LNLS

Bra z il ia n Sy nc h ro t ro n Ligh t La bo ra to r y

ISSN 1518-0204

AC T IV IT Y R E PO RT 2 0 1 0

w w w. l n l s . b r

AC T I V I T Y

R E P O RT

Brazilian Synchrotron Light Laboratory

2 0 1 0

ISSN 1518-0204

LNLS ACTIVITY REPORT 2010 Editor: Angelo Malachias Management: Claudia Izique Proofreader: Beatrice Allain The editors express their gratitude to the LNLS users and staff for their contributions, advice and patience DISCLAIMER This document was prepared as an account of work done by LNLS users and staff. Whilst the document is believed to contain correct information, neither LNLS nor any of its employees make any warranty, expresses, implies or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed within. As well, the use of this material does not infringe any privately owned copyrights.

LNLS Campus: Giuseppe Máximo Scolfaro Street, 10.000, Campinas, São Paulo, Brazil Correspondence: P.O. Box 6192 Postal Code 13083-970, Campinas, São Paulo, Brazil Telephone: +55 19 3512-1010 Fax: +55 19 3512-1004 e-mail: secre@lnls.br home page: www.lnls.br A non-profit organization Brazilian Association for Synchrotron Light Technology (ABTLuS) operate the Brazilian Syncrotron Light Laboratory (LNLS)for the Brazilian Ministry of Science and Technology.

AC T I V I T Y

Brazilian Synchrotron Light Laboratory

ABTLuS Brazilian Association for Synchrotron Light Technology Director General: Rogério Cezar de Cerqueira Leite (January to June, 2010 – pro tempore) Walter Colli (June to December, 2010) LNLS Brazilian Synchrotron Light Laboratory Director: Antonio José Roque da Silva LNBio Brazilian Biosciences National Laboratory Director: Kleber Gomes Franchini

CTBE Brazilian Bioethanol Science and Technology Laboratory Director: Marco Aurélio Pinheiro Lima

Activity Report 2010: LNLS / Brazilian Synchrotron Light Laboratory - Campinas, SP: Brazilian Ministry of Science and Technology / Brazilian Association for Synchrotron Light Technology, 2010.

Annual ISSN 1518-0204 1. Synchrotron accelerator. I. LNLS / Brazilian Synchrotron Light Laboratory CDD 539.735

This publication is available at the eletronic format in www.lnls.br/publicacoes Printed in December, 2011 Desktop publishing

R E P O RT

2 0 1 0

ISSN 1518-0204

AC T I V I T Y

R E P O RT

Brazilian Synchrotron Light Laboratory

2 0 1 0

SUMMARY 6 Introduction

9 Science Highlights

87 Facility Reports

124 Scientific Reports

INTRODUCTION

WELCOME

During 2010 we started to tackle the major challenges that LNLS was facing,

which were lack of personnel, necessity to refurbish some old beamlines, and to finish the UV undulator-based beamline – PGM. Moreover, the most important project for LNLS, the construction of a new, third generation ring, continued to evolve with a better definition of the magnetic lattice and the construction of some key prototypes, such as the permanent magnets.

As described in the section about the beamlines, the PGM was concluded by the end of 2010, and started to be commissioned. The first results are very encouraging regarding the stability and energy resolution, and the perspectives are for a competitive beamline in the energy range from 100 to 1200 eV. Regarding also the other insertion device beamline under construction, the superconducting wiggler beamline for material science, the optical section purchased from Brucker ASC arrived at the end of the year and will start to be assembled. The superconductor wiggler itself had some problems related to helium consumption which were fi xed throughout the year. Major improvements were done in the wiggler based protein crystallography beamline, with the acquisition of a new automated end-station, which will be installed and commissioned in 2011. The XAFS1 control and data acquisition system was completely remodeled, and the same concept will later on be used to refurbish the other beamlines. The diff raction beamlines had improvements in their end stations, including new detectors and new sample environments. The UV SGM beamline had also improvements in its optical section, which should improve its stability and flux. And the optics of the SAXS1 beamline was completely remodeled, which resulted in a gain of almost two orders of magnitude in flux.

Regarding personnel, by the end of 2010, the scientific division had an increase in its staff by almost 50% when compared to the beginning of the year. Even though we still need to improve, this positive change places LNLS in a better position to continue the necessary upgrades and modifications, as well as the development of the new ring project.

The light source itself had a reliability of 97.8%, delivering 4.203 hours of beam time to users. An important development was the replacement of the old klystron system by the solid state amplifiers. This should have an impact both on reliability 6 | ACTIVITY REPORT 2010 – LNLS

INTRODUCTION

as well as in the reduction of electricity costs. On average, thirteen beamlines were available to users, where 529 proposals were executed. The regional distribution of these proposals continues with the same trend as in previous years, with roughly 40% from the State of São Paulo, 40% from all other states in Brazil, and 20% from other countries, with Argentina accounting for approximately 14% of these executed proposals. An important event was the realization, for the first time outside Europe, of the Hercules course at LNLS. Regarding the project of the new ring, which is called Sirius after an internal contest to choose its name, the first prototypes of the magnets have been constructed and characterized. There were also initial studies of the injection and control system, building structure as well as advances in the magnetic lattice design. This continues to be the major project of LNLS, and it is clear that it has the support of the scientific community and the government.

It is never too much to stress that all these achievements would not be possible without the dedication and high quality of LNLS staff.

Antonio José Roque da Silva Director LNLS

ACTIVITY REPORT 2010 – LNLS | 7

SCIENCE HIGHLIGHTS 10 16 21 25 29 37 42 49 54 59 65 71 76 83

Synthesis and Characterization of Gold@Gold(I)-Thiomalate Core@Shell Nanoparticles

Dodecanethiol–stabilized Platinum Nanoparticles Obtained by a Two–phase Method: Synthesis, Characterization, Mechanism of Formation and Electrocatalytic Properties

Magnetically Recoverable Gold Nanoparticles for Catalytic Applications The Conception of a Gold Electrochemical Microcell and its Application on a Disposable Salicylate Biosensor

Structural and Biochemical Characterization of Peroxiredoxin Q of Xylella fastidiosa

Nanostructural Reorganization of Bacterial Cellulose by Ultrasonic Treatment

A Novel Approach for High Resolution Elastic Behavior Assessment of Alloyed Strained Nanostructures X-ray Bragg-surface Diffraction: a Sensitive Tool for Studying In-plane Strain Anisotropy in Fe+ Ion Implantation in Si(001) Self-organization of Diblock Copolymer Solutions in Mixed Solvents Observation of Ferromagnetism in PdCo Alloy Nanoparticles Encapsulated in Carbon Nanotubes

