Activity Report ICMAB / CSIC 2010, 2011 & 2012

Consejo Superior de Investigaciones Científicas Institut de Ciència de Materials de Barcelona Campus de la Universitat Autònoma de Barcelona 08193 Bellaterra (Catalonia) SPAIN Phone: +34 935 801 853 Fax: +34 935 805 729 www.icmab.es info@icmab.es

Graphic Dessing: Marcel Oliveres • imatge www.imatge.cat • imatge@imatge.cat Printing: Impremta Orriols • Balsareny Nº of copies: 500 issues Legal deposit: B-12355-2011

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TABLE OF CONTENTS REPORT • 2010/2011/2012 FOREWORD BY THE DIRECTOR

9

Introduction

SCIENTIFIC HIGHLIGHTS Battery materials research: new mechanisms for Li-ion and alternative Na-ion technology

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Universal Features of the electron density distribution in hydrogen bonding regions: A comprehensive study involving H···X (X=H, C, N, O, F, S, Cl, π) interactions

20

Filled and glycosylated carbon nanotubes for in vivo radioemitter localization and imaging

21

Colloquium: Structural, electronic, and transport properties of silicon nanowires

22

Single molecule magnet properties tuned by superstructure and redox state

24

Understanding and engineering the functional properties of multiferroic perovskite oxides

25

Novel concepts for organic position sensitive photodetectors and photovoltaics

26

Organic Molecules for Electronic Devices: Memories, Wires and Field-Effect Transistors

27

A close look to the atoms: advanced electron microscopies the eyes of nanoscience

28 29

Anion order in perovskite oxynitrides

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The long and winding road from metallorganic chemical solutions to epitaxial nanostructured YBa2Cu3O7 superconducting thin films Evidence of quantum confinement effects on interband optical transitions in Si nanocrystals

30

Novel multiferroic memories and materials

32 33

Nanoscale properties of novel protein based nanoparticles and their effect on cell proliferation

34

Valence transition and Pr/Co charge migration in (Pr,Ca)CoO3 cobaltites at the metal-insulator transition

36

Growth of functional oxide nanostructures by chemical solution deposition

37

Aggregation of superparamagnetic colloids in magnetic fields: the quest for the equilibrium state

38

Playing with Photonics and Plasmonics: a way to shape magneto-optical spectra

39 40

Two-dimensional electron gases in SrTiO3-based interfaces Metallacarboranes and their interactions: influence on the photoluminescence properties of high-boron content metallodendrimers

Supramolecular chirality in aromatic functional materials

41 42 43

Application of cluster-based direct methods to powder diffraction data of organic compounds

44

Relaxd but highly compact diansa metallacyclophanes

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TABLE OF CONTENTS REPORT • 2010/2011/2012 Breaking symmetry: a tool to engineer materials properties

45

Light on the light elements: a direct way to visualize O and N atoms and direct polarity determination in non-planar nanostructures

46

Crystallography of Incommensurate Magnetic Orders: Competing Ferroelectric Phases in Multiferroic Mn1-xCoxWO4

47

Electronic structure and anisotropic chemical pressure effects in single-component molecular conductors based on radical dithiolene and diselenolene gold complexes

48

Switchable resistive nanostructures embedded in low cost oxide thin films Ferromagnetism in transparent MgO thin films

49 50

Nanostrain approach to enhanced vortex pinning in solutionderived YBa2Cu3O7 superconducting thin films

52

TRAINING ACTIVITIES

55

TECHNOLOGY TRANSFER ACTIVITIES

61

THE ICMAB TEAM

64

25 YEARS

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FOREWORD BY THE DIRECTOR • 2010/2011/2012

INTRO

DUCTION

The present report of the ICMAB activities covers the years 2010-2012 and it is the twelve since the Institute’s creation in 1986. This means that during this period (2011) the Institute celebrated its first 25 years of life and so it was a perfect occasion to review our maturity as a renowned research center in advanced materials, the advancement in enhancing our international impact, our contribution to generate innovative technologies, as well as to foresee our future. Another important cornerstone of ICMAB’s life during this period was the official inauguration of our new scientific facilities belonging to the Nanotechnology Unit, the clean room Nanoquim (∼ 200 m2 of clean room composed of 5 laboratories fully equipped with diverse scientific equipment) and the Thin Film Laboratory (advanced Pulsed Laser Deposition equipment). All of them, together with the new office spaces at the 4th floor and our Photovoltaic roof, contribute to a renovated space for research (see Figure 1) and also they complete our expansion plan concerning the use of the ICMAB main building. These Laboratories have expanded our Scientific Equipment Platforms (SEPs) and they have helped to reformulate our strategy towards a progressive use of nanoscience tools in Materials R&D. This effort was completed with a strategic choice, installing a new Scanning Probe Microscopy Laboratory within the ALBA synchrotron facilities, to further enhance our commitment of using synchrotron radiation as an advanced tool in our research.

The necessary investments were performed mainly on the basis of CSIC funds and large research projects, such as Consolider Nanoselect and CIBER “Bioengineering, Biomaterials and Nanomedecine”.

The SEPs of ICMAB are now well integrated on the wide facilities of BNC-b grouped under the label of the International Excellence campus at Bellaterra, where the development of Nanoscience and nanotechnology has a top priority.

FIGURE 1 ICMAB celebrated its 25th anniversary and we gathered

many institutional personalities, colleagues and friends. This occasion was used also to inaugurate several of our new scientific facilities (clean room Nanoquim and Thin film laboratory by Laser Ablation).

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The mission of ICMAB is to generate new knowledge in Materials Science through excellent scientific research that is useful for society in general and for European industry, economy and employment. Our goals range from doing groundbreaking fundamental science on an international scene to technology transfer, with emphasis on researcher education at all levels. Contemporary materials science presents huge opportunities; new phenomenological discoveries, materials, properties and applications are anticipated. There is virtually no sector that cannot be transformed with disruptive discoveries in materials. Following these commitments we defined a flexible Strategic Program (SP) for the period 2010-2013 based on a matrix structure with three transverse methodological lines interconnected with three vertical, mission oriented, functionality lines perfectly fitting with the most outstanding challenges of our society: knowledge-based sustainable economy, new energy paradigm and improved quality of life (Figure 2).

Research and innovation in Materials Science and Engineering is a complex activity. It covers the discovery of new materials, their definition in a given form, the control of their structure and functionality at the nanometric scale to define the conditions

to achieve specific performances and finally the integration into specific devices, which should work under well determined conditions defined by the specific application. The road from the materials to the device is therefore long and winding and our Strategic Program is defined to cope at best with this reality in order to promote the reindustrialization process based on Key Emerging Technologies (KETs) which has been defined under the scheme of the European 2020 Horizon Programme. The three transverse research lines have essentially the purpose of creating new knowledge which can then be used to advance in the vertical mission-oriented research lines. The final output of the oriented research lines go beyond the generation of knowledge, they should also generate innovations and economic value through technology transfer.

The ICMAB is organized scientifically around Research Groups which are at the core of our scientific initiatives. They may contribute to several items of our Strategic Program and the matrix structure is very well adapted to promote synergetic initiatives among them. At the end of 2012 ICMAB had 57 permanent scientists (49 CSIC, 6 ICREA, 2 CIBER) and 96 non-permanent ones over a total of 208 employees.

Our scientists are distributed among ten consolidat-

FIGURE 2 Matrix structure of the ICMAB Strategic Plan: three transverse methodological lines are interconnected with three vertical,

mission oriented, functionality lines.

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FOREWORD BY THE DIRECTOR • 2010/2011/2012

FIGURE 3 List of Consolidated and Emerging Research Groups of ICMAB. The name of Group leader is indicated together with the number of PhD members and the keywords of the groups. Data corresponds to end of 2012.

FIGURE 4 Citation report of WOK for ICMAB in the period 19942012, including number of published articles and accumulated citations.

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ed research groups and 7 emerging ones (Figure 3).

Analysis of the research ouputs of ICMAB during the 2010-2012 period reinforces the idea that we have reached a strong international leadership position during the first 25 years of our life. At the end of 2012 the ICMAB researchers had published 3.370 articles which accumulated more than 70.000 citations (>8.800 cit/yr in 2012), leading to an h factor of 101, i.e. 101 articles have been cited more than 101 times (Figure 5). This is indeed an outstanding figure that not many public institutions in Spain hold. Our distinctive feature is interdisciplinarity with research areas: our publications are distributed by ISI-WOK in journals devoted to Materials – Multidisciplinary, Applied Physics and Condensed Matter Physics (25%), to Chemistry – Multidisciplinary and Physical Chemistry (20%) and Nanoscience and Nanotechnology (13%). Our objective during the last years has been to increase the impact of our articles, a feature which is clearly reflected in the increase of the mean Impact

Factor of the journals where we publish (Figure 5).

A list of the number of articles published in the most outstanding journals of the scientific areas where the ICMAB has more presence is shown in Figure 7 where it is evidenced the high standards achieved and the diversity of scientific fields where we are present. Our international competitiveness and efficiency as a research center can be monitored through a comparison of some of our research outputs with those of other leading centers around the world, as it is shown in Figure 7. A few leading research centers from Europe and Asia are included. The figure shows, for instance, that the ICMAB has the largest number of articles per researcher in the first quartile journals (journals ranked in the top 25% in terms of impact). This parameter is indicative of a large effort in being efficient in the use of our manpower and it is even more remarkable when one considers that our budget per capita is about half of that of some of these leading centers (NIMS for instance). Our in-

FIGURE 5 Evolution of the number of ICMAB scientific publications distributed by impact factor of the journals from 2004 to 2012,

together with the evolution of the mean value of the impact factor.

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FOREWORD BY THE DIRECTOR • 2010/2011/2012

FIGURE 6 Number of articles published during 2010-2012 in a selection of journals of high impact index. The scientific disciplines of

the journals are also indicated.

ternational competitiveness is confirmed by other indicators, for instance 15-20% of our articles are placed among the top 10% most cited in the world, about 60% of our articles are made with international collaboration and we lead about 40% of the published articles. In all these parameters we are ranked in positions similar to the international excellence centers included in Table 2.

In addition to our outstanding scientific achievements we also continue to make progress in our effort for training young scientists and for developing technology transfer initiatives. On one hand, we have produced during the years 2010-2012 32 new PhDs (completing 176 PhDs since the creation of the ICMAB). On the other hand, we have filed 27 patents related to energy, biomedicine, pharmaceutical, opti-

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FIGURE 7 Comparison of ICMAB scientific indicators with those of a few selected international reference centers in the area of Materials Science.

cal, electronic or magnetoelectronic applications. We have licenced 7 of our patents to industry and we have also created two spin-off companies (Oxolutia and Nanomol Technologies). Oxolutia is devoted to the preparation of low cost superconducting tapes and functional nanocoatings for electrical energy sector and the core technology is chemical solution deposition. It was promoted by members of the Superconducting materials and Large scale nanostructures group. Nanomol Technologies wants to exploit the business potential on micro and nanostructuration of active molecules for the pharmaceutical, biotech and cosmetic sectors. The company bases its activities in the development of micro and nanostructured polymeric composites and it was promoted by the Molecular nanoscience and organic materials group.

Overall, therefore, our technology transfer activities are a strategic choice.

During the period 2010-2012 four new scientific staff members were incorporated to the ICMAB, together with several promotions, in spite of the shortage in public positions. We are particularly proud that two

new ICREA research professors, a highly renowned scientific position supported by the Catalan government, have decided to joint ICMAB for their R&D activities. We welcome Prof. Max Stengel, as a renowned specialist in Solid State Theory, and Prof.

Nuria Aliaga-Alcalde, as an expert on functional molecular materials. Overall, at present a total of 6 staff members of the ICMAB are ICREA Professors, i.e. about 11 % of our scientific personnel, the largest ratio among all the CSIC centers in Catalonia. We also would like to congratulate Dr. Dino Tonti (2011) and Dr. Mariano Campoy Quiles (2012), as well as Dr. Martí Gich (2013), for their success in obtaining CSIC Tenured Scientist positions at the ICMAB. We have also incorporated Dr. Xabier Turrillas (2013), a CSIC Tenured Scientist who has been incorporated at the ICMAB under the scheme of “Long-term collaborator” associated with the synchrotron ALBA. As promotions in the CSIC within the ICMAB, we congratulate Dr. Teresa Puig who became Research Professor and Dr. Concepción Domingo and Dr. Xavier Torrelles who were promoted to Scientific Researchers. We

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FOREWORD BY THE DIRECTOR • 2010/2011/2012 are convinced that all of them will deeply contribute to enhance the excellence of the ICMAB and we wish them a very successful continuation of their scientific career at the ICMAB. Unfortunately we had during this period a very sad event when Dr. Salvador Piñol (2010), a member of our research staff, passed away.

The international flavor of the ICMAB has become a key point in our daily life: we have had a total of ∼25 nationalities cohabitating at ICMAB with about 29 % of the total scientific staff from abroad (∼15% of our permanent staff and ∼40% of our PhD students).

We would like to stress that the positive evolution of the scientific indicators of the ICMAB during the 2010-2012 period are a sign of the extreme professionalism, imagination and commitment of our scientific and support staff which have allowed to keep track under a general regressive environment for R&D support. We should stress, however, that there is a general concern about the near future and how

to keep the international competitiveness of our Institute under an environment which requires a renewed momentum and committing to a more competitive economy based on knowledge and innovation.

The ICMAB has been able to keep a reasonable stable total budget in the years 2010-2012 (11.5-12.0 M€/ yr) through a continuous increase of the competitive income which has been raised up to ∼60 %. However, the continuous decrease of the non-competitive funds from CSIC and from the competitive research funds from national origin appear as our main concern at present for the near future.

In order to gain critical mass at international level and to foster further synergy in our research program the ICMAB has given full support to the initiatives fostered by the Barcelona Nanocluster at Bellaterra (BNC-b, www.bnc-b.eu), as a virtual association including all the research Institutes (ICMAB; Institut of Nanoscience and Nanotechnology, ICN2;

FIGURE 8 H index and number of citations per article produced in the 2010-2012 period for the ICMAB and the BNC-b, compared with

several countries and Spanish regions. The statistic analysis was made in December 2013 using WOK and the output is ordered based on the number of cit/art.

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FIGURE 9 Number of articles in high Impact Factor journals, produced during the period 2010-2012 by BNC-B, Catalonia and Spain. In

parentheses we indicate the ICMAB contribution to these indicators. Articles considered from Nature, Science, Reviews of Modern Physics and Physical Review Letters are those related to the areas of Materials Science, Condensed Matter Physics, Chemistry and Nanotechnology.

Institut of Microelectronics of Barcelona, IMB), several research groups from Universitat Autònoma de Barcelona and the synchrotron center ALBA. This virtual association included ∼700 researchers in 2012, it is one of the largest hubs related to Materials Science and Nanotechnology in South Europe and at present it is coordinated by the Director of ICMAB. Actually, the BNC-b researchers produce about 40 % of the Catalan scientific publications identified by “nano” (WOK-ISI) while ICMAB contributes to about 1/3 of this knowledge generation. The relative impact of ICMAB researchers in this “nano” area is also very significant. Figure 8 compares the impact of nanorelated publications of the ICMAB and the BNC-b, as measured by the h factor and number of citations per article, with those of different countries, mainly those having a similar size to Catalonia, and also of a few Spanish regions. Additionally, Figure 9 signals the number of contributions to a selected list of the highest impact journals in the areas where ICMAB is active. As it can be seen, the relative weight of ICMAB and BNC-b to the Catalan and Spanish scientific

high impact production is very significant. Typically, 30-50% of Bnc-b, 20-40% of. Catalonia and 10-15% of Spain.

