. Novoselov, Nat. Mater., 6 (2007) 183. [3] W. Zhang, C. Chuu, J. Huang, C. Chen, M. Tsai, Y. Chang, C. Liang, Y. Chen, Y. Chueh, J. He, M. Chou, L. Li, Scientific Reports, 4 doi:10.1038/srep03826 [4] K. Roy, Me. Padmanabhan, S. Goswami, T. P. Sai, G. Ramalingam, S. Raghavan, A. Ghosh, Nature Nanotech., 8 (2013) 826Âą830 Figures

Fig. 1 (a) The fabrication process of graphene-MoS2 nanocomposite sensor. (b) The typical sensing response of graphene-MoS2 nanocomposite sensor towards methanol gas with different concentrations at room temperature with visible light irradiation.

Graphene | 243

Dendritic, Transferable, Strictly Monolayer MoS2 Flakes Synthesized on SrTiO3 Single Crystals for Efficient Electrocatalytic Applications Yu Zhang, Yanfeng Zhang,* Zhongfan Liu Department of Materials Science and Engineering, College of Engineering, Peking University, 100871, Beijing, China Email: yanfengzhang@pku.edu.cn Abstract Controllable synthesis of macroscopically uniform, high quality monolayer MoS 2 is crucial for harnessing its great potentials in optoelectronics, electrocatalysis and energy storage. To date, triangular MoS2 single crystals or their polycrystalline aggregates have been synthesized on insulating substrates of SiO2/Si, mica and sapphire, etc., via portable chemical vapor deposition methods. Herein, we report a controllable synthesis of dendritic, strictly monolayer MoS2 flakes possessing tunable degrees of fractal on a specific insulator SrTiO3. Interestingly, the dendritic monolayer MoS2 characterized with abundant edges can be transferred intact onto Au foil electrodes and serve as ideal electrocatalysts for hydrogen evolution reaction, reflected by a rather low Tafel slope of‫׽‬73 mV/decade among CVD-grown two-dimensional MoS2 flakes. In addition, we reveal that centimeter-scale uniform, strictly monolayer MoS2 films consisting of relatively compact domains can also be obtained, offering insights into promising applications such as flexible energy conversion/harvesting and optoelectronics. References [1] Voiry, D.; Salehi, M.; Silva, R.; Fujita, T.; Chen, M.; Asefa, T.; Shenoy, V. B.; Eda, G.; Chhowalla, M. Nano Lett.13(2013), 6222-6227. [2] Zhang, Y.; Ji, Q.; Han, G.-F.; Ju, J.; Shi, J.; Ma, D.; Zhang, Y.; Li, M.; Lang, X.-Y.; Zhang, Y.; Liu, Z. ACS Nano, 8 (2014), 8617±8624. Figures

244 | Graphene

(One page abstract format: including figures and references. Please follow the model below.)

The effect of oxygen content on lithium storage in graphite oxide by first principles studies Si Zhou, Guobao Li, Jijun Zhao College of Advanced Science and Technology, Dalian University of Technology, 2 Linggong Road, Ganjingzi District, Dalian, 116024, China zhousi.nju@gmail.com

Abstract (Arial 10) Nowadays, lithium ion batteries (LIBs) have been widely used in portable electronic devices, owing to their high energy densities [1]. LIBs are also considered as promising devices for electric vehicles [2]. Commercial LIBs commonly use graphite as the anode material. However, the relative low Li capacity of graphite limits the performance and hence the applications of LIBs [3]. A possible route to enhance Li storage is chemical modification of graphite by oxygen [4,5]. However, the effect of oxygen content on the performance of such anode materials is known only approximately [6]. In this work, we systematically investigated the adsorption, diffusion, and intercalation behaviors of Li ions in graphite oxide at various oxidation levels, based on density functional theory calculations. The goal is to design graphite oxide compounds with high lithium potentials, large diffusion rate for Li ions, and high Li capacity. This theoretical work will not only provide better insight into the microscopic mechanism of Li storage in graphite oxide, but also be a guidance for experimental fabrication of LIBs with improved performance.

References [1] J. R. Miller, P. Simon, Science, 321 (2008) 651–652. [2] Jiajun Chen, Materials, 6 (2013) 156-183. [3] Gaixia Luo, Jijun Zhao, Baolin Wang, Computational Materials Science, 68 (2013) 212-217. [4]T. Bhardwaj, A. Antic, B. Pavan, V. Barone, B. D. Fahlman, Journal of the American Chemical Society, 132 (2010) 12556-12558.  [5] S. W. Lee, N. Yabuuchi, B. M. Gallant, S. Chen, B. S. Kim, P. T. Hammond, Y. Shao-Horn, Nature Nanotechnology, 5 (2010) 531–537. [6] Maria E. Stournara, Vivek B. Shenoy, Journal of Power Sources, 196 (2011) 5697-5703.

Figures

Graphene | 245

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Portugal

Poland

Spain

country

249 | N a n o S p a i n B i o & M e d

Pedro E.M. Videira, Eduardo L.T. Conceição, António T.G. Portugal, Rogério M.S. Simões, Manuel J. Santos Silva

Curto, Joana

Luis Yate, Danijela Gregurec, Willian Aperador, Sergio E. Moya, Guocheng Wang

Coy, Emerson

D.M. Love, J. Llandro, J.J. Palfreyman, C.H. W. Barnes, Liz Muir, Geoff Cook, and Roger Keynes

Cimorra, Christian

Barbara M. Maciejewska, Małgorzata Jasiurkowska-Delaporte, Alicja Warowicka, Emerson Coy, Tomasz Zalewski, Stefan Jurga

Baranowska-Korczyc, Anna

Sonia Contera, Jose Angel García, Fernando Plazaola

Axpe, Eneko

Oier Aizpurua-Olaizola, Aresatz Usobiaga, Félix M. Goñi, Itziar Alkorta

Arana, Lide

H. Joda, O. Y. F. Henry, B. Werne Solnestam, L. Kvastad, E. Johansson, J. Lundeberg, N. Lladach, P. Salvo, K. Dhaenens ,A. Gielen, J. Vanfleteren, D. Latta, I. Riley and C. K. O’Sullivan Hens

Acero, Josep Lluis

authors

Optimization of polymeric nanomaterials for biomedical applications using computational simulation

Nb-C nanocomposite coatings for biomedical applications

Hetero-coated magnetic microcarriers for point-of-care diagnostics

Multi walled carbon nanotube/Fe-polymer-organic dye nanohybrids as magnetic-fluorescent contrast agent for cellular imaging

Free Volume: a New Physical Parameter in Biomaterials and Cancer

Solid lipid nanoparticles for delivery of calendula extracts

Genetic analysis of single cancer cell using a multiplexed DNA amplification strategy coupled to 64 electrode PCB sensor arrays for detection

poster title

NanoSpain2015 Bio&Med Posters list: alphabetical order

Spain

Germany

Spain

Lithuania

Spain

Czech Republic

country

250 | N a n o S p a i n B i o & M e d

Josep Lluis Acero Sanchez, Mary Luz Botero, M. Carmen Bermudo Redondo and Ciara K. O’Sullivan

Joda, Hamdi

Sjef Cremers, Paul Borm, Fabian Kiessling

Guvener, Nihan

Gaizka Garai-Ibabe, Laura Saa, Valery Pavlov

Grinyte, Ruta

Lina Ramanauskaite,Valentinas Snitka

Grinceviciute, Nora

J. Feuchtwanger, M.L. Fdez-Gubieda and A. García-Arribas

Goiriena-Goikoetxea, Maite

O. Guaresti, T. Gurrea, A. Eceiza, L. Fruk, M. A. Corcuera, N. Gabilondo

García-Astrain, Clara

Rafael Valiente, Jesús González, Juan C. Villegas, Mónica L. Fanarraga

García Hevia, Lorena

Jon V. Busto, Alicia Alonso, Félix M. Goñi

García, Aritz

Marta Pastor, Silvia Villullas, Jose Javier Aguirre, Francisco Borja Gutierrez, Enara Herran, Oihane Ibarrola, Angel del Pozo, Jose Luis Pedraz, Rosa Mª Hernandez, Manoli Igartua, Eusebio Gainza

Gainza, Garazi

Jana Drbohlavová, Jana Pekárková, Jaromír Hubálek

Fohlerová, Zdenka

authors

Evaluation of PCB based gold electrode array cleaning methods for electrochemical biosensor applications

MRI Guided Interventions needs new materials and contrast agents

Application of Photocatalytical Activity of CdS Nanoparticles to Development of Sensitive Colorimetric Enzymatic Assays Using 3,3’,5,5’- tetramethylbenzidine (TMB) as a Universal Chromogenic Compound

Investigation of bilayer lipid membranes on nanostructured Au and Ag substrates by surface enhanced Raman spectroscopy

Permalloy Nanodisks for Biomedical Applications

Bionanocomposite Hydrogels Effectively Cross-linked with Functionalized Nanoparticles

Multiwalled Carbon Nanotubes applied in cancer treatment

Complex lamellar gel lipid phases enriched in ceramide and cholesterol: an AFM study in lipid membranes

An advanced strategy for the treatment of chronic wounds: rhEGF loaded nanostructured lipid carriers (rhEGF-NLC) enhance the healing of full-thickness excisional wounds in db/db mice

Functionalized nanoparticles for bioapplications

poster title

Greece

Spain

Poland

Spain

Israel

Turkey

Spain

country

251 | N a n o S p a i n B i o & M e d

V. Karagkiozaki, D. Konstantinou,E. Pavlidou, Th. Choli-Papadopoulou, S. Logothetidis

Pappa, Fotini

Enea Sancho, Fernando Gil-Ortiz, Dalila Ciceri and Kornelius Zeth

Okuda, Mitsuhiro

Thipapun Plyduang, Ana Armiñán, Richard M. England, Ruedeekorn Wiwattanapatapee and María J. Vicent

Movellan, Julie

Francisco Martín, Gonzalo G. Fuentes

Monteserin , María

Justyna Jurga-Stopa, Alicja Warowicka

Maciejewska, Barbara

Macarena Calero, Pierre Couleaud, Antonio Aires, Alfonso Latorre, Álvaro Somoza, Aitziber L. Cortajarena, Rodolfo Miranda and Angeles Villanueva

Lazaro-Carrillo, Ana

María del Mar Encabo, Víctor Sebastián, Manuel Arruebo and Jesús Santamaría

Larrea Ibáñez, Ane

Tatiana Molotsky, Artium Khatchatouriants, Revital Krispin, Tal Hasson and Arthur Komlosh

Khatchatouriants, Artium

Burcu Bağdat Cengiz, Mehmet Doğan Aşık, Mustafa Türk, Emir Baki Denkba

Kara, Göknur

Maria José Martínez-Tomé, Rebeca Vázquez, Amalia Mira, Ricardo Mallavia and C. Reyes Mateo

Kahveci, Zehra

authors

Fabrication and Characterization of Biomimetic Scaffold based on Modified PVA/PEDOT: PSS Nano-Fiber Materials for Tissue Regeneration

Structural analysis of artificial nanoparticle formation in Listeria innocua Dps

A polyacetal-based combination therapy for the treatment of prostate cancer

Synthesis of superparamagnetic nanoparticles for magnetic hyperthermia application

Modified MWCNT carpets as potential scaffolds for tissue engineering

Ferromagnetic nanoparticles as delivery system of antitumor drugs for targeting breast cancer cells

Microfluidics, a tool to produce heterostructured nanomaterials Au-Fe3O4 for biomedical applications

Characterization of Copaxone by Atomic Force Microscopy (AFM) and Dynamic Light Scattering (DLS)

Chitosan Nanoparticles for siRNA Based Gene Silencing Therapy for Cancer

Fluorescent Conjugated Polyelectrolytes for the Potential Detection of Bacterial Infections

poster title

Various architectures of star polymers based on PEO, as a model system for the delivery of nucleic acids

The cytotoxicity and cellular interaction of MWCNT-Fe composites

Poland

Enzymatic Modulation of Shape of Gold Nanoparticles in Bioanalysis

Magnetic liposomes based on nickel ferrite nanoparticles as nanocarriers for new potential antitumor compounds

A composition for the preparation of dentifrices and other dental products

Lipid nanoparticles as tobramycin and sodium colistimethate encapsulation alternative: towards improved anti-infective therapy against Pseudomonas aeruginosa infection

poster title

Poland

Spain

Portugal

Poland

Spain

country

252 | N a n o S p a i n B i o & M e d

Alicja Warowicka, Anna Baranowska-Korczyc, Justyna Jurga-Stopa, Barbara Maciejewska

Szczesniak, Katarzyna Nanomaterials “Surface Monika Makrocka-Rydzyk, Anna Wolniak, degradation of magnetite Marcin Jarek, Lukasz Popenda, Hong Y. Cho, Stefan Jurga, Krzysztof Matyjaszewski nanoparticles” Luís Frederico Pinheiro Dick Warowicka, Alicja

M. Coronado-Puchau, V. Pavlov, L. M. LizMarzán

Saa, Laura

T. Gomes, Bernardo G. Almeida, J. P. Araújo, Maria João R.P. Queiroz, Elisabete M. S. Castanheira, Paulo J. G. Coutinho

Rodrigues, Rita

Marcin Banach

Pulit-Prociak, Jolanta

A Esquisabel, G Gainza, E Herran, S Villullas, O Ibarrola, A del Pozo, JJ Aguirre, M Castresana, E Sans, M Viñas, D Bachiller, JL Pedraz, E Gainza

Pastor, Marta

authors

Genetic analysis of single cancer cell using a multiplexed DNA amplification strategy coupled to 64-electrode PCB sensor arrays for detection 1

J. Ll. Acero Sanchez , H. Joda , O. Y. F. Henry , B. Werne Solnestam , L. Kvastad , E. Johansson , 2 3 4,5 4,5 4,5 4,5 6 J. Lundeberg , N. Lladach , P. Salvo , K. Dhaenens , A. Gielen , J. Vanfleteren , D. Latta , I. 7 1,8 Riley and C. K. O’Sullivan 1

Universitat Rovira i Virgili, Departament de Enginyeria Química Av. Països Catalans 26, 43007 Tarragona, Spain. 2 KTH Royal Institute of Technology, Science for Life Laboratory (SciLifeLab Stockholm), School of Biotechnology, Division of Gene Technology, SE-171 65 Solna, Sweden. 3 MRC Holland, Willem Schoutenstraat 6, 1057 DN Amsterdam, The Netherlands 4 University of Ghent, Centre for Microsystems Technology (CMST), Faculty of Engineering, 914A Technologiepark, B-9052 Ghent-Zwijnaarde, Belgium. 5 Interuniversity Microelectronics Centre (IMEC), 3001 Leuven, Belgium. 6 Fraunhofer (ICT-IMM), Carl-Zeiss-Str. 18-20, 55129 Mainz 7 Labman Automation Ltd., Seamer Hill, Seamer, Stokesley, North Yorkshire, TS9 5NQ, United Kingdom. 8 Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Spain. ciara.osullivan@urv.cat; joseplluis.acero@urv.cat

Abstract Novel breakthrough in the understanding of metastasis and the formulation of new cancer models have motivated the development of novel integrated analytical technologies capable of isolating and identifying single cancer cells. However, the complexity of circulating cancer cells requires deeper analysis to provide sufficient insight into the real nature and therefore malignancy of the cell. Genetic profiling can undoubtedly provide the level of information required. We report on a novel strategy towards the multiplexed genetic profiling of single tumour cell using a combination of multiplexed ligation-dependant probe amplification (MLPA) coupled to sensitive detection using electrode microarrays manufactured on standard printed circuit board (PCB) substrates. Single cancer cells were isolated by laser capture, lysed and the mRNA extracted and transcribed into DNA. Then, various relevant regions were amplified by MLPA technique. The MLPA reaction allows for multiplex amplification of multiple targets with a single primer pair. Novel synthetic MLPA probes were designed to include a unique barcode sequence in each amplified gene which acts as capture probe for microarray analysis. Capture probes complementary to each of the barcode sequences were immobilised on the electrode array surface and exposed to single-stranded MLPA products. The surface bound DNA duplexes were then detected with a secondary DNA probe bearing a HRP molecule using fast electrochemical pulse amperometry. The approach presented is simple, rapid, flexible, relatively inexpensive, capable of quantifying 7 genetic markers for breast cancer with single tumor cell sensitivity and provides an elegant methodology towards the development of integrated “amplification-to-detection” instrumentation.

References [1] Lianidou, E.S. and A. Markou, Clinical Chemistry, 57(9) (2011) 1242-1255. [2] Lips, E.H., et al., Breast Cancer Research, 13:R107 (2011) (Electronic, doi:10.1186/bcr3049). [3] Henry, O.Y., et al., Electrophoresis, 30(19) (2009) 3398-3405. [4] Henry, O.Y.F., J.L. Acero Sanchez, and C.K. O'Sullivan, Biosensors and Bioelectronics, 26(4) (2010) 1500-1506. [5] Fragoso, A., et al., Analytical Chemistry, 80(7) (2008) 2556-2563.

NanoSpain Bio&Med | 253

SOLID LIPID NANOPARTICLES FOR DELIVERY OF CALENDULA EXTRACTS 1,a

Lide Arana , Oier Aizpurua-Olaizola , Aresatz Usobiaga , Félix M. Goñi , Itziar Alkorta

Unidad de Biofísica (CSIC, UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, 48080 Bilbao, Spain 2 Analytical Chemistry Department, University of the Basque Country (UPV/EHU), 48940 Leioa (Spain) a lide.arana@ehu.es

Abstract Unfortunately, many promising drugs present low water solubility, poor absorption or unfavorable elimination from organisms. Thus, the development of new drug delivery systems in order to improve drug bioavailability has been highlighted. Among the different strategies in this field, Solid Lipid Nanoparticles (SLN) have emerged as some of the most promising nanocarriers for controlled drug delivery which can improve drug bioavalability and targeting. SLN are submicron-sized dispersions of solid lipids that should be solid at room and body temperatures. They are composed by a central solid lipid core and a surfactant (and cosurfactant) which helps the assembling of the lipophilic components in an aqueous solution. SLN present many advantages in comparison to other drug delivery systems. They are able to incorporate hydrophilic and lipophilic drugs, present no biotoxicity and their production can be easily scaled up [1,2]. Their size and liposolubility facilitates drug diffusion through some biological barriers [3]. In this work we have tested solid lipid nanoparticles (SLN) composed of longchain fatty acids, Epikuron 200, and bile salts using microremulsion technique [4]. Different SLN dispersions were characterized by photon correlation spectroscopy, differential scanning calorimetry and transmission electron microscopy. Faradiol content was quantified using HPLC-DAD DQG WKH ȕcarotene using UV-VIS spectrophotometry measures. The capacity to incorporate calendula extracts with healing properties [5] was also studied in the most promising SLN composition. Our results suggest that selected SLN are appropriate delivery systems for this type of compounds. References [1] Mehnert, W. and Mader, K. Adv Drug Deliv Rev. 47 (2001) 165-96. [2] Marengo, E., Cavalli, R., Caputo, O., Rodriguez, L. and Gasco, M.R. Part I. Int J Pharm. 205 (2000) 3-13. [3] Gastaldi, L., Battaglia, L., Peira, E., Chirio, D., Muntoni, E., Solazzi, I., Gallarate, M. and Dosio, F. Eur J Pharm Biopharm. (2014). [4] Cavalli, R., Peira, E., Caputo, O. and Gasco, M.R. Int J Pharm. 182 (1999) 59-69. [5] Zitterl-Eglseer, K., Sosa, S., Jurenitsch, J., Schubert-Zsilavecz, M., Della Loggia, R., Tubaro, A., Bertoldi, M. and Franz, C. J Ethnopharmacol. 57 (1997) 139-44. Figures B

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Figure 1. SLN characterization of the selected lipid compositions. Particle zaverage size (A and B), polidispersity index (C and D) and Zeta potential (E and F) were measured with Dynamic Light Scattering (Malvern Zetasizer Nano S)

Figure 2. TEM micrographs of studied SLN. Samples were stained with uranyl acetate and images are representative of two independent experiments.

254 | NanoSpain Bio&Med

Table 1. Thermal properties of analyzed SLN. Data obtained from DSC measurements. Average values from two closely similar measurements.

Figure 3. Incoporation rate and entrapment efficiency of carotenoids and faradiol esters in SLN. Faradiol content was measured by HPLC and carotene content was measured by UV-Vis spectrophotometry. Results are expressed as the mean ± SEM of at least three independet experiments.

Free Volume: a New Physical Parameter in Biomaterials and Cancer 1,2

Eneko Axpe , Sonia Contera , Jose Angel GarcĂa , Fernando Plazaola

University of the Basque Country, Sarriena s/n 48940, Bilbao, Spain University of Oxford, Clarendon Laboratory, Parks Road OX1 3PU, Oxford, United Kingdom eneko.axpe@ehu.es

Abstract Free volume is a key parameter in physics, nanomechanics and diffusion properties of biopolymers, biomembranes and other biomaterials. Positron annihilation lifetime spectroscopy (PALS) is a unique technique for measuring the free volume void sizes and distributions inside these materials. Previous work has shown the potential of PALS in biophysics and cancer research. In this presentation we are introducing the concept of free volume in biomaterials and discuss the results of PALS in combination with other techniques in (i) biopolymer-based scaffolds, (ii) biomembranes and (iii) living cultured cancer cells [1]. The approach used here can serve as a framework for rational design of materials for tissue engineering and contributes to a better understanding of the biophysics behind biomembranes and cancer.

References [1] Eneko Axpe, Tamara Lopez-Euba, Ainara Castellanos-Rubio, David Merida, Jose Angel Garcia, Leticia Plaza-Izurieta, Nora Fernandez-Jimenez, Fernando Plazaola and Jose Ramon Bilbao, PLoS ONE, 9 (2014) 1.

NanoSpain Bio&Med | 255

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256 | NanoSpain Bio&Med

Hetero-coated magnetic microcarriers for point-of-care diagnostics 1

C. Cimorra Eusey* , D.M. Love , J. Llandro , J.J. Palfreyman , C.H. W. Barnes , Liz Muir , Geoff Cook , and 2 Roger Keynes 1 Cavendish Laboratory, Madingley Road, Cambridge University, Cambridge, CB3 0HE, UK2 2 Department of Physiology, Development and Neuroscience, University of Cambridge, CB2 3DY, UK *Corresponding author: Email: cc650@cam.ac.uk Abstract Summary: We report on the latest advances in the development of our magnetic encoded microcarriers [1,2] comprised of a polymer backbone, magnetic elements and surface functionalisation with biomolecules for medical diagnostic applications. Introduction: Thin magQHWLF VWULSV µELWV¶ DUH HQFDSVXODWHG LQ D ELRFRPSDWLEOH SRO\PHU EDFNERQH WR IRUP CWDJV¶ 7KH WDJV can be used to generate a large library of magnetically labelled bio-chemical analytes. Since the magnetic encoding can be applied post fabrication, all microcarriers are nominally identical, which makes them a cost effective micro-tagging strategy [3]. The number of unique codes doubles with every extra bit added, which also makes magnetic encoding extremely scalable. For instance a 7-bit tag offers 27=128 codes, but a 32bit tag would offer over 4 billion unique codes. Applications range from DNA/protein analysis for genotyping and point-of-care diagnostics to drug development and combinatorial chemistry. We will be focussing on some novel aspects of surface chemistry and the effects of various linker molecules on binding efficiency [4]. Since then we have introduced a thin nanostructured gold interface on to one side of the microcarriers to provide a second functional coating. With this, we can now pursue two different chemical routes (carbodiimide chemistry and thiol-containing self-assembled monolayers) to add particular probe molecules to each side. While one probe remains specific to the analyte of interest, the other acts as a hybridisation control to inWHUURJDWH WKH DVVD\¶V ELQGLQJ FRQGLWLRQV

Figure: Exploded schematic of a hetero-functional magnetic microcarrier (centre) and line-intensity profiles showing microcarriers dual-labelled with fluorescein and TAMRA. The peaks and troughs are indicative of whether the fluorescence is on the top or bottom side respectively. The complimentary target (pre-labelled with TAMRA) is added to the sample serum as a positive control. This eliminates the possibility of seeing no fluorescence and not being confident of whether the analyte was absent (true negative) or whether the binding conditions were insufficient (false negative). The target strand can be labelled with a different colour, e.g. with PicoGreen in an additional step, so that now a positive result causes the microcarrier to fluoresce red on one side and green on the other. As can be seen from the figure, there is a clear signature (peaks vs. WURXJKV LQ WKH LQWHQVLW\ SURILOH FRUUHVSRQGLQJ WR WKH PLFURFDUULHU¶V orientation. The microcarriers are read in-flow through a 50µm wide channel, which includes a TMR sensor able to detect the stray field (magnetic signature) of the passing microcarrier [5]. Thus, by combining the fluorescence data and the TMR data it is possible to conduct a multiplexed assay very quickly and costeffectively on a small footprint device. Acknowledgements This work was supported by the EPRSC within the nano Doctoral Training Centre. References [1] T. Mitrelias, T. Trypiniotis, C.H.W. Barnes et al., JAP 105, 07B301 (2009) [2] J.J. Palfreyman, C.H.W. Barnes et al., IEEE Transactions on Magnetics 49, 285-295 (2013). [3] B. Hong, T.J. Hayward, C.H.W. Barnes et al., JAP 105, 034701 (2009) [4] J.J. Palfreyman, P. Beldon, C.H.W. Barnes et al., AIP Conf. Proc 1311, 184-191 (2010) [5] K.N. Vyas, J.J. Palfreyman, C.H.W. Barnes et al., Lab-on-a-chip (2012)

NanoSpain Bio&Med | 257

Nb-C nanocomposite coatings for biomedical applications Luis Yate1, L. Emerson Coy2, Danijela Gregurec3, Willian Aperador4 , Sergio E. Moya 3, Guocheng Wang 3* 1

Surface Analysis and Fabrication Platform, CIC biomaGUNE, Paseo Miramón 182, 20009 Donostia-San Sebastian, Spain 2 NanoBioMedical Center, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland 3 Soft Matter Nanotechnology Laboratory CIC biomaGUNE, Paseo Miramón 182, 20009 Donostia-San Sebastian, Spain 4 School of Engineering, Universidad Militar Nueva Granada, Carrera 11 #101-80, 49300 Bogotá, Colombia Corresponding author: gwang@cicbiomagune.es * Presenting author: coyeme@amu.edu.pl Abstract Hard-elastic coatings with bioactive properties are very promising for many biomedical applications, specifically in the field of implantology. Carbon, especially amorphous (a-C) and diamondlike carbon films (DLC) films have attracted much attention in biomedical fields due to their biocompatibility and low coefficient of friction. However, they are unsuitable for uses as a “bioactivity enhancer” of orthopedic implants due to their bioinertness. In this work, we use the non-reactive magnetron sputtering technique to produce a-C films including the biocompatible niobium (Nb) element to alter the surface chemistry and nanotopography of the aC films with the purpose of bioactivating the a-C film coated implants. Results show that the nanocomposite films/coating (Nb-C) formed by the addition of Nb into the a-C films not only have improved corrosion resistance, but also possess enhanced mechanical properties (nanohardness, Young´s modulus and super-elastic recovery). Preosteoblasts (MC3T3-E1) cultured on the Nb-C films have enhanced adhesion and upregulated alkaline phosphatase (ALP) activity, compared to those cultured on the a-C film and TiO2 films used as a control, which are thought to be ascribed to the combined effects of the changes in surface chemistry and the refinement of the nanotopography caused by the addition of Nb. Results are very promising and encouraging due to their potential impact in both protective coatings and biomedical fields. References [1] Yate, L.; Coy, L. E.; Wang, G.; Beltrán, M.; Díaz-Barriga, E.; Saucedo, E. M.; Ceniceros, M. A.; Zaleski, K.; Llarena, I.; Möller, M.; et al. Tailoring Mechanical Properties and Electrical Conductivity of Flexible Niobium Carbide Nanocomposite Thin Film. RSC Adv. 2014, 4, 61355–61362. [2] Luis Yate, L. Emerson Coy, Danijela Gregurec, Willian Aperador, Sergio E. Moya, Guocheng Wang. Nb-C nanocomposite films with enhanced biocompatibility and mechanical properties for hard-tissue implant applications submitted jan -2015 Figures

Figure shows, proliferation studies (left & right top) and mechanical properties (bottom right)

258 | NanoSpain Bio&Med

Optimization of polymeric nanomaterials for biomedical applications using computational simulation Joana M.R. Curto1, Pedro E.M. Videira1, Eduardo L.T. Conceição2, António T.G. Portugal2, Rogério M.S. Simões1, Manuel J. Santos Silva1 1

Fibre Materials and Environmental Technologies Research Unit, University of Beira Interior, Portugal

Chemical Process Engineering and Forest Products Research Center, Chemical Engineering Department, University of Coimbra, Portugal.

Corresponding author: Professor Joana M. R. Curto, jmrc@ubi.pt, University of Beira Interior, Dep. Química, Av. 0DUTXrV G¶ÈYLOD H %ROkPD Q 54, 6200-001 Covilhã, Portugal. Phone: +351966485662 Abstract An innovative approach is used to develop nanopolymeric fibrous materials with optimized porosity and thickness. Using our own materials simulator we are able to design a new material with optimized properties for biomedical applications. The material optimization is fundamental for obtaining functionalities like the transport of molecules, support and structure coating [1]. The use of a validated computational simulator is an important tool to optimize structural properties [2-3]. In this study nanofibers of polyamide-6 and polyvinyl alcohol were prepared by electrospinning which is a technique that allows the creation of fibers with diameters down to nanoscale. We have used scanning electron microscopy to measure fiber dimensions, porosity and thickness. Using 60 SEM images, and selecting 20 fiber and 25 pores per image, we have obtained an average value of fiber diameter and pores, for polyvinyl alcohol 352±2,6nm and 1,29±0.0068µm and for polyamide-6 381±2,2nm and 1,23±0,0060µm. The material optimization was done using the computational simulator, adapted to nanoscale. In conclusion, using the experimental characterization and the simulation model for porous materials we were able to simulate and produce a nanomaterial with optimized porosity and thickness. References [1] Liang, D., Hsiao, B.S., Chu, B., Advanced Drug Delivery Review, 14 (2009), 1392±1412. [2] Curto, J.M.R., Conceição, E.L.T., Portugal, A.T.G., Simões, R.M.S., Materialwiss Werkstofftech, 42 (2011), 370±374 [3] Curto, J.M.R., Hekmaty, A.H., Drean, J.Y., Conceição, E.L.T Portugal A.T.G., Simões, R.M.S., Santos Silva, M.J. In Proc. of the 11th World Textile Conference, Autex2011, Mulhouse, France, 2 (2011) 639-643 Figures

Figure 1: Scanning electron microscopy images of polyvinyl alcohol and polyamide-6. In the top, from right to left, fiber diameter, pore width and thickness, for polyvinyl alcohol structures. The bottom images are fiber diameter, pore width and thickness for polyamide-6 structures.

Figure 2: Methodology using simulation and experimental characterization to optimize and develop new porous nanomaterials for biomedical applications.