The Role of Lys122 and Ca2+- Binding Loop Region for the Catalytically Inactive Lys49-Phospholipases A2 from Snake Venoms Effects of Adding La and Ce to Ni/Mg/Al Hydrotalcite Catalyst Precursors on Ethanol Steam Reforming Reactions Phase Formation in RDE Grown Iron Silicide Nanodots

Citrus Greening Disease Investigation Using Micro Synchrotron Radiation X-ray Fluorescence in Association with Soft Independent Modelling of Class Analogy (SIMCA)

1

SYNTHESIS AND CHARACTERIZATION OF GOLD@GOLD(I)THIOMALATE CORE@ SHELL NANOPARTICLES

Gastón Corthey1, Lisandro J. Giovanetti1, José M. Ramallo-López1, Eugenia Zelaya2, Aldo A. Rubert1, Guillermo A. Benitez1, Félix G. Requejo1, Mariano H. Fonticelli1, Roberto C. Salvarezza1

Instituto de Investigaciones Fisicoquímicas, Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata – CONICET, Sucursal 4, Casilla de Correo, 16 (1900), La Plata, Argentina 2 Centro Atómico Bariloche, Comisión Nacional de Energía Atómica – CONICET, Av. Bustillo 9500, Bariloche, 8400 Rio Negro, Argentina.

1

In this work the detailed morphology of gold@gold(I)-thiolate core@shell nanoparticles is described for the �irst time, based on a multitechnique approach. The prepared particles consist of gold metallic cores with a diameter of about 1 nm surrounded by stable gold(I)-thiomalate shells (Au@Au(I)-TM). The results presented in this work give new insights in the synthesis and characterization of metallic and core@shell nanoparticles.

Facilities: SXS, XAFS 2, SAXS 2 Publication: ACS Nano, 2010, 4(6), p. 3413-3421 Funding: ANPCyT, CONICET, UNLP Corresponding author: Mariano H. Fonticelli – mfonti@inifta.unlp.edu.ar

SYNTHESIS AND CHARACTERIZATION OF GOLD@GOLD(I)-THIOMALATE CORE@SHELL NANOPARTICLES

The interest in the investigation of gold

XPS spectra (Mg Kα XR50 source and a hemispherical

nanoparticles covers a wide range of specific areas,

electron energy analyzer PHOIBOS 100, Specs) of

such as heterogeneous catalysis, optics, sensitive

the synthesized nanoparticles is shown in Figure 1.

analysis or medicine. Thiols are particularly

It can be observed, as already has been reported,

important in the synthesis and applications of gold

that Au(III) was not completely reduced5, in contrast

nanoparticles since these molecules act as a capping

to what is generally observed in the synthesis of

agent and allow a precise control of the particle

alkanethiol-protected gold nanoparticles. The Au 4f

size by tuning the hydrocarbon chain length and

signal (Figure 1a) shows that the Au(0) contribution

gold:thiol concentration ratio. While it is relatively

(84.0 eV) was only 30% of the overall signal,

easy to prepare stable thiol monolayer-protected

while the 70% corresponds to Au(I) (84.5 eV)6.

nanoparticles soluble in organic solvents (by using

Interestingly, there was a one to one correspondence

standard procedures such as the Brust-Schiff rin

between the number of sulfur and Au(I) species.

two-phase method1), isolable, stable and water-

The assignment of the component at 84.5 eV to

soluble thiolate-protected gold nanoparticles are

Au(I)-TM species is supported by previous XPS data

more difficult to prepare. For the synthesis of this

of Au(I)-thiolate complexes6. The XPS S 2p spectrum

kind of nanoparticles, several parameters have to

shown in Figure 1b was well fitted considering

be precisely controlled, such as solution pH, solvent

two components which were found at 162.9 and

composition and the thiol terminal group.

161.8 eV, corresponding to thiolate (Au(I)-thiolate)6,7

In the present work we have studied the synthesis

and sulfide species8, respectively. The presence of

and structure of water-soluble gold nanoparticles

unbound TMA molecules was discarded considering

protected by thiomalic acid (TMA, also known as

the XANES spectra at the S-K edge region (LNLS

mercaptosuccinic acid, MSA). This capping agent,

D04A-SXS beamline) (Figure 1c).

TMA (thiomalate, TM, in its deprotonated form), is

In order to further reduce the obtained

particularly interesting, as the highly soluble Au(I)-

Au(I) species in the as-prepared nanoparticles, a

TM complexes have a wide range of applications in

post-reduction process was carried out adding a

medicine, mainly in the treatment of rheumatoid

NaBH4 excess to a portion of the Au@Au(I)-TM

arthritis2. The synthesis of these nanoparticles was

nanoparticles dispersed in water. It is worth noting

first reported by Chen and Kimura3 and a controversy

that with the post-reduction process, Au(I) was

in the size of these particles was evidenced in the

reduced in some extent (Au(0):Au(I) ratio increased)

literature. While the authors proposed, by means of

and the S(total):Au(total) ratio decreased after

X-ray diff raction, a structure composed by a 1 nm

the borohydride treatment. It is also interesting to

gold core surrounded by a TMA monolayer, gold

note that the post-reduction process produced an

cores of 3.4 nm were measured later by TEM4 and

increase in the plasmon peak intensity of the UV/vis

an incomplete gold reduction was subsequently

spectrum, which indicates a larger size of gold cores

reported .

(Figure 1d).

5

In order to elucidate the chemical nature and

Once

the

chemical

composition

of

the

structure of the nanoparticles we have used a

nanoparticles was studied, EXAFS, SAXS and TEM

multi-technique approach, which includes: X-ray

results were used to characterize the nanoparticle

Photoelectron Spectroscopy (XPS), Transmission

geometry and structure. In order to discard the

Electron Microscopy (TEM), High Resolution TEM

possibility that Au(I) species were bonded to

(HRTEM), Small-Angle X-ray Scattering (SAXS),

the carboxylate group, an oxygen shell was first

Extended X-ray Absorption Fine Structure (EXAFS),

considered to fit the low distance contribution

X-ray Absorption Near Edge Structure (XANES)

of the EXAFS spectrum (LNLS D08B-XAFS-2

and UV-vis spectroscopy (UV/vis).

beamline) (Figure 2). However, in this case the

Gold core-gold(I)-thiomalate shell (Au@Au(I)-

fit had large errors and the corresponding Au-O

TM) nanoparticles were synthesized by the Chen and

distance was higher than that expected for Au-O

Kimura method, with a TMA:gold ratio of 2.5:1 . The

bonds (between 0.193 and 0.207 nm). In contrast, a

3

ACTIVITY REPORT 2010 – LNLS | 11

SCIENCE HIGHLIGHTS

Figure 1.