Finally, I would like to invite you to examine in the printed version of this report a selection of 31 scientific highlights achieved by the ICMAB researchers, together with some information about our training activities (PhDs hold during the three years), technology transfer initiatives, and the novelties of our scientific platforms. In the electronic version of the report (available through the web site and the QR reader system included in this printed version) a full list of all the publications, research projects and invited talks of the ICMAB researchers are provided.

Also I invite you to surf, as often as you want, through our web site (www.icmab.es) where we continuously include news, highlights, achievements, and much more relevant information that may be of your interest.

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XAVIER OBRADORS Director / ICMAB - CSIC

FOREWORD BY THE DIRECTOR • 2010/2011/2012

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Battery materials research: new mechanisms for Li-ion and alternative Na-ion technology A. Ponrouch, E. Marchante, M. Courty, J.M. Tarascon, J. Cabana, L. Monconduit, D. Larcher, P. Senguttuvan, G. Rousse, V. Seznec, M.R. Palacín Advanced Materials, 22 (2010), E170 • Chemistry of Materials, 23 (2011), 4109 Energy & Environmental Science, 5 (2012), 8572 Despite the implementation of Li-ion batteries in electric drive vehicles and their proposed use as enablers of renewable energy technologies, an intensive quest for new electrode materials that bring about improvements in energy density, cycle life, cost and safety is still underway. By moving beyond classical intercalation reactions to the conversion type mechanism, a variety of low cost compounds with very high energy densities can be attained. Nonetheless, there are several issues that still keep such compounds far from commercial application. The most relevant is the staggering voltage hysteresis observed between discharge and charge, which severely diminishes the roundtrip efficiency of the electrode. Despite the undeniable difficulties ahead, the fundamental knowledge on electrode performance in Li-ion cells that has been achieved in the last 20 years and future research efforts should enable significant progresses to be made in the next years. The promise of doubling the storage capacity certainly justifies the attention of the materials science community to this fascinating reactivity.

Aside from the above mentioned considerations, the implementation of a lithium based technology on a large scale faces controversial debates on lithium availability and cost. An appealing alternative, especially for electric grid storage, would be to use sodium, instead of lithium. While a variety of phases that can potentially be used as positive electrodes in sodium ion batteries have been reported, the choice on the negative side is much more restricted. Hard carbon is currently the most commonly used one but its potential versus composition profile exhibits a plateau very close to 0V which may rise safety concerns at high rates due to risk of sodium plating. When it comes to transition metal oxides as alternative, the choice is rather limited owing to the competition of insertion vs. conversion reactions.

We identified Na2Ti3O7 reversibly uptaking 2 Na ions

per formula unit (200 mAh/g) at a surprisingly low average potential of 0.3 V through a two phase redox mechanism (see Figure). This is the first ever reported oxide to reversibly react with sodium at such a low potential, which, for a somewhat dense material (3.4 g/cm3) is extremely beneficial in terms of energy density. As an extension of this work, studies aimed at electrolyte optimization resulted in the identification of EC:PC as the most suitable solvent mixture enabling the formation of a stable SEI layer.

FIGURE 1 Potential versus composition profile for sodium titanium oxide when tested in sodium cells.

OTHER REFERENCES:

- M. R. Palacín, Chem. Soc. Rev. 2009, 38, 2565.

- P. Senguttuvan, M.R. Palacín, J.M. Tarascon. PCT application FR2012/051518 - F. Gillot, J. Oró-Solé, M. R. Palacín. J. Mater. Chem. 2011, 21, 9997.

- A. Ponrouch, P.L. Taberna, P. Simon, M.R. Palacín. Electrochim. Acta.

2012, 61, 13.

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Universal Features of the electron density distribution in hydrogen bonding regions: A comprehensive study involving H···X (X=H, C, N, O, F, S, Cl, π) interactions I. Mata, I. Alkorta, E. Molins, E. Espinosa

Chemistry. A European Journal, 16 (2010), 2442

The quantum theory of atoms in molecules is extensively used for the analysis of hydrogen bonds from the electron density, which can be obtained from quantum chemistry calculations or experimentally, from X-ray diffraction. A series of properties, known as topological properties, may be derived from the electron density around the hydrogen bond providing information about the nature of the interaction.

It has been seen that similar hydrogen bonds present simple dependencies of these properties with the hydrogen bond distance. We have been exploring how similar hydrogen bonds need to be in order to show these dependencies and what they are telling us about hydrogen bonds.

Our analysis indicates that hydrogen bonds can be classified in families according to the acceptor atom, and that each family is characterized by the dependencies of the topological properties with the bonding distance. Notoriously, the same dependencies have been observed from theoretical and experimental data. There is a wide range of interaction distances inside each family, which means that hydrogen bonds

with the same acceptor can present a wide range of equilibrium distances. According to our picture, the substituents bonded to donor and acceptor, as well as the environment (crystal field, solvent, etc), determine the equilibrium distance and its topological properties according to the aforementioned dependencies. For a certain property, the dependencies for the different families are ordered according to the position of the acceptor atom in the periodic table (Figure 1), which suggests the effect of the electronic configuration of this atom on the hydrogen bond.

From the point of view of the electron density analysis, any hydrogen-acceptor interaction can be considered as a hydrogen bond, independently of the acceptor or of what is bonded to the hydrogen.

These results are important for understanding the nature of hydrogen bond and for the analysis of the experimental electron density. Going a step further, we are exploring the relationship of the topological properties with the interaction energy with the idea of extracting information about the interaction energies in molecular crystals from diffraction data (Figure 2).

FIGURE 1 Electron density at the bond critical point, one of the

FIGURE 2 Interaction energy as a function of the hydrogen bond distance and a parameter δ associated to the substituent, in hydrogen bonds where fluorine is the acceptor. Solid line indicates the shortening of the equilibrium distance as δ increases, strengthening the bond.

topological properties that can be calculated from the electron density, as a function of the hydrogen bond distance. Each point is a hydrogen bond at its equilibrium distance. Points are colored according to the acceptor atom. Lines corresponds to hydrogen bonds families. Lines appear ordered according to the atomic number of the acceptor atom.

OTHER REFERENCES:

- I. Mata, E. Molins, I. Alkorta, E. Espinosa, J. Phys. Chem. A (2011) 115, 12561 - I. Mata, I. Alkorta, E. Molins, E. Espinosa, Chem. Phys. Lett. (2011) 507, 185

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Filled and glycosylated carbon nanotubes for in vivo radioemitter localization and imaging S.Y. Hong, G. Tobias, K.T. Al-Jamal, B. Ballesteros, H. Ali-Boucetta, S. Lozano-Perez, P.D. Nellist, R.B. Sim, C. Finucane, J.S. Mather, M.L.H. Green, K. Kostarelos, B.G. Davis

Nature Materials, 9 (2010), 485-490

Tailored functionalization of nanomaterials for biomedical applications is an emerging trend in nanotechnology. Carbon nanotubes offer an attractive platform for the development of “smart” systems for drug delivery, diagnosis and therapy. Multifunctional carrier systems based on carbon nanotubes can be designed in which their internal cavity encapsulates a chosen payload whilst the outer surface is chemically modified to match specific needs. Yet, despite their potential as drug delivery systems and radiotracers, such filled and functionalized carbon nanotubes (carbon nanocapsules) have not been previously investigated in vivo. In this paper we report the covalent functionalization of radionuclide-filled single-walled carbon nanotubes and their use as radioprobes.

Metal halides, including Na125I, were sealed inside single-walled carbon nanotubes to create highdensity radioemitting crystals and then surfaces of these filled–sealed nanotubes were covalently modified with biantennary carbohydrates, improving dispersibility and biocompatibility (Fig. 1). Intravenous administration of Na125I-filled glyco-single-walled carbon nanotubes in mice was tracked in vivo using single-photon emission computed tomography. Specific tissue accumulation (here lung) coupled with high in vivo stability prevented leakage of radionuclide to high-affinity organs (thyroid/stomach) or excretion, and resulted in ultrasensitive imaging and delivery of unprecedented radiodose density. Nanoencapsulation of iodide within single-walled carbon nanotubes enabled its biodistribution to be completely redirected from tissue with innate affinity (thyroid) to lung.

These nanocapsules remain stable for extended periods thus guaranteeing essentially zero leakage of the radionuclides. Surface functionalisation of these

nanocapsules offers versatility towards modulation of tissue biodistribution of the radioemitting crystals in a manner determined by the nanocapsule that delivers them. The delivery of radioactivity takes place through the walls of the nanocapsules and release of the encapsulated radionuclides is therefore not needed and certainly not desired.

Further studies on these systems are now being performed within the frame of the RADDEL (RADioactive DELivery) project (http://www.icmab.es/raddel), an Initial Training Network (ITN) funded by the European Commission under the FP7-PEOPLE program (20122016).

FIGURE 1 Schematic representation of the developed radiotracers.

Carbon nanotube are shown in grey, encapsulated radionuclides in yellow and red, and the carbohydrates in white.

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Colloquium: Structural, electronic, and transport properties of silicon nanowires Riccardo Rurali

Reviews of Modern Physics, 82 (2010), 427–449

One-dimensional nanostructured systems have attracted a great attention in the last two decades, with this interest extraordinary boosted by the facile synthesis of carbon nanotubes (CNTs) reported in the beginning of the 90s. The reason is twofold: on the one hand they have proved to be an excellent test-bed to study the most intriguing physical effects, whereas on the other hand they are believed to be among the most important building blocks of the next generation of electronic devices. Nanowires are an extremely attractive alternative to CNTs, because it is much easier to control their electrical properties and, as long as the surface is properly passivated —something that occurs naturally during or right after growth—, they are invari-

ably semiconducting. Silicon nanowires (SiNWs), in particular, look like a very appealing choice, since they provide the ideal interface with the existing Si devices, while taking advantage from a tractable material technology.

Nanowires could provide the paradigm shift needed to continue improving the density and the performances of electronic circuits. For almost four decades the increase in computing power has been described by the well-known Moore’s law, which has been standing on three pillars: (a) the increase of the size of the microchips; (b) the reduction of the transistor size, and (c) the circuit cleverness, that is the reduction of the number of devices required to perform a certain function. While the first

FIGURE 1 Hexagonal cross section of <110> SiNWs. (a) TEM images of 3.8 nm SiNWs, (c) high-resolution TEM cross-sectional image, and equilibrium shapes for (b) the NW and (d) the NW cross sections predicted by Wulff construction. The scale bars are 5 nm. [Wu et al., Nano Lett. 4, 433 (2004).]

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SCIENTIFIC HIGHLIGHTS â&#x20AC;˘ 2010/2011/2012

FIGURE 2 Optimized structures of possible cross sections of H-passivated SiNWs grown along (a, b) the <110>, (c, d) the <100>, and (e) <112> orientations. Adapted from [Singh et al., Nano Lett. 6, 920 (2006)]

of these driving forces played a significant role only in the pioneering years of solid-state electronics, the reduction of device size has a pivotal role, since the physical limit of material scaling is rapidly approaching.

Nanowires can lead to an obvious benefit concerning the miniaturization, thanks to bottom-up growth that allows overcoming the limit of conventional lithography-based top-down design. Subtler are the perspective advantages concerning circuit cleverness, which can be significantly improved by taking advantage of the coexisting nature of interconnection and active device of nanowires.

Additionally, compared to classical planar device technology, nanowires can better accommodate all-around gates, which improve field-effect efficiency and device performances with respect to conventional Si devices.

Several promising applications have already been demonstrated, ranging from electron devices, logic gates, non-volatile memories, photovoltaics, photonics, to biological sensors. On top of that, giant piezoresistance effect and enhanced

thermoelectric performances have recently been reported. The control of matter at the atomic-molecular scale is one of the key targets of modern nanotechnology and theoretical modeling is essential to its achievement. Within the broad range of devices and structures, nanowires play an important role, not only because these structures may become useful in future applications, but also because of new quantum effects present. Many of the unique properties of these systems are at the same time defying challenges and opportunities for great technological advances. This Colloquium reviews some of the main aspects of the theory of Si nanowires from crystal properties to electronic behavior and is a useful reading for anyone interested in the recent developments in this fast growing field. The theory group of the Institute works actively in the computational modelling of nanowires and other one-dimensional systems such as carbon nanotubes.

OTHER REFERENCES:

- Amato, M., Ossicini, S., Rurali, R. Nano Letters 12 (6), 2717-2721 (2012) - Chaste, J., Eichler, A., Moser, J., Ceballos, G., Rurali, R., Bachtold, A. Nature Nanotech. 7 (5), 301-304 (2012)

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Single molecule magnet properties tuned by superstructure and redox state M. Gonidec, F. Luis, À. Vílchez, J. Esquena, E.S. Davies, J. McMaster, D.B. Amabilino, J. Veciana

Journal of the American Chemical Society, 132 (2010), 1756-1757 Angewandte Chemie Int. Ed. 49 (2010), 1623-1626 • Dalton Transactions, 41 (2012), 13632-13639

Molecules comprising terbium sandwiched between two phthalocyanines macrocycles behave as single molecule magnets (SMMs), and we have shown that both structural order of the molecules in soft matter and the redox state of the molecules in solution can affect this magnetic behaviour.

A liquid crystalline terbium bis(phthalocyanine) (see polarised optical micrograph below) can have its structural order modified by cooling rate. The different structures reveal a different weight in the relaxation processes taking place in the SMM. A reversible change of the magnetic properties was achieved by simple heating and cooling cycles which proved the lack of any compositional change. The discovery was achieved thanks to the synthesis of a room-temperature liquid-crystalline molecular material whose chiral groups affect dramatically its phase behaviour.

Also, the optical magnetic circular dichroism technique was used for the characterization of a bis(phthalocyaninato) terbium-based SMM in frozen solution, ensuring magnetic insulation from neighbouring molecules. The magnetic properties of three different redox states (see Figure) were studied, and we were able to show that the neutral complex has a greater coercive field than either its oxidized or reduced states.

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Understanding and engineering the functional properties of multiferroic perovskite oxides Jorge Íñiguez, Oswaldo Diéguez, Jacek C. Wojdel and Carlos Escorihuela-Sayalero

Physical Review Letters, 105 (2010), 037208 • Physical Review Letters, 107 (2011), 057601 Physical Review Letters, 109 (2012), 247202

One of the most active research lines in ICMAB’s laboratory for materials theory and simulation focuses on the functional properties of complex oxides. In particular, in recent years we have devoted much effort to the so-called magnetoelectric multiferroic materials, which exhibit coexisting and coupled magnetic and ferroelectric orders and permit novel functionalities such as, for example, the control of the magnetic state and properties by means of an applied electric bias. In particular, we have explored different routes to achieve large magnetoelectric (ME) effects at room temperature, as needed for the application of these materials in actual devices. Thanks to new quantummechanical simulation methods, some of which were developed in our own group, we were able to demonstrate two viable alternatives to achieve this goal: (1) We showed that it is possible to obtain large ME responses in a regular multiferroic by inducing structural softness, i.e., by tuning the material to make its structure strongly reactive to applied fields (see first highlighted reference). (2) We predicted that it is possible to obtain very large phase-change responses of various kinds (piezoelectric, electric, magnetoelectric) by controlling the structural phase of a suitably prepared material via the application of electric fields (see second highlighted reference). Both possibilities were predicted to occur in BiFeO 3, one of the few materials that are magnetoelectric multiferroic at room temperature, when the compound is grown either in the form of a thin film or as a solid solution with related multiferroic BiCoO 3. Preliminary experimental confirmation of our predictions has been obtained by various international groups.