NanoSpain Bio&Med | 259

Functionalized nanoparticles for bioapplications -DQD 'UERKODYRYi, =GHQND )RKOHURYi, -DQD 3HNiUNRYi -DURPtU +XEiOHN &(,7(& %87 7HFKQLFNi %UQR &]HFK 5HSXEOLF Zdenka.fohlerova@ceitec.vutbr.cz

Abstract Research on nanoparticles has evolved into biological applications with large expectations for the use of nanoparticles for imaging and drug delivery in humans and as probes at the cellular level. In our researches we are focused on several questions concerning as follow: i) production of monodispersed magnetic iron oxide nanoparticles (MNPs) as the suitable candidate for the assisted transfection of DNA expression plasmids. The nanoparticles are synthesized by co-precipitation method and stabilized with chitosan under physiological pH. DNA plasmids are expected to be integrated into the polymer coat, making the DNA-MNPs complex ready for the transfection and subsequently taken up by cells via endocytosis. Here, the DNA-MNPs complex is introduced in HEK cells to analyse the cellular toxicity and the effect on cell proliferation (1). ii) next, MNPs nanoparticles are used as a drug delivery system for miRNA to improve miRNA-based cancer treatment efficiency in glioblastoma. The delivery system was proposed on the super-paramagnetic iron oxide nanoparticles (SPIO)-based support for miRNA, covered with biopolymer protecting the active core such is chitosan (2). iii) the characterization, synthesis and functionalization of gold nanoparticles (AuNPs) based on the surface plasmon resonance imaging. Gold nanoparticles are synthetized by green methods to obtain stable colloid gold nanoparticles suitable for various biomedical applications; especially for in vivo and in vitro bioimaging. iv) the synthesis and characterization of SiO2/Au core/shell nanoparticles. The nanoparticles should, in their physical and chemical properties, improve signal of optical coherence tomography (3). v) the last point is focused on the development of biosensors based on modified semiconductor core/shell quantum dots (QDs) for protein detection. Synthesis of CdTe/ZnS core/shell QDs modified by glutathione and mercaptosuccinic acid (GSH, MSA) is performed, followed by the conjugation with biomolecules. Several coupling agents such as EDC with NHS are used. The final products were characterised by fluorescence spectroscopy and the emission spectra are analysed (4). References [1] Bertram J., Current Pharmaceutical Biotechnology 7 (2006) 277-285 [2] Starega-Roslan J., et al., Nucleic Acids Res., 39 (2011) 257-268 [3] Xue J. et al., Materials Chemistry and Physics 105 (2007) 419Âą425 [4] Stanisavljevic M. et al., Electrophoresis, 18 (2014) 2587-2592

Fig. 1 SiO2 nanoparticles

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An advanced strategy for the treatment of chronic wounds: rhEGF loaded nanostructured lipid carriers (rhEGF-NLC) enhance the healing of full-thickness excisional wounds in db/db mice Garazi Gainza1, Marta Pastor1, Silvia Villullas1, Jose Javier Aguirre1,4, Francisco Borja Gutierrez4, Enara Herran1, Oihane Ibarrola1, Angel del Pozo1, Jose Luis Pedraz2,3, Rosa Mª Hernandez2,3, Manoli Igartua2,3, Eusebio Gainza1 1

BioPraxis AIE, Hermanos Lumière 5, 01510 Miñano, Spain NanoBioCel Group, Laboratory of Pharmaceutics, School of Pharmacy, University of the Basque Country (UPV/EHU), Vitoria, 01006, Spain 3 Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBERBBN), Vitoria, 01006, Spain 4 Anatomic Pathology Service. Hospital Universitario de Álava (HUA) Txagorritxu, Vitoria, 01009, Spain ggainza@praxisph.com Abstract INTRODUCTION Chronic wounds represent a major clinical challenge for the health care systems due to their increasing incidence. Currently, the risk of suffering from chronic wounds has increased alarmingly, resulting in about the 2 % of the total European Health budgets [1]. Therefore, the development of advanced drug delivery systems (DDS) to improve the effectiveness of the current treatments and, thus, the quality of life of the patients, has become a major need. In the current work rhEGF loaded nanostructured lipid carries (rhEGF-NLC) were prepared and their efficacy was tested in vitro in BALB/c fibroblast and after topical administration in a full-thickness excisional wound model in db/db mice. RESULTS AND DISSCUSION rhEGF-NLC were prepared by a simple melted emulsification method. Remarkably, the in vitro proliferation studies evidenced that the rhEGF-NLC bioactivity was even higher than free rhEGF, suggesting that the nanoencapsulation process may promote the affinity of the rhEGF to the EGF receptor and, this could strongly impact on the cell proliferation rate. The in vivo studies revealed that 2 topical administrations of 10 or 20 µg rhEGF-NLC not only reduced the wound area by day 8 more than the control groups (untreated and empty NLC controls), but also improved the wound closure compared with 2 intralesional doses of 75 µg of free rhEGF (Figure 1A). In addition, the histological examination of the wound maturation and healing quality revealed that the lesions treated with topically administered rhEGF-NLC, regardless the dose, showed an improved healing quality than controls and a similar efficiency than a greater dose of free rhEGF administered by intralesional infiltrations (Figure 1B). Finally, the study of the re-epithelisation grade revealed that the groups treated with 20 µg rhEGF-NLC improved the re-epithelisation compared with 2 doses of 75 µg free rhEGF, however, significant differences were not achieved among the lesions treated with 10 µg rhEGF-NLC and controls. Overall, we demonstrate the promising effect of rhEGF-NLC to promote faster and more effective wound healing, and suggest its possible application in chronic wounds treatment. 2

References [1] Mustoe, TA. et al. (2006). Chronic wound pathogenesis and current treatment strategies: a unifying hypothesis. Plast Reconstr Surg. (7 Suppl):35S-41S. Figures

Figure1. Results obtained from the in vivo studies. (A) Wound closure percentages on day 8 and 11 after the wound creation. (B) Histological images of the wounds by day 8; the slides were stained with H&E.

NanoSpain Bio&Med | 261

Complex lamellar gel lipid phases enriched in ceramide and cholesterol: an AFM study in lipid membranes Aritz B. García-Arribas, Jon V. Busto, Alicia Alonso, Félix M. Goñi. Unidad de Biofísica (Centro Mixto CSIC-UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco (UPV/EHU), Barrio Sarriena s/n, 48940, Leioa, Bizkaia, Spain. Contact e-mail: aritzgarciaar@hotmail.com Abstract Atomic force microscopy (AFM) has been applied to the characterization of palmitoylceramide (pCer) and cholesterol (Chol) incorporation into phospholipid-based supported planar bilayers (SPBs) at 22ºC. Phospholipids were dipalmitoyl phosphatidylcholine (DPPC) or palmitoyl sphingomyelin (pSM). Membranes of different compositions were prepared by the vesicle adsorption or the spin-coating procedures (strictly for pCer-containing mixtures) and analyzed with a combination of AFM imaging (domain segregation, bilayer thickness and roughness) and force spectroscopy (mechanical resistance to indentation). The mixtures under study were pure phospholipids (pSM, DPPC), phospholipid:Chol (70:30), phospholipid:Chol:pCer (54:23:23) and phospholipid:pCer (90:10, 80:20 and 70:30). Binary phospholipid:pCer mixtures at increasing ceramide ratios gave rise to highly-resistant segregated domains with increasing extension but similar properties in terms of breakthrough forces, thicknesses and roughnesses. These ceramide-enriched domains are able to exclude a fluorescent lipid probe (DiIC18) due to their high intermolecular packing. Interestingly, these domains have been reported to disappear when model membranes become highly enriched in cholesterol in fluid membranes [1] or in the absence of a fluid phase [2] (our case). Indeed, the ternary mixtures (54:23:23) gave rise to a homogenous lamellar gel phase with significantly different properties when compared to all of the other mixtures studied: ternary mixtures showed a reduced thickness and an intermediate roughness and mechanical resistance when compared to phospholipid:Chol (70:30) and phospholipid:pCer. These differences were statistically significant. More importantly, at those relatively high pCer and Chol concentrations in ternary mixtures, no mutual displacement of these molecules was observed, and these lipids establish a direct interaction between the amide group of ceramide and the hydroxyl group of cholesterol [3]. The data becomes relevant in the context of sphingolipid signaling and membrane platform formation. References [1]

Castro BM, Silva LC, Fedorov A, de Almeida RFM, Prieto M. J Biol Chem 284 (2009) 22978–

22987. [2]

Busto JV, Sot J, Requejo-Isidro J, Goñi FM, Alonso A. Biophys J 99 (2010) 1119-1128.

[3]

Busto JV, García-Arribas AB, Sot J, Torrecillas A, Gómez-Fernández JC, Goñi FM, Alonso A.

Biophys J 106 (2014) 621-630.

262 | NanoSpain Bio&Med

Multiwalled Carbon Nanotubes applied in cancer treatment Lorena García-Hevia1, Rafael Valiente2, Jesús González3, Juan C. Villegas4, Mónica L. Fanarraga1 1Departamento

de Biología Molecular, 2Departamento de Física Aplicada, 3CITIMAC, 4Departamento de Anatomía y Biología Celular. Universidad de Cantabria-IDIVAL, Santander 39011, Spain. lorena.garciah@alumnos.unican.es

Abstract Drug resistance is the outcome of chemotherapy promoting the selection of resistant clones of cells within the heterogeneous tumor cell mass [1, 2]. Nanomaterials offer new alternatives to traditional cytotoxic anti-cancer treatments displaying radically different mechanisms to kill cancer cells. Among nanomaterials, multi-walled carbon nanotubes (MWCNTs) can enter inside cells and interfere with the cell´s biomechanics [3], producing cytotoxic effects similar to those of traditional microtubule-binding agents such as taxol®. We have evaluated the cytotoxic properties of serum dispersed MWCNTs on different human cancer cell lines of different origins as well as cells obtained from surgical explants of primary tumors. Our results reveal that MWCNTs have the intrinsic ability to produce anti-proliferative and cytotoxic effects in all these cancer cell models. Understanding and improving the biomimetics of MWCNTs with microtubules could serve to develop new anticancer therapies that can boost traditional chemotherapy, bypassing the drug resistance mechanisms in cancer cells that can be used as broad spectrum cytotoxic nanomedicines against cancer in the nearest future.

References [1] Navin N, et al. Tumour evolution inferred by single-cell sequencing. Nature 472 (2011) 90. [2] Greaves M, Maley CC. Clonal evolution in cancer. Nature 481 (2012) 306. [3] Rodriguez-Fernandez L, et al. Multiwalled carbon nanotubes display microtubule biomimetic properties in vivo, enhancing microtubule assembly and stabilization. ACS Nano 6 (2012) 6614.

NanoSpain Bio&Med | 263

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264 | NanoSpain Bio&Med

Permalloy Nanodisks for Biomedical Applications M. Goiriena-Goikoetxea1*, J. Feuchtwanger2, M.L. Fdez-Gubieda1,2 and A. García-Arribas1,2 1BCMaterials,

Universidad del País Vasco (UPV/EHU), Barrio de Sarriena s/n, 48940, Leioa, Spain. de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), Barrio de Sarriena s/n, 48940, Leioa, Spain. maite.goiriena@ehu.es

2Departamento

Magnetic nanoparticles are extensively studied for biomedical applications because their size are comparable to biological entities, while providing remote capabilities of actuation [1]. Disk shaped ferromagnetic nanoparticles add attractive possibilities to these characteristics. First, Permalloy (Py) nanodisks display much higher saturation magnetization values than oxide nanoparticles and second, depending on their geometry, they can present a spin vortex configuration which leads to net zero magnetization at remanence, eliminating the problem of particle agglomeration. Therefore, Py nanodisks present a huge potential for biomedical applications, ranging from cancer cell destroy by hyperthermia or mechanical actuation to MRI contrast enhancement and drug delivery [2]. While oxide nanoparticles are chemically synthetized, nanodisk physical fabrication methods offer higher control on particle size and the possibility of choosing among a larger spectrum of materials. Electron beam lithography (EBL) and Photolithography allow for tightly controlled fabrication of particles with virtually any size, shape and composition. The use of these techniques, though, imply a very low yield production (in the case of EBL) and the use of quite sophisticated and expensive equipment. As an alternative, self-assembling fabrication routes provide high volume and low cost production of well-defined Py nanodisks. In this work we present the results obtained by Hole-mask Colloidal Lithography (HCL) [3]. HCL utilizes the definition of a dense hole-pattern in a sacrificial resist layer onto which a layer of Py is deposited. Py disks are produced after lift-of of the resist layer. The results obtained show promising structures. The magnetic characterization performed by MagnetoOptical Kerr Effect (MOKE) indicates that vortex and single-domain states can be present [4]. [1] Q. A. Pankhurst et al., Journal of Physics D: Applied Physics (2003), 167. [2] D.-H. Kim, et. al., Nature Materials (2009), 9 165. [3] H. Fredriksson et al., Advanced Materials (2007), 19 4297. [4] G. Shimon et al., Physical Review B (2013), 87 214422.

Figure 1 (left): hole-patterned resist. Figure 2 (right): Permalloy nanodisks on SiO2 substrate.

NanoSpain Bio&Med | 265

Investigation of bilayer lipid membranes on nanostructured Au and Ag substrates by surface enhanced Raman spectroscopy Nora Grinceviciute, Lina Ramanauskaite, Valentinas Snitka Research Centre for Microsystems and Nanotechnology, Kaunas University of Technology, Studentu 65, LT-51369, Kaunas, Lithuania nora.grinceviciute@ktu.lt Abstract Membranes are essential components of any living cell and therefore, bilayer lipid membranes (BLMs) are simplified planar models of cell membranes, commonly employed for both fundamental and applied studies [1-2]. Raman spectroscopy is a well-established, analytical tool that has been widely applied to biological and medical research. However, the sensitivity and spatial resolution of Raman spectroscopy at the nanoscale is very weak [3] and it is inappropriate method for studying single lipid bilayers. The aim of our study was evaluate the suitability of surface enhanced Raman spectroscopy (SERS) to the investigations of BLMs. While single-bilayer sensitivity could be achieved by SERS, adsorption on a roughened metal surface, what is specific for SERS, may be unsuitable for phospholipids. In our study BLMs were formed on optically active surfaces based on Ag or Au nanostructured film deposited by chemical reduction using HF etched silicon. To illustrate the use of this technique, we present a study of bilayer lipid membranes formed of one part of negatively charged phospholipids (DOPS) and four parts of neutral phospholipids (DOPC) and compare the behavior of the BLMs on different SERS substrates. The Raman spectra of BLMs on silicon surface are presented for comparison (fig.1). It was found that Au SERS substrates were not suitable for lipid membrane formation, but after using the binding 1-dodecanothiol layer the appropriate results were obtained. In conclusion we demonstrate that SERS can be efficiently used for investigation of a thin layer of lipids. Acknowledgements: This work was funded by the European Social Fund under the Global Grand measure (Grand No: VP1-3.1-창00-07-K-03-044). References [1] Stimberg, V. C., van Uitert, I., Le Gac, S., & van den Berg, In: MicroTAS conference, Groningen (NL), (2010) 830-832. [2] Taylor, R. W., Benz, F., Sigle, D. O., Bowman, R. W., Bao, P., Roth, J. S., & Baumberg, J. J., Scientific reports, 4 (2014) [3] Sweetenham, C. S., & Notingher, ISpectroscopy: An International Journal, 24.1 (2010) 113-117. BLM's Raman spectra on different SERS substrates 1 Ag- Si 400 Si (control) 2 3 Au- Si 4 Au-Si with binding layer Intensity

300

C-H

C-H-C

200

C=C N-CH3 100 O-P-O

0 1000

1500

2000

Raman shift, cm

2500

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Figure 1. Raman spectra of bilayer lipid membranes on different SERS substrates in PBS solution

266 | NanoSpain Bio&Med

Application of Photocatalytical Activity of CdS Nanoparticles to Development of Sensitive Colorimetric Enzymatic Assays Using 3,3’,5,5’tetramethylbenzidine (TMB) as a Universal Chromogenic Compound Ruta Grinyte, Gaizka Garai-Ibabe, Laura Saa, Valery Pavlov Biofunctional Nanomaterials, CIC biomaGUNE, Parque tecnológico de San Sebastian, Paseo Miramon 182, 20009 Donostia- San Sebastian, Spain rgrinyte@cicbiomagune.es Abstract Metallic and semiconductor nanoparticles (NPs) can be very conveniently employed for signal transduction and signal amplification by physical methods. Their chemical and physical properties are defined by three dimensional structure of NPs, therefore very slight changes in shape and size lead to drastic variation in absorption and emission spectra. Semiconductor NPs can be photo-excited producing electron/hole couples, which recombine to yield emission of light. Quantum effects in inorganic NPs give rise to fluorescence, therefore such fluorescent particles are referred to in the literature as quantum dots (QDs).1 Our laboratory has introduced application of in situ growth of QDs to development of flourogenic 2 enzymatic assays. This concept is based on registration of fluorescence originating from CdS QDs influenced by products of an enzymatic reaction. Those fluorogenic assays showed low detection limits and high signal to noise ratio, but unfortunately the read-out signal was not stable with time. The size of semiconductor QDs defines quantum effects governing fluorescence emission. It was found out that semiconductor CdS nanoparticles (NPs) are able to catalyze photooxidation of the well known chromogenic enzymatic substrate 3,3’,5,5’-tetramethylbenzidine (TMB), traditionally employed in quantification of peroxidase activity in the presence of hydrogen peroxide. The photocatalytical oxidation of TMB by oxygen does not require hydrogen peroxide and its rate is directly 2+ 2proportional to the quantity of CdS NPs produced in situ through the interaction of Cd and S ions in an aqueous medium. The present concept permits to extend utility of the enzymatic substrate TMB, traditionally employed for detection of horseradish peroxidase activity, to other enzymes participating in formation of semiconductor NPs. In other words, the new approach allows to employ inexpensive commercially available TMB as a universal chromogenic substrate for quantification of different classes of enzymes. This phenomenon was applied to development of colorimetric sensitive assays for glucose oxidase and glutathione reductase based on enzymatic generation of CdS NPs acting as light-powered catalysts as demonstrated in Figure 1. Sensitivity of the developed chromogenic assays was of the same order of magnitude or even better than that of relevant fluorogenic assays. The present approach opens the possibility for the design of simple and sensitive colorimetric assays for a number of enzymes using inexpensive and available TMB as a universal chromogenic compound. References

[1] Parak, W. J.; Manna, L.; Simmel, F. C.; Gerion, D.; Alivisatos, P. In Nanoparticles; WileyVCH Verlag GmbH & Co. KGaA, (2005) 4-49 [2] Malashikhina, N.; Garai-Ibabe, G.; Pavlov, V. Anal Chem, 85 (2013) 6866-6870. Figures

Figure 1. Chromogenic detection of enzyme activity using photocatalytical oxidation of TMB enhanced by enzymaticaly produced CdS NPs.

NanoSpain Bio&Med | 267

MRI Guided Interventions needs new materials and contrast agents

Nihan GĂźvener

1,2

, Sjef Cremers , Paul Borm

Fabian Kiessling ,

Nano4Imaging GmbH, Zentrum fr Biomedizintechnik, Aachen, Germany Experimental Molecular Imaging ExMI, University Hospital RWTH Aachen, Germany nguvener@nano4imaging.com

Abstract Magnetic resonance imaging (MRI) is primary a diagnostic tool, with or without the use of contrast agents. To enable the use of MRI for interventional purposes, devices are needed that are nonmagnetic and non-conductive and visible in MRI. Fiber-composite materials provide enough strength to replace classic metal-based devices, and at the same time provide opportunity to include contrast agents as part of the matrix. Gadolinium chelates are clinically being used ad contrast agents by delivery into the vascular space, and then diffusing into the site (tumor, scar, vessel) of interest, Apart from incomplete diffusion, they are rapidly washed out of the site, and some gadolinium chelates cause specific renal toxicity [1]. With the gradual elimination of commercially available paramagnetic iron oxides from the market, a need for new contrast agents is becoming apparent. Porphyrins are potential MR contrast agents, considering their stable form within chelate complexes that comprises paramagnetic metal ions and their retention by the site selectively [2]. Hemin, is a protoporphyrin structure that contains a ferric iron ion with a chloride ligand. Hemin occurs in organisms as a prosthetic group of which refers to the ability of use as a biomaterial to perform its imaging function with respect to a medical diagnosis. The present study aims to evaluate the site enhancing imaging characteristics of novel metalloporphyrin derivatives. In this project we investigate the MRI characteristics of metalloporphyrin derivatives as potential biocompatible MR contrast agent. However, to enable this several technical issues have to be resolved. Hemin is sparingly soluble in aqueous media. Therefore, derivatives of Hemin have been processed for enhancing the solubility as PEGylated Hemin, Hemin Arginate or Hemin Lysinate. This new contrast agent has achieved a high molar Relaxivity in MRI allowing decrease of the required dose for in vivo applications. These derivatives suggest that the size, geometry, and polarity of hemin can be modified to optimize their relaxivities ,pharmacokinetic properties, and biocompatibility.

References [1] Penfield JG, Reilly RF Jr., Nat Clin Pract Nephrol. Dec 3/12, (2007), 654-68. [2] Mathew T, Kuriakose S, J. Porphyrins Phthalocyanines 3, (1999), 316Âą321.

268 | NanoSpain Bio&Med

Evaluation of PCB based gold electrode array cleaning methods for electrochemical biosensor applications 1

Hamdi Joda , Josep Lluis Acero Sanchez , Mary Luz Botero , M. Carmen Bermudo Redondo and 1, 2 Ciara K. O’Sullivan 1

Universitat Rovira i Virgili, Departament de Enginyeria Química, Av. Països Catalans 26, 43007 Tarragona, Spain 2 Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Spain ciara.osullivan@urv.cat, hamdi.joda@urv.cat

Abstract 1

Gold electrode arrays are widely used for biosensor applications . However, photolithography which is the most common method for array microfabrication is very expensive and needs clean room facilities. Electrode surface cleaning (pretreatment) is crucial step for biosensor development as it affects 2 efficiency of self-assembly monolayers (SAM) and formation of the recognition element. Soft gold electroplating on printed circuit board (PCB) is emerging method providing cheap and 3 alternative process for biosensor array fabrication . We report the first evaluation for different surface pretreatments of PCB based gold electrode array for electrochemical biosensor applications. In this study, several cleaning methods were investigated including physical, chemical and electrochemical. We tested: UV/ozone; plasma etching; potassium hydroxide–hydrogen peroxide; sulfuric acid–hydrogen peroxide (Piranha); nitric acid–hydrochloric acid (aqua regia) and electrochemical cyclic voltammetry in sulfuric acid. For optimization, we tested different exposure times, concentrations and combination of two or more methods. Following cleaning, gold electrode surface was characterized by electrochemical cyclic voltammetry in sulfuric acid and peak-current potential differences in potassium hexacyanoferrate, contact angle to evaluate hydrophobicity, and finally a DNA hybridization assay after functionalization of gold surface with DNA capture probe. A peak separation equal or below 100 mV was used as criteria to determine a cleanness of gold surface. PCB arrays treated with UV/ozone for 10 minutes and with a solution of potassium hydroxide (50 mM) / hydrogen peroxide (25%) for 10 minutes exhibited the best performance.

References [1] Henry, O. Y.; Fragoso, A.; Beni, V.; Laboria, N.; Sanchez, J. L. A.; Latta, D.; Von Germar, F.; Drese, K.; Katakis, I.; O'Sullivan, C. K. Electrophoresis, 30 (2009) 3398-3405. [2] Yang, Z.; Gonzalez-Cortes, A.; Jourquin, G.; Vire, J. C.; Kauffmann, J. M.; Delplancke, J. L. Biosens. Bioelectron., 10 (1995) 789-795. [3] Salvo, P.; Henry, O. Y. F.; Dhaenens, K.; Acero Sanchez, J. L.; Gielen, A.; Werne Solnestam, B.; Lundeberg, J.; O'Sullivan, C. K.; Vanfleteren, J. Bio-Med. Mater. Eng., 24 (2014) 1705-1714.

NanoSpain Bio&Med | 269

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270 | NanoSpain Bio&Med

Chitosan Nanoparticles for siRNA Based Gene Silencing Therapy for Cancer 1 1 2 3 2 Burcu Bağdat Cengiz , Mehmet Doğan Aşık , Göknur Kara , Mustafa Türk , Emir Baki Denkbaş 1

Nanotechnology and Nanomedicine Division, Hacettepe University, Beytepe, 06800, Ankara, Turkey Chemistry Department, Biochemistry Division, Hacettepe University, Beytepe, 06800, Ankara, Turkey 3 Bioengineering Department, Kırıkkale University, Yahşihan, 71451, Kırıkkale, Turkey goknurkara@hacettepe.edu.tr

Abstract Small interfering RNA (siRNA) based gene silencing that reduces the synthesis of specific harmful proteins at mRNA level is one of the effective targeted therapies for cancer [1,2]. However, siRNA delivery into the cells is limited due to its rapid decomposition by nucleases and poor cellular uptake [3]. The polycationic, non-toxic, biodegradable and biocompatible polymer such as chitosan (CS) can be bound effectively to siRNA molecule and it can be protected against to enzymatic degradation [4]. In this study CS nanoparticles (NPs) were produced via ionic gelation method and sodium tripolyphosphate (TPP) was used as crosslinker. pH value of the CS solution (4.0 to 5.0) and CS/TPP mass ratio (2.5:1 to 5:1) were changed to optimize the NPs size and surface charge for efficient gene transfection. Morphological characterization of the CS-NPs was evaluated by AFM and SEM. The genes for ABCE1 (ATP-binding casette E1) and eRF3 (eukaryotic release factor 3) proteins which play significant roles in protein synthesis were chosen as target genes to be loaded with CS-NPs, individually and together. Loading efficiencies of 98.69%±0.051 and 98.83%±0.047 were achieved when ABCE1 siRNA and eRF3 siRNA were entrapped into the NPs, respectively. Cellular uptake of fluorescein labeled CS-NPs into MCF-7 cells, WST-1 cytotoxicity and Real Time Cell Analyzer (RTCA) assays of the NPs were carried out. Mean diameter of the CS-NPs was obtained between 105-230 nm and the zeta potential was 27 mV at pH 4.5 and 3:1 CS/TPP mass ratio values. Fig. 1 shows that CS-NPs are spherical in shape by SEM analysis. Both WST1 and RTCA assays revealed that ABCE1 siRNA, eRF3 siRNA and ABCE1/eRF3 siRNA loaded NPs significantly reduced the cell viabilty and proliferation (Figure 2). This work demonstrated that the CS-NPs suitable in size and surface charge are promising vectors for siRNA based targeted cancer therapy. References [1] Ozpolat B, Sood AK, Lopez-Berestein G, Advanced Drug Delivery Reviews, 66 (2014) 110-116. [2] Oh YK, Park TG, Advanced Drug Delivery Reviews, 61 (2009) 850-862. [3] Piao L, Li H, Teng L, Yung BC, Sugimoto Y, Brueggemeier RW, Lee RJ, Nanomedicine-Nanotechnology, Biology and Medicine, 9 (2013) 122-129. [4] Ravi Kumar MNV, Reactive Functional Polymers 46 (2000) 1-27.

Figure 1. SEM micrographs of CS-NPs

Figure 2. Cell proliferation curve of MCF-7 cells treated with control and siRNA loaded CS-NPs

NanoSpain Bio&Med | 271

International Conference on NanoScience and NanoTechnology, ImagineNano 2015 March 10-13, Bilbao, Spain

Characterization of Copaxone by Atomic Force Microscopy (AFM) and Dynamic Light Scattering (DLS) 1

Tatiana Molotsky , Artium Khatchatouriants , Revital Krispin , Tal Hasson and Arthur Komlosh

Analytical Development, Discovery & Product development, Global R&D, Teva Pharmaceutical

Industries Ltd., Netanya, Israel 2

Micro and Nano central Characterization and Fabrication facility (MNCF) at Tel Aviv University Center

for Nanoscience and Nanotechnology ®

Copaxone is an immunomodulator drug used to treat multiple sclerosis. Copaxone is an aqueous solution containing 20mg/mL of the active ingredient Glatiramer Acetate (GA) and 40mg Mannitol. GA is a complex mixture of synthetic amino acid polypeptides composed of a multitude peptide sequences containing L-alanine (Ala), L-Lysine (Lys), L-Glutamate (Glu), and L-Tyrosine (Tyr). This complex mixture of linear polypeptides results in varying chain length, therefore the molecular weight distribution of the GA components span over the range of about 2,500 ± 20,000Daltons. Atomic Force Microscopy (AFM) and Dynamic Light Scattering (DLS) are two orthogonal techniques commonly used in the characterization of polymers and aggregates. AFM generates 3D topographical images of the surface ultra structure with molecular resolution and provides detailed information on the height, size, and shape of molecules. DLS measures the Brownian motion of molecules in a solution (diffusion rate) by using a laser beam. By measuring this diffusion rate it is possible to extrapolate the hydrodynamic radius and size of the molecule. ® AFM and DLS methods were developed as part of efforts to characterize aggregates in Copaxone . ® Using AFM Copaxone aggregates appeared as fiber like with no globular aggregates showing good batch to batch consistency of the aggregates shape. Purported generic samples were also tested using AFM. The aggregates in these samples displayed various shapes (globular) which were ® ® dissimilar from the ones seen in Copaxone . In addition, Copaxone was also characterized using DLS. The DLS analysis revealed two types of populations: one population having an average hydrodynamic radius of 5.6nm and the other with an average of 111nm with good batch to batch consistency (as shown in the AFM analysis). The generic copies also contained two populations: one ® with an average dynamic radius of 5.6nm (similar to Copaxone ) and the other ranging from 140nm to ® 300nm i.e. larger than that Copaxone . Both AFM and DLS have been proven to be sensitive and ® robust methods to characterize Copaxone aggregates.

272 | NanoSpain Bio&Med

MICROFLUIDICS, A TOOL TO PRODUCE HETEROSTRUCTURED NANOMATERIALS Au-Fe3O4 FOR BIOMEDICAL APPLICATIONS Ane Larrea, María del Mar Encabo, Víctor Sebastián, Manuel Arruebo and Jesús Santamaría Department of Chemical Engineering, Institute of Nanoscience of Aragon (INA), Universidad de Zaragoza, C/Mariano Esquillor Gómez S/N 50018 Zaragoza, Spain larrea@unizar.es; victorse@unizar.es

The production of nanocomposites involving magnetic and metallic elements has attracted much interest because of their potential applications such as drug delivery, tissue engineering, magnetic resonance imaging (MRI), cancer therapy and nanodiagnostics [1]. Iron oxide nanoparticles are one of the magnetic nanoparticles widely used for biomedical applications, because of their low toxicity, chemical stability and biocompatibility [2]. Moreover, the anchoring of gold nanoparticles to the surface of the iron oxide, improve their stability and increase their functionality, therefore the range of applications in which they can be used. In the past decade micro-reactors have emerged for the highly controlled nanoparticle synthesis, RIIHULQJ PXOWLSOH DGYDQWDJHV RYHU FRQYHQWLRQDO V\QWKHVLV PHWKRG LQ ZKLFK WKH UHDFWRU ³EDWFK´ Ls used. These benefits include improvements in the crystallization process, good reproducibility and automation of the process. Laminar flow micro-reactors, however, are not enough suitable for the synthesis of nanoparticles with fast growth kinetics or where the presence of a specific reaction atmosphere is necessary. Segmented flow reactors are a good alternative, using an immiscible fluid (liquid or gas) to isolate the reagent segments. Key advantages of segmented flow include removing the dispersion, control of the reaction atmosphere and reduced reactor fouling [3]. This work has focused on the synthesis and characterization of hybrid nanomaterials based on iron oxide and gold (see Figure 1), for use in biomedical and catalytic applications. This synthesis was carried out using a segmented flow reactor under 4 minutes residence time in an aqueous media.

References [1]

L. H. Reddy, J. L. Arias, J. Nicolas, and P. Couvreur, Chem. Rev 112, Magnetic nanoparticles: design and characterization, toxicity and biocompatibility, pharmaceutical and biomedical applications (2012) 5818±78.

[2]

M. P. Calatayud, et.al, J. Mater. Chem. B 1, Neuronal cells loaded with PEI-coated Fe3O4 nanoparticles for magnetically guided nerve regeneration (2013) 3607.

[3]

A. M. Nightingale and J. C. Demello, Adv. Mater. 25, Segmented flow reactors for nanocrystal synthesis (2013) 1813±21.

Figures a)

50 nm

20 nm

Figure1. Heterostructured nanoparticles Au-Fe3O4 obtained using segmented flow micro-reactor: a) TEM. b) STEM-HAADF.