(a)

(b)

(c)

(d)

a) Au 4f XPS signals of the as-prepared Au@Au(I)-TM nanoparticles. b) S 2p signals of the as-prepared Au@Au(I)-TM nanoparticles. c) S K-edge XANES spectra of Au@Au(I)-TM nanoparticles and hexanethiol. The lower spectrum corresponds to S-K XANES signal for unbound (free) thiols. d) UV/vis spectra of the as-prepared and post-reduced nanoparticles.

shell of sulfur atoms fitted the data very well, leading

metallic phase and a second phase with sulfur atoms

to Au-S distances of 0.231 nm, in good agreement

in the first coordination sphere for Au(I) species can

with previously reported results. A contribution

reproduce this result. While Au atoms inside the

from a second Au shell was also considered to fit

metallic phase are surrounded by another twelve

the 0.14-0.35 nm region, which is associated with

Au atoms, Au species in the second phase would

the Au-Au distances of the Au core. For spherical

contribute with zero to the Au-Au coordination

nanoparticles, the average coordination number

number. Therefore, we can conclude that these

(N) decreases as the particle size decreases, up to a

nanoparticles mainly consist of Au(I)-TM with some

limit value of 5.53, which is the N for an ideal Au13

Au(I)-sulfide and a small amount of metallic Au.

cuboctahedron. In our case, we got a lower value

The distribution and geometrical arrangement of

(N ≈ 4.4), which is an indication that not only

Au(0) and Au(I)-TM species was inferred from SAXS

metallic Au is present: another different Au-phase

measurements (LNLS D02A-SAXS-2 beamline). The

must be consider to explain such small N value. A

obtained SAXS curve for the nanoparticles solution

12 | ACTIVITY REPORT 2010 – LNLS

SYNTHESIS AND CHARACTERIZATION OF GOLD@GOLD(I)-THIOMALATE CORE@SHELL NANOPARTICLES

in water is shown in the inset of Figure 3. The best

It has already been stated that Au(I)-thiolate

curve fitting was obtained proposing a two electronic

polymeric species are the precursors in many thiolate-

density model: a constant density attributed to

protected nanoparticles synthetic routes10. Certainly,

the Au(0) core and a Gaussian electronic density

the reduction of the Au(I) polymer by NaBH4 led

distribution for a shell associated with the Au(I)-TM layer (Figure 3). A Log Normal distribution for the radius of the Au(0) core was introduced in the fitting routine to take into account the size dispersion.

This result indicates that the product is formed by nanoparticles consisting of a Au(0) core with an average radius of 0.51(2) nm and Au(I)-TM shell (Au@Au(I)-TM), discarding the possibility of gold cores immersed in a bulk Au(I)-TM polymer.

The

Au@Au(I)-TM

nanoparticles

to the formation of the metallic Au nanoparticles.

However, a more complex scenario for the Au(I)-TM has to be considered. In contrast to the commonly observed behavior of Au(I)-thiolate towards NaBH4 reduction, in the current case an incomplete reduction of the Au(I)-TM could be obtained, even with a post reduction procedure, originating goldcore Au(I)-TM-shell nanoparticles. It is remarkable

were

also characterized by TEM (FEI CM 200 UT).

Surprisingly, the mean diameter obtained was

by SAXS, as it can be observed in Figure 4a, and the one expected from the UV/vis spectrum (Figure 1d).

However, this can be explained considering the proposed Au(I)-TM shells which cover the nanoparticles. The Au(I) from Au(I)-TM shell of as-prepared nanoparticles can be reduced by the

Fourier transform (a.u.)

3.7 ± 1.3 nm, which is higher than the one obtained

(a)

electron beam of the TEM, incrementing the size of the metallic Au cores. In fact, Kim et al.8 synthesized gold nanoparticles irradiating a Au(I)-alkanethiolate

(b)

with a TEM electron beam9. Hence, the size determined by TEM is related to the metallic Au

0

coming from both the metallic cores originally synthesized and also the metallic Au generated by electron beam reduction of Au(I). This result is consistent with the size reported later by the group

1

2

3

4

5

6

°

R(A ) Figure 2.

Fourier Transforms of Au-L3 edge EXAFS spectra of: a) Au foil,

Figure 3.

Scheme of the electronic density proposed to fit the SAXS data.

and b) Au@Au(I)-TM nanoparticles, red line shows the EXAFS fits.

of Kimura, who have used a TMA:Au ratio of 3:110.

In that paper they reported a diameter, obtained by TEM (3.4 nm), larger than the one they obtained earlier by XRD (1.02 nm) when almost the same TMA:Au ratio was employed (2.5:1)3. For the sake of comparison, in Figure 4c it can also be observed the TEM and SAXS results obtained for alkanethiol monolayer-protected gold nanoparticles, prepared by the two-phase Brust method1. In that case the diameters obtained by TEM (3.8 nm) and SAXS (3.6 nm) are very close, in contrast to the case of Au@Au(I)-TM nanoparticles. Since most of the gold atoms in these nanoparticles are reduced (Au(0)) they are, in principle, not affected by radiolysis damage under the TEM electron beam.

Inset: SAXS data for Au@Au(I)-TM nanoparticles.

ACTIVITY REPORT 2010 – LNLS | 13

SCIENCE HIGHLIGHTS

Counts (a.u.)

s s s Au s Au s Au Au s Au Au s Au Au s Au Au s Au s Aus s Au s AuAu s

10 nm 0

2

4

6

8

10

(b)

Diameter (nm) (a)

Counts (a.u.)

S S S S S

S S S

Au S S S

S S S S S

50 nm 0

2

4

6

8

10

(d)

Diameter (nm) (c) Figure 4.

a) Size distribution of the Au@Au-TM nanoparticles. b) Bright field TEM image of Au@Au-TM nanoparticles. c) Size distribution of the dodecanethiol monolayer-protected Au nanoparticles. d) Bright field TEM image of dodecanethiol monolayer-protected Au nanoparticles. In a, c: bars: histogram from TEM; red line: Log normal fit of the TEM histogram; blue line: Log normal distribution calculated from the SAXS fitting routine.

to notice that NaBH4 does not allow a complete

months. Finally, it has been shown the importance

reduction of oxidized gold, even when it is used in

of attacking this kind of systems with a multi-

a tenfold excess. This condition provides enough

technique approach (combining local techniques

driving force for the Au(I) reduction, although it is

with average ones) to avoid misunderstanding of

forming a stable complex. Then, a kinetic hindrance,

some properties of the nanoparticles such as the size

which is the motivation of further studies, might be

obtained by TEM.

the responsible for the partial Au(I) reduction.