Our work also covers the investigation of the peculiar electric and magnetic properties of novel phases that can be obtained in materials grown as thin films, which display strained states that are not accessible

otherwise. For example, the third highlighted reference is devoted to the investigation of the magnetic properties of the so-called super-tetragonal phases of BiFeO3, which is one of the best-studied and most promising states recently discovered. Remarkably, we found out that such a structure presents a novel form of magnetically-frustrated state, even though there is nothing in its lattice topology that would hint at such an unconventional behavior.

FIGURE Calculated energy of a BiFeO 3 thin film as a function of

the in-plane strain exerted by the substrate. Results are given for two competing phases – bulk-like rhombohedral (R) and supertetragonal (T) – and we indicate the structural instabilities that lead the transition from one to the other at the boundaries of the coexistence region. (Taken from first reference cited above.)

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Novel concepts for organic position sensitive photodetectors and photovoltaics T. Agostinelli, S. Lilliu, J.G. Labram, M. Hampton, E. Pires, J. Rawle, O. Bikondoa, D.D.C. Bradley, T. D. Anthopoulos, J. Nelson, J.E.MacDonald, M. Campoy-Quiles

Advanced Functional Materials, 21 (2011), 1701-1708 • Advanced Materials, 22 (2010), 3942

Position sensitive detectors (PSD) are a type of device that allows to detect where light hits the surface of the detector. This has multiple application from telecommunications (laser alignment) to robotics (following the movement of objects) and in medical imaging. Small area PSD are based on single pixel resistive components with good accuracy over small distances, while large area are based on arrays of detectors which often have lower resolution and increased complicated electronics to drive them.

We have introduced a novel concept for the fabrication and configuration PSD based on organic semiconductors which allows simultaneously large area and high resolution on a single pixel. This concept is based on organic photodiodes deposited on a configuration consisting of a donor/acceptor bilayer with opposed complementary thickness gradients (Fig. 1

a). The new PSD rely on the strong dependence of the optical field on thickness to achieve spatially dependent spectral responses (Fig. 1b), a proof-of-concept for position sensitive detection. Ratiometric photocurrent values at two wavelengths allow for position determination (Fig. 1c) independently of the light intensity with a spatial resolution below 500 micrometers over six milimiters.

This new technology, including the concept, fabrication and method for measuring, has been patented (PCT/ES2011/070841) by researchers at ICMAB in collaboration with the IMDEA Nanociencia. Based on our advances on the understanding of how morphology influences performance, we are working on extending the above results to solution processable photovoltaics.

(a) Configuration of the organic position sensitive photodetector. (b) Spectral response at four different points. (c) Position sensitive photorresponse.

OTHER REFERENCES:

FIGURE 1

- J. Cabanillas–Gonzalez, O. Peña–Rodríguez, I. Suarez Lopez, M. Schmidt, M. I. Alonso, A. R. Goñi and M. Campoy–Quiles, Applied Physics Letters, 99, 103305 (2011) - M. Campoy Quiles and J. Cabanillas Gonzalez, Fotodetector sensible a la posición, procedimiento de obtención del mismo y procedimiento de medida de la respuesta del fotodetector. Patent reference: PCT/ES2011/070841 - M. Campoy-Quiles, T. Ferenczi, T. Agostinelli, P. G. Etchegoin, Y. Kim, T. D. Anthopoulos, P. N. Stavrinou, D. D. C. Bradley and J. Nelson, Nature Materials, 7, 158-164 (2008)

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Organic Molecules for Electronic Devices: Memories, Wires and Field-Effect Transistors R. Pfattner, I. Bilotti, A. Brillante, S. Milita, F. Liscio, F. Biscarini, T. Marszalek, J. Ulanski, A. Nosal, M. Gazicki-Lipman, M. Leufgen, G. Schmidt, L. W. Molenkamp, V. Laukhin, C. Simão, M. Mas-Torrent, N. Crivillers, V. Lloveras, J. M. Artés, P. Gorostiza, J. Veciana, C. Rovira Advanced Materials, 22 (2010), 37, 4198 Nature Chemistry, 3 (2011), 359 • Chemical Reviews, 111 (2011), 4833

The increasing interest in miniaturizing electronic devices to achieve denser circuits and memories will eventually entail the utilization of molecules as active components. In particular, self-assembled monolayers (SAMs) of bi-stable molecules offer great perspectives to develop memory devices. We recently have reported the functionalization of surfaces (SiO2, ITO and Au) with electroactive molecules such as polychlorinated triphenylmethyl (PTM) radicals and tetrathiafulvalenes (TTF). Such hybrid organic/inorganic surfaces behave as chemical and electrochemical redox switches with bi or tri-stable optical (absorption and fluorescence), wettability and magnetic responses. Importantly, these systems exhibit an exceptionally high long-term stability and excellent reversibility and reproducibility (Figure 1).

All these robust molecular platforms permit hence to write, store and read information, which is very promising for developing non-volatile memory devices, of great interest in Molecular Electronics. We have also demonstrated conductivity thorough single molecules both in solution and grafted to surfaces.

From a different perspective, organic-based devices are currently attracting great attention for applications where low-cost, large area coverage and flexibility are required. In addition, the versatility of

FIGURE 2 Up. Optical microscopy image of a single crystal fieldeffect transistor based on DT-TTF. Down. Output characteristics of a single crystal DT-TTF OFET.

organic synthesis allows for the preparation of materials “à la carte”. We have shown that organic fieldeffect transistors (OFETs) based on TTFs exhibit excellent OFET mobility (up to 6 cm2/Vs) as well as easy processability. Our recent work is related to explore the influence of crystal structure, polymorphism, electronic structure and device configuration and interfaces in TTF OFETs (Figure 2).

OTHER REFERENCES:

Self-assembled monolayers (SAMs) of PTM radicals on ITO surfaces showing their bi-stability and the optical and magnetic outputs that can be employed as read-out.

FIGURE 1

- C. Simão, M. Mas-Torrent, J. Casado-Montenegro, F. Otón, J. Veciana, C. Rovira. J. Am. Chem. Soc. 2011, 133, 13256.

- C. Simão, M. Mas-Torrent, J. Veciana, C. Rovira, Nano Lett. 2011, 11, 4382.

- F. Otón, V. Lloveras, M. Mas-Torrent, J. Vidal-Gancedo, J. Veciana, C. Rovira. Angew. Chem. Int. Ed. 2011, 50, 10902 - V. Lloveras, et al. J. Am. Chem. Soc., 2011, 133, 5818.

- N. Crivillers, M. Paradinas, M. Mas-Torrent, S. T. Bromley, C. Rovira, C. Ocal, J. Veciana. Chem. Commun. 2011, 47, 4664 - F. Oton, et al. Chem. Mater., 2011, 23, 851.

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A close look to the atoms: advanced electron microscopies the eyes of nanoscience E. González, J. Arbiol, V.F. Puntes

Science, 334 (2011), 1377-1380

New materials for future applications are nowadays being synthesized at nanoscale (ultrathin layers, complex nanoparticles, nanowires, soft matter nanostructures or nanotubes, functionalized for novel applications). As developments in Materials Science are pushing to the size limits of physics and chemistry, there is a critical need for the structural, chemical and morphological characterization of the synthesized nanostructures at atomic scale in order to correlate these results with the physical and chemical properties and functionalities they have. In this way, a worldwide increasing interest for electron microscopy is emerging. Imagine being able to hold an electron beam over a single atom for 2 entire seconds in order to actually directly SEE and acquire information. The answer nowadays is “YES, we can make it and SEE single atoms!” The advent of aberration-corrected transmission electron microscopy technology

is now giving resolutions below 0.05 nanometers enabling single atoms to be directly viewed and analyzed. The Group of Advanced Electron Nanoscopy at ICMAB-CSIC, leaded by Prof. Jordi Arbiol is pushing the resolution of electron microscopy to the limits.

As consequence of this, looking face to face at single atoms is the daily task of this group. Despite that the advanced facilities they require are placed at the moment abroad, the multiple collaborations they have with some of the top most labs and universities are resulting in the consecution of great results as the ones highlighted here: as visualizing for the first time the atomic structure of dreamed complex nanoparticles, untangling new growth mechanisms or novel electronic properties of nanomaterials or obtaining the structure and chemical properties at the atomic scale of novel nanostructures.

FIGURE Atomic scale structural analysis of Au/Ag and Au/ Pd/ Ag of double-walled nanoboxes and chemical analysis at the nanoscale.

OTHER REFERENCES:

- A. Llordés, et al. Nature Materials, 11 (2012), 329-336.

- I. Ojea-Jiménez, et al. ACS Nano, 6 (2012), 2253-2260.

- M. Epifani, et al. Adv. Funct. Mat., 22 (2012), 2867-2875.

- A. Carretero-Genevrier, et al. J. Am. Chem. Soc., 133 (2011), 4053-4061.

- M. Ibáñez, et al. J. Am. Chem. Soc., 134 (2012), 4060-4063.

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Anion order in perovskite oxynitrides M. Yang, J. Oró-Solé, J. A. Rodgers, A.B. Jorge, J. P. Attfield and A. Fuertes

Nature Chemistry, 3 (2011), 47

Transition metal oxynitrides with perovskite type structures are an emerging class of materials with important properties, for example, as photocatalysts that generate hydrogen from water for clean energy applications, as high permitivity dielectrics and colossal magnetoresistance materials. Their properties are expected to be sensitive to any ordering of oxide and nitride anions, but the ordering principles in this class of materials were unclear. The properties of perovskites are known to be sensitive to small structural distortions that may arise from tilting or rotations of the MX6 octahedra.

We have investigated anion order in the representative oxynitride perovskites SrNbO2N and SrTaO2N using electron diffraction and powder neutron diffraction patterns collected at temperatures between 25 and 750 °C. At high temperatures (≥ 300 °C for SrNbO2N or ≥ 200 °C for SrTaO2N) only the peaks expected from a cubic perovskite are observed.

However, refinements of anion site occupancies in a tetragonal model gave a stable fit with the anion distribution shown in figure 1a. This sensitivity to anion populations arises from the high neutron scattering contrast between oxygen and nitrogen. The anion order is observed up to the highest measured temperature of 750 °C for SrTaO2N. At 25 °C, SrNbO2N and SrTaO2N both adopt a perovskite superstructure in which rotations of MX6 octahedra are ordered. The rotational perovskite superstructure is usually described by the tetragonal space group I4/mcm, but the observed anion order is predicted to lower symmetry through loss of the c-glide operation. This is confirmed by electron diffraction studies of both materials, and of other perovskites EuNbO2N, EuTaO2N and EuWON2, which show that the coupling between rotational and anion orders is a common phenomenon in oxynitride perovskites. The robust partial anion order observed in SrMO2N (M = Nb, Ta) by neutron diffraction is consistent with a well-defined short range order. This is driven by covalent effects which stabilise the cis- (90°) configuration of MN2O4 octahedra, as nitride is more strongly bonded to the d0 transition metal M cations than oxide. The combination of cis-coordination of each M cation by two nitrides and the linear coordination of each nitride

by two M cations results in the formation of zig-zag -M-N- chains within planes of the perovskite lattice as represented in figure 1b. The chains are similar to those of organic polymers and are susceptible to disorder as there are two choices for the 90° turn at each M atom, resulting in randomised chains and rings within the planes (figure 1b) that average to the experimentally observed anion distribution shown in figure 1a. The above principle of local anion order driven by differing M-N and M-O bond strengths predicts local structure across the range of AMO 3-xNx perovskites (figure 1c). a)

b)

c)

FIGURE 1 (a) Powder neutron diffraction patterns for SrNbO 2 N. The atom distributions are shown in the insets (Sr/Nb/O/N = green/grey/red/blue spheres). (b) Planes of disordered cischains arising from local anion order in SrMO 2 N (M = Nb, Ta) perovskites. Heavy/light lines correspond to M-N-M/M-O-M units. (c) Predicted polymer-like anion orders across the range of AMO3-x Nx perovskites OTHER REFERENCES:

- A. Fuertes, J. Mat. Chem., 22 (2012), 3293 - P. Camp, A. Fuertes and J.P. Attfield, J. Am. Chem. Soc., 134 (2012), 6762 - A. Fuertes, Dalton Transactions 39 (2010) 5942 - M. Yang, J. Oró-Solé, A. Kusmartseva, A. Fuertes, and J. P.Attfield, J. Am. Chem. Soc., 132 (2010), 4822 - A.B. Jorge, J. Oró-Solé, A.M. Bea, N. Mufti, T.T. Palstra, J.A. Rodgers, J.P. Attfield and A. Fuertes. J. Am. Chem. Soc., 130 (2008), 12572.

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The long and winding road from metallorganic chemical solutions to epitaxial nanostructured YBa2Cu3O7 superconducting thin films H. Chen, K. Zalamova, A. Llordés, P. Abellán, F. Martínez-Julián, M.Vilardell, M. Gibert, S. Ricart, F. Sandiumenge, A. Pomar, A. Calleja, A. Palau, X. Granados, T. Puig, X. Obradors Chemistry of Materials, 22 (2010), 1686 Superconductor Science & Technology, 23 (2010), 014012 • Acta Materialia, 59 (2011), 2075 Chemical solution deposition (CSD) has become one of the most appealing alternatives in the race towards successful development at affordable cost of long length superconducting tapes for power applications and magnets. The challenge is huge, however, because there exist poor knowledge of the many processing steps involved: i/ high purity metallorganic precursor preparation and deposition (Ink Jet Printing, for instance); ii/ pyrolysis of the films having controlled thickness; iii/ phase evolution of the intermediate nanocrystalline phases; iv/ nucleation and growth rate control of epitaxial YBa2Cu3O7; v/ micro and nanostructural development and defect engineering to achieve high critical currents. Many challenging issues have been faced in the long and winding road towards the development of advanced coated conductors. First, it

was shown from a thorough analysis of the thermal decomposition of the Trifluoroacetate precursors that no HF is generated during the pyrolysis and that the undesirably porosity, as evidenced through cross section FIB images (Fig.1), can be properly mastered. On the other hand, the microstructural and chemical evolution of the intermediate phases (fluorides, oxyfluorides and oxides) was disentangled while the thermodynamic and kinetic driving forces of the complex reaction path was also analyzed. The formation of epitaxial films of YBa2Cu3O7 in this ex-situ nucleation and growth process was found to be essentially controlled by a gas-solid exchange of chemical species which requires to be thoroughly modeled to determine the parameters controlling the growth rate. For this purpose we used an in-situ electrical resistance measurement

FIGURE 1 (a) FIB image of the cross section of a pyrolyzed YBa 2 Cu3 O7 film where the formed pores are visible. (b) HRTEM image showing an interfacial BaZrO3 nanodot distorting the YBa 2Cu3 O7 lattice around it. The misfit and rotation dislocations are indicated.