NanoSpain Bio&Med | 273

Ferromagnetic nanoparticles as delivery system of antitumor drugs for targeting breast cancer cells *1,2

1,2

Ana Lazaro-Carrillo , Macarena Calero , Pierre Couleaud , Antonio Aires , Alfonso Latorre , Álvaro 2 2 2,3 1,2 Somoza , Aitziber L. Cortajarena , Rodolfo Miranda and Angeles Villanueva 1

Universidad Autónoma de Madrid, Departamento de Biología, Darwin 2, 28049 Madrid, Spain. Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia), Faraday 9, 28049 Madrid, Spain. 3 Universidad Autónoma Madrid, Departamento de Física de la Materia Condensada, Francisco Tomás y Valiente 7, 28049 Madrid, Spain. ana.lazaro@imdea.org / ana.lazaro@uam.es 2

In the last century there has been a spectacular development of chemotherapeutic drugs against cancer. Nowadays a huge amount of cancer types are treated with different antitumor agents, however they produce multiple side effects. Nanotechnology-based approaches hold substantial potential for improving the care of patients with cancer. In this work we have used biocompatible magnetic nanoparticles (MNPs) coated with dimercaptosuccinic acid (DMSA) called MF66. Anti-neoplastic drug doxorubicin (DOX) and pseudopeptide Nucant (N6L) have been immobilized onto DMSA coating by electrostatic interactions. After 24 h incubation MNP-DOX were efficiently internalized by human breast cancer cells (MDA-MB231). This fact was confirmed by fluorescence microscopy and Prussian blue staining, producing an increased uptake by MNP-N6L. We assessed DOX linked to MNPs was more efficiently retained into cells than free DOX. Up to 48 h after MNP-DOX incubation aberrant mitosis were appeared and later, 72 h after treatment, apoptosis and mitotic catastrophe cell death were triggered. We confirmed these UHVXOWV E\ Į-tubulin (see Fig. 1) and caspase 3 immunofluorescence and flow cytometry and in addition this process was filmed by time-lapse video microscopy. Finally Alamar blue assay and Trypan blue were carried out to evaluate cytotoxicity of these formulation, showing a great pharmacological activity of the drug reducing cell viability approximately to 50% and many of the remaining cells enter senescence state. In summary, these multifunctionalized magnetic nanoparticles seems a promising tool as therapeutic agent, due their ability to produce efficient drug delivery and cancer cells inactivation. * This work was partially supported by grants from EU-FP7 (no 262943) and Spanish Ministry of Economy and Competitiveness (CTQ2013-48767-C3-3-R)

References [1] Calero, M.; Gutiérrez, L.; Salas, G.; Luengo, Y.; Lázaro, A.; Acedo, P.; Morales, MP.; Miranda, R.; Villanueva, A. Nanomedicine 10 [2014] 733-43.

Figures 24 h

72 h

50.0 µm

MF66

MF66-DOX

Figure 1. Immunofluorescence for Į-tubulin (green) and DNA counterstained with Hoechst-33258 in MDA-MB-231 cells. Left image: cells incubated with MF66 without functionalization. Right image: cells incubated with MF66-DOX at the same magnification, where doxorubicin induced increased cell size.

274 | NanoSpain Bio&Med

Modified MWCNT carpets as potential scaffolds for tissue engineering a,b

Barbara M. Maciejewska , Justyna Jurga-Stopa , Alicja Warowicka

a b

NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, PL- 3R]QDÄ&#x201D; 3RODQG Department of Macromolecular Physics, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, PL- 3R]QDÄ&#x201D; 3RODQG c Poznan University of Medical Sciences, Department of Biomaterials and Experimental Dentistry, ul.Fredry Poznan, Poland bmacieje@amu.edu.pl Multi Walled Carbon Nanotubes (MWCNTs) due to their unique physical properties have been

successfully applied in biomedicine e.g in drug delivery systems, as contrast agents and for gene therapies. The novel approach is to use MWCNTs as scaffolds for tissue engineering and regenerative medicine. The modification of MWCNT based systems can improve the cell adhesion and growth. In our studies, several MWCNT based nanosystems were verified as potential scaffolds in tissue engineering. The first group of investigated systems were the as prepared MWCNT based carpets as well as purified ones. Moreover, the oxidised and non-covalently coated with methyl cellulose MWCNT based carpets were investigated. The quality of MWCNT based nanosystems were characterised by means of Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM) and Thermogravimetric analysis as well as Raman spectroscopy. The analysis of cell interaction with MWCNT based scaffolds was studied by means of SEM. The cancer cell lines (U2OS and HeLa) and normal fibroblasts (Detroit 551) were used. In our research we investigated the cell adhesion as well as cell morphology. The physical structure of MWCNTs was compatible for adhesion of cells and no cytotoxic effect was observed in all MWCNT based nanosystems. The important difference between cell adhesion with MWCNT carpets and the type of used cell line was indicated. Moreover, the type of MWCNT based scaffold surface modification, increases the efficiency of interaction between them. Therefore, the MWCNTs can be a suitable scaffold in tissue engineering and for cell culturing.

Acknowledgements Financial support from the 1DWLRQDO &HQWUH IRU 5HVHDUFK DQG 'HYHORSPHQW XQGHU UHVHDUFK JUDQW ÂłNanomaterials and Their $SSOLFDWLRQ WR %LRPHGLFLQHÂ´ &RQWUDFW PBS1/A9/13/2012 as well as UDA POKL04.01.01-00-049/13-00 is gratefully acknowledged.

NanoSpain Bio&Med | 275

Synthesis of superparamagnetic nanoparticles for magnetic hyperthermia application María Monteserín, Francisco Martín, Gonzalo G. Fuentes Centro de Ingeniería Avanzada de Superficies, AIN_tech, AIN, Carretera de Pamplona, nº1, Cordovilla, Navarra, España mmonteserin@ain.es Abstract Magnetic nanoparticles (MNPs) have attracted increasing interest during the last decades due to their unique properties and potential applications in biomedicine, such as magnetic separation, drug delivery, magnetic resonance imaging (MRI) or magnetic hyperthermia.[1] Among them, magnetic hyperthermia is a promising approach for the treatment of isolated tumours on which magnetic nanoparticles are subjected to an alternating magnetic field in order to generate a specific amount of heat. This heating allows raising the temperature of the tumour and activates mechanisms of cellular damage.[2] However, due to the rapid advances in the use of magnetic nanoparticles for biomedicine, it is especially important to develop synthetic routes that allow a rigorous control of the microstructure of the magnetic core, as well as their size, monodispersity and magnetic properties.[3] Besides, for all these in vivo applications, where the target concentration is very small, or the encapsulation efficiency is quite low, it is important to achieve the temperature enhancement with as low as possible amount of MNP. Therefore, the specific loss power (SLP) of the magnetic nanomaterial must be as high as possible. Superparamagnetic iron oxide nanoparticles, also known as SPIONs, are the most used materials for this kind of applications due, principally, to their low toxicity and good biocompatibility.[4] Other superparamagnetic nanoparticles based on metals or metallic alloys, have remarkable high SLP and magnetic susceptibility. However, they are highly toxic, so different approaches should be addressed to avoid their side effects. In this study, either SPIONs, or metallic suparamagnetic nanoparticles have been synthesized in order to optimize their magnetic properties as well as for improve the hyperthermia effect that they can induce for their use in cancer treatments. The influence of the parameters of the synthesis on the structure and properties of the nanoparticles has been studied. The effect of different functionalization of the MNPs has also been addressed. The crystalline structure of the nanoparticles as well as, size, shape, stability and, more importantly, magnetic hyperthermia behaviour have been determined. This exhaustive characterization has allowed the optimization of each synthesis procedure in order to obtain monodisperse and homogeneous nanoparticles with high specific absorption rates which is a very important improvement, compared with the same kind of nanoparticles available in the literature. Moreover, these magnetic nanoparticles with tailored magnetic hyperthermia will be integrated in further stages of the research into drug delivery systems with specific cell recognition for their implementation for cancer hyperthermia treatments. References [1] M.V. Yigit, A. Moore, Z. Medarova, Pharma Res. 29 (2012) 1180-1188 [2] Kobayasi, T. Biotech. J. 6 (2011) 1342-1347. [3] C.S.S.R Kumar, F. Mohammad, Adv. Drug. De Rev. 63 (2011), 789-808 [4] S. Laurent, S. Dutz, U.O. Häfeli, M. Mahmoudi, Adv. Col. Int. Sci, 166 (2013), 8-23 Figures

Figure 1. TEM image of SPION magnetic nanoparticles. Figure 2. Magnetic hyperthermia heating curves of different MNPs.

276 | NanoSpain Bio&Med

Polyacetals as versatile drug delivery systems a

Julie Movellan , Ana ArmiĂąĂĄn , Vanessa GimĂŠnez , Richard M. England , Esther MasiĂĄ , Thipapun b b a Plyduang , Ruedeekorn Wiwattanapatapee , MarĂa J. Vicent a

Polymer Therapeutics Lab., Centro de InvestigaciĂłn PrĂncipe Felipe (CIPF), C/Eduardo Primo YĂşfera 3, Valencia 46012, Spain b Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Prince of Songkla University, Hat Yai, Songkla 90112, Thailand jmovellan@cipf.es

Abstract Polymer therapeutics is a rapidly developing technology and can be considered amongst the most successful nanomedicines. Due to their intrinsic characteristics this class of pharmaceuticals can exhibit XQLTXH DGYDQWDJHV L WKH\ DUH DEOH WR JHW WR SODFHV WKDW RWKHU ODUJHU ÂľQDQRFDUULHUVÂś FDQQRW UHDFK LL they are more able to cross biological barriers and can display architecture specific intracellular trafficking and (ii) they allow a greater control on drug pharmacokinetics due to the use of bioresponsive chemical conjugation [1]. One of the research lines of our group is focused on the development of polyacetal-drug conjugates. These particular conjugates are of great interest because of their ability to include drugs having a diol functionality directly into the polymer backbone since polyacetals are prepared by reaction between divinyl ethers and diols. Besides, they can be functionalized in their lateral chain by other drug or dye molecules allowing the preparation of versatile polymer conjugates. One great advantage of these polymers over others is the degradation of the polymer backbone in the acidic environment of the lysosome or the extracellular fluid of some tumors, which triggers drug release thus eliminating the need for a biodegradable linker [2]. Polyacetals developed in our laboratory are mainly designed for applications in regenerative medicine for the treatment of spinal cord injury, and for projects related with cancer treatment, mainly prostate cancer. This presentation will focus on the application of these polymers to the treatment of prostate cancer and review the results obtained in our group with single drug polymers and combination therapy [3].

References [1] R. Duncan, M.J. Vicent. Advanced Drug Delivery Reviews 65 (2013) 60. [2] a) J. Heller, D.W.H. Penhale, R.F. Helwing, J. Polym. Sci. Part C: Polym. Lett. 18 (1980) 5. b) R. Tomlinson, M. Klee, S. Garrett, J. Heller, R. Duncan, S. Brocchini, Macromolecules 35 (2002) 473. c) R. Tomlinson, J. Heller, S. Brocchini, R. Duncan, Bioconjugate Chem. 14 (2003) 1096. d) M.J. Vicent, R. Tomlinson, S. Brocchini, R. Duncan, J. Drug Target. 12 (2004) 491Âą501. , R. Schweins, A. Paul, M.J. Vicent, J. Control. Release 159 (2012) 290. b) R.M. England , R. Lucas, M.J. Vicent. J. Control. Release 164 (2012) 314. c) T. Plyduang, A. ArmiĂąĂĄn, J. Movellan, R.M. England, R. Wiwattanapatapee, M.J. Vicent. Submited

NanoSpain Bio&Med | 277

Structural analysis of artificial nanoparticle formation in Listeria innocua Dps Mitsuhiro Okuda

1,2,3

, Enea Sancho , Fernando Gil-Ortiz , Dalila Ciceri and Kornelius Zeth

2,5

CIC nanoGune, 20018 Donostia-San Sebastian, Basque Country, Spain IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Basque Country, Spain 3 Unidad de Biofisica (Centro Mixto CSIC-UPV/EHU), 48940, Leioa, Spain 4 CELLS-ALBA Synchrotron Light Source, 08290 Barcelona, Spain 5 Universidad del Pais Vasco (UPV/EHU), 48940, Leioa, Spain m.okuda@nanogune.eu

Abstract Biomineralization is an essential phenomenon in our nature, which leads to the formation of inorganic structures such as bone, tooth and so on. One of the cage shaped proteins, ferritin, has a pivotal role to maintain the iron concentration in living. Ferritin can form iron oxide nanoparticles (NP: 7 nm) through biomineralization at the center of their cavity (8 nm). As the size of NPs is regulated by protein shell, researchers have fabricated of artificial NPs, such as Fe3O4, Co3O4, In2O3 or CdSe [1,2], in the ferritin cavity to use them for electrical and magnetic applications [3, 4]. In order to minimize the structures, smaller cage shaped protein has been paid attention of. Dps (DNA-binding protein from starved cells) has a spherical form with a cavity at the center. Since the diameter of the cavity is 4.5 nm, the size of NPs can be regulated within less then 4.5 nm. Recent literature reports the production of artificial NPs in Dps proteins, however, the mechanism of NPs formation in Dps is still not clear. Iron oxide mineralization in Listeria innocua Dps has been reported to occur through ions translocated through ion channels (IC) of Dps and are gathered at feroxidase centers (FOC). This site can potentially induce nucleation and iron oxide NPs formation. Through those sites on the Dps, Iron oxide NPs can be formed through oxidation of divalent iron ions in the Dps in vivo and in vitro. The reason of the preference and ease is unknown part on the formation of iron oxide NP. Especially, the characteristic of iron ions states including divalent and trivalent states makes it difficult to understand the phenomena. In this work, we analyzed the structures of Listeria innocua Dps including metal ions such as Fe, divalent Co and trivalent Yb ions using synchrotron radiation. As Co and Yb ions are redoxstable in neutral solutions, the positions of metal ions can be analyzed by X-ray analysis without oxidation. At the ICs, the number of the metals ions were different depending on ion species and the conformation of the Glutamic acids were changed from that in apo-Dps (without metal ions). These results indicate that the conformational change would assist the uptake of metals ions into the Dps cavity. FOC had all metals ions regardless of the difference of charge state. On the other hand, the conformations of negative charged amino acid are changed from the positions in apo-Dps, suggesting that the FOC can act for nucleation center for artificial NPs formations and the conformation change would encourage to form nuclei of NPs.

References [1] M.Okuda, J-C. Eloi, S.E. Ward Jones, A. Sarua, R. M. Richardson, W. Schwarzacher, Nanotechnology, 23 (2012) 415601. [2] M. Okuda, Y. Suzumoto, K. Iwahori, S. Kang, M. Uchida, T. Douglas, I. Yamashita, Chem. Commun. 46 (2010) 8797-8799. [3] K.Yamada, S. Yoshii, S. Kumagai, I. Fujiwara, K. Nishio, M. Okuda, N. Matsukawa, I. Yamashita, Jpn. J. Appl. Phys., 45(5A) (2006), 4259-4264. [4] V. V. Kruglyak, M. Dvornik, R. V. Mikhaylovskiy, O. Dmytriiev, G. Gubbiotti, S. Tacchi, M. Madami, G. Carlotti, F. Montoncello, L. Giovannini, R. Zivieri, J. W. Klos, M. L. Sokolovskyy, S. Mamica, M. Krawczyk, M. Okuda, J.-C. Eloi, S. E. Ward Jones, W. Schwarzacher, T. Schwarze, F. Brandl, D. Grundler, D. V. Berkov, E. Semenova, N. Gorn, 2012 Metamaterial, Rijeka, Croatia, InTech, Chapter 14 p341-370

278 | NanoSpain Bio&Med

Fabrication and Characterization of Biomimetic Scaffold based on Modified PVA/PEDOT: PSS Nano-Fiber Materials for Tissue Regeneration

F. Pappa , V. Karagkiozaki , D. Konstantinou , E. Pavlidou , Th. Choli-Papadopoulou , S. Logothetidis

1. Nanomedicine Group, /DE IRU Âł7KLQ )LOPV- 1DQRV\VWHPV 1DQRPHWURORJ\Â´ 'HSDUWPHQW RI 3K\VLFV Aristotle University of Thessaloniki, Greece 2. Department of Physics, Aristotle University of Thessaloniki, Greece 3. Biochemistry Laboratory, Department of Chemistry, Aristotle University of Thessaloniki, Greece Contact: pappfote@physics.auth.gr

Tissue engineering is an emerging interdisciplinary field that applies principles of biology and engineering to the development of viable substitutes that restore or improve the function of human tissues. Scaffolds play a crucial role in nerve tissue engineering due to their encouragement towards FHOOVÂś SUROLIHUDWLRQ DELOLW\ WR DOORZ QXWULHQWV WR SHUPHDWH DQG WKHLU UHVHPEODQFH ZLWK WKH ([WUD &HOOXODU Matrix (ECM), thus forming a unique microenvironment for cells, allowing them to interact in vivo. To this end, via electrospinning, a versatile process, we fabricated conductive nanofiber-based scaffolds, consisted of the biodegradable polymer Polyvinyl alcohol (PVA) and conductive polymer Poly (3, 4ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS), and proceed towards the evaluation of their surface properties, emphasizing on the way that manipulate cell growth and adhesion. A neural cell-line was deposited onto the fabricated scaffolds in order to evaluate their cytocompatibility behavior. MTT cytotoxicity assay was used for the examination of cellsÂś proliferation and revealed excellent compatibility. In agreement with MTT findings, methylene blue staining and SEM imaging further reinforced scaffoldÂśs cytocompatibility. Degradation and Swelling studies were carried out in order to examine scaffoldÂśV SK\VLFRFKHPLFDO EHKDYLRU Results indicated that the conductive non-woven scaffolds are cytocompatible with promising cell proliferation properties, thus providing good potential for further utilization in nerve tissue engineering applications.

NanoSpain Bio&Med | 279

Lipid nanoparticles as tobramycin and sodium colistimethate encapsulation alternative: towards improved anti-infective therapy against Pseudomonas aeruginosa infection 1*

2,3,*

2,3

M Pastor , M Moreno-Sastre , A Esquisabel , G Gainza , E Herran , S Villullas , O Ibarrola , A del 1 1 1 4 4 5,6 2,3 1 Pozo , JJ Aguirre , M Castresana , E Sans , M Viñas , D Bachiller , JL Pedraz , E Gainza 1

BioPraxis AIE, Hermanos Lumière 5, 01510 Miñano, Spain NanoBioCel Group and CIBER-BBN Laboratory of Pharmaceutics, School of Pharmacy, University of the Basque Country (UPV/EHU), 4 Vitoria, 01006, Spain Dept. Pathology and Experimental Therapeutics. Medical School. Univ. 5 Barcelona-IDIBELL Fundación Investigaciones Sanitarias Islas Baleares (FISIB), Development and 6 Regeneration Program, Ctra. Sóller km 12,07110 Bunyola (Balearic Islands),Spain Consejo Superior de Investigaciones Científicas (CSIC), Ctra. Sóller km 12, 7110 Bunyola (Balearic Islands), Spain mpastor@praxisph.com Abstract Antibiotic resistance is becoming a major threat for the society [1]. In this framework, Pseudomonas aeruginosa plays a major role as it is responsible for 10% of nosocomial infections leading to severe and life-threatening infections [2]. As a strategy to enhance the antimicrobial therapy against Pseudomonas aeruginosa, herein we developed sodium colistimethate (SCM) or tobramycin (TOB) loaded lipid nanoparticles, namely, nanostructured lipid carriers (NLC). Lipid nanoparticles were elaborated following an organic solvent free hot-melt homogenization technique. Subsequently, NLCs were freeze dried. The nanoparticles obtained displayed a 200-400 nm size, high drug entrapment (§94%) and a sustained drug release profile over 48h. As TEM images showed (Fig.1.) particles were spherical and homogeneous. Formulation

Size (nm)

PDI

Zeta potential (mV)

EE (%)a

SCM-NLC

412.5 ± 13.9

0.442

-21.97 ± 1.72

94.79±4.20

TOB-NLC

254.05 ± 14.50

0.311

-23.03 ± 2.76

93.14 ± 0.13

Moreover, the formulations were active against clinically isolated Pseudomonas aeruginosa as MIC test revealed, where both formulations showed a MIC value ranging from 0.5 to 1 µg/ml (see Fig 2). Altogether, the work reported here seems to us an encouraging step towards an improved therapy against Pseudomonas aeruginosa. References [1] E Leung, DE Weil, M Raviglione, H Nakatani on behalf of the World Health Organization World Health Day Antimicrobial Resistance Technical Working Group, Bulletin of the World Health Organization, 89 (2011) 390-2. [2] V Aloush, S Navon-Venezia, Y Seigman-Igra, S Cabili, Y Carmeli. Multidrug-Resistant Pseudomonas aeruginosa: Risk Factors and Clinical Impact. Antimicrobial Agent and Chemotherapy, 50 (2006) 43-48. Figures 100%

Fig. 1-SEM images, left TOB-NLC and right SCM-NLC

90%

80%

70%

60%

50%

40%

30%

0,5

20%

0,25

10%

0,125 <0,125

0% Free SCM

SCM-NLC

Free Tobra

Tobra-NLC

Fig.2. MIC values of free and encapsulated antibiotics in µg/ml Acknowledgement M Moreno-Sastre thanks the University of the Basque Country for the ZabaldUz fellowship grant. The authors acknowledge the support of UPV/EHU (UFI11/32 and SGIker), of the CSIC and FISIB.

280 | NanoSpain Bio&Med

A composition for the preparation of dentifrices and other dental products Marcin Banach, Jolanta Pulit-Prociak Cracow University of Technology, Warszawska 24, Cracow 31-155 City, Poland jolantapulit@chemia.pk.edu.pl Abstract The present invention consists of a composition which may be used in process of obtaining dentifrices and other dental products. It may find application in the production of oral hygiene and dental filling materials for dental cavities. Final products may be used independently or along with toothpastes. Dentifrices help to maintain hygiene in mouth and thanks to proper polishing of tooth surface they provide their white colour. Dentifrices may be supplied in the form of paste, powder, gel or liquid [1]. The composition comprises ions of tin (II), fluoride, phosphorus, and nanoparticles of silver, gold or copper. The presence of tin ions gives a number of benefits, of which the most important are: the reduction of plaque, anti-inflammatory and antimicrobial effect, combating odour and reduction of tooth sensitivity [2]. The composition also contains fluoride ions, which are omnidirectional. Due to the presence of fluoride ions in dental products, it is possible to improve the overall health of the mouth. Properties of fluorinecontaining formulations promote the strengthening of teeth. The coating on the tooth surface with a thin layer of fluorine-containing compounds, allows to reminalizate the tooth enamel, which occurs due to the slow but continuous release of fluorine and its penetration into the tooth structure [3]. The addition of polyphosphates to the composition is also a novelty in the presented invention. These compounds are essential so that tin ions are stabilized. Polyphosphates prevent the formation of tartar and discoloration of teeth surface [4]. An additional innovation is the use of nanomaterials in the form of silver, gold or copper nanoparticles. In presented technology, they may be obtained directly during the preparation of the composition. Metals present in the nanocrystalline form are characterized by unique biocidal properties [5]. The use of nanomaterials allows to enhance antimicrobial effects, which is especially desirable in the case of oral hygienization. References [1] S.M.A. de OliveiraI, T.C. Torres; S.L. PereiraI, O.M. MotaII, M.X. Carlos, Journal of Applied Oral Science, 16 (2008) 293. [2] F.N. Hattab, Journal of Dentistry, 17 (1989) 47. [3] A.C.B. Delbem, K.T. Sassaki, A.M. de Castro, L.M.C.P. Pinto, M. Bergamasch, Journal of Applied Oral Science, 11 (2003) 319. [4] J.L. Winston, S.K. Fiedler, T. Schiff, R.A. Baker, Journal of Contemporary Dental Practice, 8 (2007) 1. [5] J. Pulit, M. Banach, R. SzczygĹ&#x201A;owska, M. Bryk, Acta Biochimica Polonica, 60 (2013) 795.

NanoSpain Bio&Med | 281

Magnetic liposomes based on nickel ferrite nanoparticles as nanocarriers for new potential antitumor compounds Ana Rita O. Rodrigues,1,* I.T. Gomes,1,2 Bernardo G. Almeida,1 J. P. Araújo,2 Maria João R.P. Queiroz,3 Elisabete M. S. Castanheira,1 Paulo J. G. Coutinho1 1

Centro de Física, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal IFIMUP/IN - Instituto de Nanociência e Nanotecnologia, R. Campo Alegre, 4169-007 Porto, Portugal 3 Centro de Química, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal *ritarodrigues@fisica.uminho.pt

Guided transport of biologically active molecules (most of them toxic and with systemic side effects) to target specific sites in human body has been a focus of research in therapeutics in the past years. Magnetoliposomes (liposomes entrapping magnetic nanoparticles) are of large importance, as they can overcome many pharmacokinetics problems and can be guided and localized to the therapeutic site of interest by external magnetic field gradients [1,2]. In this work, nickel ferrite nanoparticles (NPs) with size distribution of 11±5 nm were obtained. Synthesized NPs show superparamagnetic behaviour at room temperature (magnetic squareness of 7.2×10-5 and coercivity field of 12 Oe), being suitable for biological applications. These NPs were either entrapped in liposomes, originating aqueous magnetoliposomes (AMLs), or covered with a lipid bilayer, forming dry magnetoliposomes (DMLs), the last ones prepared by a new promising route. Recently, AMLs and DMLs containing nickel-based nanoparticles were successfully prepared and characterized [3]. A potential antitumor compound [4] was successfully incorporated into the lipid bilayer of magnetoliposomes. DMLs structure was evaluated by FRET (Förster Resonance Energy Transfer) measurements between the fluorescent-labeled lipids NBD-C12-HPC (donor) included in the second lipid layer and rhodamine B DOPE (acceptor) in the first lipid layer. A FRET efficiency of 23% was calculated, with a corresponding donor-acceptor distance (r) of 3.11 nm, confirming DMLs structure. Preliminary assays of the non-specific interactions of both types of magnetoliposomes with biological membranes (modeled by giant unilamellar vesicles, GUVs) were performed, keeping in mind future applications of drug delivery using this type of magnetic systems. Membrane fusion between magnetoliposomes and GUVs was confirmed by FRET. [1] A. S. Lubbe, C. Bergemann, J. Brock, D. G. McClure, J. Magn. Magn. Mat. 194 (1999) 149155. [2] S. Dandamudi, R. B: Campbell, Biomaterials 28 (2007) 4673-4683. [3] A.R.O. Rodrigues, I.T. Gomes, B.G. Almeida, J.P. Araújo, E.M.S. Castanheira, P.J.G. Coutinho, Mat. Chem. Phys. 148 (2014) 978-987. [4] C.N.C. Costa, A.C.L. Hortelão, J.M.F. Ramos, A.D.S. Oliveira, R.C. Calhelha, M.-J.R.P. Queiroz, P.J.G. Coutinho, E.M.S. Castanheira, Photochem. Photobiol. Sci. 13 (2014) 17301740.

Figure 1 - A. Fluorescence spectra (Oexc=470 nm) of DMLs labeled with NBD-C12-HPC and Rhodamine B-DOPE, before and after interaction with GUVs. B: Illustration of the fusion between the GUVs and DMLs labeled with both NBD-C12-HPC and Rhodamine B-DOPE.

282 | NanoSpain Bio&Med

Enzymatic Modulation of Shape of Gold Nanoparticles in Bioanalysis L. Saa, M. Coronado-Puchau, V. Pavlov, L. M. Liz-Marzán CIC biomaGUNE,Paseo Miramón 182, San Sebastian, Spain lsaa@cicbiomagune.es Abstract Gold nanorods (AuNRs) are one of the most used nanostructures for biosensing and imaging 1 applications due to their unique tunable optical properties. In this work we present two examples of enzymatic modulation in the growth or shape of AuNRs, and its application for detection of biomolecules. First, we selected the enzyme acetylcholinesterase (AChE), which hydrolyzes the substrate acetylthiocholine to produce the thiol-containing molecule thiocholine. This molecule is able to modulate the seed mediated growth of AuNRs, and different plasmon bands and/or gold nanoparticle shapes are 2 obtained. On the basis of these results, a simple colorimetric assay is proposed for the detection of subnanomolar concentrations of AChE inhibitors, which are analogs of nerve agents as shown in Figure 1. In the second case the enzymatic activity of horseradish peroxidase (HRP) in the presence of AuNRs and H2O2 has been used to trigger the chemical etching of AuNRs. Increasing amounts of H2O2 or HRP lead to a gradual reduction of the NR length while the thickness remained constant. When a sufficient amount of H2O2 or HRP was added, the rod-like shape was lost and spherical particles were obtained. The coupling of this reaction to the enzymatic reaction catalyzed by glucose oxidase (GOx), 3 allowed us to develop a highly sensitive and simple colorimetric assay that can be read out by the naked eye for the detection of physiological glucose concentrations in human serum as depicted in Figure 2. References [1] J. Pérez-Juste; I. Pastoriza-Santos; L.M. Liz-Marzán; P. Mulvaney, Coord.Chem. Rev., 249 (2005) 1870. [2] M. Coronado-Puchau, L. Saa, M. Grzelczak, V. Pavlov, L.M. Liz-Marzán, Nano Today, 8 (2013) 461. [3] L. Saa, M. Coronado-Puchau, V. Pavlov, L.M. Liz-Marzán, Nanoscale, 6 (2014) 7405.

Figures

Figure 1. Enzymatic modulation of seed-mediated gold nanorod growth by AChE.

Figure 2. Enzymatic etching of AuNRs mediated by GOx and HRP.