In summary, the synthesis and characterization of core@shell nanoparticles composed by a metallic Au core and a multilayer thiolate shell has been

Acknowledgements

The authors are grateful to LNLS for access to the

described. These particles are very stable in water,

beamlines. We thank J. C. AzcĂĄrate for the synthesis

observing only little degradation after several

of alkanethiol-protected gold nanoparticles.

14 | ACTIVITY REPORT 2010 – LNLS

SYNTHESIS AND CHARACTERIZATION OF GOLD@GOLD(I)-THIOMALATE CORE@SHELL NANOPARTICLES

References [1]

Brust, M.; Walker, M.; Bethell, D.; Schiffrin, D.J.; Whyman, R. Synthesis of thiol-derivatised gold nanoparticles in a two-phase Liquid-Liquid system. J. Chem. Soc., Chem. Commun. 801-802 (1994).

[2]

van Vollenhoven, R.F. Treatment of rheumatoid arthritis: state of the art 2009. Nat. Rev. Rheumatol. 5, 531-541 (2009).

[3]

Chen, S.; Kimura, K. Synthesis and Characterization of Carboxylate-Modified Gold Nanoparticle Powders Dispersible in Water. Langmuir 15, 1075-1082 (1999).

[4]

Yao, H.; Kojima, H.; Sato, S.; Kimura, K., Interparticle Spacing Control in the Superlattices of Carboxylic AcidCapped Gold Nanoparticles by Hydrogen-Bonding Mediation. Langmuir 2004, 20, (23), 10317-10323.

[5]

Ackerson, C.J.; Jadzinsky, P.D.; Kornberg, R.D. Thiolate Ligands for Synthesis of Water-Soluble Gold Clusters. J. Am. Chem. Soc 127, 6550-6551 (2005).

[6]

Bourg, M.-C.; Badia, A.; Lennox, R.B. Gold−Sulfur Bonding in 2D and 3D Self-Assembled Monolayers: XPS Characterization. J. Phys. Chem. B 104, 6562-6567 (2000).

[7]

Walton, R.A. The x-ray photoelectron spectra of metal complexes of sulfur-containing ligands: sulfur 2p binding energies. Coordination Chemistry Reviews 31, 183-220 (1980).

[8]

Zhong, C.-J.; Brush, R.C.; Anderegg, J.; Porter, M.D. Organosulfur Monolayers at Gold Surfaces: Reexamination of the Case for Sulfide Adsorption and Implications to the Formation of Monolayers from Thiols and Disulfides.

Langmuir 15, 518-525 (1999).

[9]

Kim, J.-U.; Cha, S.-H.; Shin, K.; Jho, J.Y.; Lee, J.-C. Synthesis of Gold Nanoparticles from Gold(I)−Alkanethiolate Complexes with Supramolecular Structures through Electron Beam Irradiation in TEM. J. Am. Chem. Soc. 127, 9962-9963 (2005).

[10]

Brinas, R.P.; Hu, M.; Qian, L.; Lymar, E.S.; Hainfeld, J.F. Gold Nanoparticle Size Controlled by Polymeric Au(I) Thiolate Precursor Size. J. Am. Chem. Soc. 130, 975-982 (2008).

ACTIVITY REPORT 2010 – LNLS | 15

2

DODECANETHIOL– STABILIZED PLATINUM NANOPARTICLES OBTAINED

BY A TWO–PHASE METHOD: SYNTHESIS, CHARACTERIZATION, MECHANISM OF FORMATION AND ELECTROCATALYTIC PROPERTIES Eryza G. Castro1, Rodrigo V. Salvatierra1, Marcela M. Oliveira2, Aldo J.G. Zarbin1

Departamento de Química, Universidade Federal do Paraná – UFPR, CP 19081, CEP 81531–990, Curitiba, PR, Brazil 2 Departamento Acadêmico de Química e Biologia, Universidade Tecnológica Federal do Paraná – UTFPR, Curitiba, PR, Brazil 1

Dodecanethiol–stabilized platinum nanoparticles (less than 3 nm) have been synthesized by the �irst time through a modi�ied two-phase liquid-liquid route, starting from H2PtCl6 as precursor. According to the data obtained

by Raman spectroscopy and XAS, in the presence of dodecanethiol the platinum precursor reacts to originate a stable Pt(II) complex that can not be reduced by sodium borohidride. So, the Pt nanoparticles were obtained by the reduction of the platinum precursor before the introduction of the dodecanethiol. The time interval in which the dodecanethiol was mixed in the reaction was used to control the size of the nanoparticles. The formation of dodecanethiol-stabilized Pt nanoparticles with fcc structure and medium size of 1.7, 2.2 and 2.4 nm was con�irmed by X–ray diffractometry, transmission electron microscopy, XANES and EXAFS. The obtained nanoparticles were electrocatalytically active for methanol oxidation.

Facilities: XAFS1, LME Publication: Chemistry of Materials, 22, 360-370 (2010) Funding: CAPES/PROCAD, CNPq Corresponding author: Aldo Zarbin – aldo@quimica.ufpr.br

DODECANETHIOL-STABILIZED PLATINUM NANOPARTICLES OBTAINED BY A TWO-PHASE METHOD: SYNTHESIS, CHARACTERIZATION, MECHANISM OF FORMATION AND ELECTROCATALYTIC PROPERTIES

A variety of different approaches have been

of sodium borohydride, which means that the sodium

developed for the preparation of metal nanoparticles

borohydride was not able to reduce the platinum

(NPs). Brust et al. developed one of the simplest

ions to metallic platinum. Our hypothesis was that

and most popular synthetic routes to produce

the failure of this reduction was due to formation

thiol-stabilized gold nanoparticles ; this method

of a toluene-soluble complex between the platinum

involves phase transfer of [AuCl4]- anions from

precursor and dodecanethiol. So, we repeated the

aqueous to organic solution in a two-phase liquid/

experiment but sodium borohydride was omitted,

liquid system, followed by reduction with sodium

in order to characterize the soluble compound.

borohydride in the presence of dodecanethiol .