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SCIENTIFIC HIGHLIGHTS â&#x20AC;˘ 2010/2011/2012

FIGURE 2 Anisotropy of the critical currents of a nanostructured YBa 2 Cu3 O7 film as compared to a conventional one where the

enhancement effect of the interfacial nanodots is visualized.

set-up which was extremely useful to quantify the influence of the most relevant parameters: total, water and oxygen pressures; temperature and gas flow. Achieving growth rates in the range of 1 nm/s was demonstrated to be feasible thus opening the door to prepare thick films (â&#x2C6;ź 1 micra) with reasonable processing times.

Controlling the growth process turned out to be the clue to nanoengineer films through processing: insights on how to control porosity, grain orientation, epitaxial quality, interface structure, defect formation, etc., have been generated. For instance, growing YBa2Cu3O7 films on substrates nanopatterned with self-assembled BaZrO 3 nanodots, also prepared by CSD, allowed inducing long range uniaxial strain in the YBa2Cu3O7 lattice which enhanced anisotropically the critical currents (Figure 2). Substrate decoration has been found to be a very useful approach to disclose how the atomic scale structure modifications at the in-

terfaces may induce enhanced superconducting properties. In conclusion, transforming chemical solutions into atomic scale engineered films is a scientific endeavor key to nanomanufacture high current superconductors with high throughput and at affordable costs.

OTHER REFERENCES:

1. H. Chen, K. Zalamova, A. Pomar, X. Granados, T. Puig, X. Obradors. J. Mater. Res. 25 (2010), 2371 2. X. Obradors, T. Puig, A.Palau, A. Pomar, F. Sandiumenge, P.Mele, K. Matsumoto. In Comprehensive Nanoscience and Technology, Vol. 5, pp. 303, Elsevier (2011)

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Evidence of quantum confinement effects on interband optical transitions in Si nanocrystals M.I. Alonso, I.C. Marcus, M. Garriga ,A.R. Goñi, J. Jedrzejewski,I. Balberg

Physical Review B, 82 (2010), 045302

FIGURE (Left) Summary of measured transition energies and (right) imaginary part of the dielectric functions determined for different Si nanocrystal sizes.

Research on silicon nanostructures has been continuously stimulated by the obtention of light emission at room temperature with tunable energy and usable efficiency despite the indirect nature of the fundamental gap of bulk Si. For this purpose it is crucial to understand the physical effects of reduced dimensionality on the electronic band structure of Si. The importance of this subject motivated many investigations, both experimental and theoretical. From the experimental point of view, a review of the extensive literature evidenced considerable discrepancies and even contradictory results. While the phenomenology of ultrathin films or nanoslabs seemed better established, the evolution of the band structure of Si nanocrystals (NCs) as a function of nanostructure size remained unsettled: the most complete experimental reports that considered the NC size showed conflicting results and, moreover, they did not study the effect of quantum confinement (QC) on the energies of interband optical transitions.

In particular, no study was available where the more commonly studied optical processes – the band-gap absorption and the photoluminescence (PL) – was correlated to higher energy transitions which can be connected to parameters of the electronic band

structure. In this work we investigated this correlation by performing different spectroscopic measurements on a set of samples with rather spherical Si NCs embedded in a SiO2 matrix. We followed systematically the optical transitions as a function of NC diameter in the relevant size range between 4 and 8 nm (see Figure). We determined the complex dielectric function ε = ε1+iε2 using spectroscopic ellipsometry by a numerical fit which allowed to observe QC shifts on the interband transition energies E1 and E 2, obtaining in parallel the band gap energies from transmission measurements and PL on the same samples. The comprehensive picture arising from all our spectroscopic results enabled us to find semiquantitative trends for the QC effect and to conclude that the whole band structure shifts to higher energies with the decrease in size of the NCs, showing that confinement is well manifested at least up to NCs of 5.5 nm size and that the quantum confinement effect, in transitions with higher energy than the band gap, is the same as the one that is reflected by the commonly available PL data.

OTHER REFERENCES:

- M.I. Alonso et al. Physica Status Solidi (A) 2008;205(4):888-891

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Novel multiferroic memories and materials I.C. Infante, J. Juraszek, S. Fusil, B. Dupe, P. Gemeiner, O. Dieguez, F. Pailloux,S. Jouen, E. Jacquet, G. Geneste, J. Pacaud, J. Íñiguez, L. Bellaiche, A. Barthelemy, B. Dkhil, M. Bibes, X. Martí, V. Skumryev, V. Laukhin, L. Fàbrega, I. Fina, M. Gospodinov, N. Dix, R. Muralidharan, J.M. Rebled, S. Estrade, F. Peiro, M. Varela, J. Fontcuberta, F. Sánchez Physical Review Letters, 107 (2011), 237601 • Physical Review Letters, 106 (2011), 57206 Physical Review Letters, 107 (2011), 257601 • ACS Nano, 4 (2010), 5985

Among other reasons, the need of non-volatile memories, such as magnetic memories, which could be addressed by electric fields, has triggered an enormous research activity during the last decade. The ultimate reason being that these devices would allow a lower energy cost and higher density memories. However, modification of the magnetic state of a magnetic material by an electric field, i.e. a magnetoelectric response, faces fundamental limitations and requires either quite unique materials or an exclusive materials arrangement. The so-called multiferroic materials could in principle do the job if the ferroelectric and ferromagnetic responses were coupled. We have focused our research on two different directions. In the first, we have explored the magnetoelectric response of some oxides which are antiferromagnetic at about 40 K and develop a cycloidal magnetic order at lower temperature (≈ 20 K). Of relevance here is that magnetic cycloidals can display ferroelectric polarization (P). We have been able to grow epitaxial thin films YMnO 3, preserving the cycloidal order and displaying ferroelectricity.

The cycloidal order, resulting from a competition of different magnetic interactions, is very subtle and thus the corresponding cycloidal plane can be easily flopped by application of a magnetic field (H) which in turn, flops the polarization direction by 90°. We have shown, for the first time in thin films, that P can be controlled by H (Fig. 1a), and thus polarization infor-

FIGURE 1 (a) Sketch indicating magnetically induced flop of the ferroelectric polarization in YMnO3 thin films. (b) Sketch indicating electric-field induced switching of the magnetization in LuMnO3 single crystal (or h-YMnO3 thin films) and a soft ferromagnet.

FIGURE 2 Sketch shows the tetragonal-BiFeO 3 , rhombohedral-

BiFeO3 and CoFe2 O4 crystal structures and the topology of a sample grown on LaNiO3/LaAlO3 (001). The 3D view is result of combining different filtered SEM images.

mation can be stored magnetically in helicity of the antiferromagnetic material and read electrically.

In a second approach, magnetoelectric coupling is designed to be operated through the exchange magnetic field occurring across the interface between a multiferroic (ferroelectric and antiferromagnetic material, YMnO 3 and LuMnO 3) and a soft ferromagnet. We have made pioneering works showing that the existing exchange bias can be modulated by electric pulses and thus the magnetization of the ferromagnetic layer can be switched between on/off states (Fig. 1b), opening a way towards electrically controlled magnetic memories.

In an alternative approach, the magnetoelectric coupling is achieved by interface-mediated elastic coupling in ferroelectric-ferromagnetic systems in such a way that field-induced lattice deformation of one of the elements is sensed by the other. In epitaxial ferroelectric/ ferromagnetic BiFeO 3-CoFe2O4 columnar nanocomposites (Fig. 2), we have shown that the orientation of P and the magnetic easy axis, can be tuned by appropriate choice of the substrate on which the bilayers is grown, thus allowing to engineer the multiferroic response.

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Nanoscale properties of novel protein based nanoparticles and their effect on cell proliferation C. Diez-Gil, J. Seras-Franzoso, S. Krabbenborg, E. Garcia-Fruitos, E. Vazquez, E. Rodriguez-Carmona, I. Ratera, N. Ventosa, O. Cano-Garrido, N. Ferrer-Miralles, A. Villaverde and J. Veciana Biomaterials, 31, (2010), 5805-5812 â&#x20AC;˘ Nanomedicine, 7(1), (2012), 79-93

The synergism between biotechnology and materials Science has generated an intense activity in recent years due to the huge interest shown in practical applications in areas like biomedicine; specifically for drug delivery and tissue engineering.

Bacterial inclusion bodies (IBs) are highly pure protein aggregates in the size range of a few hundred nanometers produced by recombinant bacteria.

The polypeptide chains that form IBs usually retain a certain amount of native structure, keeping their biological activity (e.g., fluorescence or enzymatic activity). Therefore, a wide spectrum of uses as functional and biocompatible materials might arise from them upon convenient engineering.

Although theoretically feasible through adjusting

genetic and production conditions, the biophysical features of these proteinaceus nanoparticles, such as activity and size, have been never engineered.

Recently, we characterized the relevant nanoscale properties of IBs formed by green fluorescent protein (GFP) as novel particulate materials using AFM, SEM and fluorescence confocal microscopy.

Moreover, we have also explored at which extent the produced particles can be tailored by simple approaches. At a nanoscale level, IBs are pseudospherical, proteinaceous nanoparticles ranging from around 50-500 nm (Fig. 1) [2]. Being the size of IBs within the range of cell micro- and nano-environmental topology influencing cell proliferation, patterning of IBs using the microcontact printing (ÂľCP) technique has a significant and positive im-

FIGURE 1 Nanoparticles (IBs) formed by the green fluorescence protein. a) SEM images of wt IBs aged for 1 (top) and 3 (bottom) hours; b) 600 nm x 600 nm 3D AFM image and c) topography cross-section of an isolated nanoparticle

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012

pact on cell growth, stimulating mammalian cell proliferation exclusively on the IBs patterned areas making them promising biomaterials for tissue engineering.

In this work the chemical and mechanical properties of bacterial inclusion bodies, produced in different Escherichia coli genetic backgrounds, have been characterized at the nanoscale level. The mechanical properties of the protein based nanoparticles produced in different genetic backgrounds have been assessed using Force Spectroscopic AFM measurements and the wettability data using model Self Assembly Monolayers (SAMs) with different ratios of hydrophilic and hydrophobic molecules and the contact angle technique. In regard to wild type, DnaK- and ClpA-, strains produce protein nanoparticles with distinguishable wettability, stiffness and stiffness distribution within the nanoparticle (Fig. 2). Furthermore it was possible to observe how cultured mammalian cells respond differentially to inclusion body variants when used as particulate materials to engineer the nanoscale topography, proving that the actual range of referred mechanical properties is sensed and discriminated by biological systems. The obtained data show that IBs are highly bioadhesive materials, and that mammaliam cell expansion on IBs is synergistically supported by both enhanced adhesion and mechanical stimulation of cell division. The biologic significance of IB’s nanoscale profiling opens intriguing possibilities for the fine genetic tuning of this particulate nanomaterial and the resulting macroscopic impact when applied in biological interfaces.

FIGURE 2 a) Histograms of the number of events vs. Young

modulus for protein nanoparticles (IBs) produced in different bacterial mutants (Wt DnaK-, ClpA- and ClpP); b) 2D elasticity map of selected protein nanoparticles (IBs) from four genetic backgrounds. a) wt, b) DnaK, c) ClpA and d) ClpP- IBs. Observations infer the existence of a homogeneously spread distribution of Young modulus values over the wt IBs. On the other hand, maps obtained for the others indicate the existence of two elasticity populations, with the harder areas segregated from the softer ones.

OTHER REFERENCES:

- E. Vazque et al. Nanomedicine, 2010, 5(2), 259 - Patent ES-200900045 and PCT/ES2009/070616E - García-Fruitós et al. Trends in Biotechnology, 2012, 30 (2), 65-70 - Elizondo, E., Veciana, J., Ventosa, N. Nanomedicine , 2012, 7(9), 1391-1408

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Valence transition and Pr/Co charge migration in (Pr,Ca) CoO3 cobaltites at the metal-insulator transition J. Herrero-Martín, C. Frontera, A.J. Barón-González, S. Valencia , J. Blasco, C. Ritter , G. Subías, R. Abrudan, F. Radu, E. Dudzik, and R. Feyerherm, J.L. García-Muñoz Physical Review B, 84 (2011), 115131 • Physical Review B, 84 (2011), 045104 Physical Review B, 81 (2010), 132405 • Physical Review B, 81 (2010), 054427

Metal-insulator transitions in perovskite cobaltites are a fundamental research topic due to the relevance of the spin state of Co for electron mobility in these strongly correlated oxides. Pr 0.5Ca0.5CoO 3 exhibits a metal-insulator transition (MIT) and it is considered a strongly correlated spincrossover system. It is possible to generate metallic domains in the insulating low temperature phase of Pr 0.5Ca0.5CoO 3 by ultrafast photoexcitation.

Charge ordering or a simply sudden spin-state transition from IS Co 3+ to diamagnetic LS Co 3+ (S = 0, t62g) were previously proposed by different groups to justify the metal-insulator transition at TMI∼75K in the mixed valent half-doped cobaltite Pr 0.5Ca0.5CoO 3, isostructural to the famous halfdoped manganite Pr 0.5Ca0.5CoO 3.

We have discovered a more complex and rather unique mechanism for the metal-insulator transition in the family of (Pr,Ln)1-xCaxCoO 3 perovskites, using synchrotron X-ray absorption and neutron diffraction techniques. The MIT is characterized by a sudden drop of the magnetic susceptibility in the insulating phase and a simultaneous volume contraction (∼-2%) and Co-O-Co bending (-3°) in the Pnma cell forced by the anomalous shortening of some Pr-Oap bondlengths.

An exceptional electronic mechanism based on a first-order valence transition of Pr and electron migration from Pr to Co at the MIT has been found out in Pr 0.5Ca0.5CoO 3 and other (Pr,Ln)1-xCaxCoO 3 cobal-

FIGURE 1 (left) Volume, ρ and χ changes at the MIT. (center) Pr 0.5 Ca 0.5 CoO3 structure. (right) Experimental absorption spectra and FDMNES cluster calculations at the Pr L 3 edge.

FIGURE 2 Experimental (circles) and pseudo-Voigt composed fitting curves (solid lines) of Pr L 3 absorption spectra at 10 K. Black triangles and black line are the result of the subtraction of 300–10K experimental spectra and fitting curves, respectively.

tites. The valence change from Pr 3+ [4f 2] to Pr4+ [4f 1] was monitored and quantified by means of X-ray absorption spectroscopy measurements at the Pr M4,5, Pr L 3 and the Co-L 2,3-edges. Spectral changes were analyzed by different methods, including multiple scattering simulations. We conclude that in the insulating phase of Pr 0.5Ca0.5CoO 3 a fraction [15(±5)%] of Pr 3+ undergoes a further oxidation to adopt a hybridized configuration composed of an admixture of atomiclike 4f1 states (Pr4+) and f-symmetry states on the O 2p valence band (Pr 3+L states) indicative of a strong 4f-2p interaction. In addition, our study of the spectra recorded with hard x rays rules out intermediate valence models for praseodymium (Pr 3+δ) in these cobaltites. Neutron diffraction data and XAS spectra analysis indicate that the average valence of cobalt should decrease approaching the trivalent state. Instead of a charge ordered inhomogeneous state, the insulating phase of Pr 0.5Ca0.5CoO 3 is an homogeneous Co 3.5-δ state stabilized by a charge transfer from Pr-4f to Co-3d-t 2g orbitals. In addition, electrons leaving Pr sites are used to stabilize the trivalent low-spin state of Co. Namely, the experiments performed lead us to conclude that there is a stabilization of the trivalent LS state of Co in the localized phase induced by a destabilization of the trivalent valence state of praseodymium.