NanoSpain Bio&Med | 283

Various architectures of star polymers based on PEO, as a model system for the delivery of nucleic acids .DWDU]\QD 6]F]HÄ&#x17E;QLDN , Monika Makrocka-Rydzyk $QQD :RÄ¨QLDN , Marcin Jarek Ă XNDV] a c a,b c Popenda , Hong Y. Cho , Stefan Jurga , Krzysztof Matyjaszewski a,b,c

NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland Department of Macromolecular Physics, Faculty of Physic, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland c Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA k.wegner@amu.edu.pl

Abstract In the times of the harmful effects of the external environment on our bodies, many genetic diseases appear which results from our way of life and the influence of environment. Therefore, it becomes extremely important to discover and to synthesize the new materials that could prevent these diseases as well as to study the effects of such nanoparticles on compounds of natural origin - biomolecules. The method which involves the nanoparticles as modern vectors for transfection is known as gene therapy. We want to report the preparation of poly(ethylene glycol) (PEG)-based star polymers by an ATRP method. Our strategy in this area is to construct the efficient, biocompatible polymeric carriers for nucleic acids delivery using PEG-based star polymers with a cationic and degradable core. Four different architectures are considered including: multi-arms stars with biodegradable, and cationic core; 4-arms with biodegradable, cationic arms; linear polymers which are equivalent with other architectures in terms of molecular weight and chemical composition. Their structural characteristics were characterized by various methods such as DSC, NMR, NMR diffusion, DLS, microscopic techniques such as SEM, TEM) and polarizing optical microscopy (POM). The biological investigations were revealed on porcine skin fibroblast NT14 cell line. Methodology involved WST-1 proliferation assay and bioimaging INCell Analyzer 2000 system. Experiments carried out by DSC allowed the determination of the thermodynamic parameters of the synthesized polymers, i.e. melting and crystallization temperatures as well as their degree of crystallinity. DLS and NMR measurements were used to determine the sizes of star polymers in solution, and the behavior of the polymers in the solution was characterized by determining the diffusion coefficients. The investigation shows, that there is no cytotoxic effect in analyzed range of polymer concentrations in biological schemes. These results lead to the conclusion, that star polymers represent high biocompatibility profile, which enable their use in biomedicine. Thanks to extensive research, the cationic, biodegradable star-shaped polymers were obtained and their physical and chemical properties were investigated. Combined results of carried out measurements have allowed us to select the most suitable and promising candidates as nonviral vectors for gene therapy. Acknowledgements: The work was supported by the International PhD Projects Programme of Foundation for Polish Science operated within the Innovative Economy Operational Programme (IE OP) 2007-2013 within European Regional Development Fund References [1] Makrocka-Rydzyk, M., Wegner, K., Matyjaszewski, K., et al. Z Phys Chem, 226 (2012) 1271 [2] Cho, H., Averick, S. E., Wegner, K., Matyjaszewski, K., et al. Biomacromolecules, 14 (2013) 1262 [3] Li W. i Matyjaszewski K. Macromol. Rapid Commun,32 (2011) 74 Figures

Fig. Structures of synthesized star polymers

284 | NanoSpain Bio&Med

The cytotoxicity and cellular interaction of MWCNT-Fe composites 1

Alicja Warowicka , Anna Baranowska-Korczyc , Justyna Jurga-Stopa , 1,3 Barbara Maciejewska 1

NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61- 3R]QDÄ&#x201D; Poland

Poznan University of Medical Sciences, Department of Biomaterials and Experimental Dentistry, Fredry 10, 61- 3R]QDÄ&#x201D; 3RODQG

Department of Macromolecular Physics, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61- 3R]QDÄ&#x201D; 3RODQG

There has been growing interest in applying mutli-walled carbon nanotubes (MWCNTs) in biology and medicine. MWCNTs due to their one-dimensional, hollow nanostructure and special physicochemical properties have won enormous attention in nanomedicine. The knowledge about the toxicity of those nanomaterials is still not satisfactory. It is likely that toxicity of MWCNTs will depend not only on concentration but many other morphology related factors e.g length, diameter, type of functionalization and the type of attached molecules. Thus, evaluation and characterization of the toxic potential of synthesized nanomaterials and their cellular interactions are necessary. The aim of the research was to analyse the cytotoxicity and the impact of MWCNTs on the cells response. MWCNTs were synthesised by Chemical Vapor Deposition (CVD) technique. Consecutively, were oxidized and functionalized by selected polymers. Polyethylene glycol (PEG) with different molecular weight was covalently attached to MWCNTs surface to increase their solubility in liquids, thus biocompatibility. For in vitro investigation of MWCNTs two human cell lines (HeLa and normal human fibroblasts) were used. The effect of MWCNTs on the viability of the cells was analysed by cytotoxicity assays (WST-1 and MTT) as well as by In Cell Analyzer. The intracellular localisation of MWCNTs in HeLa cells was observed in confocal microscopy after organelles staining. Our research indicated the cytotoxicity increase with the higher MWCNTs concentration. However, the PEG-MWCNT treated cells investigation has revealed the higher viability and unchanged cell morphology in comparison with non functionalized MWCNT samples.

Acknowledgements The research was supported by National Centre for Research and Development (PBS1/A9/13/2012), the European Social Fund (POKL.04.03.00-00-015/12), National Science Centre UMO-2013/11/D/ST5/02900 and NCN/2012/05/N/NZ9/01337.

NanoSpain Bio&Med | 285

EĂŶŽ^ƉĂŝŶ ŚĞŵŝƐƚƌǇ ϮϬϭϱ

Ireland

Spain

Korea

Spain

Brazil

Spain

Turkey

Spain

country

289 | N a n o S p a i n C h e m i s t r y

Jeseelan Pillay, Robert Tshikhudo, Baljit Singh, Brian Seddon, Eithne Dempsey

Delaney, Aoife

Marina Solange Lozano García, Vicente Sánchez Escribano, and Jorge Antequera

Del Hoyo Martinez, Carmen

Md. Shahinul Islam,Ha-Jin Lee

Choi, Wonsan

M.P. Aguilar-Caballos, A. Gómez-Hens

Castillo García, María Luisa

L. Cano,J. Gutierrez, R. Fernandez, A. Tercjak

Carrasco-Hernández, Sheyla

Andreu Gonzáles-Calabuig, Andrea Cipri, Nelson Ramos Stradiotto and Manel del Valle

Cardoso de Sá, Acelino

A. E. Di Mauro, J. Gutierrez, M. Striccoli, M. L. Curri,A. Tercjak

Cano, Laida

Hatice Turhan, Prof. Levent Trabzon, Associate Prof. Huseyin Kizil

Bahmani Jalali, Houman

M.A. Molina, A. Gómez

Aguilar-Caballos, María de la Paz

authors

ImmunoCAP-An Electrochemical Immunosensor for Bovine Progesterone Assessment

Modified Nanoclays for an Environmental Application

Hydrogen Bond-Triggered Synthesis of Mesoporous SiO2 Nanoparticles for Environmental Remediation Nanomaterials

Dispersive solid-phase extraction with anew Fe3O4:Eu,Tb nanocomposite as sorbent for antibiotic determination

Preparation and characterization of PE-b-PEO block copolymer and HOBC or EBBA liquid crystals polymeric blends

Determination of carbohydrates in sugarcane bagasse employing a voltammetric electronic tongue formed by GCE/MWCNT/Metalsoxy-hydroxide modified electrodes

Hybrid nanocomposite films based on polystyrene-block-polymethyl methacrylate block copolymer and synthesized colloidal nanoparticles

A comparative study on optical properties of silver doped and silver decorated TiO2 thin films prepared by sol-gel dip-coating method

Usefulness of silver nanotriangle formation for the simultaneous determination of ascorbic acid and gallic acid

poster title

NanoSpain2015 Chemistry Posters list: alphabetical order

Spain

Lithuania

Poland

Spain

Korea

Ireland

Spain

Mexico

Spain

Czech Republic

country

290 | N a n o S p a i n C h e m i s t r y

A. Abhervé, J. Canet-Ferrer, M. ClementeLeón, E. Coronado, A. Cantarero

Recio, Maria Jose

H. Xu, Rasa Zukiene, Valentinas Snitka

Ramanauskaite, Lina

L.E. Coy, A. Warowicka,T. Zalewski, K. Załęski, K.K. Kozioł, S. Jurga

Maciejewska, Barbara

Carmen Del Hoyo Martínez, Jorge Cuéllar and Vicente Sánchez Escribano

Lozano Garcia, Marina Solange

Md. Shahinul Islam, Won San Choi

Lee, Hajin

Sujin Lee, Hyunjoo Yoo, Minsoo Jung

Kim, Seongjeen

Aoife Delaney, Brian Seddon and Eithne Dempsey

Kelch, Jessica

Soledad Peresin, Galder Kortaberria and Alvaro Tejado

Hidalgo, Joaquin

A. Hernández-Hernández and B.Marel Monro

Gutiérrez Amador, María del Pilar

Virginia Martinez-Martinez, Iñigo LopezArbeloa, Sylvie Lacombe, Eduardo PeñaCabrera

Epelde-Elezcano, Nerea

Radim Hrdy, Hana Kynclova, Katerina Prikrylova and Jaromir Hubalek

Drbohlavová, Jana

authors

Micro-Raman spectroscopy applied to the study of spin-crossover Fe(II) compounds

The synthesis of silver nano-wedges decorated substrates for the detection of molecular traces by Surface Enhanced Raman Spectroscopy

Synthesis of hydrophilic MWCNT-Fe composites as potential MRI contrast agents

Technique for adsorption of contaminants by nano clays

Mesoporous Calcium Silicates with Ultrahigh Drug Loading Capacity and pH-Triggered Release Behavior

Response Properties of Tantalum Oxide for Hydrogen Gas Detection

Synthesis of Nano-gold labeled steroid derivatives for electrochemical immunoassays

Microscopic Characterization of Nanofibrillated Cellulose-Inorganic Nanoparticle Hybrid Systems

Low temperature photoluminiscence in ZnS:Mn2+ nanoparticles

Mesoporous Core-shell Silica Nanoparticles grafted with new Halogenated Bodipy for PDT applications

Nanostructured Metallic Surfaces for Biological and Biomedical Applications

poster title

Korea

Mexicol

Spain

country

291 | N a n o S p a i n C h e m i s t r y

Jong-tae Son

Yang, Su-bin

Cabrera-Lara Lourdes Isabel

Torres Cadena, Raúl

Paradelo, M., Pérez-Rodríguez, P., De La Calle, I., López-Periago, J.E.

Soto, Diego

Virginia Martínez-Martínez, Raquel García, Luis Gómez Hortigüela, Joaquín PérezPariente, Iñigo López-Arbeloa

Sola, Rebeca

Irene García-Díaz, Francisco José Alguacil, Miguel Ángel Valdés, Felix Antonio López

Rodriguez, Olga

authors

Synthesis and Electrochemical test of Li-rich (0.5Li2MnO3-0.5LiNi1/3Co1/3Mn1/3O2) doped with Ba cathode material by using the Anodic Aluminum Oxide Template (AAO)

Electrodeposited bimetallic nanoparticles Au/Cu on semiconductor metal oxide substrates

Characterization of Cephalopod Ink Dispersions Using Tunable Resistive Pulse Sensing Technology. Comparison with SEM and DLS

Encapsulation of xanthene dyes into nanochannels of MgAPO-11 for optical applications

Application of Carbon Nanofibers to Recover Gold (III) from Waste PCBs

poster title

Usefulness of silver nanotriangle formation for the simultaneous determination of ascorbic acid and gallic acid a

M.A. Molina-Delgado , M.P. Aguilar-Caballos, A. G贸mez-Hens a

Analytical Chemistry Department, Institute of Fine Chemistry and Nanochemistry, Faculty of Sciences, University of Cordoba. Annex to Marie Curie (C-3). Campus of Rabanales. 14071-C贸rdoba. Spain. qa1gohea@uco.es

Abstract Antioxidant compounds have an important role in human health owing to some benefits, such as radical scavenging properties, which can decrease the prevalence of vascular diseases or cancer. Polyphenols and ascorbic acid are among the most relevant antioxidants, being the total content of polyphenols of these compounds traditionally estimated using the Folin Ciocalteu method. However, this method is affected by the presence of ascorbic acid and other reducing substances, so an overestimation of total polyphenol content can be obtained. The method presented here is aimed at the simultaneous determination of ascorbic acid and phenolic antioxidants, using gallic acid as the model analyte. The method developed allows the simultaneous determination of gallic acid and ascorbic acid and is based on the formation of silver nanotriangles observed by reacting silver nanoparticles of small size (10 nm), silver nitrate and citrate in the presence of the analytes. Under the experimental conditions assayed, the formation of silver nanotriangles was confirmed by the use of TEM images and UV-vis absorption spectra. Silver nanotriangles exhibit two different absorption maxima (450 and 590 nm), which allow the use of the proportional equation method to solve mixtures of ascorbic and gallic acids. A systematic study of the variables involved in the process has been performed in order to obtain additive signals to solve the equation system for binary mixtures in the PM range for both analytes.

NanoSpain Chemistry | 293

A comparative study on optical properties of silver doped and silver decorated TiO2 thin films prepared by sol-gel dip-coating method Houman Bahmani Jalali1, Hatice Turhan2, Prof. Levent Trabzon1,2, Associate Prof. Huseyin Kizil1,3 1Department

of Nano Science and Nano Engineering, Istanbul Technical University, Istanbul, Turkey of Mechanical Engineering, Istanbul Technical University, Istanbul, Turkey 3Department of Materials Engineering, Istanbul Technical University, Istanbul, Turkey hbahmanijalali@gmail.com

2Department

Abstract In this study, silver doped and silver decorated TiO2 thin films were prepared by sol-gel dip-coating method. Silver nitrate was dissolved in the TiO2 sol to obtain Ag-doped samples with different dopant concentration. The silver decorated TiO2 samples were prepared by dip-coating pure TiO2 thin film in AgNO3 aqueous solution. Thermal decomposition of AgNO3 at 414 Â°C was the idea to prepare silver decorated TiO2 thin films and coated samples were annealed at different temperatures. The structure and composition of prepared samples were characterized by X-Ray diffraction (XRD) and X-Ray photoelectron spectroscopy (XPS). The optical transmission spectra of the samples were measured using UV-Vis spectroscopy. The refractive index of thin films was recorded by NKD. The optical band gap was calculated using TDXF SORW YDULDWLRQ RI ÄŽKČŁ) 0.5 ZLWK KČŁ REWDLQHG IURP WKH DEVRUSWion spectra of the samples. Surprisingly, it was observed that silver cations were reduced to metallic silver in sample which was annealed at 120 Â°C [1]. The high band gap value of pure and silver doped TiO2 thin films are attributed to thermal stress effects produced in the films [2-5]. References [1] Ji-Woon Kwon et al., Bull. Korean Chem. Soc. 2005, Vol. 26, No. 5 [2] S.A Tomas et al, Thin Solid Films, 518, (2009), 1337Âą1340 [3] J. Yu et al. , Appl. Catal. B 60 (2005) 211 [4] T. Ivanova et al., Optical Materials 36 (2013) 207Âą213 [5] Ch. Yang et al. , Appl. Surf. Sci. 254 (2008) 2685Âą2689

Figure 1 UV-Vis absorption spectra of prepared samples

Figure 2 Tauc plot of prepared samples

294 | NanoSpain Chemistry

Hybrid nanocomposite films based on polystyrene-block-polymethyl methacrylate block copolymer and synthesized colloidal nanoparticles a

L. Cano , A. E. Di Mauro , J. Gutierrez , M. Striccoli , M. L. Curri , A. Tercjak

Group `Materials + Technologies´, Chemical Engineering and Environmental Department, Polytechnic School, University of the Basque Country (UPV/EHU), Plaza Europa 1, 20018 Donostian, Spain b

CNR-IPCF Bari Division, Chemistry Department, University of Bari, Via Orabona 4, 70126 Bari, Italy laida.cano@ehu.es

Abstract The development of novel hybrid nanocomposites by means of the combination of block copolymers acting as matrices with nanometric materials is gaining increasing interest in the material science field. Block copolymers are ideal materials for this purpose as chemically different blocks are covalently linked with each other, giving them the ability to self-assemble into different ordered nanoscale morphologies. On the other hand, nanoscale materials, in particular nanoparticles, possess interesting properties, such as electrical, magnetic, mechanical or optical, among others. Thus, the combination between nanostructured block copolymers and nanoparticles will result in hybrid inorganic/organic materials with functional properties. In the past decade, many researchers have used polystyrene-block-polymethyl methacrylate (PS-bPMMA) block copolymer as a template to create hybrid inorganic/organic nanocomposites by adding different inorganic nanoparticles (NP) to the polymeric matrix [1-4]. In this case, both ex-situ synthesized titanium oxide nanorods and iron oxide nanocrystals have been incorporated into the PS-b-PMMA block copolymer [3,4]. The synthesis procedure carried out to obtain colloidal titanium oxide nanorods and iron oxide nanocrystals [5] led to oleic acid capped nanoparticles, which make them more compatible with one block of the block copolymer, the PS block in particular. The characterization of the nanoparticles was performed by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) in order to analyze the size and shape of nanoparticles and to confirm the presence of surfactant on their surface. Thank to this capping layer, the content of nanoparticles in the block copolymer can achieve values up to 50-60 wt % in respect to the block copolymer content. NP/PS-b-PMMA nanocomposites were characterized in terms of their morphology by atomic force microscopy (AFM) and scanning force microscopy (SEM) and also their optical, electrical and magnetic properties were studied. References [1] Weng C. C., Wei K. H., Chemistry of Materials, 15 (2003) 2936-2941. [2] Xu C., Ohno K., Ladmiral V., Milkie D. E., Kikkawa J. M., Composto, R. J., Macromolecules, 42 (2009) 1219í1228. [3] Cano L., Gutierrez J., Tercjak A., Journal of Physical Chemistry C, 117 (2013) 1151-1156. [4] Cano L., Di Mauro A. E., Striccoli M., Curri M. L., Tercjak A., Applied Materials & Interfaces, 6 (2014) 11805-11814. [5] Buonsanti R., Grillo V., Carlino E., Giannini C., Curri M. L., Innocenti C., Sangregorio C., Achterhold K., Parak F. G., Agostiano A., Cozzoli P. D., Journal of the American Chemical Society, 128 (2006) 16953-16970. Figures

Figure 1. AFM phase images (2 µm x 2 µm) of a) neat PS-b-PMMA diblock copolymer and its nanocomposites with b) 1, c) 10 and d) 50 wt % synthesized TiO 2 nanorods.

Acknowledgements Financial support from Spanish Ministry of Economy and Competitiveness in the frame of MAT201231675 project and from the Basque Government funded Grupos Consolidados project (IT776-13) is gratefully acknowledged. L. C. thanks Basque Government for the PhD Fellowship (Programas de becas para formación y perfeccionamiento de personal investigador (BFI-2011-218)).

NanoSpain Chemistry | 295

Determination of carbohydrates in sugarcane bagasse employing a voltammetric electronic tongue formed by GCE/MWCNT/Metals oxy-hydroxide modified electrodes 1,2

Acelino Cardoso de Sรก* , Andreu Gonzรกles-Calabuig , Andrea Cipri , Nelson Ramos Stradiotto and 2 Manel del Valle 1

Institute of Chemistry - UNESP, Rua Prof. Francisco Degni, 55, Araraquara-SP, Brazil. Sensors and Biosensors Group, Department of Chemistry, Universitat Autรณnoma de Barcelona, Edifici Cn, 08193 Bellaterra, Barcelona, Spain. *acelino2@hotmail.com

Abstract: The biomass consisting of sugarcane bagasse is a byproduct of the process of producing sugar and ethanol. New applications to make the most of bagasse have been developed, among them we can highlight the production of biofuels (ethanol) of second generation. The second generation ethanol is produced from the carbohydrates released from the cell wall of bagasse and straw of sugarcane [1]. Accurate measurement of the carbohydrates content present in the samples of sugarcane bagasse is very important, because its quantification is directly linked to the production of second generation ethanol. Classical methods for the determination of carbohydrates in biomass will be using the chromatographic technique, which allow individual identification of carbohydrates, but these require specific equipment, laboratory conditions and/or trained people. The use of sensors is a desired way to solve such problems, but there are not perfectly ideal sensors for all applications. A new methodology in the use of sensors entails multiple sensing devices plus advanced data treatment of the information generated. This is known as electronic tongue, and it is a highly versatile approach capable of simultaneously monitoring the level of different analytes and/or counterbalancing potential interferents. Main goals of this work are then the application of a voltammetric electronic tongue formed by glassy carbon electrodes modified with multi-walled carbon nanotubes decorated using metals oxyhydroxide towards the analysis of carbohydrates (galactose, glucose, xylose and mannose) in biomass (sugarcane bagasse). As such, it combines the responses from an array of voltammetric GCE/MWCNT/Metals oxy-hydroxide sensors (Cu, Ni, Co, Au, Pd), plus an advanced response model obtained using artificial neural networks (ANN) [2]. Since the departure data is highly complex, providing each sensor in the array a complete voltammogram, initial pretreatment of the data is also necessary, for which different compression methods are evaluated. Simultaneous determination of galactose, glucose, xylose and mannose is therefore feasible, by simple cyclic voltammetry and optimized data treatment. -1

Table1: Demonstration of cross-sensitivity (A.mol .L) found for the sensors used in the electronic tongue showing it is feasible for resolution of carbohydrates (galactose, glucose, xylose and mannose) Glucose

Xylose

Galactose

Mannose

Copper

0.0492

0.0519

0.0581

0.075

Gold

0.0067

0.0065

0.0053

0.0062

Palladium

0.0172

0.0122

0.0309

0.0143

Nickel

0.0364

0.0369

0.0462

0.0415

Cobalt

0.0768

0.0654

0.0705

0.0661

References [1] SLUITER, J. B. et. al. J. Agric. Food Chem. v. 58, 2010, p. 9043-9053. [2] del VALLE, M. Electroanal, v. 22, 2010, p. 1539-1555.

296 | NanoSpain Chemistry

Preparation and characterization of PE-b-PEO block copolymer and HOBC or EBBA liquid crystals polymeric blends S. Carrasco-Hernandez

, L. Cano, J. Gutierrez, R. Fernandez, A. Tercjak

Group Materials + Technologies, Chemical Engineering and Environmental Department, Polytechnic School, University of the Basque Country (UPV/EHU), Plaza de Europa 1, 20018 Donostia- San SebastiĂĄn, Spain. sheyla.carrasco@ehu.es Abstract The polymer blend technology is one of the main areas of research and development in polymer science. This technology leads to developed novel materials with interesting applications. The polymer blends offer opportunities to create novel materials with tailored properties, which can improve their properties if compare with properties of the neat components. As it is well known, organic low molecular weight molecules can provoke higher miscibility in polymer blends. Consequently, low molecular weight liquid crystals were in many occasions used as one of the component of the polymeric blends [1-4]. In the present work, polymeric blends based on PE-b-PEO block copolymer with two different types of low molecular weight liquid crystals, 4'-(hexyloxy)-4-biphenylcarbonitrile (HOBC) and N-(4etoxibenciliden) 4-butylaniline (EBBA) was fabricated and investigated. Different advanced techniques were employed to study miscibility and thermal stability of design polymeric materials; Fourier transform infrared spectroscopy (FTIR), optical microscopy (OM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). OM micrographs taken in the same temperature for different content of HOBC or EBBA liquid crystals are shown in the Figure 1. As expected different types of spherulites of HOBC or EBBA rich phase was detected suggesting different miscibility between liquid crystals and blocks of PE-b-PEO block copolymer. References [1] Gao C., Zhang S., Li X., Zhu S., Jiang Z., Polymer, 55 (2014) 119-125. [2] Panapitiya N. P., Wijenayake S. N., Huang Y., Bushdiecker D., Nguyen D., Ratanawanate C., Kalaw G. J., Gilpin C. J., Musselman I. H., Balkus Jr K. J., Ferraris J. P., Polymer, 55 (2014) 2028-2034. [3] Tercjak A., Serrano E., LarraĂąaga M., Mondragon I., Journal of Applied Polymer Science, 108 (2008) 1116-1125. [4] Yang D., Lin J., Li T., Lin S., Tian X., European Polymer Journal, 40 (2004) 1823-1832. Figures

Figure 1. OM micrographs of a1) HOBC and PE-b-PEO/HOBC blends with 2) 5, 3) 10, 4) 20 and 5) 50 wt % of PE-b-PEO block copolymer and b1) EBBA and PE-b-PEO/EBBA blends with 2) 5, 3) 10, 4) 20 and 5) 50 wt % of PE-b-PEO block copolymer.

Acknowledgements Financial support from Spanish Ministry of Economy and Competitiveness in the frame of MAT201231675 project and from the Basque Government funded Grupos Consolidados project (IT776-13) is gratefully acknowledged. S. C.-H. thanks Spanish Ministry of Economy and Competitiveness for the PhD Fellowship BES-2013-066734.

NanoSpain Chemistry | 297

Dispersive solid-phase extraction with a new Fe3O4:Eu,Tb nanocomposite as sorbent for antibiotic determination M.L. Castillo-García, M.P. Aguilar-Caballos, A. Gómez-Hens Analytical Chemistry Department, Institute of Fine Chemistry and Nanochemistry, Faculty of Sciences, University of Cordoba.Annex to Marie Curie (C-3).Campus of Rabanales. 14071-Córdoba. Spain. qa1gohea@uco.es Abstract A novel Fe3O4:Eu,Tb nanocomposite has been synthesized for its use as sorbent in dispersive solid phase extraction, which has been applied to the determination of quinolone and tetracycline antibiotics in meat samples. These nanocomposites have been synthesized [1] in two simple steps, which consist in the formation of the magnetic core by a co-precipitation method and a further treatment with Eu(III) and Tb(III) salts obtaining magnetic nanomaterial with these lanthanide ions in its surface. The magnetic properties of these hybrid nanoparticles ease the performance of dispersive solid phase extraction and the presence of Eu(III) and Tb(III) in their composition allows a relatively selective interaction with antibiotics bearing E-diketonate and carboxylic acid groups, such as quinolones and tetracyclines, which have been chosen as model analytes. Oxolinic acid (OXO), nalidixic acid (NAL), flumequine (FLU), oxytetracycline (OTC), tetracycline (TET) and chlortetracycline (CTC) have been simultaneously determined using ultra high performance liquid chromatography with fluorometric determination in less than 5 min. Chromatograms were simultaneously detected at two excitation/emission pairs of wavelengths, which are 255/360 and 390/512 nm for quinolones and tetracyclines, respectively. Under the optimum conditions, the dynamic ranges and detection limits for the analytes were 0.5 ± 2000 -1 -1 -1 and 0.25 ng mL for OXO; 1.5 ± 2000 and 0.7 ng mL for NAL; 2.5 ± 2000 and 1.2 ng mL for FLU; 2 ± -1 -1 -1 7500 and 1 ng mL for OTC; 3 ± 7500 and 1.5 ng mL for TET; and finally, 10 ± 1000 and 3.8 ng mL for CTC. Intra- and inter-day precision data were assessed for retention times and areas at two concentration levels of each antibiotic, yielding values in the range of 0.07 ± 0.21% and 2.6 ± 9.1% for retention times and areas, respectively, in intra-assay precision experiments, and 0.5 ± 1.8% and 4.2 ± 14.4% for retention times and areas obtained after inter-assay experiments, respectively. The method was applied to the analysis of different meat samples, such as chicken and pork muscle, which were -1 spiked at 50, 100 and 200 Pg kg , giving mean recovery values for each analyte in the range of 79.1 ± 91.8%. These results prove the usefulness of the developed method to the control of these antibiotic residues in meat samples.

References [1] Ma, Z.Y.; Dosev, D.; Nichkova M.; Gee, S.J.; Hammock, B.D.; Kennedy, I.M. J. Mat. Chem., 2009, 19, 4695.

298 | NanoSpain Chemistry

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|KZDOG $QJHZ &KHP ,QW (G Â± > @ : 6 &KRL - + 3DUN + < .RR - < .LP % . &KR DQG ' < .LP $QJHZ &KHP ,QW (G Â±

NanoSpain Chemistry | 299

Modified Nanoclays for an Environmental Application Carmen Del Hoyo Martínez, Marina Solange Lozano García, Vicente Sánchez Escribano, and Jorge Antequera Department of Inorganic Chemistry. University of Salamanca. Plaza de la Merced s/n. 37008 Salamanca. Spain. hoyo@usal.es The clay materials have led to numerous applications in the field of public health (del Hoyo, 2007; Volzone, 2007) having been demonstrated its effectiveness as adsorbents of all contaminants. Some biodegradable materials are used for for adsorption of chemical contaminants: lignins (Valderrabano et al., 2008) and also clays and clay minerals, whose colloidal properties, ease of generating structural changes, abundance in nature, and low cost make them very suitable for this kind of applications. Thanks to the development of the science and the technology of the nourishment in the last 50 years, there have revealed itself several new substances that can fulfill beneficial functions in the food, and these substances, named food additives, are today within reach of all. The food additives recover a very important role in the complex nourishing supply. The additives fulfill several useful functions in the food, which often we give for sat. Nevertheless the widespread use of food additives in the food production also influences the public health. The food industries, which are very important for the economy, spill residues proved from its activity that they have to be controlled to evaluate the environmental impact and to offer the necessary information about the quantitative evaluation of the chemical risk of the use of food additives for the public health. The clay materials have led to numerous applications in the field of public health (del Hoyo, 2007; Volzone, 2007) having been demonstrated its effectiveness as adsorbents of all contaminants. Some biodegradable materials are used for for adsorption of chemical contaminants: lignins (Valderrabano et al., 2008) and also clays and clay minerals, whose colloidal properties, ease of generating structural changes, abundance in nature, and low cost make them very suitable for this kind of applications. Among the strategies used at present to preserve the quality of the water and this way to diminish the environmental risk that supposes the chemical pollution, stands out the use of adsorbents of under cost, already they are natural or modified, to immobilize these compounds and to avoid the pollution of the water with the consequent reduction of environmental and economic costs. We have studied the adsorption of several contaminants related to the food industry by natural or modified clays, searching their interaction mechanisms and the possible recycling of these materials for environmental purposes and prevention of the health. We have used the FT-IR spectroscopy and DTA/TG studies to confirm the reciclability of these materials and the possible application in the industry to prevent the contamination. References [1] del Hoyo, C. Applied Clay Science. Layered Double Hydroxides and human health: An overview. (2007). 36, 103-121. [2] Valderrábano, M., Rodríguez-Cruz, S., del Hoyo, C., Sánchez-Martín, M.J. 4th International Workshop "Bioavalailability of pollutants and soil remediation". Physicochemical study of the adsorption of pesticides by lignins. (2006). 1, 5-6. [3] Volzone, C. Applied Clay Science. Retention of pollutant gases: Comparison between clay minerals and their modified products. (2007). 36, 191-196.

300 | NanoSpain Chemistry

ImmunoCAP - An Electrochemical Immunosensor for Bovine Progesterone Assessment 1

Aoife Delaney* , Jeseelan Pillay , Robert Tshikhudo , Baljit Singh , Brian Seddon , Eithne Dempsey 1

Centre for Research in Electroanalytical Technologies (CREATE) Institute of Technology Tallaght, Dublin 24, Ireland. 2 Mintek, Nanotechnology Innovation Centre, Johannesburg, South Africa, 2125 *aoife.delaney@live.ie

Abstract Profitability in the dairy industry is heavily dependent on the accuracy of progesterone (P4) measurement, with periodic assessment of hormone levels in herds being utilised to determine the most fertile ovulation time for artificial insemination [1]. Point of care and in-line instruments, coupling ELISA techniques with electrochemical detection have been explored in order to quantify P4 in bovine milk and serum [2], yet practical implementation of a sensitive, rapid, low cost test remains a technical challenge. The Immuno-CAP device proposed here may be described as a micro-capillary biosensor incorporating a thin-layer mesofluidic system involving rapid flow immunochromatography with electrochemical detection based on the redox activity of nanogold (AuNP) - the signalling element of a competitive ELISA format. Competition between P4 in the sample and AuNP labelled P4 for binding sites on the internal wall of the anti-P4 antibody coated capillary facilitates electrochemical detection of AuNP reaching the electrode which is in turn related to the free P4 concentration in the milk sample (Fig. 1).

Figure 1

Fig. 1. a) Schematic representation of immunocapillary device (ImmunoCAP) illustrating the structure of a singlechannel device (device dimensions 85 x 15 mm, channel L 74 mm, W 1 mm and D 0.16 mm b) exploded view of detection mechanism following the competitive immunoassay protocol for progesterone.

References

[1] Audrey Chanvallon, Stéphanie Coyral-Castel, Julie Gatien, Jean-Michel Lamy, Daniéle Ribaud, Clément Allain, Pierre Clément, Pascal Salvetti, Theriogenology, 82 (2014) 734±741. [2] J.V. Samsonova, V.A. Safronova, A.P. Osipov, Talanta, 132 (2015) 685±689.