After transferring [PtCl6]2- to the organic phase, the

Although the two-phase route developed by Brust

dodecanethiol (DT) was added to the system in two

has met with great success in the preparation of thiol-

different Pt/DT molar amounts, Pt/DT–1/2 and

functionalized Au and Ag NPs, there were no reports

Pt/DT–1/4. A blank solution (without the addition

on the utilization of this route for the preparation

of the DT) was also prepared simply by isolating the

of Pt nanoparticles, which was the main objective

organic phase after transferring [PtCl6]2- (Pt/TOAB). It

of this work. Platinum NPs are important materials

was observable by Raman spectroscopy that the Pt-Cl

that have been used extensively as efficient catalyst-

bands disappear in the presence of excess of thiol. The

electrodes in the electro-oxidation of alcohols in fuel

normalized XANES and Fourier transformed EXAFS

cell technology .

spectra (Pt L3-edge) of these samples are presented in

1

1

2

3

The first attempt to prepare the Pt NPs was

Figure 1. The absorption hump located approximately

carried out following the route described by Brust

3 eV past the edge (marked A in Figure 1, left) is

et al.1, but substituting the gold precursor HAuCl4

commonly called the “white line”. In Pt XANES, it is

with the platinum precursor H2PtCl6. The aqueous-to-

known that the higher the intensity of the white line,

toluene transfer of the [PtCl6] ions by the tetraocthyl

the lower the electron density of the platinum atoms

ammonium bromide (TOAB) was evidenced by a

(or in other words, the higher the oxidation state of

color change (colorless to pale yellow) observable

Pt)4. Quantitative determination of the platinum

in the organic phase after 10 minutes of stirring

oxidation state is possible based on the intensity

in the presence of TOAB. The pale-yellow color of

of the absorbance of peak A relative to the baseline

the organic phase became more intense after the

under B (see Figure 1, left). The highest A/B ratio of

addition of dodecanethiol. However, no changes to

2.51 corresponds to 100% Pt(IV) and the lowest A/B

the system were observed after the addition of excess

ratio of 1.52 corresponds to 100% Pt(II). Intermediate

2-

Figure 1.

XANES spectra (left) and Fourier transformed EXAFS (right) spectra: (black, filled square) aqueous solution of [PtCl6]2-; (red, open circle) toluene solution of [PtCl6]2- after the phase transfer (Pt/TBOA); (green, filled triangles) toluene solution of [PtCl6]2- after the addition of dodecanethiol in a Pt/thiol ratio of 1/2 (Pt/DT-1/2) and (blue, cross) toluene solution of [PtCl6]2- after the addition of dodecanethiol in a Pt/thiol ratio of 1/4 (Pt/DT-1/4); (right).

ACTIVITY REPORT 2010 – LNLS | 17

SCIENCE HIGHLIGHTS

values are attributed to mixtures of the two oxidation

and the sodium borohydride are introduced to the

states in different proportions. Figure 1 left shows a

solution. Instead of the original procedure, we would

significant reduction in the white line intensity for

introduce the sodium borohydride solution before

the toluene solutions of [PtCl6] after addition of

the dodecanethiol, aiming for the initial reduction

dodecanethiol, characterized by A/B ratios of 1.6 and

of [PtCl6]2- to Pto, followed the introduction of

1.5 for the samples Pt/DT–1/2 and Pt/DT–1/4,

dodecanethiol, which could attach to the surface of

respectively. These results indicate a Pt(IV) to Pt(II)

the freshly-formed nanoparticles. So, the control of

reduction caused by the presence of dodecanethiol.

the nanoparticle size was achieved by altering the time

2-

The EXAFS FT profile of the [PtCl6] aqueous

between the beginning of the reduction (introduction

solution shows one intense peak due to a Pt

of the borohydride solution) and the dodecanethiol

coordination sphere consisting of six chlorine ions

introduction. Times of 30, 60 and 90 seconds have

2-

at a Pt-Cl distance of 2.32 Å . After the there is a

been used, yielding the samples PtNP–30, PtNP–60

clear reduction in the amplitude of the FT peak

and PtNP–90, respectively.

5

Figure 2.

(Figure 1, right). The fit structural parameters for

The X-ray diffractograms of the samples showed

both Pt/DT–1/2 and Pt/DT–1/4 show platinum

the occurrence of broad and characteristic peaks of

coordination numbers of four, as expected for Pt(II)-

fcc platinum in all samples. The TEM images indicate

based square-planar complexes.

very small and non-agglomerated nanoparticles for

The complementary data obtained by Raman and

all three samples, with medium particle diameters of

XAS indicate that the Pt(IV) ions are reduced to Pt(II)

1.7 ± 0.3, 2.2 ± 0.4 and 2.4 ± 0.5 nm for the samples

in toluene after dodecanethiol addition, and this

PtNP–30, PtNP–60 and PtNP–90, respectively.

reduction is accompanied by a decrease in the platinum

Figure 2 presents the HRTEM images of

coordination number from six to four, resulting

individual particles collected from samples PtNP-30

in the formation of a Pt(II)-dodecanethiol highly

(Figures 2a,b), PtNP–60 (Figure 2c) and PtNP-90

stable towards sodium borohydride reduction, which

(Figures 2d,e). The high crystallinity of the particles is

precludes the synthesis of Pt NPs via this route. To

evidenced by the atomic arrangement or lattice fringes

avoid this obstacle, we proposed a small modification

observed, which can be attributed to crystalline planes

to the synthetic procedure, characterized by an

of fcc platinum. It is clear from the images shown

inversion of the sequence in which the dodecanethiol

in Figure 2 that the particles have characteristics of

HRTEM images of the Pt nanoparticles samples: a,b) PtNP–30; c) PtNP–60; and d,e) PtNP–90.

18 | ACTIVITY REPORT 2010 – LNLS

DODECANETHIOL-STABILIZED PLATINUM NANOPARTICLES OBTAINED BY A TWO-PHASE METHOD: SYNTHESIS, CHARACTERIZATION, MECHANISM OF FORMATION AND ELECTROCATALYTIC PROPERTIES

single crystals. Figure 2e show several particles found

the system. The images in Figure 2e shows clearly some

in sample PtNP–90. Contrary to the majority of the

set of nanoparticles nanoparticles in the beginning of

particles observed in other samples, this image show

the coalescence.

structures with elongated shape, characterized by two

The nanoparticle samples were also characterized

or more nanoparticles connected through necks. These

by XAS. The intensities of the white lines in the

results are evidence of the beginning of the growing

XANES spectra of all nanoparticle samples and of

process in which two (or more) individual particles

bulk platinum are comparable, corroborating the

aggregate to initiate formation of a larger particle.

previous data that the nanoparticles in PtNP-30,

The growing process was probably interrupted by

PtNP–60 and PtNP–90 consist of zero-valent

the adsorption of dodecanethiol molecules onto the

platinum. The experimental EXAFS spectra of the

surface of the joining particles. At the start of the

nanoparticle samples were fitted (Figure 3) and

reaction several nuclei are formed, and each begins

Fourier transformed (Figure 4). The FTs show an

to grow. The growing is quickly interrupted in the

intense peak between 2 and 3 Å, corresponding to a

sample PtNP–30, which results in nanoparticles

Pt-Pt scattering path related to the first coordination

with smaller diameters (Figures 2a,b). If the time

shell around the absorber. The amplitude of this

before dodecanethiol addition is increased (as with

peak is highest for bulk platinum and is strongly

sample PtNP–90), the unprotected nanoparticles

reduced for the nanoparticle samples. The amplitude

have mobility in solution and can coalesce, until the

decreases gradually from sample PtNP–90 to

moment at which the dodecanethiol is introduced in

PtNP-60 to PtNP–30, and this decrease is caused by

Figure 3.