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Growth of functional oxide nanostructures by chemical solution deposition A. Carretero-Genevrier, M. Gibert, J. Zabaleta, P. Abellán, J. Gázquez, J. Arbiol, A. García, F. Sandiumenge, N. Mestres, T. Puig, X. Obradors Small, 6 (2010), 2716 -2725 • Physical Review B, 82 (2010), 165415 1-8 Nanotechnology, 21 (2010), 025302 1-8 • Advanced Functional Materials, 20 (2010), 892-897 Journal of the American Chemical Society, 133 (2011), 4053–4061 Chemical solution deposition (CSD) is a very versatile chemical method to grow epitaxial nanostructured films and nanostructures with inherent low cost and scalability. The generation of interfacial oxide nanoislands by CSD is a promising route towards the development of new multifunctional materials. However, their potential applications in electronic, optoelectronic or biological devices requires an increasing control on key parameters such as nanoisland distribution, morphology and orientation. Through the tuning of growth conditions, we can control the generation of two types of interfacial Ce1−xGdxO2−y (CGO) nanostructures with different in-plane shape, isomorphic or anisotropic base, on single crystalline (001)-perovskite-type substrates. Self-organized and stable uniform square-based (001) nanopyramids form in O2 rich atmosphere. In contrast, in Ar-H2 highly elongated (011) nanowires with ultrafast kinetics grow aligned along the substrate soft axes [100] and [010]. Thermodynamic analysis has been applied to understand the nucleation and growth stages. We found that the trade-off between surface and strain relaxation energy is what drives the system to such different in-plane morphologies. In this way, the intrinsic orientational order of the (011) nanowires can be modified in a nanoscratched substrate. The local compressive anisotropic elastic strain field imposed by the nanoscratches breaks the pre-existing orientation energy degeneracy and makes essentially all nanowires orient parallel to the indentation lines.

Moreover, a novel and general methodology for preparing complex-oxide nanostructures combining sol–gel-based precursor solutions and nanoporous track-etched polymer templates supported on top of single crystalline substrates was developed. Because of the confined nucleation and coarsening in high aspect ratio nanopores, new structures with novel physical properties are obtained. Under the proper selection of process conditions and single crystal-

line substrates, different manganese oxide based nanomaterials were synthesized. Namely, vertical polycrystalline La0.7 Sr 0.3MnO 3 perovskite nanorods on SrTiO 3 and LaAlO 3 substrates; single crystalline MnO2 nanowires and molecular sieve LaSr-2×4 manganese oxide nanowires with a new monoclinic crystallographic structure on Si substrates. These monoclinic nanowires exhibit ferromagnetic ordering with strongly enhanced Curie temperature (Tc > 500K), that results from the mixed valence of manganese and from the new crystallographic order.

FIGURE (a) 5 µm x 5 µm AFM image of self-assembled (011)CGO// (001)LAO nanowires displaying the usual nanoisland distribution with the two possible nanowire orientations equally present. (b) On the patterned region of the same sample (applied load 0.2 mN line pitch 1 µm) indentation lines parallel to the [100]LAO direction promote the [ ]CGO//[100]LAO in plane orientation of the nanowires: i.e. the long axis parallel to the indentation lines. (c) Back-cover of Advanced Functional Materials journal (vol. 20, No. 6, March 2010) showing vertical polycrystalline La 0.7Sr 0.3 MnO3 perovskite nanorods on SrTiO3 .

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Aggregation of superparamagnetic colloids in magnetic fields: the quest for the equilibrium state Jordi S. Andreu, Juan Camacho & Jordi Faraudo

Soft Matter, 7 (2011), 2336–2339

Superparamagnetic particles have a peculiar and interesting magnetic behavior: at zero applied field, their magnetization is zero but in the presence of an external field, the particles acquire a magnetization dipole which can be as large as that typical of ferromagnetics (hence the term Superparamagnetism). In recent years, colloidal dispersions of superparamagnetic particles have received a great attention due to its wide range of potential applications, including for example biotechnology, biomedicine, or waste removal. However, the physics behind its behavior under magnetic fields has many fundamental open questions. One of the most basic is the prediction of the state (and stability) of the dispersion under a high magnetic field. In this theoretical and simulation study, we show that the behaviour of the system is controlled by a new quantity (the aggregation parameter N*), which depends on the magnetic response

of the particles and its concentration. Depending on the value of this parameter, there are three different possibilities for the behavior of the system: (a) equilibrium state with isolated particles (no aggregation), (b) an equilibrium state with a certain value for the average size of the chains (dictated by N*) and (c) a nonequilibrium state with a continuous growth of chains with time following a power law.

Our results have many implications from the fundamental point of view of self-assembly theory and also for many applications. Our equations allow researchers to predict in which conditions superparamagnetic particles will form (or will not form) chains, and effect which is highly desired in some applications (those involving removal of the particles, such as extraction of molecules or pollutants) but it is undesirable in other applications (typically in biomedical or imaging applications).

Left: Snapshot of a simulation in which we observe the equilibrium state of a superparamagnetic dispersion under a high magnetic field.

Right: comparison between the predictions of the mean field theory and simulations.

FIGURE

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Playing with Photonics and Plasmonics: a way to shape magneto-optical spectra J.M. Caicedo, O. Pascu, M. López-García, V. Canalejas, A. Blanco, C. López, J. Fontcuberta, A. Roig, G. Herranz ACS Nano, 5 (2011), 2957 • Langmuir, 28 (2012), 9010

The interaction of light with matter provides a way to manipulate the polarization state of light and to exploit this phenomenology for characterization as well as applications. This has spurred the research on new materials exhibiting large magneto-optical responses based on the dramatic intensification of the light-matter interaction when media are nanostructured intentionally to couple predominantly with photons of certain wavelengths. Based on these premises, we have explored two different approaches, namely, by coupling magneto-optics to photonic band-edge effects and to plasmonic resonances.

Photonic crystals are periodically arranged structures that for a particular range of wavelengths exhibit a bandgap for which the electromagnetic waves can not propagate in the crystal. At frequencies close the band edges light is dramatically slowed down and, therefore, photons of those wavelengths will couple very intensively with the medium. Exploiting this mechanism, we have achieved enhanced magneto-optical responses at near-band edge wavelengths in three-dimensional magneto-photonic crystals (3D-MPCs) (see Figure 1a). These complex systems were built by infiltrating self-assembled direct and inverse opal structures with monodisperse ensembles of different magnetic nanoparticles, including nickel, iron oxide and manganese ferrites. We have demonstrated that 3D-MPCs with a high magnetic content (up to more of 50% of the available volume) can be produced by microwave assisted sol-gel route synthesis of the nanoparticles in photonic crystals, while at the same time preserving long range structural order (over tens of millimeters) of these crystals. The feasibility of using this innovative synthesis route may open up prospecting avenues for the fabrication of novel materials beyond photonics, e,g,, for metamaterials, phononics, magnonics and others.

On the other hand, the incorporation of magnetic materials into plasmonic structures provides an alternative pathway to modulate the magneto-optical spectra and enhance the response at specific wavelengths. In this case, we have exploited the huge increase of the electromagnetic energy density associated with plasmons that are excited in extremely confined regions around metal/dielectric interfaces.

With this in mind, we have coated corrugated gold/ dielectric interfaces with magnetic (nickel and iron

FIGURE 1 (a) Spectral response of the optical transmission (blue) and the magnetic circular dichroism (b) of an inverse opal infiltrated with a MnFe2 O4 shell of nanoparticles (see a SEM image in the inset). (b) Magneto-optical spectra (θ = rotation, ε = ellipticity) of iron oxide nanoparticles deposited on nanodisck arrays with diameter d = 57, 79 and 95 nm and on a flat surface (ref.).The inset shows a SEM picture of one of the nanodisk arrays.

oxide) nanoparticles. We have found that the magneto-optical activity is enhanced by up to one order of magnitude (Figure 1b) for wavelengths that are correlated to the excitation of surface plasmons.

Our results demonstrate the potential of exploiting light polarization in plasmonic and photonic structures as a powerful strategy to customize the magneto-optical spectral response of magnetic materials and to obtain optimized materials for applications such as sensing or optical communications.

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Two-dimensional electron gases in SrTiO3-based interfaces V. Laukhin, O. Copie, M.J. Rozenberg, R. Weht, K. Bouzehouane, N. Reyren, E. Jacquet, M. Bibes, A. Barthélémy, M. Scigaj, M. Foerster, R. Bachelet, A.F. Santander-Syro, T. Kondo, F. Fortuna, S. Pailhés, X.G. Qiu, F. Bertran, A. Nicolaou, A. Taleb-Ibrahimi, P. Le Fvre, Y. Apertet, P. Lecoeur, F. Sánchez, N. Dix, J. Fontcuberta, G. Herranz Nature, 469 (2011), 189 • Scientific Reports, 2 (2012), 758 Physical Review Letters (2012), 109 (22), 226601 • Applied Physical Letters, 100 (2012), 231607 Transition-metal oxides are materials in which several physical interactions –spin, charge, lattice and/or orbital– are simultaneously active with strong electronic correlations. Microscopically, this leads to a multitude of novel exotic states of matter.

Macroscopically, this yields a wide variety of multifunctional phenomena with enormous potential in applications, including high-temperature superconductivity, colossal magnetoresistance, high thermopower or multiferroic behaviour. In this context, the recent discovery of high-mobility transport in oxide heterostructures has attracted the investigation of these systems for novel applications, with SrTiO 3 as the powerhouse of this emerging electronics, having this system a similar role as silicon has for conventional electronics. For instance, the vacuumfractured surface of SrTiO 3 spontaneously develops a highly-metallic two-dimensional electron gas with a hierarchy of electronic subbands with the hallmark of two-dimensional confinement (Figure 1).

The electronic structure of such system was unveiled through angle-resolved photoemission (ARPES) experiments by an international team of scientists with participation of the Institute of Materials Science of Barcelona. We also further uncovered the critical

role of strain on the electronic band properties of SrTiO 3 crystals. In particular, we found out that strain modulates the relative position of the heavy and light electron states in the conduction band resulting in mobility enhancements up to more than 300%.

This offers the opportunity of exploiting in SrTiO 3based electronics the strain-mediated strategies that are successfully applied in the conventional semiconductors.

On the other hand, electron gases can also be generating by coupling SrTiO 3 to other materials. For instance, we have used bottom-up processes to engineer the LaAlO 3 /SrTiO 3 interface atomic composition along the [001] orientation to locally confine twodimensional electron gases to lateral sizes of ~ 100 nm. Alternatively, we have shown that the family of two-dimensional gases can be expanded significantly by relaxing the restrictions of crystallographic orientation and even epitaxy. Thus, the two-dimensional electron gases can be created along nonconventional orientations along [110] and [111] (Figure 2), as well at the interface between different amorphous oxides and SrTiO 3. These findings open a new perspective both for materials research and for elucidating the ultimate microscopic mechanism of carrier doping.

FIGURE 1 Subband structure for the 2DEG at the surface of SrTiO 3 obtained by ARPES. The dotted lines are tight-binding representations of the bands.

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FIGURE 2 The sketch displays the LaAlO3/SrTiO3 interface along the [110)direction.

SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Metallacarboranes and their interactions: influence on the photoluminescence properties of high-boron content metallodendrimers E. J. Juárez-Pérez, P. Farràs, C. Viñas, F. Teixidor, R. Santillan, N. Farfán, R. Luque, M. Lepšik, A. Abreu, R. Yépez, and R. Núñez Macromolecules, 43 (2010), 150 • Chemical Society Review, 41 (2012), 3445

In our continuing investigation of structure/properties relationship in metallacarborane-containing materials, we have dealt with the study of metallacarboranes and their interactions with other molecules. The widespread availability of fast computers enables nowadays studies of complex compounds (e.g. metallacarboranes) from different perspectives including simulation of NMR, infrared or raman spectra and calculation of other properties such as atomic charges or inter-/intramolecular interactions. The insights gained on the basis of theoretical calculations are crucial for either finding novel or improving existing applications of metallacarboranes.

For example, in the case of enzyme inhibitors, the interactions of the metallacarboranes with the surrounding protein and how the interaction affects the efficiency is a difficult problem to study experimentally. The use of theoretical tools can provide a detailed understanding of the physico-chemical basis of the interactions and thus offers a chance to control the overall process.

One important issue is the influence of these metallacarboranes, specifically cobaltabisdicarbollide derivatives, in the photoluminescent properties of macromolecules in which the cobaltabisdicarbollide is a covalently linked component. For that reason a new family of star-shaped molecules and dendrimers, which consist of 1,3,5-triphenylbenzene unit as fluorescent core, Fréchet-type poly(aryl ether) fragments as connecting groups and three, six, nine and twelve terminal allyl ether groups have been synthesized and characterized. The regiospecific hydrosylilation reaction of the terminal allyl ether groups with [1,1’-μ-SiMeH-3,3’-Co(1,2-C2B9H10)2]-, leads to Féchet-type polyanionic metallodendrimers decorated with cobaltabisdicarbollide (cosane) units. Concerning the photoluminescent properties, the starting dendrimers exhibit fluorescence at room temperature under ultraviolet irradiation, nevertheless after functionalization with cobaltabisdicarbollide derivatives, the fluorescence was quenched. By

FIGURE 1 A graphical representation of one metallacarborane (up),

and a dendrimeric structure containing six metallacarboranes in their periphery and photo-optical data (up).

using steady-state and time-resolved luminescence measurements, it is shown that for metallodendrimers, a mechanism different to photon emission could be available to go from excited singlet state to the ground electronic state, mainly due to peripheral functionalization. Because of the anionic character of these compounds and their boron-rich content, we are actually focusing our research on biocompatibility studies and potential applications in medicine as antiviral or BNCT agents.

OTHER REFERENCES:

- González-Campo, A.; Juárez-Pérez, E. J.; Viñas, C.; Boury, B.; Kivekäs, R.; Sillanpää, R.; Núñez, R. Macromolecules 2008, 41, 8458.

- Juárez-Pérez, E. J.; Viñas, C.; Teixidor, F.; Núñez, R. Organometallics, 2009, 28, 5550 - Juárez-Pérez, E. J.; Viñas, C.; González-Campo, A.; Teixidor, F.; Kivekäs, R.; Sillanpää R.; Núñez, R. Chem. Eur. J. 2008, 14, 4924 - Núñez, R.; Juárez Pérez, E. J.; Teixidor, F.; Santillan R.; Farfán, N.; Abreu, A.; Yépez, R.; Viñas, C. Inorg. Chem. 2010, 49, 9993

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Relaxd but highly compact diansa metallacyclophanes P. Farràs, F. Teixidor, I. Rojo, R. Kivekäs, R. Sillanpää, P. González-Cardoso and C. Viñas.

Journal of the American Chemical Society, (133), (2011), pp. 16537–16552

FIGURE 1

Following our research on carboranylphosphines, a series of monoansa [μ-(-1,1’-PR-3,3’-Co(1,2-C2B9H10)2]and diansa [8,8’-μ-(1’’,2’’-benzene)-μ-(1,1’-PR-3,3’Co(1,2-C2B9H9)2]-cobaltabisdicarbollidephanes has

been synthesized and characterized by NMR, MALDITOF-MS, UV/visible spectroscopy, cyclic voltammetry and DFT calculations. Single crystal X-ray diffraction (Fig. 1) revealed a highly relaxed structure characterized by the smallest title angle for a metallacyclophane. In such compounds, the metal-to-phosphorus distance is less than the sum of their vdW radii. The availability of a phosphorus lone pair causes an electron delocalization through the metal, as shown by the abnormal 31P NMR chemical shift.