NanoSpain Chemistry | 301

Nanostructured Metallic Surfaces for Biological and Biomedical Applications Jana Drbohlavova, Radim Hrdy, Hana Kynclova, Katerina Prikrylova and Jaromir Hubalek CEITEC Brno University of Technology, Technicka 10, 616 00 Brno, Czech Republic drbohla@feec.vubtr.cz Abstract Noble metalllic electrodes, especially, gold, solid gold-amalgam, silver or palladium are very suitable for biological applications in the field of fragment biological samples detection such as microRNA or proteins as disease markers [1, 2]. Various nanostructured surfaces based on metallic nanopillars, nanorods or nanowires are usefull in microdevices . The present works deals with the fabrication of nanostructured surfaces formed by array of nanorods (see Fig 1). For the fabrication of nanostructured surfaces, the template based method is employed. Namely the nanoporous anodic aluminum oxide (AAO) has been used as a template for the growth of various functional nanomaterials and as a scaffold for nanodevices. Also, we present a new electrochemical approach of pore opening from AAO bottom. Selective perforation of an oxide barrier on AAO bottom using re-anodization technique and oxide ingrowth of metal oxides were developed. The skip phasing of oxide barrier wet etching is the significant advantage in comparison to other techniques, since it does not suffer from size increase of the naturally grown pore. Obtained nanowires have various lengths ranging from 50 nm up to Â&#x2014;P DQG GLDPHWHU LQ the range of 10Âą300 nm. In this case, the surface characterization and following protein detection was performed by EIS (electrochemical impedance spectroscopy). The EIS has showed the high dependence between the rate of nanomachining and active electrochemical surface area, which is directly related to the level of sensitivity [3]. References [1] Juskova, P., et al., Anal. Chem. 827 (2010): p. 2690-2695. [2] Cernei, N., et al., Int. J. Electrochem. Sci. 75 (2012): p. 4286-4301. [3] Hrdy, R., et al., Int. J. Electrochem. Sci. 84 (2013): p. 4384-4396. Figures

Fig. 1. SEM images of microelectrodes with gold nanostructured surface (left) and an array of palladium nanopillars prepared for the hydrogen detection (right)

302 | NanoSpain Chemistry

Mesoporous Core-shell Silica Nanoparticles grafted with new Halogenated Bodipy for PDT applications 1,2

Nerea Epelde-Elezcano , Virginia Martinez-Martinez , Iñigo Lopez-Arbeloa , Sylvie Lacombe , 3 Eduardo Peña-Cabrera 1

University of the Basque country UPV-EHU, Aptd 644 48080, Bilbao, Spain IPREM, UMR CNRS 5254, Université de Pau et des Pays de l'Adour, Hélioparc 64039, Pau, France 3 University of Guanajuato, Col. Noria Alta S/N, 36050, Guanajuato, GTO, Mexico nerea.epelde@ehu.es

Nanostructured hybrid materials, are gaining interest for photodynamic therapy (PDT) application as a non-invasive treatment to fight diseases such as cancer. PDT consists in the accumulation of a photosensitizer (PS) containing nanomaterial in tumour tissues for their irradiation by VIS or NIR light in order to locally produce singlet oxygen able to kill tumour cells. In this work mesoporous silica core-shell nanoparticles are selected as ideal drug curries due to their low-toxicity, tuneable size and a surface easily to be functionalized. The silica nanoparticles were synthesized by so-gel process in order to control the particles size (around 50 nm), shape (spherical) and porosity and PS was grafted at the external surface grafted with original PSs. The most important properties of suitable SKRWRVHQVLWL]HU¶V DUH: strong VIS/NIR absorption bands and intersystem crossing (ISC) efficiency to generate singlet oxygen. New halogenated Boron DiPyrromethene (BODIPY) were studied as PSs because of their high singlet oxygen efficiency, which were measured by different (direct and indirect) methods. Besides comparing singlet oxygen quantum yields of various halogenated BODIPYS, two of them with suitable grafting groups were grafted onto mesoporous silica nanoparticle for singlet oxygen generation. The singlet oxygen quantum yield ĭǻ) of these functionalized BODIPYS will be compared before and after grafting in order to obtain suitable materials for PDT applications. References [1] Indrajit Roy, Tymish Y. Ohulchanskyy, Haridas E. Pudavar, Earl J. Bergey, Allan R. Oseroff, Janet Morgan, Thomas J. Dougherty, Paras N. Prasad, J. Am. Chem. Soc. 125 (2013) 7860. [2] Ronzani, F; Blanc, Sylvie; Bordat, P; Pigot, T; Cugnet, C; Arzoumanian, E; Oliveros, E; Sarakha, M; Richard, C; Lacombe, S. Phys. Chem. Chem. Phys, 15 (2013) 17219. [3] Ortiz, M.J; Agarrabeitia, A.R; Dueran-Sampedro, G; Bañuelos Prieto, J; Arbeloa Lopez, T; Massad, W.A; Montejano, H.A; Garcia, N.A, Lopez Arbeloa, I. Tetrahedron, 68 (2012) 1153.

Figures a) and b) TEM image of core-shell silica nanoparticles before grafting; c) Singlet oxygen emission at 1270 nm in ACN of a new synthesized BODIPY. 1800

1600

Singlet oxygen emission

1400 1200 1000 800 600 400 200 0 1240

1260

1280

1300

1320

wavelength(nm)

NanoSpain Chemistry | 303

Low temperature photoluminiscence in ZnS:Mn 1

nanoparticles

M.P. Gutiérrez , A. Hernández-Hernández and B. Marel Monroy 1

Escuela Superior de Apan, UAEH. Chimalpa Tlalayote, Municipio de Apan, Hidalgo, 43920, México. 2 Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, A. P. 70-360, C.P.04510, Coyoacán, México DF, México. amadorg@uaeh.edu.mx

Abstract Nanosized inorganic semiconducting materials such as ZnS have elicited recently a great interest for research due to their chemical and physical properties, which differ from those of bulk materials. These important inorganic materials have been studied for a variety of potential applications including photoconductors, solar cells, photoconductors, solar cells, field effect transistors, etc. When doped with transition metal ions, ZnS can become an efficient light emitting material. In this work, the nanocrystalline solid solution Zn(1-x)MnxS (0.010≤x≤0.20) was synthesized by a soft chemistry method. The average size of the luminescent nanoparticles is in the range of the 3-5 nm. A pure single phase with cubic blenda structure was confirmed from X-ray powder diffraction patterns. The UV-visible diffuse reflectance spectra were used to calculate the band gap energy across the compositional series at room temperature. This band gap value decreased from 3.58 eV (for ZnS) to 3.24 eV for Zn0.80Mn0.20S. The samples with manganese content between 0.05 and 0.15 showed the photoluminescence effect when they were illuminated with ultraviolet light. We found that the fluorescence intensity showed a maximum for a manganese content of x=0.10. In adition, we will present the photoluminescence behavior as a function of the temperature in the range of 10 K to room temperature. The orange emission from the 4 6 2+ T1- A1 transition of Mn ions were observed in the Mn-doped samples. It was found that all of these emission bands decrease as temperature increases. The activation energies were estimated for the Mnorange emissions. References [1] Authors, Journal, Issue (Year) page.

304 | NanoSpain Chemistry

Microscopic Characterization of Nanofibrillated Cellulose-Inorganic Nanoparticle Hybrid Systems 1,3

Jokin Hidalgo , Soledad Peresin , Galder Kortaberria and Alvaro Tejado

Tecnalia Research & Innovation, Mikeletegi 2, Donostia-San Sebastian, Spain 2 VTT-Technical Research Centre, Biologinkuja 3, Espoo, Finland 3 University of the Basque Country, Plaza Europa 1, Donostia-San Sebastian, Spain Jokin.Hidalgo@tecnalia.com Abstract The establishment of a new bio-based industry largely depends on the development of new valueadded products based on cellulose, by far the most abundant biopolymer on Earth. In line with this, an intensive research has been carried out over the last decade on nanostructured cellulose products, often combined with inorganic nanocompounds, with the potential of being used in a wide range of valuable applications (biomedical devices, polymer reinforcements, flexible electronic substrates, FRQVWUXFWLRQ FRPSRQHQWVÂŤ ,Q SDUDOOHO WKH DYDLODELOLW\ RI ODUJH YROXPHV RI QDQRFHOOXORVH DW PRGHUDWH cost is rapidly progressing with the setting-up of pilot-scale and commercial facilities. The market for these products will be growing millions of euros by 2020 [1]. In this work, a preliminary microscopic study of organic-inorganic hybrid nanocomposites was carried out using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) on different substrates. Three different types of cellulose substrates, i.e. cellulose microfibres, cellulose nanofibres and dicarboxylated cellulose nanofibres, the latter prepared as reported elsewhere [2,3], were combined with three types of inorganic nanoparticles, namely titanium dioxide, sodium montmorillonite and organically modified montmorillonite (see example in Figure 1). This study has a provided a better understanding over the structure of organic-inorganic hybrid systems made of nanocellulose and titanium dioxide/nanoclay, especially on the processability problems that may arise within the production of this type of hybrids.

References [1] Future Markets. The global market for nanocellulose to 2020 (2014) p.85. Retrieved from http://www.futuremarketsinc.com/index.php/nanoreports-63/nanocellulose. [2] 7HMDGR $ $ODP 1 0G $QWDO 0 <DQJ + DQG YDQ GH 9HQ 7 * 0 Âł(QHUJ\ UHTXLUHPHQWV IRU WKH GLVLQWHJUDWLRQ RI FHOOXORVH ILEHUV LQWR FHOOXORVH QDQRILEHUVÂ´ &HOOXlose 19 (2012), 831-842. [3] YDQ GH 9HQ 7 * 0 $ODP 1 0G $QWDO 0 DQG 7HMDGR $ Âł+LJKO\ FKDUJH-group modified cellulose fibers which can be made into cellulose nanostructures or super-absorbing cellulosic materials and PHWKRG RI PDNLQJ WKHPÂ´ :2 119229A1. Figure

Figure 1: Organic-inorganic hybrid: inorganic clay (montmorillonite) and cellulose nanofibres

NanoSpain Chemistry | 305

Synthesis of Nano-gold labeled steroid derivatives for electrochemical immunoassays. 1

Jessica Kelch , Aoife Delaney , Brian Seddon and Eithne Dempsey 1

Centre for Research in Electroanalytical Technologies, Centre for Applied Science for Health, Institute of Technology Tallaght, Tallaght, Dublin 24, Ireland. Jessicajadekelch@gmail.com

Abstract On site fertility testing is of particular interest to the dairy industry, where milk is a readily available matrix for such hormone analysis. Optimum fertility rates are achieved when artificial insemination (AI) is performed 3 days after the level of progesterone has fallen to less than 16 nM (<5 ng/ml) in whole milk and a reliable on-the-spot progesterone-milk test for use by farmers and dairy technicians is a proven [1] requirement . Immunosensing technology takes advantage of the latest developments in nanomaterials science Âą benefiting from their unprecedented optical tenability as well as electrical and electrochemical qualities. Here we present immunochemically modified gold nano-materials and will demonstrate synthesis routes for novel linker thione molecules and their self-assembly, co-ordination [2] complex reactivity, to nano-Au .Focus is directed at forming a class of progesterone/steroid thiosemicarbazone derivatives which are physico-chemically characterised, with data on reaction yield and purity, molecular structure and electronic properties, and know-how extendable to other C3 carbonyl steroid molecules. Subsequent utilisation of the new steroid nano-Au reagents will be realised ZLWK WKH GHYHORSPHQW RI D VHQVLWLYH ÂłUHGR[ JROG LPPXQRDVVD\Â´ LQ D PLFURZHOO IRUPDW VHH )LJ Overall, the project will advance thione-hapten coupling chemistry and gold-ligand co-ordination chemistry resulting in functionalised nano-Au, possessing defined electrochemical properties. This will provide a means of sensitive progesterone measurement (pM concentration level).

Fig 1: Progesterone conjugate binding to surface confined anti-progesterone antibody, enabling nanogold redox detection for progesterone quantitation.

References

[1]

1 )RUGH 0 ( %HOWPDQ 3 /RQHUJDQ 0 'LVNLQ - ) 5RFKH DQG 0 $ &URZH Âł2HVWURXV F\FOHV LQ %RV taurus cattle Ăž Â´ Anim. Reprod. Sci., vol. 124, no. 3Âą4, 2011, pp. 163Âą169.

[2]

X. Huang, I. H. El-sayed, and M. A. El-VD\HG Âł*ROG QDQRSDUWLFOHVŕŻ&#x2014; LQWHUHVWLQJ RSWLFDO SURSHUWLHV DQG UHFHQW DSSOLFDWLRQV LQ FDQFHU GLDJQRVWLFV DQG WKHUDS\ Â´ YRO 2007, pp. 681Âą693.

306 | NanoSpain Chemistry

Response Properties of Tantalum Oxide for Hydrogen Gas Detection Sujin Lee, Hyunjoo Yoo, Eun Kim, Minsoo Jung, Seongjeen Kim Kyungnam University, Changwon, Kyungnam-Do, South Korea sjk1216@kyungnam.ac.kr Abstract Hydrogen is highly combustible as 4% v/v concentration in air forms an explosive mixture, and also is a major cause of corrosion for steel and other metals, especially at elevated temperature. Therefore, hydrogen gas sensors have been demanded widely in industries, where hydrogen leakage is unavoidable. There are many hydrogen sensors [1-3]. Among them, sensors using metal-oxide film are widely used because of their good sensitivity and reliability. We fabricated an SiC-based hydrogen gas sensor with MIS (metal-insulator-semiconductor) structure, enable to operate at high temperatures, where a thin tantalum oxide (Ta2O5) layer was especially investigated with the purpose of sensitivity improvement because tantalum oxide has good stability with high permeability for hydrogen gas. The 2 tantalum oxide layer was formed by oxidizing a tantalum (Ta), sputtered on 1cm SiC substrates for 2min with 300W of power, by rapid thermal processing (RTP) at 500Č&#x201D; for 3min in an atmosphere containing oxygen. And then Palladium (Pd) was deposited on the tantalum oxide film with a shadow mask to complete Pd/Ta2O5/SiC hydrogen gas sensors. The fabricated sensors were examined with an SEM and an X-ray diffraction (XRD) to know crystal structure and uniformity of Ta 2O5 film, as shown in Figure 1, and 2, respectively. We measured and analyzed both the variation in capacitance and I-V characteristics for different hydrogen concentrations from 0 to 2,000 ppm with a variation in temperature ranging from room temperature to 500 Â°C. As the result, the I-V curve shifted slightly to the lower voltage and the forward current increased at a fixed voltage when the hydrogen concentration increased. The average value of C/Co was observed to be about 15 percent per 1,000 ppm hydrogen concentration (where Co indicates the value in capacitance at the state of zero hydrogen concentration, and C is the variation in capacitance). Consequently, our hydrogen sensor showed promising performance in respect to the sensitivity and the adaptability at high temperature. Acknowledgement This research was financially supported by the Ministry of Education, Science Technology (MEST) and National Research Foundation of Korea (NRF) through the Human Resource Training Project for Regional Innovation. References [1] J. Kanungo, H. Saha and S. Basu, Sens. Actuators, B 147, (2010) 145. [2] Y. Wong, W. Kang, J. Davison, A. Wisitsora and K. Soh, Sens. Actuators, B 93, (2003) 327. [3] S. Kim, J. Choi, M. Jung, S. Joo and S. Kim, Sensors, 13, (2013) 13573. Figures

Fig.1. SEM image of the tantalum oxide layer

Fig.2. XRD analysis of the tantalum oxide layer

NanoSpain Chemistry | 307

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È&#x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Â± > @ , , 6ORZLQJ % * 7UHZ\Q 6 *LUL DQG 9 6 < /LQ $GY )XQFW 0DWHU Â±

308 | NanoSpain Chemistry

Technique for adsorption of contaminants by nano clays Marina Solange Lozano García, Carmen Del Hoyo Martínez, Jorge Cuéllar and Vicente Sánchez Escribano

Department of Inorganic Chemistry. University of Salamanca. Plaza de la Merced s/n. 37008 Salamanca. Spain. hoyo@usal.es.

The extended use of toxic organic compounds in many industrial or agricultural activities and their frequent presence in water, soils and sediments represents an important environmental concern nowadays. Among the strategies used at present to preserve the quality of the water and soil and this way to diminish the environmental risk that supposes the chemical pollution, stands out the use of adsorbents of under cost, already they are natural or modified, to immobilize these compounds and to avoid the pollution of the water with the consequent reduction of environmental and economic costs. (del Hoyo et al. 2014) Clay minerals and clays are very extended compounds on the earth surface so they constitute the main component of soils and sedimentary rocks. Due to their presence and special properties that they have, mankind has used for different applications, not being rare to find references to this subject in works of classic authors. (del Hoyo. 2007) We have studied the adsorption of several contaminants related to water by natural or modified nanoclays, searching their interaction mechanisms and the possible recycling of these materials for environmental purposes and prevention of the health using ultrasounds techniques as it has been proved to be a very useful tool in enhancing the reaction rates and enhances the mass transfer or sorption processes. (Breitbach. 2001) We also have used the FT-IR spectroscopy and DTA/TG studies to confirm the reciclability of these materials and the possible application in the industry to prevent the contamination.

References

[1] del Hoyo Martínez, C., Lozano García, M. S., Antequera, J. and Sánchez Escribano, V. Searching for reciclability of modified clays for an environmental application Vol. 16, EGU2014-707-1, 2014. EGU General Assembly 2014 [2] del Hoyo C. Layered double hydroxides and human health: An overview. Applied Clay Science 36 (2007) 103±121 [3] Breitbach, M., Bathen, D. Influence of ultrasound on adsorption processes. Ultrasonics Sonochemestry 8 (2001) 277-283

NanoSpain Chemistry | 309

Synthesis of hydrophilic MWCNT-Fe composites as potential MRI contrast agents B.M. Maciejewska , L.E. Coy , A. Warowicka ,T. Zalewski . =DĂĄÄ&#x160;ski . . .R]LRĂĄ , a,b S. Jurga a,b

NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, PL- 3R]QDÄ&#x201D; 3RODQG Department of Macromolecular Physics, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, PL- 3R]QDÄ&#x201D; 3RODQG c University of Cambridge, Department of Materials Science and Metallurgy, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom bmacieje@amu.edu.pl b

There is a considerable number of scientific reports stating that carbon nanotubes (CNTs) and magnetic nanoparticles have a potential for medical applications like contrast agents for Magnetic Resonance Imaging (MRI) or guided drug delivery. Functionalised, multi-walled carbon nanotubes are usually considered to be less toxic than the long and pristine ones. Such nanotubes would make a water-soluble shell for pure iron nanoparticles, or other magnetic material-based structures. Multi-walled CNTs (MWCNTs) filled with three selected amounts of iron were synthesised by a floating catalyst chemical vapour deposition (FCCVD) route. Consecutively, three oxidation protocols were explored in order to select the most efficient route for the production of a highly soluble and biocompatible material. Ultracentrifugation was used to sort the resulting MWCNT-iron nanocomposite by length. The properties of these structures were characterised by several techniques i.e. scanning electron

microscopy

(SEM),

high

resolution

transmission

electron

microscopy

(HRTEM),

thermogravimetric analysis, Raman spectroscopy, superconducting quantum interference device (SQUID), NMR and MRI. A highly effective and simple MWCNT dispersion technique, resulting in particles that remained suspended for months, was developed. The MWCNTs filled with well-defined iron particles were successfully obtained as well as some magnetic properties of nanocomposite were shown. Significant enhancements in MRI contrast were observed. Moreover, the cytotoxicity of the MWCNT-Fe nanocomposites was studied in two cell lines.

Acknowledgements Financial support IURP WKH 1DWLRQDO &HQWUH IRU 5HVHDUFK DQG 'HYHORSPHQW XQGHU UHVHDUFK JUDQW ÂłNanomaterials and Their $SSOLFDWLRQ WR %LRPHGLFLQHÂ´ &RQWUDFW PBS1/A9/13/2012.

310 | NanoSpain Chemistry

The synthesis of silver nano-wedges decorated substrates for the detection of molecular traces by Surface Enhanced Raman Spectroscopy 1

1, 3

Lina Ramanauskaite , H. Xu , Rasa Zukiene , Valentinas Snitka Research Centre for Microsystems and Nanotechnology, Kaunas University of Technology, Studentu 65, LT-51369 Kaunas, Lithuania 2 Physics Department, St. John's University, 8000 Utopia Parkway Queens, New York, 11439718-9902000, USA 3 Department of Biochemistry, Vytautas Magnus University, K. Donelaicio 58, LT- 44248 Kaunas lina.ramanauskaite@ktu.lt 1

Abstract Surface enhanced Raman spectroscopy (SERS) is a highly sensitive technique that allows detecting analytes at low concentrations [1, 2]. However, it remains challenging to perform SERS-based detection of target molecules in aqueous solutions, even more at nanomolar (nM) or picomolar (pM) concentrations. For this reason, there is a need to develop new methodologies for the preparation of substrates that exhibit high SERS effect. Such substrates should have a high-curvature features leading to the high content in µ¶KRW VSRWV¶¶ ZKLFK FDQ IDFLOLWDWH WKH GHWHFWLRQ RI PROHFXODU WUDFHV In this work we demonstrate the preparation of ordered silver nano-wedges array fabricated by chemical reduction of silver ions on hydrofluoric acid etched silicon wafers. Given that the surface morphology is determined by the several factors such as reagents concentrations or substrate exposure time in/over the reaction solution, we optimized the synthesis conditions in order to prepare SERS substrates with ordered structure of silver nano-wedges. The characterization of prepared SERS substrates was carried out using Atomic Force microscopy (AFM), Scanning Electron Microscopy (SEM) and UV-vis spectroscopy. The theoretical model of electromagnetic field distribution on the substrate surface was performed using COMSOL software. The enhancement effect of Raman scattering for single molecule was tested by evaporating monolayer of pentacene (2 nm) on bare silicon wafer and SERS substrate. The 5 enhancement factor was found to be 10 . Silver nano-wedges decorated SERS substrates were successfully applied for the detection of proteins and peptides in liquid at nanomolar concentrations. Therefore, this work is a significant step towards detecting biological targets in their natural environment as well as understanding their behavior at bionano interface. This work was funded by the European Social Fund under the Global Grant measure. Grant No. VP1-3.1-â00-07-K-03-044. References [1] Mike Hardy, Matthew D. Doherty, Igor Krstev, Konrad Maier, 7RUJQ\ 0|OOHU, *HUKDUG 0 OOHU, Paul Dawson, Analytical Chemistry, 86:18 (2014), p. 9006±9012. [2] Truc Quynh Ngan Luong, Tuan Anh Cao, Tran Cao Dao, Advances in Natural Sciences: Nanoscience and Nanotechnology 4:1 (2013), p. 1-5.

Figure 1. Silver nano-wedges decorated SERS substrate: a) AFM height image; b) theoretical model of electromagnetic field distribution of double wedge with a 5 nm gap: Log10(|E|^2/|E0|^2) in the X-Y plane at z= 50 nm; c) Raman and SERS measurements of pentacene monolayer evaporated on bare silicon wafer and SERS substrate.

NanoSpain Chemistry | 311

Micro-Raman spectroscopy applied to the study of spin-crossover Fe(II) compounds. 1*

M. José Recio , A. Abhervé , J. Canet-Ferrer , M. Clemente-León , E. Coronado , A. 1 Cantarero 1 2

Instituto de Ciencia de Materiales (ICMUV), Universidad de Valencia, 46071 Valencia, Spain Instituto de Ciencias Moleculares (ICMOL), Universidad de Valencia, 46071 Valencia, Spain maria.jose.recio@uv.es

Spin-transition compounds, also named spin-crossover (SCO) compounds, are switching materials proposed for several technological applications in molecular memories, sensors and 1-4 displays . Particular interest was attracted by the SCO of Fe(II) metal ions in an octahedral 6 ligand field because by populating the respective t2g and eg d-orbital sets, their 3d valence shell may exists in its diamagnetic (S=0) low-spin (LS) state as well as in its paramagnetic (S=2) high-spin (HS) state. The switching process is due to the change in splitting of the d-level of the transition metal that induces the electron redistribution in d-levels. Importantly, the spin transition can be driven by external stimuli such as temperature, pressure or light radiation. An interesting series of spin crossover compounds are bischelated iron(II) complexes of tridentate ligands based on 2,6-bis(pyrazol-1-yl)pyridine (1-bpp), which can be functionalized at its periphery with a variety of substituents. The spin change in these materials is usually very abrupt and takes place with thermal hysteresis close to room temperature. In addition, [Fe(12+ bpp)2] salts have the advantage of exhibiting SCO induced by irradiation: Light-Induced Excited Spin State Trapping effect (LIESST). In this work we have carried out micro-Raman spectroscopy measurements on the II [Fe (bppCOOH)2](ClO4)2 compound, to be compared with previous structural and magnetic characterization. We can identify the LS state signatures at the room temperature Raman spectra and monitoring the transition towards the HS state above 380 K. High intensity signals can be obtained from isolated crystals (of a few microns diameter). As another advantage, the lateral resolution of our experimental set-up is determined by the excitation spot and focus depth (~O), which allows obtaining spatially resolved spectra from our crystals and distinguishing undesired phases or low quality crystals. As a result, Raman spectroscopy is shown a valuable technique for the characterization of SCO compounds since we can determine the spin transition with a minor waste of synthesis products while giving insights about the compounds quality. [1] Letard, J. F.; Guionneau, P.; Goux Topics in Current Chemistry , 235 ( 2004) 221. [2] Kahn, O.; Krober, J.; Jay, C. Adv. Mater. 4, (1992) 718. [3] Cavallini, M.; Facchini, C; Biscarini, F. J. Phys. Chem. B, 110, (2006) 11607. [4] M. A. Halcrow, Coord. Chem. Rev., 249, (2005) 2880. [5] Abhervé A.; Clemente-león, Miguel.; Coronado, E.; Gómez-García, C. J.; López-Jordá, M. Dalton Trans., 43 (2014) 9406.

312 | NanoSpain Chemistry

Application of Carbon Nanofibers to recovery gold (III) from waste PCBs Irene García-Díaz, Francisco José Alguacil, Miguel Ángel Valdés, Olga Rodríguez, Felix Antonio López National Center for Metallurgical Research (CENIM), CSIC, Avda. Gregorio del Amo, 8, Madrid, Spain irenegd@cenim.csic.es Abstract Being gold a valuable metal, its recovery from various sources is a challenge both form an environmental and profitable point of view. In the treatment of the wastes printed circuit boards (PCBs) gold normally appeared after leaching the 3&%¶V ZDVWHV with hydrochloric and nitric acids mixture in a volume relation (3/1). A solution containing gold (III) and valuables metals as commonly obtained. This paper investigates the performance of carbon nanofibers in the recovery of gold (III) from these solutions. The adsorption of gold (III) by carbon nanofibers (CN) system was studied. The influences of several experimental variables on gold adsorption were investigated, i.e. stirring speed of aqueous solutions, adsorbent dosage, acid concentration, etc. The carbon nanofibers were obtained from Grupo Antolin carbon. The main characteristic of the material is presented in Table 1. Table 1.-Characteristics and chemical composition (%) of the carbon nanofibers Density 1.9-2.0 g/mL Purity >94 % Particle Diameter 0.03- ȝP 2 SBET 107 m /g Elemental Chemical Composition (wt,%) C: 99.4; H:0.0; N: 0.03; O: 0.36 Figure 1a) shows the effect of the HCl concentration on the adsorption of gold (III) by the carbon nanofibers. More than 95% of gold (III) is adsorbed onto the carbon nanofibers after 30 minute of reaction. The adsorption of gold (III) was studied in presence of copper (III). The copper is not adsorbed by the carbon nanofibers. Under these conditions the 97% of gold is adsorbed. Carbon nanofibers appeared to be a promising material for the recovery of gold (III) from this type of acid solutions.

100

Adsorption (%)

100

0,1 M HCl 1 M HCl 10 M HCl

Au (III) Cu (II)

0 0,0

0,5

Time (h)

1,0

0,0

0,5

1,0

Time (h)

Figure 1.- a) Influence of the HCl concentration in the adsorption of Au (III), conditions; adsorbent -1 dosage: 0.025 g (CN), aqueous phase: 0.05 g/l Au (III), temperature=20ºC, stirring speed: 2000 cm . b) Mixture of gold (III) and copper (II), conditions; adsorbent: 0.1 g (CN), aqueous phase: 0.05 g/L Au (III) -1 and 0.016 g/L Cu (II) in 6 M HCl, temperature 20ºC, stirring speed: 2000 cm . Acknowledgements To the CSIC Agency (Spain) for support. Thanks to the Grupo Antolín Carbon for supplying carbon nanofibers. Dra. I. García-Díaz expresses her gratitude to the Ministry of Economy and Competitiveness for their Postdoctoral Junior Grants (Ref. FPDI-2013-16391) contracts co-financed by the European Social Fund.

NanoSpain Chemistry | 313

Encapsulation of xanthene dyes into nanochannels of MgAPO-11 for optical applications a

Rebeca Sola Llano, Virginia Martínez-Martínez, Raquel García, Luis Gómez Hortigüela, Joaquín a Pérez-Pariente, Iñigo López-Arbeloa b

Universidad del País Vasco (UPV/EHU), Aptdo 644, 48080 Bilbao, Spain, Instituto de Catálisis y Petroleoquímica (CSIC), Marie Curie 2, 28049, Madrid, Spain rebeca.sola@ehu.es

The incorporation of photoactive molecules into ordered nanostructured systems is an emerging field for the development of new functional optical materials. In particular, one-dimensional nanochanneled crystalline systems allow a supramolecular organization of the embedded molecules and an improvement of their properties. For this purpose, several xanthene type dyes with absorption and emission bands in the whole visible spectrum range have been encapsulated into magnesium aluminophosphate-11 (MgAPO-11) by inclusion during crystallization. The selected host material, owing to the special size and topology of the nanochannels allows a tight fit to the molecular dimensions of the forementioned dyes. As a result, highly luminescent materials have been obtained, since the encapsulation of monomeric units of the dyes is only allowed. Not only do we improve the luminescence properties of the dyes in the hybrid material, but we have also obtained a particular anisotropic response of the particles under polarized light, due to the preferential alignment of the dye molecules along the 1D MgAPO-11 channels. Pursuing new enhanced properties, two dyes have been encapsulated in this host, acridine (AC) and pyronine Y (PY), with perpendicular orientation of their transition dipole moments. This property, together with an appropriate dye-loading rate that enables a FRET process, has resulted into a blue-to-green color switching, instantaneous, efficient, reversible, reproducible and with high fatigue resistance.

References [1] Martínez-Martínez, V.; García, R.; Gómez-Hortigüela, L.; Pérez-Pariente, J.; López-Arbeloa, I., Chem. Eur. J., 19 (2013) 9859. [2] Martínez-Martínez, V.; García, R.; Gómez-Hortigüela, L.; Sola Llano, R.; Pérez-Pariente, J.; LópezArbeloa, I., ACS Photonics, 1 (2014) 205.

Figures

Figure 1. (Right) Fluorescence image of a PY-AC/MgAPO-11 particle upon UV excitation light, with parallel (up) and perpendicular (down) polarizations to the MgAPO- FKDQQHOV¶ F-axis. (Left) Their corresponding emission colors in CIE.

314 | NanoSpain Chemistry

Characterization of Cephalopod Ink Dispersions Using Tunable Resistive Pulse Sensing Technology. Comparison with SEM and DLS. 1

Soto-Gómez, D. ; Paradelo, M.

1, 2

; Pérez-Rodríguez, P. ; De La Calle, I. ; López-Periago, J.E.

Área de Edafoloxía e Química Agrícola, Depto. Bioloxía Vexetal e Ciencia do Solo, Facultade de Ciencias, Universidade de Vigo, Ourense 32004, España. 2

Departement of Agroecology, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, P.O. Box 50, 8830 Tjele, Denmark. 3

Ultra Trace Analyses Aquitaine UT2A/ADERA. Hélioparc Pau-Pyrénées, 2 avenue du Président Angot, 64053 PAU cedex 9, Pau, France. diego.cerreda@gmail.com MarcosP.Perez@agrsci.dk paulaperezr@uvigo.es edelperi@uvigo.es incaller@uvigo.es Abstract We have investigated the utility of Tunable Resistive Pulse Sensing (TRPS) technology for characterization aqueous suspensions of cephalopod ink nanoparticles, which are being studied as surrogates for assessing the environmental dispersion of pathogenic virus. We aim to compare TRPS with two techniques frequently used for determining particle size: scanning electron microscopy (SEM) and dynamic light scattering (DLS), and (ii) to examine the influence of the pore diameter in the TRPS measurements. SEM images (Figure 1) showed sepia ink as quasi-spherical particles, slightly rough, and a variable size close to 100 nm. DLS data (Cordouan Technology VASCO-2 particle size analyzer) showed the size distribution based on the hydrodynamic diameter (Figure 2). The majority of the particles have a diameter less than 211±18 (CV=8 %) nm (Table 1). 7536 DQDO\VLV ,=21¶V T1DQR ZDV GRQH RQ an ink sample diluted (1/50) in TRIS buffer (tris(hidroximetil)aminometano, 15 mM, pH 8), and filtered by 0.45 µm. The nanopore used in this experiment was an NP200, with a size range from 100 to 400nm.Figure 3 shows two of the size distributions carried out with different parameters (voltage and stretch of the nanopore), and the mean diameter obtained is between 136 and 138 nm. Moreover, we did some experiments without filtering the sample in order to know the concentration of the bigger particles in the ink solution using a nanopore NP400 (for 200-800 nm). The results showed that the concentration of the particles with a smaller 11 -1 diameter (<200nm) is 1.6 x 10 particles mL , while for molecules larger (between 200-800 nm) is 1.3 x 9 -1 10 particles mL . Using TRPS we can obtain the surface potential too (Figure 4). For ink (in TRIS buffer) it is ranged between 41 and 46 mV. The majority of the particles are in a range of 100 to 180 nm, but, as can be observed in Table 1, with the DLS the size is slightly larger. This may be because the diameter determined by DLS is a hydrodynamic size, and is bigger than the dry particle size. We concluded that TRPS gives a size distribution with a higher resolution and sensitivity than SEM and DLS; the replication between samples is acceptable, even using different instrumental adjustments; and data are easily quantified and processed.