Experimental (continuous line) and fitted (doted line) Pt L3-edge EXAFS spectra: a) Pt foil; b) PtNP-30; c) PtNP-60; and d) PtNP-90.

ACTIVITY REPORT 2010 – LNLS | 19

SCIENCE HIGHLIGHTS

Table 1. Structural parameters obtained from EXAFS analysis at the L3 edge of Pt. Sample

Coordination number

R (Å)

Pt foil PtNP–30 PtNP–60 PtNP–90

12 6.72 7.59 8.42

2.771 2.747 2.758 2.748

σ2 3.68 6.26 5.71 5.45

× × × ×

10-3 10-3 10-3 10-3

surface6. This effect was followed by an increase in the Debye-Waller factor (proportional to the decrease in particle size) indicating a small disorder in the lattice according the reduction in the particle size, as expected.

In conclusion, a successful route for the preparation of dodecanethiol-stabilized platinum nanoparticles through a two-phase liquid-liquid route was described. The occurrence of a stable complex between the platinum precursor and the dodecanethiol molecules was demonstrated for the first time, and previous unsuccessful attempts to prepare Pt NPs by this route were attributed to the Figure 4.

Fourier transformed EXAFS spectra: a) Pt foil; b) PtNP–30;

stability of this complex to borohydride reduction. A

c) PtNP–60; and d) PtNP–90.

simple inversion in the sequence of reagent additions was proposed, resulting in an efficient route for

the reduction in the average Pt coordination number, which is associated with the large number of surface atoms in very small particles6. As the particle gets smaller, the ratio of surface-to-bulk atoms increases, and the average coordination number is expected to be lower. The coordination number obtained by the EXAFS data decreases gradually from sample PtNP-90 to PtNP–60 to PtNP–30 (Table 1), following the nanoparticle size trend. A slight contraction in the Pt-Pt bond lengths was also observed in the nanoparticle samples (related to the bulk platinum,

preparing stable and very small Pt nanoparticles.

The electrocatalytic activity of the nanoparticles was tested in methanol oxidation, and the results indicate very good performance for the sample PtNP–90.

Acknowledgements The authors acknowledge the financial support from CNPq, CAPES/PROCAD, Brazilian Network on Carbon Nanotubes Research (MCT/CNPq) and INCT-Nanocarbono (MCT/CNPq). We also acknowledge CME–UFPR for the TEM images and LNLS – National Synchrotron Light Laboratory,

Table 1), and this effect has been correlated with a

Brazil (project HRTEM 6777 and D04B-XAF1-8236)

contraction of the lattice due a higher energy surface

for the HRTEM images and XAS data. EGC and RVS

caused by incomplete coordination of the atoms at the

acknowledge CAPES for fellowships.

References [1] Brust, M.; Walker, M.; Bethell, D.; Schiffrin, D.J.; Whyman, R. J. Chem. Soc. Chem. Commun. 1994, 801.

[2] Oliveira, M.M.; Zanchet, D.; Ugarte, D.; Zarbin, A.J.G. J. Colloid Interf. Sci. 2005, 292, 429.

[3] Tian, N,; Zhou, Z.-Y.; Sun, S.-G.; Ding, Y.; Wang, Z.-L. Science 2007, 316, 732.

[4] Hall, M.D.; Foran, G.J.; Zhang, M.; Beale, P.J.; Hambley, T.W. J. Am. Chem. Soc. 2003, 125, 7524.

[5] Bel’skaya, O.B.; Karymova, R. Kh.; Kochubey, D.I.; Duplayakin, V.K. Kin. Catal. 2008, 49, 720.

[6] Roman-Martinez, M.C.; Macia-Agullo, J.A.; Vilella, I.M.J.; Cazorla-Amoros, D.; Yamashita, H. J. Phys. Chem. C 2007, 111, 4710.

20 | ACTIVITY REPORT 2010 – LNLS

MAGNETICALLY RECOVERABLE GOLD NANOPARTICLES FOR CATALYTIC APPLICATIONS Rafael L. Oliveira1, Pedro K. Kiyohara2, Liane M. Rossi1

1 2

Instituto de Química, Universidade de São Paulo – USP, São Paulo, SP, Brazil Instituto de Física, Universidade de São Paulo – USP, São Paulo, SP, Brazil

The immobilization of catalysts on magnetically responsive solid supports has been a powerful strategy for catalysts recovery and recycling. In this work we have used a core-shell magnetite-silica nanostructured composite material for the controlled deposition of catalytic active gold nanoparticles on it. The iron oxide magnetic core responds to an external magnetic �ield allowing the manipulation and recovery of gold nanoparticles from other components of the sample.

The magnetic separation approach rendered the recovery of the gold catalyst from liquid-phase reactions much easier than by �iltration and centrifugation, with negligible metal leaching. The catalytic properties of gold nanoparticles are strongly affected by the nanoparticle size and size distribution in a way that the control of these parameters is necessary to dial up the active sites and improve catalytic performances.

We have used high resolution transmission electron microscopy and X-ray energy dispersive spectroscopy to study the morphology and composition of the supported catalyst.