Remarkably (Fig. 2), the combination of a phosphine donor and a phenyl acceptor moieties causes a synergistic effect that is observed through the different techniques used in this study. The importance of having an available lone pair is demonstrated by the oxidation of PIII to produce the corresponding PV compounds. When the electron lone pair is used to form the bond with the corresponding chalcogen atom (O, S, Se), the communication between the donor and acceptor moieties on the diansa metallacyclophane is shut down.

FIGURE 2

OTHER REFERENCES:

I. Rojo, F. Teixidor, C. Viñas, R. Kivekäs and R. Sillanpää, Chemistry A European Journal, 2004, 10, 5376-5385.

R. Núñez, P. Farràs, F. Teixidor, C. Viñas, R. Sillanpää and R. Kivekäs, Angewandte Chemie. International Edition, 2006, 45, 1270 –1272.

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Supramolecular chirality in aromatic functional materials I. Danila, F. Riobé, F. Piron, J. Puigmartí-Luis, J.D. Wallis, M. Linares, H. Ågren, D. Beljonne, N. Avarvari, P. Iavicoli, H. Xu, L.N. Feldborg, M. Linares, M. Paradinas, S. Stafström, C. Ocal, B. NietoOrtega, J. Casado, J.T. López Navarrete, R. Lazzaroni, S. De Feyter, D.B. Amabilino Journal of the American Chemical Society, 132 (2010), 9350–9362 Journal of the American Chemical Society, 133 (2011), 8344–8353

The introduction of chirality into molecular materials can have important consequences on their chemical and physical behaviour. Specifically, the twist between aromatic segments can be modified, and therefore the orbital overlap which dictates charge transport can be modulated.

We prepared a series of porphyrins (see structure) which contained between one and four stereogenic centres and established the effect that they have in different states of matter of the molecule. Firstly, the self-assembly of the molecules in monolayers gave lamellae twisted with respect to the surface reference axis, and this angle was shown to depend strictly on the number of stereogenic centres. Also, in solution, the stacks of molecules show optical activity (chirality measured by Circular Dichroism Spectroscopy) which depends on the number of stereogenic

centres. Bulk materials were prepared through gelation of organic solvents (see photograph below) which contain a complex mesh of fibres (shown in the Atomic Force Microscope image). The ability to form a gel also depended critically on the number of stereogenic centres. In all cases, chirality could be induced on aggregates by only one stereogenic centre, in a molecule with molecular weight over 2000 Da. This observation points to interesting approaches for the preparation of chiral materials with tunable transport properties.

In other research concerning non-amphiphilic aromatic molecules, we witnessed the transfer of chirality from the single supramolecular fibre level up to the chirality of acicular objects which whose helicity was clearly visible in an optical microscope.

OTHER REFERENCES:

1. P. Iavicoli, H. Xu, L.N. Feldborg, M. Linares, M. Paradinas, S. Stafström, C. Ocal, B. Nieto-Ortega, J. Casado, J.T. López Navarrete, R. Lazzaroni, S. De Feyter, D.B. Amabilino. J. Am. Chem. Soc., 2010, 132, 9350–9362 2. I. Danila, F. Riobé, F. Piron, J. Puigmartí-Luis, J.D. Wallis, M. Linares, H. Ågren, D. Beljonne, D.B. Amabilino, N. Avarvari. J. Am. Chem. Soc., 2011, 133, 8344–8353

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Application of cluster-based direct methods to powder diffraction data of organic compounds J. Rius, O. Vallcorba, C.Frontera, C.Miravitlles

Acta Crystallographica Section A, 67 (2011), 63-67

A new direct methods (DM) strategy specially thought for dealing with powder diffraction data has been developed. This strategy is based on the partitioning of the powder pattern in intensity clusters (D) and on the posterior maximization of the coincidence function

as a function of the Φ set of phases of the structure factors. For an arbitrary i cluster, ni denotes the number of contributing reflections. As illustrated in Figure 1, intensity information which remains unused in conventional DM is now actively used. In this way the effective resolution of the data set is increased which allows optimizing the coincidence function by means of the S-FFT algorithm.

FIGURE 1 Traditional DM only use intensities of resolved reflections in an exact way. However, the resolution of the powder pattern often extends to higher 2θ angles. At present this additional information is only exploited during the Rietveld refinement. With the recently developed cluster-based DM also the intensities at high 2θ angles can be used at the phasing stage. (dmin= minimum d-spacing)

The new cluster-based DM strategy has been implemented in XLENS_PD6 which uses the intensity information previously extracted from the powder pattern with the DAJUST software (XLENS_PD6, www. icmab.es/ crystallography/ software).

The viability of the procedure has been demonstrated by using synchrotron data of various organic compounds collected at the Swiss Light Source by Dr. Fabia Gozzo. The application of clustered DM to ibuprofen powder diffraction data is illustrated in Figure 2.

FIGURE 2 (up) Unit cell of ibuprofen showing the two symmetry independent molecules (space group P21); (down) Detail of the dimer with experimental bond lengths as obtained from clustered DM. OTHER REFERENCES:

Rius J., Crespi A., Frontera C. (2007) Acta Cryst., A63, 131-134.

Vallcorba O., Rius J., Frontera C., Peral I., Miravitlles C. (2012) J.Appl.

Cryst., 45, 844-848 Freer,A., Bunyan,J., Shankland,N. & Sheen,D. (1993) Acta Cryst. C49, 13781380.

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Breaking symmetry: a tool to engineer materials properties D. Pesquera, M. Foerster, D. Gutiérrez, I. Fina, N. Dix, X. Martí, D. Fritsch, C. Ederer, M. Iliev, M. Barchuk, A. Barla, E. Pellegrin, F. Bondino, E. Magnano, F. Sánchez, G. Herranz and J. Fontcuberta

Advanced Functional Materials, 22 (2012), 4344 • Physical Review B, 86 (2012), 125309 Nature Communications, 3 (2012), 1189 The properties of materials are directly related to their electronic structure, i.e. the electron distribution among the different electronic bands. The symmetry plays a fundamental role as it determines the interatomic and intraatomic orbital overlapping and so the electronic structure of solids. In bulk, crystalline symmetry is an intrinsic property of the material but when reducing dimensions, as in thin films, epitaxial strain induced by the substrates and the presence of interfaces with different materials both break and reduce the symmetry possibly affecting their properties.

Aiming to exploit these effects by creating or tailoring the functionalities of transition metal oxide thin films, we have first addressed the effects of epitaxial strain on robust insulating materials having a very open structure; these materials could give us the opportunity to explore strain effects without dramatic changes of the electronic structure. We have chosen CoFe2O4. It has been found, for instance, that an in-plane epitaxial compressive strain produces an expansion of the unit cell along the out-of-plane direction in an amount that is not large enough to compensate in-plane compression. As a result, the unit cell volume shrinks (Fig. 1a). This observation has allowed to understand a long standing problem related to the intriguing behavior of some Raman modes dominated by out-of-plane atomic vibrations, which in spite of the c-axis expansion, when increasing inplane strain they get harder rather than softer, as a simple picture based on unit cell volume preservation under strain would predict. The same reason accounts for the variation of the out-of-plane permittivity that largely reduces under in-plane compressive strain. Ab-initio first principle calculations have confirmed both, the anomalous elastic response under strain and the change of permittivity, although some quantitative discrepancies still persist.

In materials with partially filled bands, strain and surface/interface effects may have more dramatic effects. This is the case of La2/3 Sr 1/3MnO 3 perovskites, where due to the pseudo-cubic symmetry of the bulk material, the partially filled 3d-t2g0.3 orbitals of 3d-x 2-y 2 and 3d-z2parentage are degenerate and give the material a net metallic character. Epi-

taxial strain should reduce the symmetry from cubic to tetragonal, thus breaking the degeneracy of the 3d-x 2-y 2 and 3d-z 2 orbitals with subsequent electronic redistributions. By using X-ray absorption linear dichroism (Elettra Synchrotron) we have made a systematic study of the electron occupancy of these t2g orbitals of Mn-ions in La2/3 Sr 1/3MnO 3 thin films of different thickness grown on substrates imposing distinct epitaxial strain. The simple guess of inplane x 2-y 2 orbitals favorably occupied under tensile strain and z2 under compressive strain has been fully confirmed. More interestingly however, we have disclosed that symmetry breaking at the free surface promotes an additional orbital energy splitting that favors z 2 occupancy. Therefore, strain acting on the bulk of the film and free surface allows to tailor orbital occupancy of thin films oxides (Fig. 1b). These findings may have profound effect on surface related properties, such as catalysis, hydrophobicity etc.

FIGURE 1a

FIGURE 1b

FIGURE 1 a) Variation of unit cell volume of epitaxial thin films of

CoFe2O4 under compressive in-plane stress (red symbols; left axis) and out-of-plane expansion (blue symbols; right axis). b) Illustration of the preferred occupancy of x 2 -y 2 and z 2 orbitals at the bulk (under in-plane tensile stress in the example shown) and surface, respectively, of a transition metal thin film.

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Light on the light elements: a direct way to visualize O and N atoms and direct polarity determination in non-planar nanostructures M. de la Mata, C. Magen, J. Gazquez, M.I.B. Utama, M. Heiss, S. Lopatin, F. Furtmayr, C.J. FernรกndezRojas, B. Peng, J.R. Morante, R. Rurali, M. Eickhoff, A. Fontcuberta i Morral, Q. Xiong, J. Arbiol Nano Letters, 12 (2012), 2579-2586

The newly developed aberration corrected annular bright field (ABF) STEM imaging is used to directly visualize the light elements, e.g.: O and N atomic columns. In different works published in top ranked journals we demonstrate that mapping of individual elements at the atomic scale allows the study of new phenomena in materials science that were impossible to be resolved with such a resolution until now. This State of the Art technique has been applied for example to define a new guideline for the direct atomic resolution polarity determination of semiconductor nanowires (NWs) and non-planar nanostruc-

tures from binary compounds, even in the case where one of the atoms is extremely light (O or N: ZnO and GaN/AlN). The theoretical fundaments of these procedures allow us to overcome the main challenge in the identification of dumbbell polarity. It resides in the separation and identification of the constituent atoms in the dumbbells. The proposed experimental via opens new routes for the fine characterization of nanostructures, e.g. in electronic and optoelectronic fields, where the polarity is crucial for the understanding of their physical properties (optical and electronic) as well as their growth mechanisms.

FIGURE (left) Direct visualization of the Zn-O atomic stacking in a Nanowire and determination of its polarity, by means of ABF-STEM. (right) Polarity induced morphological modulation in non-planar ZnTe nanostructures.

OTHER REFERENCES:

- E. Uccelli, et al. Nano Letters, 11 (2011), 3827-3832.

- B. Ketterer, et al. ACS Nano, 5 (2011), 7585-7592.

- F. Schuster, et al. Nano Letters 12 (2012), 2199-2204.

- D. P. Weber, et al. Nano Letters 12 (2012), 6139-6144.

- Q. Zhang, et al. Nano Letters 12 (2012), 6420-6427.

- M.I.B. Utama, et al. Nano Letters 12 (2012), 2146-2152.

- J. Arbiol et al., Nanoscale 4 (2012), 7517-7524.

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012 Crystallography of Incommensurate Magnetic Orders: Competing Ferroelectric Phases in Multiferroic Mn1-xCoxWO4 I. Urcelay-Olabarria, E. Ressouche, A. Muhkin, V.Yu. Ivanov, A. M. Balbashov, V. Skumryev and J.L. Garcia-Muñoz Physical Review B, 85 (2012), 224419 • Physical Review B, 86 (2012), 184412 Physical Review B, 85 (2012), 094436 New future applications in information technology are envisaged after the discovery of new ways of combining electric and magnetic dipole orders in frustrated oxides with complex magnetic structures.

Broken symmetries between structural, magnetic or electronic orders are the key for coupling the electrical and magnetic degrees of freedom. The emphasis of this research line is focused on the symmetry properties of single-phase magnetoelectric (ME) multiferroics (MF) with cycloidal or modulated spin orders.

In the reference MnWO4 frustrated multiferroic magnetic and ferroelectric orders coexist and mutually interact. It undergoes three successive magnetic phase transitions. Below 13.5 K the AF3 phase is incommensurate and paraelectric. In the AF2 phase (7.5 K < T < 12.5 K) a spontaneous polarization along b axis coexists with a cycloidal spin order (k=(-0.214, 1/2, 0.457)). Below 7.5 K the system is collinear commensurate (k = (±1/4, 1/2,1/2), AF1)). We have studied a variety of ferroelectric and magnetic phase transitions induced by temperature or magnetic field up to 12 T in Mn1-xCoxWO4 multiferroics (x=0.05, 0.10, 0.20) by single crystal and powder neutron diffraction experiments, magnetic and polarization measurements. A rich variety of competing multiferroic ME phases was found. The magnetic structures varying T or H were determined (modulated, cycloidal, transverse conical incommensurate orders, ..) and the compatibility of the structure, magnetic symmetry and polarization anisotropy have been theoretically analyzed .

Compared to pure MnWO4, the ground state in Mn0.9Co0.1W0 4 is substituted by the cycloidal acplane spin structure (AF2*, producing Pa and Pc), due to a significant reduction of the magnetic anisotropy in the ac-plane.

In Mn0.8Co0.2WO4 multiferroic competing commensurate collinear (AF4, k1=(0.5, 0, 0), TN ≈ 20 K) and incommensurate cycloidal (AF2, k 2 =(0.211, 0.5, 0.452)) spin structures were found to stabilize an exotic transverse conical spin order, proved to be responsible for the ferroelectric phase below TFE≈ 8.5 K. The

AF4 spin modulation aligns along the easy direction, while the cycloidal modulation develops in the magnetically hard directions. As predicted, ferroelectric polarization is along b-axis.

Several field induced transitions are described when H is applied parallel to the different crystal axis. The details of the magnetic transitions under magnetic field and the observed flipping of the electric polarization were analyzed in the light of the inversed Dzyaloshiskii-Moriya interaction and spin-current mechanisms in this system.

Relationship between magnetic order and electric polarization in spin induced (Mn1-x ,Cox)WO4 multiferroics.

FIGURE 1

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Electronic structure and anisotropic chemical pressure effects in single-component molecular conductors based on radical dithiolene and diselenolene gold complexes G. Yzambart, N. Bellec, G. Nasser, O. Jeannin, T. Roisnel, M. Fourmigua, P. Auban-Senzier, D. Lorcy, A. Audouard, J.-Y. Fortin, D. Vignolles, R.B. Lyubovskii, L. Drigo, F. Duc, G.V. Shilov, G. Ballon, E.I. Zhilyaeva, R.N. Lyubovskaya, J. Íñiguez, E. Canadell Journal of the American Chemical Society, 134 (2012), 17138 • Europhysics Letters, 97 (2012), 57003

FIGURE 1 Known systems of the [AuX4 (=Y)2] (X = Se, S; Y = S, O) family of single-component molecular conductors. Crystal structure of the [AuSe4 (=O)2] member of this family. The other systems are isostructural.

FIGURE 2 Simulation of the pressure effect on the band structure of [AuS4 (=S)2] when the molecules are rigidly brought closer by 0.2Å along the stacks direction (i.e. b).