References [1] Cheng J, Moss SC, Eisner M, Zschack P, Pigment Cell Research, X-Ray Characterization of Melanins ± I (1994) 255 ± 262. [2] DeBlois RW, Bean CP, Review of Scientific Instruments, Counting and sizing of submicron particles by the resistive pulse technique (1970) 909±916 [3] Frisken B, Applied Optics, Revisiting the method of cumulants for the analysis of dynamic lightscattering data (2001) 4087±91. [4] Bajzer Z et al, Biophysical Journal, Padé-Laplace method for analysis of fluorescence intensity decay (1989) 79±93.

Figures

NanoSpain Chemistry | 315

Figure 1. Scanning Electron Microscopy images of sepia ink. Left x40,000; Right x180,000.

Figure 2. Summary of the cumulative size distribution for the three dilutions: 1/10, 1/100, 1/200.

Figure 3: Histogram of the size distribution of two samples with two different instrumental settings. Green: Mean diameter 138 nm; Voltage 0.78 V, Stretch of the nanopore 44.02 mm. Blue: Mean diameter 136 nm; Voltage 1.1 V, Stretch of the nanopore 43.02 mm

Figure 4: Representation of the surface potential of each particle in an ink sample (filtered 0.45Âľm, TRIS buffer 15 mM, NP150). The results showed a zeta potential between -41 and -46 mV.

Technique

<149nm diameter

<181 nm diameter

<211nm diameter

DLS

10%

50%

90%

TRPS

79.5-72.4%

91.9-92.2%

96.9-97.7%

Table 1: Comparative percentages obtained with DLS-PadĂŠ Laplace and TRPS for particles with smaller diameters than 149, 181 and 211 nm. (Results of TRPS where carried out considering the entire sample, i.e. unfiltered).

316 | NanoSpain Chemistry

Electrodeposited bimetallic nanoparticles Au/Cu on semiconductor metal oxide substrates Torres-Cadena RaĂşl, Cabrera-Lara Lourdes Isabel Centro Conjunto en InvestigaciĂłn QuĂmica Sustentable UAEMex-UNAM Km. 14.5 Carretera TolucaAtlacomulco C.P. 50200, Toluca, Estado de MĂŠxico, MĂŠxico. tcruloo@gmail.com Abstract Bimetallic nanoparticles have gained attention as a new class of advanced materials, since they are attractive because of their bifunctionality in contrast with their individual components. Therefore, bimetallic nanoparticles have potential applications in diverse fields, such as catalysis, electrocatalysis, magnetic storage, and photovoltaic cells [1,2]. Nowadays, it has been shown that noble metal nanostructures, deposited on semiconductors metal oxide substrates improve the process of photoexcited electron transfer due to the formation of the Schottky barrier in the semiconductor-metal interface. ZnO is a n-type semiconductor with a band gap value of 3.37 eV. However, when ZnO is in contact with noble metals nanoparticles such as Au and Pt, its band gap increases to 5.1 eV and 5.65 respectively [3]. This inhibits the electron-hole pair recombination. On the other hand, the use of bimetallic nanoparticles such as Au/Cu, not only allows the formation of the Schottky barrier, it also offers a new approach to effectively capture energy in the visible and infrared regions of the solar spectrum when used in photoelectrochemical cells [4]. In this work, we electrodeposited Au/Cu nanoparticles by multipulse chronoamperometry on ZnO nanorods surface, which were previously electrodepositated on a glass-indium tin oxide (ITO) substrate. The system was characterized by UVVis spectroscopy, which showed a surface plasmon resonance (SPR) at Č&#x153;max= 580 nm, when the Au is typically observed at Č&#x153; QP DQG &X DW Č&#x153; QP (Figure 1). X ray diffraction (XRD) showed the phases corresponding to ZnO, Au and Cu. The presence of Au and Cu in the system was also confirmed by performing a cyclic voltammetry in the potential range of -1 V to 1.8 V vs saturated calomel electrode (SCE) in a 1 M HClO4 aqueous solution, as supporting electrolyte. Au oxidation was observed at E = 1.2 V vs. SCE, while for Cu, it was observed at E1 = -0.22 V vs SCE and E2=-0.37 V vs SCE. The authors will like to acknowledgment financial support from PAPIIT (UNAM) with the project number IB200113-RR260113. Also, the authors acknowledge Professor Abel Moreno, Ph.D. Ivan GarcĂa Orozco, Ph.D. Rosa MarĂa GĂłmez Espinosa, and Ph.D. Marco Antonio Camacho LĂłpez for their support in the analytical characterization. References [1] Hai, Z. Kolli, N. Bahena, D. Beaunier, P., J. Mater. Chem. A, Vol. 1 (2013)10829-10835. [2] Chen, S. Jenkins, S. Tao, J., J. Phys. Chem. C, 117 (2013) 8924-8932 [3] Zhang, K.; Ronda, R.; Y Holloway, T., Vol. 7646 76461 p-1-76461 p-7 [4] Rusen, E.; Mocanu, A.; Somoghi, R., Colloid Polym Sci, Vol. 290 (2012) 1937-1942 Figure 1. UV-Vis absorption spectra of the systems ITO/ZnOfilm, ITO/ZnOnanorods and ITO/ZnO/AuCu.

NanoSpain Chemistry | 317

Synthesis and Electrochemical test of Li-rich (0.5Li2MnO3-0.5LiNi1/3Co1/3Mn1/3O2) doped with Ba cathode material by using the Anodic Aluminum Oxide Template (AAO). 2

Su-bin Yang , Ma-rip Kim and Jong-tae Son

Department of Nano Polymer Science & Engineering, Korea National University of Transportation, Chung-ju, Chung-buk, 380-702, Korea cara0831@naver.com Abstract The Li rich cathode material is promising material. Because it provides large specific capacity more than 200 mAh/g when they are charged over 4.6V are promising cathode materials. However, Li-rich materials have low rate capability. To solve this problem, many strategies have been proposed to change the structures and morphologies of the Li-rich materials through nano-architecture and ion-doping [1]. st And the 1 key-point is to solve the kinetic problem associated with solid state diffusion of lithium ion intercalation and electronic conductivity. Recently, Xiao Xia et al. reported that the diffusion length becomes shorter as the particle size is smaller and as a result faster kinetics are expected [2]. nd 2 point is to solve the structure stability. Ion-doping is used to improve structural stability. So, barium 2+ substitution has also been considered to enhance the stability of structural properties. Because, Ba -O 2+ (563eV (Âą42) has a high binding voltage than Ni -O (391.6eV (Âą38)). So, Li-rich material can be structurally stabilized. In recent times, anodic aluminum oxide(AAO) templates have attracted considerable attention to the growth of adjustable self organized, highly ordered nano-rods. Also, it used to make higher surface to volume ratio nanostructure from the capillary phenomenon. In this study, we put the intention to effect of xLi2MnO3-xLiNi1/3-xBaxCo1/3Mn1/3O2. To make the nanorods, we synthesized by the template method with AAO template. To observe the nano-rod, we analyzed by scanning electron microscope(SEM) and atomic force microscope(AFM). The nano-rod was analyzed by X-ray diffraction patterns (XRD) to observe the structure stability. And we analyzed electrochemical test such as charge-discharge curve, cycle performance, EIS, etc.

References [1] W. HE, D. Yuang, J. Qian, X. Ai, H. Yang and Y. Cao*, J. Mater. Chem. A, 1, (2013), 11397. [2] P. Lv, H. Zhao, J. Wang, X. Liu, T. Zhang and Q. Xia, J. Power Sources. 237, (2013), 291-294.

Figures

318 | NanoSpain Chemistry

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Egypt

country

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Alena Ševců

Štryncl, Martin

Belaidi Nouria

Sabri, Samira

Marics L, Mitjans M, Vinardell MP

Llanas Marco, Hector

Unai Vicario-Parés, Eider Bilbao, Miren P. Cajaraville, Amaia Orbea

Lacave , Jose Maria

Karolina Urbaś, Rafał Rakoczy, Ewa Mijowska

Jedrzejczak, Magdalena

Valea, A. ; Miguez, J.C.; González, B.; Juanes, F.J.

Gonzalez, Maria Luz

Valea, A.Juanes, F.J.; Miguez, J.C.; González, M.L.

Gonzalez, Beatriz

Irizar A., Gandariasbeitia M., Urionabarrenetxea E., Soto M

Garcia-Velasco, Nerea

Delgado Alba Jimeno-Romero,Leire Basarte, Mathilde Mikolaczyk, Jörg Schäfer, Eider Bilbao and Miren P. Cajaraville

Duroudier, Nerea

Ana - Guillem, Carlos Fito, Oscar Andreu

Araque, Eva

-Freese C, Schreiner D, Bantz C, Maskos M, Unger RE, Kirkpatrick C Hens

Anspach, Laura

Ayman Kamal, Sahar Zaki and Desouky AbdEl-Haleem

Abu-elreesh, Gadallah

authors

Data Processing of Nanoparticle Agglomeration from Differential Centrifugal Sedimentation

The study of heavy metal pollution in the surface fauna and hyporheic fauna

Hemocomptability study of ZnO nanoparticles

Nanotoxicogenomics: transcription profiling for the assessment of nanomaterials toxicity mechanisms

The evaluation of cellular response of mammalian cells co-incubated with Fe3O4/graphene oxide to magnetic field

Outward issues in nanotechnology

Contaminants with special attention to the asbestos fibers

Toxicity screening of AgNPs and integrative assessment of soil health through biomarker responses in Eisenia fetida Earthworm at different levels of biological organization

Molecular and cellular responses of mussels Mytilus galloprovincialis fed with the microalgae Isochrysis galbana exposed to PVP/PEI-coated silver nanoparticles at different seasons

REACHnano Tool: a new web based toolkit to support the chemical safety assessment of engineered nanomaterials

Physiological cyclic stretch–impact of silica nanoparticle uptake into human endothelial cel

Employment of a genetically modified bioluminescent bioreporter to assess formation and toxicity of biosynthesized nanosilver

poster title

NanoSpain2015 Toxicology Posters list: alphabetical order

Employment of a genetically modified bioluminescent bioreporter to assess formation and toxicity of biosynthesized nanosilver Gadallah Abu-Elreesh, Ayman Kamal, Sahar Zaki and Desouky Abd-El-Haleem Environmental Biotechnology Department, Genetic Engineering and Biotechnology Research Institute (GEBRI), City of Scientific Research and Technological Applications, New Burg-Elarab City, Alexandria, Egypt E-mail address: g_abouelrish@yahoo.com Abstract: From both industrial and environmental points of view, production of nanosilver biologically is environmentally friendly compared to physical and chemical methods. As well as, looking for efficient microorganisms able to produce nanosilver in a large amount and short time is one of the priorities of the researchers in this field. In this regard recently, we discovered a strain of yeast could convert silver nitrate to nanosilver in a good amount to be used as a disinfector of water and wastewater. However, to determine if the disinfection effect comes from the use of nanosilver or silver nitrate and to monitor nanosilver formation by the yeast strain, DF4/PUTK2 bioreporter was employed. Previously, the genetically constructed bioluminescent bioreporter DF4/PUTk2 was successfully employed to assess the toxicity of phenolics, polyaromatics, heavy metals, antibiotics, and cosmetics. In the present study, the toxicities of 3.5 mM of silver nitrate, sodium nitrate and potassium nitrate were assessed. Comparing to the control, no bioluminescent inhibition (BI%) was observed with all nitrate species, reflecting the absence of any toxic effect of these substances on the bioreporter. Preparation of the nanosilver particles from the yeast strain was occurred by incubation of the yeast cells with 3.5 mM silver nitrate for five days. The data clearly reported that after 24 h the produced nanosilver particles were able to inhibit the bioluminescence of the bioreporter to ~ 30% and gradually increased to reach 97% inhibition at the end of the experiments (5 days). In addition, the DF4/PUTK2 bioreporter was very sensitive to the presence of nanosilver from 1 to 100 Âľl. The best contact time gave the best BI% was 25 min with all examined nanosilver concentrations. Out of these results, we conclude that the bioreporter DF4/PUTK2 can assess both formation and toxicity of nanosilver. It could be used as a sensitive, fast and cheap kit in discovering of novel nanosilver bio-factories. Ď

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References 1- Sahar Zaki, M.F. El Kady, Desouky Abd-El-Haleem, Materials Research Bulletin, 46 (2011) 1571–1576. 2- Sahar Zaki, M.F. Elkady, Soha Farag, Desouky Abd-El-Haleem, Materials Research Bulletin, 47 (2012) 4286–4290.

Figure 1 Illustrate the effect of different concentration of biosynthesized nanosilver on the bioluminescent Acinetobacter bioreporter with time.

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Physiological cyclic stretch Âą impact of silica nanoparticle uptake into human endothelial cells 1

Anspach L , Freese C , Schreiner D , Bantz C , Maskos M , Unger RE , Kirkpatrick C

Repairlab - Institute for Pathology, University Medical Center Mainz, Germany 2

Fraunhofer ICT-IMM, Mainz, Germany

anspach@uni-mainz.de

In vitro static cell culture systems are often used to test cytotoxicity as well as efficacy of engineered nanoparticles for the application in humans. Indeed, those static in vitro models are not that sufficient for testing the effects of nanoparticles intended for intravenous administration. After injection, nanoparticles circulate within the bloodstream in vivo and interact immediately with proteins and cells. One of the first cell types that come in contact with nanoparticles are endothelial cells. They line the luminal side of blood vessels and built the first barrier nanoparticles have to overcome to reach their final destination. Since endothelial cells are known to be affected by physical forces such as shear stress and strain caused by pulsatile blood flow in vivo the phenotype of endothelial cells in living species are distinct to cells in static in vitro cell culture; even primary cells are used. Since shear stress has already been addressed by many groups we focused our examination of nanoparticles-cell interaction on another prominent force; cyclic stretch. In the present study, the impact of amorphous silica nanoparticles with different sizes and surface modifications on primary endothelial cells, which are cultured under physiological cyclic stretch conditions (1Hz, 5% stretch) was investigated and compared to cells maintained under standard static conditions. Cytotoxicity of silica nanoparticles to endothelial cells did not alter significantly under stretch compared to static culture conditions. Nevertheless, the uptake of nanoparticles decreased in cell cultures under stretch. Furthermore, it was shown, that the decreased uptake of the nanoparticles was neither due to inflammatory processes nor due to the induction of exocytosis. However, further results indicated that the reduced endocytosis of nanoparticle seemed to be a consequence of cyclic stretch itself (proven by the formation of stress fibres) and might finally be a result of membrane flattening [1] caused by cell stretching. This study demonstrates, that the impact of silica nanoparticles is not altered by the more physiological culture conditions but that in addition to shear stress stretch is a prominent factor, which should be considered to study cell-nanoparticle interactions in vitro. Furthermore, our improved in vitro cell culture model is valuable for the prediction of nanoparticle-cell interactions in vivo [2]. Hence, specified cell culture models that reflect the in vivo situation more precisely might play a pivotal role in reducing animal experiments and in consequence development costs of drug delivery systems and new pharmaceutics (e.g. bi-specific antibodies). References [1] Sinha B, KĂśster D, Ruez R, Gonnord P, Bastiani M, Abankwa D, Stan RV, Butler- Browne G, Vedie B, Johannes L, Morone N, Parton RG, Raposo G, Sens P, Lamaze C, Nassoy P. Cell, 144 (2011) 402413 [2] Freese C, Schreiner D, Anspach L, Bantz C, Maskos M, Unger RE, Kirkpatrick C. Particle and Fibre Toxicology, 11 (2014) 68

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REACHnano Tool: a new web based toolkit to support the chemical safe ty assessment of engineered nanomaterials Carlos Fito1, Eva Araque1, George Boulougouris 1, Paula Beltran2, David Carlander3 1

Instituto Tecnol贸gico del Embalaje, Transporte y Log铆stica. Albert Einstein, 1. Paterna (Spain) 2 Instituto Valenciano de Seguridad y Salud en el Trabajo. C/ Valencia, 32. Burjassot (Spain) Nanotechnology Industries Association. EC Rebelva - Carcavelos Rebelva (Portugal) cfito@itene.com

Abstract: REACHnano is a LIFE + project (LIFE11 ENV/ES/549) focused on the development of innovat ive instruments to improve the implementation of the European Union Regulation concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) when manufacturing or handling materials or substances at the nanometer scale. To this end, the project was structured to allow the development of a web based Help Desk tool to support the risk assessment and promote the safety use of nanomaterials along their life cycle , providing the industry and stakeholders with easy to use tools to support the implementation of REACH regulation. The toolkit developed within REACHnano project takes into account the needs and specifications of endusers and stakeholders, including advanced functionalities that supports the industry and authorities to fulfill their main task under REACH, with special concern to those provisions aimed at ensuring high levels of human health and environmental protection such as the generation of reliable information in terms of REACH information requirements , the assessment of risk for the specific uses of the substances (i.e. exposure scenarios) and the characterization of effective risk managements measures (RMMs). The main contents of the web based tookit are a ENMs database module, the risk assessment plug-in and the advanced query tool. The design of the toolkit was done in collaboration with the partners of the consortium, including LEITAT Technological Centre, NIA - Nanotechnology Industries Association, and INVASSAT. Figure 1 illustrates the toolkit front end. The ENMs database has been designed following the structure of the IUCLID substance datasheets, allowing companies and relevant stakeholders to capture, store, submit and exchange data. The advanced query tool, it is aimed to serve as an innovative web-based data mining tool to support the identification of safer alternatives to hazardous nanomaterials. The risk assessment module consists of two risk assessment plug-ins for occupational and environment al exposure respectively. The Environmental exposure plug-in is a probabilistic Material Flow Analysis (pMFA) multi-media model based on Monte Carlo (MC) methodology, while the occupational risk assessment module is based on a combination of control banding approaches , exposure estimation tools, and newly developed exposure scenario templates, allowing the uses to estimate the exposure on the basis of the operative conditions and RMMs applied in generic and/or specific exposure scenarios (GES / SES).

References

326 | NanoSpain Toxicology

Figures Figure 1. REACHnano Toolkit Front-end

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Molecular and cellular responses of mussels Mytilus galloprovincialis fed with the microalgae Isochrysis galbana exposed to PVP/PEI-coated silver nanoparticles at different seasons 1

Nerea Duroudier , Alberto Katsumiti , Alba Jimeno-Romero , Leire Basarte , Mathilde 2 2 1 1 Mikolaczyk , Jörg Schäfer , Eider Bilbao and Miren P. Cajaraville 1

CBET Research Group, Science and Technology Faculty and Plentzia Marine Station, University of the Basque Country (UPV/EHU), Basque Country, Spain 2 Univ. Bordeaux, UMR 5805 EPOC, Allée Geoffroy St Hilaire, 33615 Pessac Cedex, France nerea.duroudier@ehu.es Bivalve mollusks have been identified as an important target group for nanoparticle (NP) toxicity because they are filter-feeding organisms able to uptake and process particles of different sizes. Several studies have been carried out in mussels exposed to NPs via water; however, there is scarce information on the effects of NPs ingested through the diet, especially at environmentally relevant concentrations. Further, the potential influence of season on mussel´s responses to NPs has not been explored. Silver NPs (Ag NPs) are being increasingly used due to their antimicrobial properties and therefore, concerns about their potential input and hazards in aquatic ecosystems are growing. Thus, with the aim of determining molecular and cellular responses to Ag NP exposure in mussels Mytilus galloprovincialis, dietary exposure experiments were performed both in autumn and in spring. Mussels were fed daily with the microalgae Isochrysis galbana previously exposed for 24 h to two different doses of PVP-PEI coated 5 nm Ag NPs: a dose of 1 µg Ag/L of Ag NPs close to estimated environmental levels and a higher dose of 10 µg/L Ag NPs. After 24 h of exposure, Ag concentration was measured in algae by ICP-MS while TEM and SEM analysis were performed in order to study NP fate. After 1, 7 and 21 days of mussel dietary exposure, total Ag concentration was measured in mussel soft tissues by ICP-MS and Ag deposits were measured at the light microscope after autometallography and localized by TEM followed by X-ray microanalysis. Microarray studies were performed to get a specific gene expression signature. Lysosomal membrane stability was measured in digestive cells as a general indicator of health status and genotoxic effects were assessed in hemocytes by Comet assay and the micronucleus test. Chemical analysis showed that microalgae exposed to 10 µg/L Ag NPs significantly accumulated Ag after 24 h. By TEM, electron dense deposits were observed between the scales and the membrane of microalgae and inside cells, indicating internalization of Ag NPs in algae. Mussels fed with exposed microalgae significantly accumulated Ag after 7 and 21 days in both seasons. Regarding genotoxic effects, DNA strand breaks increased significantly along the 21 days in spring and micronuclei frequency showed an increasing trend after 1 and 7 days of exposure to 1 µg/L Ag NPs in spring and to 10 µg/L in both seasons. Thus, PVP-PEI coated 5 nm Ag NPs were successfully transferred from algae to mussels and caused significant alterations in mussels. Funded by: Spanish MINECO (MAT2012-39372), Basque Government (SAIOTEK SPE13UN142 and GIC IT810-13), UPV/EHU (UFI11/37 and PhD fellowship to N.D.) and French Ministry of Higher Education and Research (PhD fellowship to M.M.)

328 | NanoSpain Toxicology

Toxicity screening of AgNPs and integrative assessment of soil health through biomarker responses in Eisenia fetida earthworm at different levels of biological organization Garcia-Velasco N., Irizar A., Gandariasbeitia M., Urionabarrenetxea E., Soto M. CBET Research Group, Dept. Zoology and Animal Cell Biology; Research Centre for Experimental Marine Biology & Biotechnology PiE-UPV/EHU, Univ. Basque Country UPV/EHU, Basque Country nerea.garcia@ehu.es In recent years the number of applications and products containing silver nanoparticles (AgNP) has widely increased, mainly due to the antimicrobial properties of silver, thus their release into different environmental compartments such as soil is already occurring. The major source of AgNP deposition onto soil is currently though the disposal of wastewater treatments plant sludge (after land application of the sludge or incineration and posterior deposition) which could modify the terrestrial community. However, the hazards of nanosized silver in soils are poorly investigated despite the great complexity of soil matrix and the potential interactions of its components with pollutants. Besides, little is known about the effects of AgNPs on organisms inhabiting soils. Earthworms have been broadly used for soil health assessment due to their pivotal role in the soil and their quick and measurable responses after exposures to pollutants. Soil health can be assessed measuring these responses in model organisms at different levels of biological organization. Recently, in vitro assays with primary cultures of earthworm immune cells, coelomocytes, have been set up as rapid tools for toxicity assessment of chemicals. At organism-level, as earthworms are able to take up chemicals from soil ingestion as well as from soil pore water, through the outer skin, the Paper Contact Toxicity Test (OECD-207) is an initial screening method to identify toxic substances and to obtain relevant toxicity data (LC50 and EC50). Such screening reflects dermal contact exposure while the Artificial Soil Toxicity Test (OECD-207) gives a more representative toxicity data after earthworm exposure though soils. Regarding population-level, the Earthworm Reproduction Test (OECD-222) is designed to be used for assessing the effects of chemicals in soil on the reproductive output. The aims of this work were (a) to determine the toxicity profile of AgNPs with responses achieved at different levels of biological organization, cell-level biomarkers and viability test (Neutral Red Uptake -NRU- and Calcein-AM Viability assays) combined with organism and population level bioassays performed with the aid of Standard Toxicity Tests (OECD207 and 222) and (b) to establish toxicity threshold of AgNPs which will be helpful to obtain an integrative view of the biological responses in Eisenia fetida earthworms. For that purpose, at cell-level, coelomocytes extruded from E. fetida were maintained in primary cultures and exposed to PVP-PEI coated Ag-NP (5.5±2 nm, water dispersed) in concentrations ranging 0-100 mg/l, and to PVP-PEI coating agent separately (0.0001-10,4 mg/l) for 24 h. After exposure NRU and Calcein-AM cytotoxicity and viability assays, and flow cytometric analyses were applied in order to decipher coelomocyte subpopulation dynamics and their sensitivity against AgNPs. For the Paper Contact toxicity test E. fetida earthworms were exposed to PVP-PEI coated Ag-NPs and to PVP-PEI agent as well, in a range of 2 concentrations (0-200 µg/cm ). After 48 h mortality and weight loss were assessed, morphological alterations in the digestive tract and in the epidermis were addressed after Alcian Blue staining, and Ag concentrations were quantified by ICP-MS in earthworm tissues. In the Artificial soil test, earthworms were maintained in OECD standard soils spiked with 0-500 mg AgNP/kg for 3 and 14 days. Complementarily NRU and Calcein-AM Viability tests were performed in coelomocytes extruded from exposed earthworms, autometallography was applied on fixed tissue sections (5 µm) to address the distribution of Ag in tissues, and Ag concentrations in soils and tissues were quantified by ICP-MS. Effects on reproduction were assessed after 8 weeks by counting the number of cocoons (hatched/nohatched) and juveniles present in the soils. PVP-PEI appeared not to be cytotoxic while coated AgNPs exerted an initial stress at low doses and severe toxicity at highest concentrations as revealed NRU and Calcein AM assays. In addition, a clear difference in the sensitivity of the cell-types was detected. Paper Contact test revealed a LC50 of 346.5 ppm Ag-NP and Artificial Soil test of 144.2 mg Ag-NP/kg. Histological and histochemical analyses proved that the primary uptake of AgNPs was via soil ingestion. A decrease in the number of viable cells occurred after 3 d of exposure to 50 mg Ag-NP/kg and after 14 d to 5 mg Ag-NP/kg. Reproduction was severely impaired at high Ag-NP doses. All measurements were integrated in the Integrated Biomarker Response (IBR) index. In conclusion, the combination of in vitro test with the Standard Toxicity Tests was useful to establish AgNPs toxicity thresholds and thus this approach can be used for assessing the potential risks of AgNPs in soils. The IBR provided complementary information concerning the mechanisms of biological response to AgNP exposure. References [1] Earthworm, Acute Toxicity Tests-207. OECD guideline for testing of chemicals. 1984. [2] Earthworm Reproduction Test (Eisenia fetida / Eisenia andrei)-222. OECD guideline for testing of chemicals. 2004. Acknowledgements: Basque Government (Cons. Res. Groups; IT810-13), Univ. Basque Country (UFI 11/37) and Spanish MINECO (Nanosilveromics Project, MAT2012-39372).

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CONTAMINANTS WITH SPECIAL ATTENTION TO THE ASBESTOS FIBERS Valea, A.; GonzĂĄlez, B.; Juanes, F.J.; Miguez, J.C.; GonzĂĄlez, M.L. Dpto. IngenierĂa QuĂmica y del Medio Ambiente de Univ. PaĂs Vasco-E.H.U. Escuela de IngenierĂa TĂŠcnica Industrial (PÂş Rafael Moreno Pitxitxi,3)(48013-BILBAO) angel.valea@ehu.es

INTRODUCTION There are lots of materials of our daily life that were built with asbestos. Agree with the information that we have, only a little percentage of the buildings built with asbestos are now subjected to reform in order to remove it. In the same way, the asbestos can be present in pipes, heat-isolated devices, union joints or insulators, stopped cords, oven closes and muffles, vinyl surfaces, in wavy ceilings plate, decorative elements like flower beds. There are others frequent materials like plastics reinforced by glass fibre (PRFV), plastics reinforced by carbon fibre (PRFC) and reinforced with other fibres, that there are no evidence of their nocivity, but their tendence of releasing fibres is similar. This extended tendency, accord to the difficulty of knowing if any object contains asbestos, imply the first objective of decontaminate jobs, to identificate it. Once we have obtain the identification of asbestos and his presence is confirmed, the question is what to do with it: try to eliminate it or maybe to controlate and consolidate it. Obviusly the first step we come in mind is to eliminate it, but maybe isnÂ´t the adecuate choose. The most important technical aspect is the evaluation of the risk of be in contact with the asbestos, that must be worked before starting any other work, so that the risk is evaluated and the measures must be included in the work planning. The fourth aspect to considerate is the establishment of the working exposition limits. Although in the R.D. 396/2006 we can find the limit values of the daily exposition (VLA-ED), considering an eight hours period, the technical handbook extends this daily expositions, considering some different forms of this exposition, including short times of exposition. This is exactly the sequence of aspects that can be found in the technical guide of asbestos exposition. Precisely this are the interpretative aspects, that can be explained in the R.D. 396/2006. 1. LEGAL STATUS AND APLICATION FIELD The R.D. 396/2006 establish the DSSOLFDWLRQ ILHOG LQ WKH ÂłGHPROLWLRQ ZRUNV GLVPDQWOH works, removal, elimination and maintenance of asbestos materials, where are in contact with persons or supposing they can be in contact with. The mentioned R.D. has some exceptions like the sporadic expositions of low intensity. In this cases it is not compulsory to carry out with the articles of the R.D. that are referred to working plans, security of human health and it is not compulsory the inscription in the RERA, too.

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2. IDENTIFICATION OF MATERIALS CONTAINING ASBESTOS The process of identification of materials that contain asbestos must start putting into effect an inventory of suspicious materials that can have asbestos. For that reason the building materials must be under investigation, their functional nature for what they where conceived, etc. So that finally we have the intuition that maybe a material can content asbestos. When we finish this inventory, the next step is to classify this suspicious materials of containing asbestos. For that normally is necessary to make a proof in order to obtain fibre materials that later must be investigated. This is the step where there is the potential exposition with the asbestos, so it is necessary to take preventive measures. 3. WHAT TO DO WITH THE ASBESTOS MATERIALS When we detect asbestos in a material, the first reaction is to remove it, because the asbestos is normally related with high toxicity, asbestosis and cancer. Nevertheless not always is the best solution, and sometimes is preferable consolidate it in order to control the chaotic liberation of fibres and subject it to a conservation control. In this fact, there are lots of references in the technical guide. To remove this materials with asbestos will be the first option when this materials can not be controlled and preserved, so that it is guarantee that there are no liberation of fibres into the environment. In the bibliography there are some methods that can help us with the decision of what to do with this kind of materials that contain asbestos. 4. VALORATION OF THE EXPOSITION It is already said that this is the most important fact under the technical point of view, and it is so important that it has not be forgotten for the persons that have made the technical guide for R.D. 396/2006, because this aspect is considered in detail. The previous evaluation can be make with bibliography facts, database or previously information, and in case of not having facts, it must be supposed that the limit values are exceeded, and that is a proof of low knowledge. After making the previously evaluation, it is necessary to make other evaluations in order to determinate the level of exposition, and to proof if the preventive measures have take effect. The previously evaluation and the risk evaluation must be done for the activities in contact with asbestos and equally for this activities that have any residual risk to be in contact with asbestos, and even the zones that accidentally could be contaminated by asbestos. Limits of asbestos contamination exposures, orientated criterions contributed by the Technical Guide and ways of improvement won't be included in this summary, in order to reserve them to a more extended exposition of the work.