Facility: LME Publication: Green Chemistry, 12: 144-149 (2010) Funding: FAPESP, CNPq, INCT-Catalise Corresponding author: Liane M. Rossi – lrossi@iq.usp.br

3

SCIENCE HIGHLIGHTS

Gold in the bulk form has long been regarded

coated magnetite nanoparticles (Fe3O4@SiO2)

as being chemically inert and an uninteresting

prepared following the procedure described by

metal from the point of view of catalysis. However,

Jacinto et al.11. The approach to prepare AuNPs

very interesting catalytic properties are revealed

is based on the uptake of Au 3+ ions from HAuCl4

when the size is reduced to few nanometers,

aqueous solution by the silica-coated magnetic

particularly with dimension less than 10 nm. A

nanoparticles, previously functionalized with

variety of interesting catalytic properties of gold

–NH 2 groups, followed by metal reduction

nanoparticles (AuNPs) in both oxidation and reduction reactions has been reported1-5. However, less attention has been paid on possible difficulties to separate colloidal NPs from the products. An alternative is the use of supported NPs, or more recently

magnetically

responsive

supported

NPs 6-10. Magnetic supports are mostly made of superparamagnetic NPs that have the property to be attracted to relatively low static magnetic field strengths and are easily re-dispersed since no residual magnetization is observed when the magnetic field is removed. Consequently, metal NPs properly attached to this kind of support can be easily recovered from the reaction medium and re-dispersed for further use. In this work we studied the deposition of catalytic active AuNPs on the surfaces of a core-shell magnetite-silica nanostructured support.

under mild conditions. Two different reduction methods were used: thermal treatment (catalyst 1) or H 2 reduction (catalyst 2). The localization and composition of each kind of NPs of the nanocomposite was revealed by X-ray energy dispersive spectroscopy (EDS) analysis using a nanoprobe in the Jeol-3010 ARP microscope (LNLS, Campinas). The HRTEM image of a single nanocomposite unit of the catalyst 2 and the corresponding EDS analyses are shown in Figure 1. The core NPs were found to be exclusively composed of Fe atoms, which correspond to the magnetic Fe3O4 NPs (Figure 1b), and the darker NPs on the surface of Au atoms (Figure 1c), through a detailed EDS analysis of the image areas shown in box (b) and box (c), respectively. The EDS analysis shown in Figure 1a corresponds to the whole nanocomposite which contains Fe, Au and Si (Cu from sample holder), as expected.

A schematic illustration of the step-by-step

The AuNPs mean diameter in both solids

approach used for the preparation of magnetically

(catalyst 1 and 2) was estimated at 5.9 nm with

responsive AuNP catalysts is shown in Scheme 1.

polydispersity of 18% for catalyst 2 and 32% for

The magnetically responsive support used

catalyst 1. The AuNPs are fairly well-distributed

in this study consists of core-shell silica-

over the support in both catalysts as revealed in

Scheme 1. Step-by-step preparation of magnetically responsive AuNPs. 22 | ACTIVITY REPORT 2010 – LNLS

MAGNETICALLY RECOVERABLE GOLD NANOPARTICLES FOR CATALYTIC APPLICATIONS

TEM images (not shown), however the particle

is that this difference in particles size distribution

size distribution of catalyst 2 is sharper if

caused a pronounced difference in the catalytic

compared to catalyst 1. A very interesting fi nding

performance of each catalyst. As it can be seen in Figure 2, catalyst 1, the one with broad particle size distribution, is less active and requires higher pressure to become active in the oxidation of benzyl alcohol, although the selectivity was maintained in the pressure range studied. On the other hand, catalyst 2, the one with narrow particle size distribution, is more active, reaching 100% conversion at 3 atm of O2 and, because the catalyst is very active, the selectivity to benzaldehyde drop to ca. 50%. These results exemplify how important is to keep a good control on gold particles size distribution for catalytic applications. Many catalysts studied so far have a very poor control on AuNP size and probably only a small fraction of the gold present is catalytic active and contributes to the catalytic performance observed.

Figure 2.

Pressure dependence of the catalytic performance of supported AuNPs: catalyst 1 (circle) and catalyst 2 (square). Reaction conditions: 1.5 mmol of benzyl alcohol, 50 mg catalyst, 70 mg K2CO3, 2 mL toluene, 100 °C, 6 h.

Figure 1.

HRTEM image and EDS analysis of the AuNP magnetically responsive catalyst in different areas of the image: a) corresponds to the whole area; b) corresponds to the iron oxide NP shown in box b; and c) corresponds to the gold NP shown in box c.

Figure 3.

Illustration of magnetic separation of AuNP catalyst.

ACTIVITY REPORT 2010 – LNLS | 23

SCIENCE HIGHLIGHTS

The catalysts reported here are very efficiently

catalyst was elucidated by HRTEM and EDS

recovered by magnetic separation, with negligible

analysis. We were able to localize the iron oxide

Au leaching to the solution (Figure 3). Th is

and the AuNPs present in each catalyst unit,

separation procedure is an efficient and green alternative

to

the

conventional

separation

techniques used for the recovery of solids, such as fi ltration and centrifugation, since it is fast, clean, easy to scale-up and constitutes a waste minimizing

and

low

energy

consumption

procedure.

In summary, the morphology and composition of a multifunctional magnetically responsive

which confi rmed the successful preparation of AuNPs immobilized on a core-shell silica-coated magnetite nanocomposite. The catalytic studies have shown that the control of the AuNP size distribution, which is not trivial in the preparation of supported nanoparticles, is a key parameter to dial up the active sites and improve catalytic performances.

References

[1] Hutchings G. J.; Catalysis by gold, Catal. Today, v.100, n. 1, p.55-61, 2005.

[2] Hutchings G. J.; Haruta M. A golden age of catalysis: A perspective, Appl. Catal. A, v. 291, n. 1, p. 2-5, 2005 [3] Haruta M. Gold as a Novel Catalyst in the 21st Century: Preparation, Working Mechanism and Applications, Gold Bull., v. 37, n.1, p. 27-36, 2004.

[4] Astruc F. L. D.; Aranzaes J. R. Nanoparticles as Recyclable Catalysts: The Frontier between Homogeneous and Heterogeneous Catalysis, Angew. Chem. Int. Ed., v. 44, n. 48, p. 7852-7872, 2005 and references therein.

[5] Hashmi A. S. K.; Hutchings G. J. Gold Catalysis, Angew. Chem., Int. Ed., v. 45, n.47, p. 7896 – 7936, 2006 [6] Zhu Y.; Stubbs L. P.; Ho F.; Liu R.; Ship C. P.; Maguire J. A.; Hosmane N. S. Magnetic Nanocomposites: A New Perspective in Catalysis, ChemCatChem, v. 2, n. 4, p. 365-374, 2010.

[7] Oliveira, R. L.; Kiyohara, P. K.; Rossi, L. M. High performance magnetic separation of gold nanoparticles for catalytic oxidation of alcohols, Green Chem., v.12, n.1, p.144-149, 2010.

[8] Panella, B.; Vargas, A.; Baiker, A. Magnetically separable Pt catalyst for asymmetric hydrogenation, J. Catal., v. 261, n. 1, p. 88-93, 2009.