The long date challenge of preparing a metallic solid based on closed-shell molecules without the help of any doping (a single-component molecular metal) was realized only recently. Several neutral metal bis(dithiolene) complexes bearing a non-innocent tetrathiafulvalene backbone have been developed and exhibit either semiconducting or metallic behavior. Another pathway toward neutral single-component dithiolene complexes is based on neutral gold complexes lacking this TTF backbone. The synthesis and properties of a very promising system based on the dithiolene ligand [Au(Et-thiazdt)2], noted as [AuS4(=S)2] (see Figure 1) was recently reported.

In the solid state, the radical complex organizes into uniform, non-dimerized stacks, with sizeable interstack interactions. Its room temperature conductivity is strongly pressure dependent (0.33 S cm–1 at ambient pressure up to 1000 S cm–1 at 21 kbar). Furthermore, from the room temperature semiconducting behavior, a metallic state can be stabilized above 13 kbar. First-principles DFT band structure calculations led us to demonstrate that: (i) a delocalized (metallic) and localized (antiferromagnetic) states

differ by a small energy amount and compete for the ground state of the system, and (ii) the indirect gap observed at ambient pressure can be indeed suppressed by contracting the conducting slabs along the b stacking direction (see Figure 2) and/or the a interstack direction .

The chemical pressure effects in this family of single-component molecular conductors were also examined by considering the four systems shown in Figure 1. Despite a contracted unit cell volume reflecting the positive chemical pressure effect, oxygen substitution on the outer thiazoline ring decreases the conductivity by a factor of 100, because actually there is an elongation along the b direction decreasing the band dispersion. On the other hand, the S/Se substitution in the metallacycle increases the conductivity by a factor of 100 because the substitution strongly increases the π-π interactions along the stacks while only slightly increasing the b parameter.

This leads to a net increase of the band dispersion.

The DFT approach thus provides a simple rationale for the different and somewhat unexpected pressure effects on the conductivity of this family of phases.

OTHER REFERENCES:

- A. Kobayashi, E. Fujiwara and H. Kobayashi, Chem. Rev. 2004, 104, 5243.

- N. Tenn, N. Bellec, O. Jeanin, L. Piekara-Sady, P. Auban-Senzier, J. Íñiguez, E. Canadell and D. Lorcy, J. Am. Chem. Soc. 2009, 131, 16961.

- G. Yzambart, N. Bellec, G. Nasser, O. Jeannin, T. Roisnel, M. Fourmigué, P. Auban-Senzier, J. Íñiguez, E. Canadell and D. Lorcy, J. Am. Chem. Soc. 2012, 134, 17138.

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SCIENTIFIC HIGHLIGHTS â&#x20AC;˘ 2010/2011/2012 Switchable resistive nanostructures embedded in low cost oxide thin films C. Moreno, C. Munuera, S. Valencia, F. Kronast, X. Obradors, C. Ocal

Nanoletters, 10 (2010), 3828-3835

On the basis of a scanning probe microscopy strategy, we have proposed a combined methodology capable to program nonvolatile multilevel data and read them out in a noninvasive manner. In the absence of the common two-electrode cell geometry, this nanoscale approach permits, in addition, investigating the relevance of inherent film properties.

The main result of the work is the reversible transition from low resistive (LR) to high resistivity (HR) states, also referred as ON and OFF states, in well characterized thin films of the robust metallic ferromagnet La0.7 Sr 0.3MnO 3. The transitions are induced by means of conductive scanning force microscopy (C-SFM) and are observed in situ at the nanoscale by both C-SFM and Kelvin probe microscopy (KPM).

Local chemical analysis using PEEM points to unexpected changes in the cation distribution within the modified regions, data without precedent. Retention times of several months have been tested for both ON

and OFF states. Spectroscopy modes have been used to investigate the IV characteristics for the different resistive states, which has permitted correlating device rectification (reset) with the voltage employed to induce each particular state. Analytical simulations using a non-linear dopant drift within a memristor device explain the experimental IV bipolar cycles.

The results are of fundamental importance in oxide materials for ReRAM based memories, which have nowadays an impressive repercussion in both academics and applications.

Our capability to fabricate and read multilevel and switchable resistive nanostructures embedded in low cost oxide thin films are proposed as a suitable approach towards active electronic elements, which constitutes a promising approach in particular for the fabrication of high-density data storage nonvolatile memory devices.

FIGURE Top left: Hysteretic bipolar switching I-V curves for a 10 nm thick LSMO thin film. Starting from a conducting (LR) state, the voltage ramp is applied to the tip from negative to positive values and back to complete the cycles as indicated by the arrows. SET (LR to HR) and RESET (HR to the initial LR) points are marked in what is the first I-V cycle. LR and HR are identified as ON and OFF, indicating the pass or blockage of electronic current through the device. Writing (top right) and erasing (bottom) the local conducting properties of LSMO consist in the reversible transition between low resistive (LR) and high resistive (HR) by applying appropriates voltages to the tip of a conducting scanning force microscope (C-SFM) while scanning.

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Ferromagnetism in transparent MgO thin films

C. Martínez-Boubeta, J. I. Beltrán, Ll. Balcells, Z. Konstantinović, S. Valencia, D. Schmitz, J. Arbiol, S. Estrade, J. Cornil and B. Martínez

Physical Review B, 82 (2010), 024405 The possibility of using charge and spin degrees of freedom as control variables will allow to put together processing and magnetic storage of information and to exploit the quantum nature of electronic spin for the development of spintronic devices with new functionalities. Noteworthy, most of the practical applications of spintronics will require the use of magnetic semiconductors at room temperature (RT).

Some ferromagnetic (FM) semiconductors, such as

de case of EuO, and others of the III-V and II-VI semiconducting families doped with FM impurities are already known but all of them have low magnetic transition temperature, TC, fact that severely limits their practical applications. The possibility of inducing FM at room temperature RT in wide bandgap oxides by doping with magnetic atoms, particularly in TiO2 and ZnO, have been recently suggested. However, there is no clear consensus with respect to the intrinsic

FIGURE 1 a) HRTEM general view of the MgO layer (10 nm) grown on the STO substrate. Both layers grow along their respective [001]

axis. b) HRTEM detail of the MgO layer corresponding to the red squared area in (a). c) HRTEM computer simulation of the same area in (b). d) 3D intensity map of the experimental HRTEM image shown in (b). e) 3D intensity map of the nine central atomic columns squared (cyan) in the experimental detail (b). f) 3D intensity map of the nine central atomic columns squared green in the HRTEM computer simulation in (c). g) Frontal view of the MgO supercell used to obtain the simulated image in (c). h) Side view of the same supercell in (g).

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SCIENTIFIC HIGHLIGHTS â&#x20AC;˘ 2010/2011/2012

origin of the FM signal observed in these materials and a clear connection between microstructure and magnetic behavior is still lacking. For these reasons, the search for RT FM in wide bandgap oxides has broadened and new materials, such as In2O 3, CeO2, Al 2O 3, SnO2 and MgO, are now in focus. The term d0 FM has been coined to characterize the behavior of these latter materials, in which magnetism is not coming from partially filled d or f orbitals. In particular, it is thought that defects and associated charge trapping can play a significant role in this behavior. Thus, crystalline quality becomes of utmost importance for the investigation of unconventional magnetic properties. MgO is one of the simplest oxides with RT FM potential, with the advantage that its properties can be calculated with high accuracy within the conventional approximations of the density functional theory. In our work, we report evidence of the existence of intrinsic d0 FM in MgO films. Using first-principles calculations we predict the formation of local moments in MgO due to the existence of Mg vacancies which create holes on acceptor levels near the O 2p-like valence band. Magnetic measurements demonstrate experimentally the feasibility of RT FM in samples with Mg-vacancies as evidenced by microstructural characterization (See Fig. 1).

Hysteresis loops at RT are shown in Fig. 2. Similar saturation magnetization, Msâ&#x2C6;ź20 emu/cm3, is found at T=10 K for samples having different thicknesses, which could safely discard interfacial contributions to FM. In addition, as shown in the inset of Fig. 2, films are colorless, shiny and highly transparent. Finally, by applying the element specificity of the X-ray magnetic circular dichroism technique, we provide direct evidence of the spin polarization of the oxygen atoms around Mg vacancies.

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FIGURE 2 Hysteresis M(H) curves of MgO (001) films of different thicknesses on SrTiO3 taken at room temperature and at T=10 K. Magnetic field was applied parallel to the film surface. The films are transparent enough in the visible region to make the background text readable (inset on the right).

Nanostrain approach to enhanced vortex pinning in solutionderived YBa2Cu3O7 superconducting thin films A. Llordés, A. Palau, J. Gázquez, M. Coll, R. Vlad, A. Pomar, J. Arbiol, R. Guzmán, S. Ye, V. Rouco, F. Sandiumenge, S. Ricart, T. Puig, M. Varela, D. Chateigner, J. Vanacken, J. Gutiérrez, V. Moshchalkov, G. Deutscher, C. Magen, X. Obradors

Nature Materials 11, 329 (2012) ing performances. We have discovered a new highly effective mechanism of APC generation in solutionderived HTS nanocomposites based on the generation of nanostrained regions where Cooper pair formation is suppressed. This new vortex-pinning mechanism is supported on the bond-contraction pairing model where tensile strain quenches Cooper pair formation. Experimentally the nanostrained regions have been identified by Scanning Transmission Electron Microscopy and X-ray diffraction patterns and they are associated with a huge enhancement of the concentration of partial dislocations surrounding intergrowths. The intergrowths are in turn promoted by randomly oriented non-superconducting nanoparticles, such as BaZrO 3, Ba2YTaO6, BaCeO 3 or Y2O 3, and a distinguishing feature is that nanostrain and vortex-pinning evolve towards an isotropic behavior. Although it is still a tantalizing task to specifically engineer the nanostructure of these materials, as required by the complex behavior of vortex matter in HTS, our discovery opens a completely novel and promising path.

FIGURE 1a

FIGURE 1b

FIGURE 1 (a) HRSTEM image (Z-contrast) of a YBa 2 Cu3 O7/

BaZrO3 nanocomposite film where the lattice bending of the YBa 2Cu3 O7 matrix is visible around a randomly oriented BaZrO3 nanoparticle. (b) Strain map determined from analysis of interatomic distances of STEM images. The deformation along c-axis is visualized around a intergrowth region.

Boosting large-scale superconductor applications require nanostructured conductors with artificial pinning centers immobilizing quantized vortices at high temperatures and magnetic fields. Several approaches have been followed to generate nanocomposite high temperature superconductors (HTS) which are effective in inducing artificial pinning centers (APC) with varied geometry, size and dimensionality. These novel nanomaterials have open completely new avenues to maximize their superconduct-

FIGURE 2 Isotropic pinning force increase with the nanostrain of

the films for all the nanocomposite series.

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SCIENTIFIC HIGHLIGHTS • 2010/2011/2012

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TRAINING ACTIVITIES • 2010/2011/2012

Training Activities Training of the future generations of scientists is part of the overall mission of ICMAB. We aim at training high level researchers providing them with both a solid fundamental background in materials science and an applied practical mindset to allow them to evolve smoothly and adapt rapidly to any research environment, either academic or industrial. The full time dedication of CSIC scientific staff to their research, allows a close assessment of the progress of doctoral and post-doctoral researchers under their guidance, while technical staff also plays a key role in training them on the hands-on equipment in the Institute. In addition, participation of PhD students in international meetings is actively encouraged: The majority of Doctors leaving the ICMAB will have given oral presentations at International meetings.

During this period 32 PhD Theses were successfully defended and many of these enjoyed an International flavour in their research through the many cooperation projects that exist in the centre. Moreover, every year we receive a sizable number of national and international university students as summer internships, seventy seven in these three years. The students have the opportunity to be introduced to research in Materials Science by carrying out short term projects. Younger researchers are encouraged to be the supervisors of these internships.

ICMAB also has an in-house complementary training program comprising diverse activities coordinated by a specific commission. It includes seminars with bi-weekly periodicity and which are open to everyone in the campus where internationally renowned speakers are asked to deliver a lecture for a broad audience. Selected topflight speakers in 2012 were Ignacio Cirac, Francesco

Stellaci, Yasumoto J. Uemura and Masahiro Yamashita and in 2011 Luis Liz-Marzan, C. N. Rao, Stephen Mann or Nazario Martín just to mention a few. In addition thematic workshops are organized dedicated to the characterization techniques available as facilities. The workshops that have been organized so far include: Proximity Microscopies, X-ray Diffraction, NMR and EPR Spectroscopies, Transmission Electron Microscopy, Computational methods and Modeling and Optical characterization techniques.

The permanent staff of the Institute participates actively in many official Masters programs, notably in the Materials and the Nanoscience and Nanotechnology programs at the UAB, as well as in the organisation of Workshops and Schools at the national and International level aimed at the training of early stage researchers.

ICMAB is proud to have a comprehensive approach to training and in that sense, aside from the activities mentioned above, we endeavor to reach primary and secondary schools with guided visits to our center and our program ‘advanced materials in the classroom’ encourages our researchers to visit secondary schools as well as to offer guidance for high school science projects. Furthermore, ICMAB researchers often appear in the media and write articles targeting broad audiences.

In general the training in the ICMAB, as is characteristic of the area of materials science, is highly interdisciplinary. This facet is noted by future employers, and an important indicator is the fact that private enterprises or technological centers employ 52 of the 180 PhD students that have been trained at the doctoral level at the ICMAB since 1991. The pie chart shows where all these researchers are employed at the present time.

PROFESSIONAL DESTINATIONS OF ICMAB PhD GRADUATES Total 180 at December 2012

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César Moreno Sierra New features in solution derived LSMO thin films: spontaneous outcropping and nanoscale reversible switching Universitat Autònoma de Barcelona (15/01/2010) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Xavier Obradors Prof. Mª Carmen Ocal Currently: NIMS, Tsukuba, Japan

Mathieu Gonidec Synthesis and properties of multifunctional single molecule magnets Universitat Autonòma de Barcelona (03/09/2010) Grade: Excel·lent “Cum Laude” Award: Premi Extraordinari de Tesis Doctorals de Ciència de Materials de la UAB Supervisors: Prof. Jaume Veciana

Prof. David B. Amabilino Currently: Harvard University, USA

Anna Llordes Gil Superconducting nanocomposite films grown by chemical solution deposition: synthesis, microstructure and properties Universitat Autònoma de Barcelona (03/05/2010) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Xavier Obradors Dr. Susagna Ricart Currently: Lawrence Berkeley National Laboratory, USA

Ana Milena Cruz Rodríguez Obtención y caracterización de materiales electroactivos para soporte de crecimiento neural Universitat Autonòma de Barcelona (13/09/2010) Grade: Excel·lent “Cum Laude” Prof. Nieves Casañ Supervisor: Universitat Rovira i Virgili, Spain Currently:

Franco Rigato Epitaxial Spinel Ferrite films for spin-polarized transport Universitat Autonòma de Barcelona (06/07/2010) Grade: Excel·lent “Cum Laude” Supervisor: Prof. Josep Fontcuberta Currently: INDO Lens Group, Spain

Juan Antonio Collado Gómez Relevancia de los fenómenos de separación de fases en óxidos magnetoresistivos Universidad de Málaga (26/10/2010) Grade: Excel·lent “Cum Laude” Prof. José Luís García Supervisor: Currently: Universidad de Málaga, Spain

Dirk Heinrich Strukturbildung in Ferrofluiden unter Einfluss magnetischer Felder Technische Universität Berlin (02/09/2010) Grade: 4 (1.0 Sehr Gut) Supervisor: Prof. Alejandro R. Goñi

César Diéz Gil Processing and structuring of molecular materials for environmental and biomedical applications Universitat Autònoma de Barcelona (05/11/2010) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Jaume Veciana

Dr. Imma Ratera Currently: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain

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TRAINING ACTIVITIES • 2010/2011/2012 Adrián Carretero Genevrier Synthesis and self-assembly of 1D manganese-based complex oxides from template directed chemical solution deposition Universitat Autònoma de Barcelona (19/11/2010) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Teresa Puig

Dr. Narcís Mestres Currently: Laboratoire de Chimie de la Matière Condensée de Paris, UMR7574, France

Claudia Delgado Simão Surface self-assembly of electroactive molecules as wires and switches Universtitat Autònoma de Barcelona (15/04/2011) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Concepció Rovira

Dr. Marta Mas Currently: ICN2, Spain

Elisa Elizondo Sáez de Vicuña Preparación con fluidos comprimidos de materiales nanoestructurados para la liberación controlada de fármacos y su posterior caracterización Universitat Autònoma de Barcelona (25/11/2010) Grade: Excel·lent “Cum Laude” Dr. Nora Ventosa Supervisor: Currently: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain

Patrícia Abellán Baeza Interfacial structure and microstructural evolution of solution-derived dissimilar oxide nanostructures.