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Outward issues in nanotechnology Valea, A. ; Miguez, J.C.; González, B.; Juanes, F.J.; González, M.L. Dpto. Ingeniería Química y del Medio Ambiente de Univ.País Vasco-E.H.U Escuela Ingeniería Técnica Industrial (Pº Rafael Moreno Pitxitxi,3)(48013-BILBAO) angel.valea@ehu.es

Over the last decades much progress has been made in order to search solutions for the control and treatment of conventional pollutants generated by human and industrial activities, on which the legislation makes an exhaustive control and the science and engineering have given different solutions (1). The progress of science and technology has introduced a number of potential contaminants which, especially in the future, will suppose a major challenge both for detection and for quantification; preliminary steps needed to undertake the purpose of their elimination or reduction. In our case, we refer to the micro and nanomaterials. The presence of these compounds presents numerous technical and institutional challenges to society, to environment and for professionals who need to address solutions to what is seen as the next scientifictechnological revolution, which has been described as the nanotechnology. The discovery of fullerenes by Curl, Kroto and Smalley in 1985 (Nobel prize in Chemistry in 1996) (2) represents, together with the discovery in 1981 of scanning tunneling microscope by Binnig and Rohrer (Nobel Prize in Physics in 1986), two of the first great achievements in the development of nanoscience (1). In 1991 Iijima observed the formation of needle-shaped species, when using the method of vaporization of graphite by electric arc discharge for the production of fullerenes in multigram quantities (4). By transmission electron microscopy (TEM) it was found that each of these clusters consisted of needles containing concentric layers of graphite. These structures are known today under the name of carbon nanotubes (CNT's) multiwall (MWNT's) (5). Later Iijima himself et al. (6) and Bethune et al. (7), found that the addition of some metallic elements such as iron or cobalt, to one of the electrodes, produced tubular structures with a single sheet of graphite, i.e, what today is known as single wall nanotubes (SWNT's). One year earlier, Dr. Ugarte discovered by observing the microscope fullerenes and nanotubes, the presence of a new type of concentric circular structures which are now called as carbon nano-onions (NOC's) (8). In addition to these structures, all of them three-dimensional, we should mention the graphene, two-dimensional structures, that are constituted by hexagonal rings of carbon atoms with sp2 hybridization, i.e, are sheets of graphite. Nanotechnology is one of the most important drivers of growth in developed countries (1). In 2011 the estimated economic impact in Europe will be nearly 300 miliardo dollars, and in 2016 it will exceed one billion U.S. dollars; it is not unreasonable to think that the continent's economic health depends on safe development of these emerging technologies ( 2).

Every technological advance brings risks, and in the case of nanotechnology and nanoscience the risk are high, and they should be properly monitored and evaluated to avoid serious consequences on health and environment (2,3), as it was evidenced in a article published in Nature (4). It is essential to know whether exposure to nanoparticles supposes risks to the health of workers and the general public, because this type of materials are included as consumer products today, and they will increase in future. On the other hand, it must create and maintain confidence about the production and handling of nanomaterials, based on a correct assessment and control of potential health risks from exposure to nanomaterials (5). Traditionally, risk evaluation is based on describing the elements of exposure and danger. This approach can be used to evaluate the risks of exposure to engineered nanomaterials. The sequence of a risk evaluation (6) can be: 1 .- IDENTIFICATION OF DANGER 2 .- EVALUATION OF DOSE-RESPONSE

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3.- EVALUATION OF EXPOSURE AND RISK 4 .- RISK MANAGEMENT In this work we will deal separately with each of these aspects to get evaluate the risk associated with these activities and the state of current knowledge. The identification of danger is a key aspect in any evaluation of risks. The danger represents the potential to produce adverse effects and the risk is the probability of occurrence of these adverse effects. The primary exposure to nanoparticles may occur through the lungs, skin or gastrointestinal tract, but its metabolism or displacement to other organs causes them to different mechanisms of toxicity, depending on the route by which are transported nanoparticles and, of course, depends on the functionalities that they have been equipped on its surface. . The physicochemical properties of the surface of the nanoparticles seem to play an important role in the effects on systemic circulation after his arrival in the lung (13). It is unknown the exact nature of the toxicity and the TLV for inhaled or cardiovascular system. The toxic process might arise from the ability of nanoparticles to activate platelet aggregation or affect the endothelium, so as to promote the formation of thrombi or could arise from oxidation reactions of nanoparticles in the lungs. In any case, it seems obvious that it needs to understand the mechanisms by which nanoparticles can cause adverse effects on the body. . The methodology to evaluate and quantify the danger associated with nanoparticles are specified in the guidelines of the OECD and the European Regulation REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) in order to be considered.

NanoSpain Toxicology | 333

The evaluation of cellular response of mammalian cells co-incubated with Fe3O4/graphene oxide to magnetic field Magdalena Jedrzejczak , .DUROLQD 8UEDÄ&#x17E; 5DIDĂĄ 5Dkoczy , Ewa Mijowska 1

Laboratory of Cytogenetics, West Pomeranian University of Technology, Dra Judyma 6, 71-466 Szczecin, Poland 2 Department of Environmental and Chemical Engineering, West Pomeranian University of Technology, Szczecin, Piastow Avenue 45, 70Âą311 Szczecin, Poland 3 Institute of Chemical Engineering and Environmental Protection Process, West Pomeranian University of Technology, Piastow Avenue 42, 71-065 Szczecin, Poland mjedrzejczak@zut.edu.pl Abstract The biological effectiveness of magnetic fields (MFs) on tumor cells has been studied since the 1970s. Some of the MF molecular mechanisms that affect tumor cells still remain unclear, but it has been shown that the magnetic field can inhibit cancer cell growth and induce apoptosis (Feng et al. 2013). Localized hyperthermia induced by a magnetic field (ablatherm) is an alternative cancer treatment. It is a form of non-invasive therapy that gives low side-effects and can be an alternative to the traditional treatment Âą surgery Âą that can cause harm and often dreadful side-effects. An important element of that type of treatment is magnetic properties of hybrid composed of Fe3O4 deposited on graphene oxide platform (GO-Fe3O4) that determine the desirable effect on tumor cells. The aim of the study was to evaluate the cellular response of L929 fibroblast cells to a rotating magnetic field incubated with the graphene oxide nanosheet/Fe3O4 nanoparticles (GO-Fe3O4). The three types of nanomaterials: graphene oxide, iron oxide and hybrid of Fe3O4 deposited on graphene oxide (GO, GO-Fe3O4, and Fe3O4, respectively) tested in the present experiment were synthesized using methods described previously by Urbas et al. (2014). L929 mouse fibroblasts were 3 seeded into 96-well plates at the density of 7.4 x 10 per well, and cultured in DMEM supplemented with 10% fetal bovine serum, 2 mM L-glutamine, 0.4% streptomycin/penicillin and 10 mM Hepes. Cells were maintained in standard cell culture conditions at 37Â&#x192;C, 5% CO2 and 95% humidity. After 24-h incubation period, the three types of nanomaterials (GO, GO-Fe3O4, and Fe3O4) were added to the cell culture to obtain final concentrations of 0.0, 3.125, 6.25, 12.5, 25.0, 50.0 and Â&#x2014;J Pl. The cells were incubated with nanomaterials for 48 h. Experiments on the influence of rotating magnetic field (RMF) on L929 cell cultures, incubated with three types of NPs, were performed using an exposure system previously described by Masiuk et al. (2008). Microplates with cells were placed in a glass container in the centre of the coil. All experiments were temperature-controlled at 37Â&#x192;&Â&#x201C;0.5Â&#x192;C. Magnetic induction was determined inside each hole of the 96-well plate using the Hall probe. The recorded values of magnetic induction were 10.06, 6.58, 3.95, 2.36, 1.57 and 1.23 mT (average values of different wells on a culture plate) for the magnetic field frequency of 50 Hz. Firstly, the effects of nanomaterials and rotating magnetic field on the cultured L929 cells were tested using the WST-1 Cell Proliferation Reagent. The WST-1 solution was added after 48-h incubation with nanoparticles and 8-h exposition to a rotating magnetic field of each microplate well, and incubated. The absorbance was measured at 450 nm using a Sunrise Absorbance Reader. Cytotoxicity effects of RMF Â&#x160; and nanoparticles were also determined using the LDH CytoTox 96 Non-Radioactive Cytotoxicity Assay. Absorbance of the tested probes was measured at 490 nm using a spectrophotometer. The influence of the rotary magnetic field on the activity of L929 cells (without nanoparticles) showed that the mitochondrial metabolism was highest in cells incubated at 10.06 mT and lowest in cells incubated at 1.23 mT of RMF. When cell cultures were exposed to NPs and rotating magnetic field, the most significantly reduced cellular activity was recorded for graphene oxide particles at a concentration of 6.25-100.0 Â&#x2014;J Pl, 10.06 mT of RMF, while in the case of GO-Fe3O4 and Fe3O4 nanoparticles it was 100 Â&#x2014;J Pl at 10.06 mT of RMF. In summary, it can be concluded that the combination of NPs and the magnetic field may have a synergistic effect on cellular metabolism. Cancer cell lines will be utilized in further studies to determine the adequate co-effect of NPs and RMF for therapeutic aspects of the presented method. Acknowledgement: The authors are grateful for the financial support of National Science Centre within OPUS program (UMO-2011/03/B/ST5/0329). References [1] Feng J., Sheng H., Zhu C., Jiang H., Ma S., BioMed Research International, 10 (2013) 657259. [2] Urbas K., Aleksandrzak M., Jedrzejczak Magdalena, Jedrzejczak Malgorzata, Rakoczy R., Chen X., Mijowska E., Nanoscale Research Letters, 9 (2014) 656. [3] Masiuk M., Rakoczy R., Masiuk S., Kordas M., International Journal of Radiation Biology, 84 (2008) 752.

334 | NanoSpain Toxicology

Nanotoxicogenomics: transcription profiling for the assessment of nanomaterials toxicity mechanisms JosĂŠ M. Lacave, Unai Vicario-ParĂŠs, Eider Bilbao, Miren P. Cajaraville, Amaia Orbea

CBET Research group, Dept. of Zoology and Animal Cell Biology; Research Centre for Experimental Marine Biology and Biotechnology PIE, University of Basque Country (UPV/EHU). Sarriena z/g, E48940, Leioa, Basque Country, Spain. *amaia.orbea@ehu.es

Abstract Recent studies show that certain nanomaterials (NMs) are toxic to living organisms, both in in vitro and in vivo studies. Main common mechanisms of toxicity, such as immunotoxicity, inflammation and increased production of oxygen reactive species which, in turn, provoke oxidative stress, have been already demonstrated for NMs. Nevertheless, specific mechanisms for different materials and key properties (i.e., solubility, size, shape) influencing toxicity remain to be elucidated. Toxicogenomics is a high throughput tool to investigate the molecular and cellular mechanisms of action of chemicals and other environmental stressors, including NMs, on biological systems, predicting toxicity before any functional damages, and allows classification of materials based on signatures of gene expression [1]. In this work, we studied the transcriptomic response in the liver of adult zebrafish (Danio rerio) exposed to 10 Âľg metal/L of CuO nanoparticles (NPs) of ~100 nm, maltose-coated Ag NPs of 20 nm and CdS quantum dots (QDs) of 3.5-4 nm, as well as to their ionic counterparts (CuCl 2, AgNO3 or CdCl2). After 3 and 21 days of exposure, the liver of 20 males was dissected out and a microarray study was performed using the Agilent technology Zebrafish (v3), 4x44k Gene Expression Microarray. Copper exposures caused a weak effect on liver transcriptome compared to the response elicited by silver and cadmium compounds. CuO NPs differentially regulated 69 transcripts (LIMMA adjusted p<0.05 value) after 3 days of exposure while ionic copper significantly altered the expression of 30 transcripts after 21 days of exposure. Most of the GO terms (9 out of the 11) were shared in both WUHDWPHQWV *HQHUDO WHUPV LQYROYLQJ EDVLF ELRORJLFDO SURFHVVHV VXFK DV ÂłFHOOXODU SURFHVVÂ´ ÂłVLQJOH RUJDQLVP SURFHVVÂ´ ÂłPHWDEROLF SURFHVVÂ´, ÂłELRORJLFDO UHJXODWLRQÂ´ and ÂłUHVSRQVHV WR VWLPXOXVÂ´ appeared enriched. Sequences related to ÂłUK\WKPLF SURFHVVÂ´ Zere only regulated after 3 weeks of exposure to ionic copper. Exposure to silver for 3 days significantly regulated 243 different genes (Ag NPs) or 399 genes (ionic silver). After 21 days, the opposite trend was found: ionic silver regulated 265 transcripts and Ag NPs altered 990 different genes. At 3 days, ionic silver produced a strong disturbance of the energetic metabolism, inducing fatty acid catabolism, biosynthesis of unsatured fatty acids and peroxisome proliferator activated receptor signaling pathway and inhibiting glycolysis, among others. All these alterations did not remain after 21 days. Exposure for 3 days to Ag NPs inhibited steroid biosynthesis and induced fatty acid catabolism and several amino acids catabolism. After 21 days, pentose phosphate pathway, ether lipid metabolism, most of the amino acids metabolism and many ribosomal proteins were up-regulated. CdS QDs significantly regulated 9 and 3638 genes after 3 and 21 days, respectively, while the ionic form regulated 37 and 11224 genes. Both cadmium forms upregulated RNA degradation related biological processes after 21 days. In addition, ionic cadmium altered the DNA repair metabolism and down-regulated the carboxylic acid, alcohol and glycerol metabolic processes and amino acid and derivative metabolic processes, among others. QDs exposure inhibited actin cytoskeleton including focal adhesions and metabolism of carbohydrates and some amino acids, among others. Overall, these results show distinct gene transcription signatures for the three metals, being the nonessential metals, silver and cadmium, those eliciting the strongest response in the zebrafish liver. Copper only altered general biological processes. In addition, transcription profiles distinguished metal forms (NP versus ionic form) and exposure times (3 versus 21 days), appearing as an useful tool to unveil nano-specific mechanisms of toxicity. Funded by EU 7th FP (CP-FP 214478-2), Spanish MICINN and MINECO (CTM2009-13477 and MAT2012-39372), UPV/EHU (UFI 11/37), and Basque Government (IT810-13). Technical and human support provided by the UPV/EHU SGiker is acknowledged. References [1] Zhou T, Chou J, Watkins PB, Kaufmann WK. In: Molecular, Clinical and Environmental Toxicology. Vol 1: Molecular Toxicology. Ed. Luch A. 2009. BirkhĂ¤user Verlag/Switzerland. Pp 325-366

NanoSpain Toxicology | 335

Hemocomptability study of ZnO nanoparticles Llanas H, Marics L, Mitjans M, Vinardell MP Departament de Fisiologia, Facultat de FarmĂ cia, Av. Joan XXIII s/n, 08028 Barcelona, Spain KOODQDV#XE HGX

Abstract The interactions of nanomaterials with membrane cells are an important research area because such interactions are critical in many applications such as biomedical imaging, drug delivery, disease diagnostics and DNA/protein stricter probing [1]. More and more nanomaterials are designed for biological applications, and this raises new concerns about the safety of nanotechnology [2,3]. Among the various types of nanomaterials that have been developed, nanostructured metal oxides have recently aroused much interest in biomedical applications. ZnO is biomimetic and exhibits high electron transfer property, a relevant property for potential applications in biosensors. In recent years, various ZnO nanostructures have been widely used for enzyme immobilization. The antimicrobial potential of ZnO has also been well explored in the past [4]. In this study, we have evaluated the hemocompatibility of ZnO nanoparticles (50 and 100 nm) and microsized ZnO. Hemocompatibility of biomaterials refers to the degree of mutual adaptation between the materials and blood. This property arises from the interactions between each component of blood and the surface character of biomaterials, as well as the consequences of and effects produced by interactions [5]. The assays included the effects on blood coagulation, which were centered on prothrombin time (PT) and activated partial thromboplastin time (APTT), adsorption of plasma proteins and erythrocyte hemolysis test. Results show that ZnO is capable to modify blood coagulation time (Figure 1), and this effect is related to particle dimensions. Similarly, we concluded that ZnO can form a certain complex with albumin (BSA), which is the most abundant protein in blood plasma, attending the diminution of fluorescence in the presence of ZnO (Figure 2). Finally, we found that ZnO nanoparticles are more haemolytic than microsized ZnO after 24h incubation. References [1] Verma A, Stellaci F, Small 6 (2010) 12. [2] Nel E, Madler L, Velegol D, Xia T, Hoek EMV, Somasundaran P, Klaessig F, Castranova V, Thompson M, Nat. Mater. 8 (2009) 543. [3] Ai J, Biazar E, Jafarpour M, Montazeri M, Majdi A, Aminifard S, Zafari M, Akbari HR, Rad HG. Int J Nanomedicine. 6 (2011) 1117. [4] Bhogale A, Patel N, Sarpotdar P, Mariam J, Dongre PM, Miotello A, Kothari DC. Colloids Surf B Biointerfaces. 102 (2013) 257. [5] Liu Y, Cai D, Yang J, Wang Y, Zhang X, Yin S. Int J Clin Exp Med. 7 (2014) 1233. Figures

Figure

1. Effect of ZnO and ZnO Figure 2. Fluorescence spectra of BSA in absence and presence nanoparticles (NPs) on blood coagulation time. of ZnO nanoparticles (100nm) at different concentrations after 30 APTT: Activated Partial Thromboplastin Time. min incubation.

336 | NanoSpain Toxicology

The study of heavy metal pollution in the surface fauna and hyporheic fauna Presenting Author: Samira Sabri, Co-Authors:Belaidi Nouria UNIVERSITY Abu Bakr BELKAID-TLEMCEN. Department of Ecology and Environment Laboratory of Ecology and Natural Ecosystems Management. , Tlemcen, Algeria. eco_alg2008@yahoo.fr Abstract: The stydy of upstream and downstream evolution of hyporeic fauna compared to here of surface environment ,it is realised in average and low Tafna on downstream dam . Listed fauna includes understands 28 tax,dominated by the larvae of insects 続Ln particular Chironomidae 続 DQG WKH 2OLJRFKHWHV 続Tubificidae卒 the indicator fauna of pollution). the diversity of fauna is particular influence by the environment conditions(heavy metal pollution). The results are indicating diminution of fauna in hyporeic and surface environment ,it is cither due to the extinction or the migration of the fauna to deeper layers. The composition of fauna in three stations is show to the station T6 called receptive of dam water is more affected by pollution of heavy metals with low diversity. Keys words: North-west of Algeria-hyporeic fauna-surface fauna-pollution- heavy metals-Tafna wadi References: Malard,F.,REYGROBELLET, J.L,MATHIEU,J.et LAFONT M., The use of invertebrate.communities to describe ground water flow and contaminate transport in a factured rock aquifer.Archir fur hydrobiology(1994) 131:93p MARMONIER,P et CREUZE DES CHATELLIERS,Effects of spates on interstitiel assemblages of the Rhone River importance of heterogeity(1991)46 :78p. MESTROV, M. ,et LATTINGER-PENKO,R.investigation of the mutuel influence between a polluted River and its hyporheic(1981) 98-120p. NOTENBOOM,J.et SERRANO,R.the phreatic aquifer of the plasma de catellon(Spain): Relation ships between animal assemblage and groundwater pollution.Bull.hydrologia.279Spain (1995) 241-249p [1] Authors, Journal, Issue (Year) page.

Figures

NanoSpain Toxicology | 337

Data Processing of Nanoparticle Agglomeration from Differential Centrifugal Sedimentation 0DUWLQ Ă˘WU\QFO $OHQD Ă˘HYFÄ¤ Technical University of Liberec, Studentska 1402/2, 461 17 Liberec 1, Czech Republic martin.stryncl@tul.cz Abstract Nanoparticles dispersed in liquid environment are an unstable system. Even if the nanoparticles are stabilised, they tend to form agglomerates. The agglomeration is the time dependent spontaneous phenomena which have to be considered during designing experiments or commercial products. The Differential Centrifugal Sedimentation (DCS) is a technique which allow to obtain size distribution of agglomerates with very high resolution. Here, we present how to analyse time-dependent data of mixture distribution of nanoparticle agglomerates. The data processing is based on searching for parameters of individual components from normal distribution within mixture distributions. The measured mixture distributions are interpolated against time and plotted on graph. The results are then mathematical functions describing trends of parameters of individual components of a mixture distribution in time. The presented method is useful to estimate ageing processes of nanoparticle agglomerates.

338 | NanoSpain Toxicology

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341 | P P M

J.J. López, F. Javier García de Abajo

Martinez Saavedra, Jose Ramon

Seonhee Lee, Min Su Kim, Seki Park, Yongjun Lee, Hyunjung Shin, and Jeongyong Kim

Lee, Jubok

Juan F. Galisteo-López and Hernán Míguez

Jiménez-Solano, Alberto

I. Ben Miled and S. Jaziri

Hichri, Aida

M.B. Belonenko, Ju.V. Nevzorova

Galkina, Elena

K. Kim, B. Song, W. Lee, W. Jeong, J. Feist, F. J. Garcia-Vidal, J. C. Cuevas, E. Meyhofer and P. Reddy

Fernandez, Victor

F. Javier García de Abajo

Delgado de Vega Esteban, Sandra

María Concepción Serrano, Álvaro Blanco, Cefe López

Hens Moreira Espinha, André Costa

P. Koval, F. Marchesin, R. Esteban, A. G. Borisov,J. Aizpurua, D. Sanchez-Portal

Barbry, Marc

authors

Spain

Korea

Spain

Tunisia

Russia

Spain

country

Probing nanographene phonons with electron energy-loss spectroscopy

Measurement of photocatalytic efficiency of single Au/TiO2 core-shell nanowires using dark-field scattering spectroscopy

Fine tuning of the emission properties of nano-emitters in multilayered structures by deterministic control of their local photonic environment”

Plasmons in graphene at terahertz frequencies

Discrete solitons in a Bragg medium with carbon nanotubes

Radiative heat transfer through nanometer-size gaps

Plasmonics inatomically flat gold structures

Engineering light transport in titania-doped multifunctional elastomers

First-principles calculation of plasmonic resonances and electric field enhancement in metalcluster dimers

poster title

ImagineNano 2015 PPM Posters list: alphabetical order

Xu,Tomas

342 | P P M

F.J. Recio, L Bergamini, A. Ayuela, A. Rivacoba, P. Crespo, A. Hernando and P.M. Echenique

Zabala, Nerea

Cristian Kusko, Mihai Kusko, Paul Schiopu

Tomescu, Roxana

Lina Ramanauskaite, Huizhong Gadisauskas, Rasa Zukiene

Snitka, Valentinas

J. M. Plaza Ortega, and F. Javier García de Abajo

Silveiro, Iván

M. Schnell, A. Chuvilin and R. Hillenbrand

Sarriugarte, Paulo

Sabri, Ghoutia Naima

André Espinha, Luz Karime Gil, Álvaro Blanco and Cefe López

Pariente, Jose Angel

N. Soriano, C. Redondo, A. Arteche, D. Navas, and R. Morales

Mora, Beatriz

Andre Espinha, F. Bayat, Carlos Pecharroman, Cefe Lopez, and Alvaro Blanco

Montesdeoca Cárdenes, Denise

authors

Spain

Romania

Lithuania

Spain

Algeria

Spain

country

Optical spectroscopy study of colloidal gold nanostructures: model for thiolate-covered nanorods

FDTD simulations of plasmonic metasurfaces

Novel plasmonic probes for Tip-Enhanced Raman Spectroscopy

Quantum nonlocal effects in individual and interacting grapheme nanoribbons

Near-Field Mapping of Extremely Confined(λ0/310) IR Modes on FIB Fabricated Transmission Lines

Magneto-optical properties of ferrite in high frequency

Fine control transition from photonic crystals to photonic glasses

Relationship between AFM topography and magnetic properties of trench-patterned thin films

Fast fabrication of photonic glasses achieved by pressure

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PPM | 343

Engineering light transport in titania-doped multifunctional elastomers a

André Espinha, María Concepción Serrano, Álvaro Blanco, Cefe López

Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Calle Sor Juana Inés de la Cruz 3, Cantoblanco, 28049 Madrid, Spain b Hospital Nacional de Parapléjicos, Finca de la Peraleda s/n, 45071 Toledo, Spain acmespinha@icmm.csic.es

Abstract

Composites incorporating an optically functional phase embedded in polymeric matrices are a platform of choice for the development of optical systems such as flexible, transparency preserving materials with high refractive index [1]. In these cases, the size of the fillers is usually much smaller than light wavelength, so that scattering is minimized. To facilitate the high refractive index, titania nanoparticles are frequently selected [2]. On the other turn, the Mie regime is reached if the size of the particles is of the order of the wavelength, situation in which the scattering is significantly enhanced. Due to multiple scattering [3], light transport on those media becomes diffusive. Important advances have been realized in the materials community in search for multifunctional features impacting the performance of systems and devices and, in this sense, photonics is not an exception. As an example, we recently reported the possibility of programming the lattice parameter of a two dimensional photonic crystal [4] by making use of multifunctional shape memory polymers [5]. While well-ordered structures are essential in photonic crystals, disordered materials, presenting diffusive transport, may be also extremely interesting [6] and they have proven impact on applications such as random lasers or imaging through opaque media. In this work [7], we fabricated elastomeric composites by embedding titania particles with an average size of ca. 230 nm in a shape memory polymer belonging to the family of polydiolcitrates. As shown by modulated differential scanning calorimetry, these composites displayed a melting transition in range with previous reports [8], which is responsible for the physical switching mechanism originating the shape memory effect. Depending on the temperature or on the concentration of fillers, the proposed materials may be highly translucent or opaque. The light transport, specifically the transport mean free path, was characterized using coherent backscattering measurements and shown to depend on the amount of titania incorporated. The reported composites may find application as a new kind of actuators or as part of novel programmable materials for exploring new avenues in photonics.

This work was partially supported by EU FP7 NoE Nanophotonics4Energy grant No. 248855, the Spanish MICINN project MAT2012±31659 (SAMAP), and Comunidad de Madrid S2009/MAT-1756 (PHAMA) program. A.E. was supported by the FPI Ph.D. program from the MICINN. M.C.S. acknowledges Instituto de Salud Carlos III - MINECO for a Miguel Servet contract (CP13-00060).

References

[1] L. Beecroft, C. Ober, Chemistry of Materials, 9 (1997) 1302. [2] A. Chandra, L. Turng, S. Gong, D. C. Hall, D. F. Caulfield, Polymer Composites, 28 (2007) 241. [3] B. Van Der Mark, M. P. Van Albada, A. Lagendijk, Physical Review B, 37 (1988) 3575. [4] A. Espinha, M. C. Serrano, A. Blanco, C. López, Advanced Optical Materials, 2 (2014) 516. [5] M. Behl, M. Razzaq, A. Lendlein, Advanced Materials, 22 (2010) 3388. [6] D. S. Wiersma, Nature Photonics, 7 (2013) 188. [7] A. Espinha et al. Submitted (2015). [8] M. C. Serrano, L. Carbajal, G. Ameer, Advanced Materials, 23 (2011) 2211.

344 | PPM

Plasmonics in atomically flat gold structures 1

S. de Vega , F. Javier García de Abajo

1,2

ICFO Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain 2 ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 (Barcelona), Spain sandra.devega@icfo.es, javier.garciadeabajo@icfo.es Abstract Plasmons in atomically thin gold structures have been experimentally observed over the past decade, in particular for atomic gold wires formed at the steps of Si(557) when it is decorated with a low-coverage gold layer [1 - 4]. The observation of plasmons in these systems has been carried out using electron energy-loss spectroscopy, as they are ultra-confined, so that their coupling to light is too weak to be observed. Stimulated by these results, we theoretically study finite-length atomically thin nanowires and nanoribbons. Our purpose is to increase the coupling to light in order to use these structures as atomicscale plasmonic units. As a first step we revisit experimental data of plasmons in infinitely long atomic gold wires and fit them to both classical and quantum-mechanical models based on the dielectric theory and the random-phase approximation, respectively. These models fit the plasmon dispersion relation extremely well for reasonable choices of parameters. We then calculate absorption cross section of finite nanowires (see Fig. 1). We predict absorptivities of ~5% for arrays of nanorods on the Si(557) surface and ~22% in vacuum. Higher unity-order cross sections are obtained for wires of finite lateral size in the atomic-scale range. Our results pave the way towards the use of atomic-scale gold structures for nanophotonics. References [1] K. N. Altmann et al., Phys. Rev. B, 64, 035406 (2001). [2] J. N. Crain et al., Phys. Rev. B, 69, 125401 (2004). [3] T. Nagao et al., Phys. Rev. Lett., 97, 116802 (2006). [4] T. Nagao et al., Sci. Technol. Adv. Mater., 11, 054506 (2010). Figures

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Fig 1. (a) Spectra of the absorption cross section of nanorods of radius a = 0.1888 nm and different lengths L for light incident with its electric along the rod axis, as obtained from the boundary-element method. (b). Light frequency at the cross section maximum (left vertical axis) and maximum value of the cross section (right axis) for rods supported on different substrates (characterized by Ή) as a function of the ratio between nanorod length and radius.

PPM | 345

Radiative heat transfer through nanometer-size gaps 1

V. Fern谩ndez Hurtado , K. Kim , B. Song , W. Lee , W. Jeong , J. Feist , F. J. Garcia-Vidal , J. C. 1 2 2 Cuevas , E. Meyhofer and P. Reddy . 1

Departamento de F铆sica Te贸rica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Aut贸noma de Madrid, Madrid, 28049, Spain 2 Department of Mechanical Engineering, University of Michigan, Ann Arbor, 48109, USA victor.fernandezh@estudiante.uam.es

One of the central open problems in nanoscience is the study of the heat transport in nanoscale devices, which has remained largely unexplored due to experimental challenges. In this context, a key issue is the understanding of the heat transfer via thermal radiation between systems separated by nanometer-size gaps. In this extreme regime, the electromagnetic near-field is expected to give rise to a dramatic enhancement of the radiative heat transfer, something that has only be quantitatively verified for gaps on the order of 20-30 nm [1]. In this work, we present a combined experimental and theoretical study of the radiative heat transfer in the extreme near-field regime (gaps of 1-10 nm). From the experimental side, we performed systematic studies using AFM-based scanning probes with integrated nanoscale thermocouples [2], which were coated with dielectrics (SiO2 or SiNx). Our experiments of heat transport between the scanning probes and a flat substrate coated with dielectrics, performed in an ultra-high vacuum environment, confirm that heat transport is dramatically enhanced in the near-field. To understand our experimental results, we investigated these near-field enhancements within the framework of the theory of fluctuational electrodynamics [3]. To be precise, we performed extensive numerical simulations making use of a combination of a fluctuating-surface-current formulation of radiative heat transfer with the boundary element method [4,5]. Such a combination allows us describing realistic geometries for our tip-sample setups. Our theoretical results are in good agreement with the measured heat flows between both dielectric and metallic surfaces, which establishes the validity of fluctuational electrodynamics in modeling near-field heat transport all the way to nanometersize separations. References [1] S. Basu, Z. M. Zhang, and C. J. Fu, Int. J. Energy Res. 33 (2009) 1203. [2] W. Lee, K. Kim, W. Jeong, L.A. Zotti, F. Pauly, J.C. Cuevas, and P. Reddy, Nature 498 (2013) 209. [3] K. Joulain, J.P. Mullet, F. Marquier, R. Carminati, and J.J. Greffet, Surf. Sci. Rep. 57 (2005) 59. [4] A. W. Rodriguez, M. T. H. Reid, and S. G. Johnson, Phys. Rev. B 86 (2012) 220302(R). [5] A. W. Rodriguez, M. T. H. Reid, and S. G. Johnson, Phys. Rev. B 88 (2013) 054305.

a Schematic diagram of the experimental setup. The AFM probes incorporate a thermocouple, made by a spherical Au/Cr junction with a diameter of 200 nm. b Numerical simulation of the spatially resolved heat transfer between a tip and a plate made of silica and separated by a distance of 1 nm. The radius of the tip is 225 nm. The color scale is logarithmic, showing the radiative heat transfer enhancement in the extreme near-field.