Implications on their functional properties Universitat Autònoma de Barcelona (23/05/2011) Grade: Excel·lent “Cum Laude” Dr. Felip Sandiumenge Supervisor: Currently: Pacific Northwest National Laboratory, USA

Fernando Martínez Julián Uso de sales inorgánicas y nanopartículas en el crecimiento de capas delgadas superconductoras por CSD Universitat Autonòma de Barcelona (14/01/2011) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Xavier Obradors Dr. Susagna Ricart Currently: Universitat Jaume I, Spain

Valentina Roxana Vlad Growth and characterization of chemical solution based nanostructured coated conductors with CeO2 cap layers Universitat Autonòma de Barcelona (30/05/2011) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Xavier Obradors

Dr. Alberto Pomar Currently: OXOLUTIA, Spain

Raphael Pfattner Organic electronics based on tetrathiafulvalenederivatives: organic field-effect transistors and sensors Universtitat Autònoma de Barcelona (18/03/2011) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Concepció Rovira

Dr. Marta Mas Currently: Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Spain

Malena Oliveros Collante Synthesis of novel PTM radical derivatives and surface functionalization Universitat Autònoma de Barcelona (06/06/2011) Grade: Excel·lent “Cum Laude” Supervisor: Prof. Jaume Veciana Currently: Politecnico di Milano, Italy

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Roberto Fabian Luccas Estudio de la deformación de la red de vórtices por redes artificiales de defectos mediante decoración magnética Bitter en superconductores de alta temperatura Universitat Autònoma de Barcelona (06/07/2011) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Teresa Puig

Dr. Xavier Granados Currently: Universidad Autónoma de Madrid, Spain

Ariadna Pepiol Martí Síntesi i funcionalització d’O-carborans i metal·locarborans com a nuclis de dendrons i dendrímers. Aplicacions en medicina Universitat Autònoma de Barcelona (19/12/2011) Grade: Excel·lent “Cum Laude” Prof. Clara Viñas Supervisor: Currently: Electroless Hard Coating, S.A (ELHCO), Spain

Judit Galcerà Julià Versatile Supramolecular Architectures in Lamotrigine Multicomponent Crystalline Materials Universitat Autònoma de Barcelona (14/07/2011) Grade: Excel·lent “Cum Laude” Prof. Elies Molins Supervisor: University of Cambridge, United Currently: Kingdom

Jone Zabaleta Llorens Growth and advanced characterization of solution-derived nanoscale La0.7Sr0.3MnO3 heteroepitaxial systems Universitat Autònoma de Barcelona (19/01/2012) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Teresa Puig Dr. Narcís Mestres Currently: Max Planck Institute for Solid State Research, Germany

Judit Guasch Camell Multifunctional molecular materials based on donoracceptor systems Universitat Autònoma de Barcelona (16/09/2011) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Jaume Veciana

Dr. Imma Ratera Max-Planck-Institut für Intelligente Currently: Systeme, Germany

Aura Janeth Barón Barón González Estudio de los mecanismos electrónicos en perovskitas de cobalto Pr0.5Ca0.5CoO3, (Pr,Y,Ca)CoO3 y La2MnCoO6 Universitat Autònoma de Barcelona (17/11/2011) Grade: Excel·lent “Cum Laude” Supervisors: Prof. José Luís García Dr. Carlos Frontera Currently: Universidad Pedagógica y Tecnológica de Colombia, Colombia

Ioana Carmen Marcus Growth, optical and structural investigation of sige nanostructures Universitat Autonòma de Barcelona (20/04/2012) Grade: Apte Supervisors: Prof. Isabel Alonso

Prof. Alejandro Goñi Currently: CEST Competence Center, Austria

Ignasi Fina Ferroelectricity and magnetoelectric coupling in magnetic ferroelectrics and artificial multiferroic heterostructures Universitat Autonòma de Barcelona (01/05/2012) Grade: Excel·lent “Cum Laude” Supervisor: Prof. Josep Fontcuberta Dr. Lourdes Fábrega Currently: Max-Planck-Institut für Mikrostrukturphysik, germany

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TRAINING ACTIVITIES • 2010/2011/2012 Oana Pascu Synthesis of Magnetic Nanoparticles and Strategies towards Magneto-Photonic Materials Universitat Autònoma de Barcelona (31/05/2012) Grade: Excel·lent “Cum Laude” Supervisors: Dr. Anna Roig

Dr. Gervasi Herranz Currently: Institut de Chimie de la Matière Condensée de Bordeaux, ICMCB-CNRS, France

Josh Malowney Ordered Patterns of Functional Oxide Nanostructures Grown from Chemical Solutions Universtitat Autònoma de Barcelona (26/07/2012) Grade: Apte Supervisors: Dr. Narcís Mestres

Dr. Xavier Borrisé Currently: DBM Coils, Italy

José Manuel Caicedo Roque Magneto-optical spectroscopy of complex systems.

Magnetic oxides and photonic crystals Universitat Autònoma de Barcelona (01/06/2012) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Josep Fontcuberta

Dr. Gervasi Herranz Currently: INDO Lens Group, Spain

Antonio Javier Moral Vico Materiales Electroactivos Polimericos e Hibridos como Sustratos de Crecimiento Neuronal Universtitat Autònoma de Barcelona (27/07/2012) Grade: Excel·lent “Cum Laude” Supervisor: Dr. Nieves Casañ Currently: Institut de Microelectrònica de Barcelona IMB-CNM (CSIC), Spain

Otto Emiliano Gonzalez Vazquez First-principles investigation of BiFeO3 and related multiferroic materials Universitat Autònoma de Barcelona (06/07/2012) Grade: Apte Supervisor: Dr. Jorge Íñiguez Currently: International Centre for Theoretical Physics, ICTP, Italy

Laura Martín Sánchez Preparación, caracterización y aplicación de aerogeles de carbono nanocompuestos con metales como catalizadores y electrocatalizadores de reacciones orgánicas.

Universtitat Autònoma de Barcelona (20/07/2012) Grade: Excel·lent “Cum Laude” Supervisors: Prof. Elies Molins

Dr. Adelina Vallribere Currently: Panreac, Spain

Lucas Romano Muniz Propiedades ópticas de semiconductores bajo altas presiones hidrostáticas Universitat Autònoma de Barcelona (28/09/2012) Grade: Apte Supervisors: Prof. Alejandro R. Goñi

Prof. Isabel Alonso Currently: Universidade de São Paulo (USP), Instituto de Física de São Carlos (IFSC), Brazil

Sébastien Thomas Matériaux nitrurés dopés à l’Eu2+ ou au Ce3+: Synthèse, luminescence et application aux diodes blanches Université de Bordeaux 1 (14/12/2012) Grade: Très Honorable Supervisor: Prof. Amparo Fuertes Currently: Aquitaine Science Transfert, France

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TECHNOLOGY TRANSFER ACTIVITIES • 2010/2011/2012

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Spin-off companies from ICMAB

OXOLUTIA SL is a technology-based spin-off company emerging from the Superconductor Materials and Large Scale Nanostructures department from the ICMAB-CSIC promoted by Prof. X. Obradors, Prof. T. Puig, Dr. X. Granados, Dr. S. Ricart adn Dr. A. Calleja.

Chemical solution methodologies for preparing functional oxide nanostructures is at the core technology of OXOLUTIA SL. Intellectual property is conveniently protected in 5 patents from CSIC. The benefits of our technology allow cost-effective and upscalable processes, in particular in the field of second-generation superconductor tapes for novel and efficient devices useful for generation, transport and use of electrical energy, medical diagnose and scientific instrumentation. Nonetheless, it could be potentially extended to other multilayered heteroepitaxial oxides with different functionalities.

After being founded in 2010, the first equity offering took place only six months later, in which the metallurgical group La Farga entered the company. In 2011, an INNPACTO project from the Spanish Ministry was accepted to strengthen the research in the continuous production of multilayer superconductor epitaxial

tapes. From 2012, OXOLUTIA is also participating in the EUROTAPES project (www.eurotapes.eu), a large scale project from FP7 aiming at long length production of high performance coated conductors together with the best European companies and laboratories in applied superconductivity.

Remarkably, one of the main objectives of this project will be the real implementation of chemically-derived nanocomposite coated conductors in long lengths, especially suited for high magnetic field applications.

The technological development being carried out towards long length 2G superconductor tapes is leading to other interesting outputs which are being currently explored for other industrial sectors as well, like planarization of substrates by chemical methods useful for thin films, inkjet printing of metalorganic solutions to yield thin layers and patterns of functional ceramics, design of isothermal furnaces specially fitted for crystal growth or ceramic targets for pulsed laser deposition.

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Website: www.oxolutia.com Contact e-mail:oxolutia@oxolutia.com

TECHNOLOGY TRANSFER ACTIVITIES • 2010/2011/2012

NANOMOL Technologies S.A., located in UAB Research Park, is a spin-off company co-founded

by Jaume Veciana, Nora Ventosa and Santi Sala, researchers of NANOMOL research group of the ICMAB-CSIC. NANOMOL belongs to TECNIO network, the brand name created by Catalan Agency ACC1Ó to join Catalan research groups with strongest activities in applied research and technology transfer.

NANOMOL Technologies aims to commercially exploit the technologies generated by researchers of NANOMOL group. This research group has developed a simple, reproducible and easy scalable Technology Platform named DELOS, based on the use of CO2-expanded solvents to prepare microand nanoparticulate materials and multifunctional nanovesicle-bioactive conjugates, with application to the development of new nanomedicine candidates..

NANOMOL Technologies is offering technology platforms, such as DELOS and QUATSOMES, and R & D services to pharmaceutical and biotechnology industries to improve drug efficacy and patient compliance in therapeutic treatments they are developing.

In addition to the life science, other sectors of high economic importance which can also take advantage of NANOMOL platforms are chemical, cosmetic and nutraceutical industries. Industries from these sectors could improve the properties and performance of dyes, adhesives, food additives and skin creams, by the outstanding structural characteristics which can provide DELOS platform, non achievable by conventional preparation routes.

The main objectives of NANOMOL technologies in its first years of existence have been: • To commercialize proprietary technology platforms by generation of new drug delivery systems and nanomedicine candidates for preclinial and clinical development • To Engineer and scale-up methodologies developed

at lab-scale following Pharma Industry requirements (GMP compliance) Recently the company has begun its participation into European Collaborative projects. Specifically, NANOMOL Technologies has joined two consortia to carry out the following R+D projects dealing with the application of Micro and Nanotechnology to biomedical purposes: - THERAGLIO: The idea of TheraGlio FP7 Cooperation project is to develop a multimodal imaging system for Theranostics (therapy+diagnosis) of patients bearing malignant glioma, the most common primary brain tumour. This technology will avail of new generation Microbubbles (MBs), in which development NANOMOL Technologies is involved, that can simultaneously act as drug delivery system and contrast agent for Magnetic Resonance Imaging, intra-operative Contrast-Enhanced Ultrasound and intra-operative fluorescence microscopic.

- NANO2FUN: The main target of this ITN network is the education of a new generation of scientists for the development, via breakthrough research, of two technologically relevant applications, namely two-photon microscopy (2PM) and two-photon polymerization (2PP), with enormous applicative potential in bioimaging, biomedicine, and rapid prototyping techniques. In this ITN, NANOMOL Technologies is involved in the scaling-up of Organic Nanoparticles (ONP) production processes to be used in photonic applications.

Finally, NANOMOL Technologies offers its wide expertise in the structural characterization of micro and nano-sized particles, which can be found in almost any type of industry and research fields, from the life science to the materials and chemicals manufacturing industries.

NANOMOL Technologies was awarded in 2011 with a special mention in the EXPOQUIMIA R+D+I awards to the best business projects from academia.

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THE ICMAB TEAM • 2010/2011/2012

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1986-2011

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25 YEARS • 2010/2011/2012

In May 2011 the ICMAB celebrated its 25 th anniversary, an excellent occasion to review the past years and gather several authorities from the CSIC, Generalitat de Catalunya and Universitat Autònoma de Barcelona together with the ICMAB personnel, as well as many friends and colleagues. We were very pleased to invite several of the present and past members of the ICMAB staff to make short comments about how being member of the ICMAB had impacted in their personal and professional lives. Certainly we greatly appreciated the warm messages received from many people who shared with us their feelings towards our center.

In the speech of the ICMAB Director, the scientific history of the Institute was reviewed, identifying the different development stages, from its infancy, through its teen years up to the present maturity stage.

This review stressed how the ICMAB has been decisive in contributing to boost the emerging knowledge of the Materials Science discipline in Spain in the 80’s towards our present widely recognized international impact in many areas. It was particularly rewarding to visualize the extent to which the discipline of Materials Science has evolved in 25 years, for instance consolidating the new area of Nanoscience and Nanotechnology where the inputs of the Materials Science merge with those from other disciplines. Certainly the contribution of some of the ICMAB staff

to promote the creation of a new research Institute within the Bellaterra Campus, i.e. the Institut Català de Nanociència i Nanotecnologia (ICN2), was very important. Now we certainly have new opportunities to create more synergy with our environment and so extending the excellence and International impact of our research. We are convinced that merging all the capabilities of the “Nano” partners located in the Bellaterra Campus into a common organization, such as the Barcelona Nanocluster-Bellaterra (BNC-b), will further boost the international and social impact of our future research.

ICMAB faces, however, new challenges for the near future. New scientific facilities were inaugurated in the occasion of the 25 th anniversary, a well equipped clean room facility devoted to materials nanostructuration tools and an advanced Laboratory of thin film growth by Pulsed Laser Deposition, but unfortunately we still have a general lack of technical support to run these laboratories. It is certainly essential to have a full commitment of our supporting institutions to keep, both, advanced laboratories and the required skilled scientific and technical staff to use them properly. We do hope that within the next 10 years the ICMAB will be consolidated as a top research center where a renewed generation of scientists and technologists continues the path initiated during these first flourishing 25 years of life!

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25 YEARS • 2010/2011/2012

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