346 | PPM

Discrete solitons in a Bragg medium with carbon nanotubes E.N. Galkina, M.B. Belonenko, Ju.V. Nevzorova Volgograd State Medical University, pl. Pavshikh Bortsov, Volgograd, Russia galkina@mail.com Abstract The propagation of few cycle optical pulses which can be considered as discrete solitons in the case when a medium in which carbon nanotubes are embedded has spatially-modulated refraction index is under investigation. The effective equation which has the form of classical sine-Gordon equation analogue was derived [1]. Analysis of dependence on the task options was performed. As it is seen from figures pulse on central waveguide doesn’t change its shape particularly dependent on initial pulse width in opposition to neighbor waveguide pulses. At side waveguides pulse has the same form as at the central one but with reduced amplitude. We can control the amplitude of electromagnetic field on neighbor waveguides by varying initial central pulse width. Moreover the wider the feeding to system pulse the greater the amplitude of neighbor pulses with the central one. This fact in its turn gives us possibility to manage few cycle pulse shape by varying both number of CNT layers and the distance between layers which is determined by a couple parameter. References [1] R.K. Bullough et al. Solitons, Berlin etc.,1980. [2] E. Smirnov, M. Stepic, C.E. Ruter, D. Kip, Opt. Let, Vol. 31, No 15 (2006) P. 2338-2340. [3] E. Smirnov, C.E. Rueter, M. Stepic, V. Shandarov and D. Kip, Optics Express, Vol. 14, No 23 (2006) P. 11248-11255. Figures

The dependence of electric field determined by potential on waveguide number (fig. a). The waveguide number N is along x axis, dimensionless value of electric field is along y axis. In presence of Bragg grating with modulation depth α at moments of time t = 250 (1a), t = 200 (2a), t = 130 (3a); and with modulation depth 2α at moments of time t = 250 (4a), t = 200 (5a), t = 130 (6a). The dependence of electric field on time (fig. b). Dimensionless value of time is along x axis, dimensionless value of electric field is along y axis. In presence of Bragg grating with modulation depth α the waveguide numbers are N = 5 (1b), N = 6 (2b); and with modulation depth 2α the waveguide numbers are N = 5 (3b), N = 6 (4b).

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Plasmons in graphene at terahertz frequencies I.Ben Miled1, A. Hichri1 and S. Jaziri 1,2 1

Laboratoire de physique des matériaux, propriétés et structures, Faculté des Sciences de Bizerte, Tunisie. 2

Laboratoire de physique de la matière condensée, Faculté des Sciences de Tunis, Tunisie. aida.ezzeddini@gmail.com

Due to the unique and excellent properties, graphene has attracted a great deal of interest. High confinement, low loss and good tunability, makes graphene a promising plasmonic material compared to the noble metals. Its two dimensional nature meets the need of surface plasmons and greatly enrich the field of plasmonics. We propose here to study the effects of temperature, doping and relaxation time in the dielectric function, on behaviors of the charge density waves (or plasmons) in graphene. In some conditions, such plasmon exists, but strongly damping, due to the interplay between the inter- and intra-band transitions. The high mobility of electrons in graphene encouraged theoretical and experimental studies in graphene based ultrahigh-speed electronic devices such as terahertz devices [1]. It has been shown that the plasmons in graphene at moderate carrier densities (10 ±10 cm ) are in the terahertz frequency range. 9

-2

40 T=300K, W=0.5ps 12 -2 p=n=0.4, 0.8, 2.5 10 cm

plasmon pulsation Zp ( THz)

35 30 25

increasing density 20 15 10

Z = v Fq 5 0 0,0

0,5

1,0

1,5

2,0

2,5 5

3,0

3,5

4,0

-1

wave vector (10 cm )

Plasmon dispersion relation in graphene at 300 K is plotted for different electron-hole densities

[1] E. H. Hwang and S. Das Sarma, Phys. Rev. B 75, 205418, 2007,20

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Fine tuning of the emission properties of nano-emitters in multilayered structures by deterministic control of their local photonic environment Alberto Jiménez-Solano, Juan F. Galisteo-López and Hernán Míguez Multifunctional Optical Materials Group. Instituto de Ciencia de Materiales de Sevilla. Consejo Superior de Investigaciones Científicas-Universidad de Sevilla. C/ Américo Vespucio 49, 41092 Sevilla, Spain alberto.jimenez@csic.es Abstract Porous nanostructured photonic materials in the shape of periodic multilayers have demonstrated their [1] [2] potential in different fields ranging from photovoltaics to sensing . On the one hand their porosity makes it feasible to infiltrate them with an electrolyte or a polymeric matrix (which allows their use in dye [3] sensitized solar cells or as flexible films ). On the other, the possibility of controlling their refractive index profile via their porosity or the choice of materials, strongly affects the way light is transported or generated within them. When applications dealing with light absorption or emission are considered, knowledge on how the local [4] density of states (LDOS) is distributed within them is mandatory in order to realize a judicious design which maximizes light matter interaction. In order to do so, access to a photonic probe which senses the LDOS at different spatial positions is desired. Such probe must have reduced dimensions (in order to achieve a high spatial resolution in the mapping of the LDOS) and should lend itself to be incorporated in the fabrication procedure in such a manner that its spatial position within the sample can be controlled. In this work we report a detailed study of how dye doped polystyrene nanospheres constitute an effective LDOS probe to study its distribution within nanostructured photonic media. Nanospheres with a diameter of 25 nm are incorporated in the fabrication procedure of nanostructured photonic multilayers (through a combination of spin and dip-coating with suspensions of oxide nanoparticles) in such a way that the high optical quality of the fabricated structure is maintained. Introducing the polymeric spheres at different stages of the fabrication process allows placing them at several positions of the structured sample. A combined use of photoluminescence spectroscopy and time resolved measurements are used to optically characterize the samples. While the former shows how depending on the probe position its PL intensity can be enhanced or suppressed, the latter allows to probe the LDOS changes within the sample, monitored via changes in its lifetime. We demonstrate how information on the local photonic environment can be retrieved with a spatial resolution of 25 nm (provided by the probe size) and relative changes in the decay rates as small as ca. 1%, evidencing the possibility of exerting a fine deterministic control on the photonic surroundings of an emitter. References [1] C. López-López, S. Colodrero, M. E. Calvo and H. Míguez, Energy Environ. Sci., 23 (2013), 2805. [2] A. Jiménez-Solano, C. López-López, O. Sánchez-Sobrado, J. M. Luque, M. E. Calvo, C. FernándezLópez, A. Sánchez-Iglesias, L. M. Liz-Marzán and H. Míguez. Langmuir, 28 (2012), 9161. [3] J. R. Castro-Smirnov, M. E. Calvo and H. Míguez, Adv. Funct.Mater, 23, (2013), 2805. [4] N. Danz, R. Waldhäusl, A. Bräuer and R. Kowarschik, J. Opt. Soc. Am. B, 19 (2010), 412. Figures

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Measurement of photocatalytic efficiency of single Au/TiO 2 core-shell nanowires using dark-field scattering spectroscopy a,b

a,b

Jubok Lee , Seonhee Lee , Min Su Kim , Seki Park , Yongjun Lee , Hyunjung Shin , and a,b,* Jeongyong Kim a

Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 440-746, Republic of Korea b Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea *E-mail: j.kim@skku.edu

Abstract A wide and indirect band-gap semiconductor, titanium dioxide (TiO2), has been applied to many potential applications such as dye sensitized solar cells, photocatalysts, photodetectors and gas sensors due to its excellent photoelectrochemical properties. Recently, metal-hybridized nanostructures of TiO2 have been reported to have better photocatalytic efficiency due to surface plasmon resonance of metal nanostructures [1]. However, a systematic study of optical properties of Au/TiO 2 core-shell nanowires are rarely performed and direct estimation of photocatalytic capability in single nanowires are not reported. In this study, we investigated dark-field scattering spectra of single strand of Au/TiO 2 core-shell nanowires using confocal microscope system. Dark-field scattering spectra obtained from single strands of Au/TiO2 core-shell nanowires showed the enhancement of scattering efficiency with Au hybridization in total magnitude and spectral coverage. The enhancement of scattering efficiency was quantitatively consistent with measurement of photocatalytic effect using AO7 (acid orange 7 = C16H12N2O4S) solution. Finite-difference time domain simulations were also performed to compare with the experimental results.

References [1] D 7VXNDPRWR HW DO - $P &KHP 6RF Ă

Figures

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Probing nanographene phonons with electron energy-loss spectroscopy 1

J.R.M. Saavedra , J.J. López , F. Javier García de Abajo

1,2

ICFO Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain 2 ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Spain jose.martinez@icfo.es , javier.garciadeabajo@icfo.es Abstract Electron energy-loss spectroscopy (EELS) performed on transmission electron microscopes (TEMs) is widely used for the characterization of optical excitations with atomic resolution [1,2]. The energy of the electrons ~100 keV's makes it difficult to resolve very low frequency excitations, such as phonons. High-resolution EELS (HREELS) offers an alternative that is capable of resolving molecular adsorption [3] and surface vibrations [4] using less energetic electrons, although this technique lacks spatial resolution below a few nanometers. Recent developments in TEMs have pushed the energy resolution down to ~10 meV [5], thus enabling the study of optical phonons with atomic resolution. Stimulated by these experimental advances, we theoretically study the high frequency vibrational modes of nanographene structures and extended graphene layers. We discuss both loss spectra and spatially resolved maps for different structures and compare them with the local density of acoustic (or vibrational) states (LDAS), showing how optical phonons can be sampled and studied by means of the new electron microscopes (see Fig. 1). We further discuss the origin of the different features in the spectra, as originating from specific vibrational modes of the structures. The limit of extended graphene is smoothly recovered for large structures. We predict large inelastic signal intensities due to the divergent character of the electron-sample interaction at low frequencies, thus anticipating that phonon losses will produce observable signals down to samples of molecular size.

References [1] Egerton, R.F., Electron energy-loss spectroscopy in the electron microscope, Springer (1996). [2] García de Abajo, FJ, Rev. Mod. Phys. 82, 209-275 (2010). [3] Whang, E.K. et al., Phys. Rev. B 63, 075401 (2001) . [4] Ibach, H., Mills, D.L., Electron energy-loss spectroscopy and surface vibrations, Academic Press (1982). [5] Krivanek, O.L., et al, Nature 514, 209-212 (2014).

Figures

Fig. 1. EELS spectrum (solid curve) and map (top inset) for a 100 keV electron passing near a triphenylene molecule. The electron arrow in the inset shows the impact parameter considered in the spectrum. The color plot corresponds to the energy loss of the 0.19 eV phonon indicated by an arrow in the spectrum. The spectrum has been broadened with a zero-loss peak (ZLP) full width at half maximum of 10 meV.

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Fast fabrication of photonic glasses achieved by pressure Denise Montesdeoca, Andre Espinha, F. Bayat, Carlos Pecharroman, Cefe Lopez, and Alvaro Blanco Instituto de Ciencia de Materiales de Madrid ICMM-CSIC c/Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, Spain d.m.c@icmm.csic.es Abstract Photonic random structures presenting multiple light scattering have been of great interest in the last few years [1] and their fabrication has led to the development of new and sophisticated fabrication methods. In these systems, important fundamental phenomena such as Anderson localization of light might take place [2]. Further, polymeric photonic glasses have recently demonstrated resonant light transport [3] in which random lasing can be controlled [4]. Here we show a new method to prepare photonic glasses from different colloidal suspensions (SiO2, Polystyrene, or PMMA) in a very fast way. Starting from raw materials in powder form (as synthesized or purchased) we propose a method for fabricating high quality photonic glasses in minutes, by applying pressure [5]. Our studies on how monodisperse building blocks pack open a new window to understand light behavior in complex optical media. Further, this work might provide deeper knowledge on random granular media at the nanoscale [6]. References [1] D. S. Wiersma, Nat. Phot. 7 (2013) 188. [2] D. S. Wiersma, P. Bartolini, A. Lagendijk, and R. Righini, Nat. Phot. 390 (1997) 671±673. [3] P. D. García, R. Sapienza, Á. Blanco, and C. López, Adv. Mater. 19 (2007) 2597. [4] S. Gottardo, R. Sapienza, P.D. García, Á. Blanco, D. S. Wiersma, and C. López, Nat. Phot. 2 (2008) 429. [5] D. Montesdeoca et al. submitted (2015). [6] Y.Kallus, S. Torquato, Ph. Rev. E, 90 (2014) 022114. Figures

Figure 1. Resonant total transmission for silica photonic glasses composed of spheres with 920 nm in diameter, for different applied pressures (up). Scanning electron microscopy images and optical image of a silica photonic glass for an applied pressure of 6t (460 MPa) (bottom).

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Relationship between AFM topography and magnetic properties of trench-patterned thin films 1

3,4

B. Mora , N. Soriano , C. Redondo , A. Arteche , D. Navas , and R. Morales . 1

Dpto. de Química-Física, Universidad del País Vasco UPV/EHU, 48940 Leioa, Spain. 2 IFIMUP-IN and Dept. Fisica e Astronomia, Universidade do Porto, Porto, Portugal 3 Dpto. de Química-Física & BCMaterials, Universidad del País Vasco UPV/EHU, 48940 Leioa, Spain. 4 IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain. beatriz.mora@ehu.es

Abstract Current lithography techniques have allowed the fabrication of nanostructured magnetic materials in which size, shape and order have dramatic influence on their magnetic properties [1, 2]. In this work we show that the topographical characterization by atomic force microscopy (AFM) of trench-patterned thin films makes available the understanding of unusual magnetic properties. Trenched ferromagnetic nanostructures present hysteresis loops with negative remanence. In common ferromagnetic materials, when an applied magnetic field H is reduced from positive saturation to zero, the remaining magnetization points also to the positive direction. It is necessary to apply an opposite magnetic field to reverse the ferromagnetic spins. In our artificially patterned thin films the remaining magnetization after removal of the external field is negative, indicating that ferromagnetic spins are inverted at positive fields. This effect strongly depends on the topography of the thin film. A theoretical model that takes into account the AFM topography features, as width, periodicity and depth of trenches, was carried out to simulate these unconventional hysteresis loops. We obtain an excellent agreement between both theoretical and experimental results for each topographical characterization. Work supported by Basque Country Government grant Nanoiker11, UPV/EHU UFI11/23 and MINECO FIS2013-45469. References [1] R.P.Cowburn, J. Phys. D: Appl. Phys. 33 (2000) R1 [2] J.I. Martín, J. Nogués, K. Liu, J.L. Vicent, I.K. Schuller 256 (2003) 449 Figures

Fig. 1. AFM topography of ferromagnetic trenches of periodicity 400 nm and depth 18 nm.

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Fine control transition from photonic crystals to photonic glasses Jose A. Pariente, André Espinha, Luz Karime Gil, Álvaro Blanco and Cefe López Instituto de Ciencia de Materiales de Madrid ICMM – CSIC C/Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain jpariente@icmm.csic.es

Abstract: The control of light transport is crucial, not only to understand the behavior of light propagating in complex media, but also to design and tailor new photonic devices [1]. In this way, selfassembly allows us to design photonic nanostructures with novel optical properties such as forbidden energy bands in photonic crystals or resonant light transport in photonic glasses [2]. However, the transition from photonic crystals to photonic glasses is not fully understood so far. One way to explore this transition is by introducing random vacancies in photonic crystals, in a controlled manner, without altering the lattice parameter [3]. This is mandatory to really discern between Bloch and Mie modes and understand the nature of laser emission in such different photonic environments [4]. Here we show how by achieving very high control on the number of vacancies (fig. 1) we can fine-tune this transition. Different behavior for light transport has been observed inside and outside the photonic band gap, depending on the number of vacancies [5]. References: [1] S. Gottardo, R. Sapienza, P. D. García, A. Blanco, D. S. Wiersma and C. López, Nat. Photonics, 2008, 2, 429. [2] J. F. Galisteo, M. Ibisate, R. Sapienza, L. S. Froufe, A. Blanco, and C. López, Adv. Mat. 2008, 23, 30. [3] P. D. Garcia, R. Sapienza, C. Toninelli, C. Lopez, and D. S. Wiersma, Phys. Rev. A, 2011, 84, 023813. [4] P.D. Garcia, and C. Lopez J. Phys. Chem C, 2013, 1, 7357. [5] J.A. Pariente et. al. Submitted (2015). Figures

Figure 1.Lambert-Beer´s law in photonic crystal. Plot ln(R+T) as a function of the sample thickness inside band gap (λi = 737 nm), for different %ρ (from 0% to 40% vacancies doping).

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Magneto-optical properties of ferrite in high frequency Magneto-optical Properties of Ferrite In High Frequency Ghoutia Naima Sabri University of Mohamed Tahri, NÂ° 417, Street Kenadsa, Bechar, Algeria sabri_nm@yahoo.fr Abstract The purpose of the paper is the study of magneto-optical properties of ferrite in high frequencies and its application in microwave devices. Another aspect involved in the paper is the integration of many passive components on chips and the knowledge of electromagnetic properties of the ferrite, which is important to show their influence on the development of modern technology connected with miniaturization of devices in telecommunication field. In a medium consisting of ferrite magnetized vertically, the wave (RF magnetic field) is elliptically polarized left and rotates in the same direction as the precession gyromagnetic causing a strong interaction of the electromagnetic wave with the ferrite. And when the magnetic field rotates in the opposite direction of the gyromagnetic precession, it produces a weak interaction with the material. Gyromagnetic resonance is one of important phenomena which are operated in the range of high frequency electromagnetic spectrum, wherein the ferrites are used. Our objective is then to study the magneto-optical properties of ferrites in hyperfrequencies when they are polarized by a static magnetic field is translates in particular into the phenomenon of nonreciprocity. It gives the material its ability to respond differently to an electromagnetic wave according to its polarization. In addition, it allows separate devices into two distinct classes: those who work at resonance (isolators, filters ...), and those who work outside the resonance (circulators. ..). Therefore the cyclotron resonance is related to the movement of precession of the magnetic moment of the electron spin around the direction of the internal magnetic field. References [1] Authors, Journal, Issue (Year) page. [1] Pardavi-Horvath, M. â&#x20AC;&#x153;Journal of Magnetism and Magnetic Materials,â&#x20AC;? Microwave of soft ferrites, Vol. 34, No. 10, 215â&#x20AC;&#x201C;216, 2000 (171-183). [2] 'REU]DÄ&#x201D;VNL / $ 'UDN 0 DQG % =LÄ&#x160;ERZLF] Âł-RXUQDO RI $FKLHYHPHQWV in Materials and Manufacturing Engineering, Vol. 17, No. 1-2, 37â&#x20AC;&#x201C; 40, 2006. Figures

Figure1: Evolution of the magnetic permeability of the material as a function of internal field (according to the model Polder)

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Near-Field Mapping of Extremely Confined (λ0/310) IR Modes on FIB Fabricated Transmission Lines 1

P. Sarriugarte , M. Schnell , A. Chuvilin

1,2

and R. Hillenbrand

2,3

CIC nanoGUNE, 20018 Donostia – San Sebastian, Basque Country, Spain IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Basque Country, Spain 3 CIC nanoGUNE and EHU/UPV, 20018 Donostia – San Sebastian, Basque Country, Spain p.sarriugarte@nanogune.eu 2

Abstract Metal antennas and transmission lines (TL) are common devices for receiving and transporting signals in the radiofrequency regime. It has been demonstrated that by reducing the size down to the micrometer range, these devices can be operated at infrared frequencies (~30 THz) [1-3]. Here we demonstrate that functional infrared TLs with gap widths down to 25 nm can be fabricated by Gallium Focused Ion Beam (FIB) milling of gold films on CaF2 substrates [1]. Interferometric and polarization-resolved near-field microscopy [4] is applied to map in real space the propagation of the TL modes. For the first time, we measured the strongly confined fields of a propagating TL mode by mapping the s-polarized scattered field. Imaging TLs with 25 nm gap width we experimentally demonstrate an infrared mode with diameter of Dm = 42 nm (λ0/220), which intriguingly, shows a propagation length of about Lm = 8 µm. Interestingly, this is more than two orders of magnitude larger than the mode diameter, Lm/Dm = 190. Applying combined Gallium and Helium FIB milling, we fabricated infrared TLs with single-digit nanoscale gap widths. Imaging a TL with 5 nm gap width we experimentally demonstrate an infrared mode with a diameter of only Dm = 30 nm (λ0/310) and a propagation length of about Lm = 4 µm (Fig. 1). Numerical calculations predict significant propagation distances (≈3 µm) for even smaller gaps down to 1 nm width. TLs comprising such nanoscale wire-separation could become highly valuable building blocks for ultra-sensitive mid-infrared sensing, spectroscopy and nanoimaging applications.

References [1] P. Sarriugarte et al., ACS Photonics, 1 (2014) 604-611. [2] M. Schnell et al., Nature Photonics, 5 (2011) 283-287. [3] P. Sarriugarte et al., Optics Communications, 285 (2012) 3378-3382. [4] M. Schnell et al., Nano Letters, 10 (2010) 3524.

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Fig. 1: Near-field imaging of a transmission line (TL) with a 5 nm gap. (a) Experimental near-field image showing the real part, Re(Ep). (b) Experimental near-field amplitude image |Es| superposed on the SEM image (grey color). (c) Numerically calculated mode profile. (d) Near-field amplitude |Es| perpendicular to the TL extracted along the dashed lines in (b,c) (dots: experimental data, line: calculation), revealing an infrared mode diameter of only 30 nm. Imaging wavelength was λ0 = 9.3 µm.

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Quantum nonlocal effects in individual and interacting graphene nanoribbons I. Silveiro1, J. M. Plaza Ortega1, and F. Javier García de Abajo1,2 1

ICFO Institut de Ciències Fotòniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain 2ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Spain ivan.silveiro@gmail.com, javier.garciadeabajo@icfo.es Abstract We show that doped graphene narrow ribbons support near-infrared plasmons with important quantum nonlocal corrections. Remarkably, the removal of single-atom rows from extended graphene is enough to separate ribbons that strongly interact with incident light. We show that highly doped graphene ribbons can support surface plasmons at near-infrared frequencies when their width W is in the nanometer range. We rely on a quantum-mechanical approach to the optical response 1 that allows us to go beyond a classical local description in order to account for nonlocal and quantum finitesize effects. The latter are important for widths below W~10 nm, as revealed by comparison with classical theory2. In our work, we assess the magnitude of these effects by comparing classical and quantummechanical models to describe graphene plasmons. We also find strong influence of nonlocal effects on the orientation of graphene edges, as well as on the hybridization between ribbon plasmons in dimers and arrays for separations below a few nanometers. Specifically, the orientation of the edges relative to the graphene atomic lattice plays a crucial role, with zigzag edges contributing to damp the plasmons at energies above the Fermi level, due to the participation of electronic edge states. In contrast, armchair ribbons can support well defined plasmons at energies above EF. Remarkably, the removal of a single line of atomic bonds in a ribbon produces a strong plasmon frequency shift, whereas the removal of bonds along an array of lines separated by several nanometers in an extended sheet causes a dramatic increase in the absorption.

References [1] S. Thongrattanasiri, A. Manjavacas, and F. J. García de Abajo, ACS Nano 6, 1766 (2012). [2] S. Thongrattanasiri, I. Silveiro, and F. J. García de Abajo, Appl. Phys. Lett. 100, 201105 (2012).

Figures

We represent the plasmon peak energies of a graphene ribbon dimer (width W = 6 nm, Fermi energy EF = 0.4 eV, and intrinsic damping of 0.02 eV) as a function of the edge-to-edge distance d using classical and quantum-mechanical (for armchair ribbons, AC) models. The left figure shows the nearest separation dmin = 31/2a0/2 considered for the quantum AC calculations, where a0 = 0.1421 nm is the carbon-carbon bond distance.

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Novel plasmonic probes for Tip- Enhanced Raman Spectroscopy 1

Valentinas Snitka ,Lina Ramanauskaite , Huizhong Xu , Tomas Gadisauskas , Rasa Zukiene

1, 3

Research Centre for Microsystems and Nanotechnology, Kaunas University of Technology, Studentu 65, LT-51369 Kaunas, Lithuania Physics Department, St. John's University, 8000 Utopia Parkway Queens, New York, 11439718-9902000, USA 3 Department of Biochemistry, Vytautas Magnus University, K. Donelaicio 58, LT- 44248 Kaunas vsnitka@ktu.lt

Abstract

Hybridization of Atomic force microscopy with plasmonic probes stimulated the development of the several new spectroscopic techniques. Tip-Enhanced Raman Scattering (TERS) is the technique utilizing a special AFM probe (nano-antenna) to localize light at the nanometer scale area near the probe apex. TERS has emerged as a potentially powerful nanochemical analysis tool [1]. However, questions about the reproducibility of TERS data still remain a challenge [2]. The TERS data of biomolecules obtained in liquid open even more questions. A deep integration of AFM with confocal Raman microscopy is required for successful TERS experiment. In this work we investigated the application of novel AFM plasmonic probes for TERS fingerprinting of proteins ( ! –synuclein) and monitoring the structural changes during the protein interaction with nanoparticles. We used a commercial novel AFM-TERS probes (NT-MDT Inc.) and home made AFM-TERS probes made by chemical silver deposition on socalled “Top Visual” AFM Si cantilevers (NT-MDT Inc.). Top-illumination AFM-Tip-enhanced Raman scattering system adapted on an upright optical microscope have been used in our experiments. Simulation of localized plasmon electromagnetic field distribution between the tip and substrate was done using COMSOL software EM package. We evaluated the Raman enhancement spectra as a function of experimental variables such as excitation power, acquisition time, molecules type and substrate. Based on the spectra obtained, the peak positions, number of bands, peak intensity ratios, and comparability to reference micro-Raman data are discussed. This study demonstrated the suitability of investigated cantilevers to be used for biological TERS applications. References a [1] Hacksung Kim, Kathryn M. Kosuda, Richard P. Van Duyne and Peter C. Stair, Chem. Soc. Rev., 2010,39, 4820-4844 [2] Carolin Blum, Lothar Opilik, Joanna M. Atkin, Kai Braun, et all, J. Raman Spectrosc. 2014, 45, 22–31

c) Figure 1. AFM-TERS probes used in experiment: a) silver chemically decorated apex of the probe, b) NT-MDT probe based on so-called “Top Visual” AFM Si cantilevers.

TERS spectra of !-synuclein ( c).

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FDTD simulations of plasmonic metasurfaces 1,2

Roxana Tomescu , Cristian Kusko , Mihai Kusko , Paul Schiopu

National Institute for R&D in Microtechnologies Âą IMT Bucharest, 126A Erou Iancu Nicolae street, 023573, Bucharest, Romania 2) Faculty of ElecWURQLFV 7HOHFRPPXQLFDWLRQV DQG ,QIRUPDWLRQ 7HFKQRORJ\ 8QLYHUVLW\ Âł3ROLWHKQLFDÂ´ of Bucharest, 1-3 Iuliu Maniu Blvd., 061071, Bucharest Romania 1)

roxana.tomescu@imt.ro

Abstract In the last years, a large interest is shown to plasmonic nanostructures. Plasmonic meta-atoms and plasmonic metasurfaces are investigated in order to obtain optical components as light emitting diodes, lasers or optical nano-antennas [1]. It is demonstrated that plasmonic nano-antennas can introduce an abrupt phase shift, this phenomenon leading to the possibility to employ these structures for realizing metasurfaces with application in flat and singular optics [2,3]. Here we analyze the phase behavior of two types of plasmonic metasurfaces. The plasmonic structures investigated here are resonant structures operating in the subwavelength region. The resonators are i) two parallel dipoles and ii) V-shape resonators, respectively. We performed 3D FDTD simulations with realistic materials and we determined the phase shift of the transmitted and reflected waves as a function of wavelength (see Fig. 1) and as a function of material and geometrical parameters of the structures. We investigate, by performing FDTD simulations, the possibility to use these structures for flat optical components. References [1] N. Meinzer, W. L. Barnes, I. R. Hooper, Nature Photonics, PUBLISHED ONLINE: 27 NOVEMBER 2014 | DOI: 10.1038/NPHOTON.2010.247 [2] N. Yu, P. Genevet, M. A. Kats, F. Aieta, J.-Philippe Tetienne, F. Capasso, Z. Gaburro, Science 334, 333 (2011), DOI: 10.1126/science.1210713 [3] N. Yu, P. Genevet, F.Aieta, Mikhail A. Kats, R. Blanchard, G. Aoust, .-Philippe Tetienne, Z. Gaburro, F. Capasso, Â´ IEEE Journal of Selected Topics in Quantum Electronics vol. 19, 4700423 (2013) Figures

Fig.1 Phase behavior of a transmitted wave as a function of wavelength, after 3D simulations of : a) two parallel dipoles plasmonic resonator structure, b) V-shape plasmonic resonator structure This work has been funded by the Sectoral Operational Programme Human Resources Development 2007-2013 of the Ministry of European Funds through the Financial Agreement POSDRU/159/1.5/S/134398; 3URMHFW Âł6HFXUHG KLJK YROXPH IUHH VSDFH RSWLFDO FRPPXQLFDWLRQV EDVHG on computer geQHUDWHG KRORJUDPVÂ´ UEFISCDI Contract PN-II-PT-PCCA-2011-3.2-0862.

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Optical spectroscopy study of colloidal gold nanorods: model for thiolated nanorods 1,2

3,4

1,2

2,5

N. Zabala , F.J. Recio , L Bergamini , A. Ayuela , A. Rivacoba , P. Crespo , A. Hernando and 2,5 P.M. Echenique 1

Dept. Electricidad y Electrónica, FCT-ZTF, UPV-EHU, Bilbao, Spain Centro de Materiales CFM-MPC (CSIC-UPV/EHU) and DIPC, San Sebastian, Spain 3 Instituto de Magnetismo Aplicado, UCM-CSIC-ADIF and Dept. Física de Materiales, UCM, Madrid, Spain 4 Dept. Química de los Materiales, Univ. Santiago de Chile, Santiago, Chile 5 Dept. Física de Materiales, UPV-EHU, San Sebastian, Spain nerea.zabala@ehu.es

Abstract We report results on the optical response of thin nanorods (NRs) produced with a seed-mediated growth method followed by a filtering process [1]. In this way, anisotropic gold NRs are obtained with different aspect ratios and lengths covering the range between tenths to a few hundred of nanometers. Because of our interest in medical applications, gold NRs are dispersed in colloidal solutions, so that some molecules are bound to their surfaces and keep them partially separated. We use well-known solvents: first a CTAB-water solution, where gold NRs of different sizes are grown from Au NP seeds, and then a thiolate solution. The short and long Au NRs are characterized using HRTEM and UV-VisNIR spectroscopy. The study focuses on the long NR samples (L >100nm) obtained after filtering. In particular, understanding the origin of a peak that appears about 960 nm for several solvents and its evolution with the Au NR colloidal concentrations is one of the main challenges concerning the characterization of their optical response (Figure 1). We perform this study with the help of full electrodynamical boundary element method (BEM) calculations. The incorporation of a dielectric model based on ab-initio calculations of thiolate-gold cluster surfaces allows us to explain the trends observed in the spectra recorded for the samples of NRs covered with thiolates.

References [1] F.J. Recio, N. Zabala, A. Rivacoba, P. Crespo, A. Ayuela, P.M. Echenique and A. Hernando, J. Chem. Phys. C, to be published.

Figures

Figure 1: Absorption spectra of the long Au NR sample (average length L=390nm and width D=26nm) in aqueous CTAB solution (left) and in a thiolate solution (right).

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