[9] Zhu, J.; Zhao, T.; Kvande, I.; Chen, D.; Zhou, X.; Yuan, W. Carbon nanofiber-Supported Pd Catalysts for Heck Reaction: Effects of Support Interaction, Chin. J. Catal., v. 29, n.11 p.1145-1151, 2008.

[10] Menini, L.; Pereira, M. C.; Ferreira, A. C.; Fabris, J. D.; Gusevskaya, E. V. Cobalt-iron magnetic composites as heterogeneous catalysts for the aerobic oxidation of thiols under alkali free conditions, Appl. Catal. A, v. 392, n. 1, p. 151-157, 2011.

[11] Jacinto, M. J.; Kiyohara, P. K.; Masunaga, S. H.; Jardim, R. F.; Rossi, L. M. Recoverable rhodium nanoparticles: Synthesis, characterization and catalytic performance in hydrogenation reactions, Appl. Catal., A, v. 338, n. 1, p. 52-57, 2008.

24 | ACTIVITY REPORT 2010 – LNLS

THE CONCEPTION OF A GOLD ELECTROCHEMICAL MICROCELL AND ITS APPLICATION ON A DISPOSABLE SALICYLATE BIOSENSOR

Rafaela Fernanda Carvalhal1, André Luis de Jesus de Almeida2, Ney Henrique Moreira2, Maria Helena Piazetta2, Angelo Luiz Gobbi2, Lauro Tatsuo Kubota1

Analytical Chemistry Department, Institute of Chemistry, State University of Campinas – UNICAMP, P.O. Box 6154, Campinas, SP, Brazil 2 Microfabrication Laboratory, Brazilian Synchrotron Light Laboratory – LNLS, P.O. Box 6192, Campinas, SP, Brazil 1

Electrochemical biosensors and sensors are versatile analytical instruments that were the inspiration of the concept of point-of-care devices.

The challenges involved in the development of those devices are the same that have been faced by electrochemical biosensors and sensors, for example, the detection or the quanti�ication of species of interest with high sensitivity and selectivity directly from sample and using small sample volumes. The use of an amperometric biosensor for rapid salicylate determination in blood is described. Photolitography was used to make gold electrodes on a polyester �ilm. The plastic microcell was characterized using cyclic voltammetry to demonstrate the electrochemical performance of the system. The biosensor was constructed by immobilizing salicylate hydroxylase onto the working electrode of the plastic electrochemical microcell. The resulting biosensor exhibited a high sensitivity (97.4 nA/mmol.L−1 salicylate) and an adequate linear response range (1.2 × 10−4 to 1.0 × 10−3 mol.L−1). The biosensor performance was veri�ied by determining salicylate in spiked blood samples and the results were statistically equivalent to the values obtained from the standard Trinder spectrophotometric method. This study shows the potential development of a portable, inexpensive and disposable device for point-of-care monitoring.

Keywords: Screen-printed electrodes; amperometric biosensor; salicylate hydroxylase; salicylate determination; biosensor; gold �ilm electrodes.

Facility: LMF Publication: Biosensors & Bioelectronics, 25, 2200-2204 (2010) Funding: CNPq, FAPESP Corresponding author: Lauro Tatsuo Kubota – kubota@iqm.unicamp.br

4

SCIENCE HIGHLIGHTS

Introduction

The market related to point-of-care devices is

solution (AZ 351, Clariant) diluted with water in the

growing around 10% annually, especially because

proportion of 1:3 (v/v), respectively, for 1 minute

of mass production techniques, resulting in low

with constant stirring. A layer of approximately

cost (disposable) devices, which have minimized the

20 nm of Ti and a second layer of 100 nm of Au

consumption of energy, space, samples and reagents,

upon the substrate was deposited by electron-beam

as well as waste . The fabrication of electrochemical

evaporation. All the photoresist under the deposited

microcells containing working, reference and

metallic layer was removed from the substrate

auxiliary electrodes in a single dispositive has

leaving the design of the electrode by using the

been considered a key factor for success especially

lift-off technique. The design of the microcell is

due to its versatility. Gold is a metal with adequate

simple: the auxiliary and the reference electrodes are

1

properties for all-electrochemical technique due to its high stability over a wide potential range, ease in making rods and fi lms and especially as a transducer in electrochemical biosensors because of its biocompatibility. Despite its advantages, the development of biosensors based upon thin or thickfi lm gold electrodes is gaining importance due to the high interfacial reactivity of those electrodes in comparison with screen-printed ones, even if printed with different ink materials2.

The monitoring of salicylate levels in blood is of great importance in cases of suspicion of acute poisoning and in chronic therapy3. Here is described the development of a disposable electrochemical biosensor for point-of-care monitoring of salicylate in blood. It is based on the immobilization of salicylate hydroxylase with glutaraldehyde and bovine serum albumin (BSA) upon a plastic electrochemical microcell.

Results and Discussion

Gold electrodes were assembled on 100 µm

polyester fi lms. The substrate was cleaned and then covered with a positive photoresist (S1811, Shipley

rectangular with an area of 3 mm2 and the working electrode has an area of 1.5 mm2 (Figure 1). The electrodes were rinsed twice with dilute sulphuric acid and then washed copiously with water and let dry. This pre-treatment step was evaluated and effectively improves the electrochemical reversibility of potassium ferrocyanide upon screen-printed gold interface.

Salicylate hydroxylase was immobilized by dissolving 1.0 mg of the enzyme in 100 µL of phosphate buffer (0.1 mol.L-1, pH 7.6) containing 0.5 % (v/v) of glutaraldehyde and 1.0 mg of BSA. An aliquot of 5 µL of this solution was disposed on the gold working electrode surface and let dry in air for 1 hour. This modified electrode was used as a biosensor for salicylate, without any other treatment of the surface. The measurements were performed using a drop that is deposited on a confined area of the electrode system. The volume used in measurements was 20 µL. However, volumes of up to 80 µL can be used.

The reference thin-fi lm gold electrode does not accomplish all the requirements of a standard reference electrode, so it was compared with a

Co.) in a spinner. The substrate was fi xed on a glass support in order to be properly held by the spinner and the process was concluded in 30 seconds at 4000 rpm. After that, the photoresist solvent was volatilised by placing the substrate on a heating plate at 90 °C for 5 minutes. The substrate was exposed for 20 seconds to UV light using a maskaligner (MJB3, Karl Suss) whose lamp intensity is about 9.5 mW cm-2.

The photomask was designed to define the traditional three-electrode configuration disposed on the same strip. The revelation step was carried out by putting the photoresist layer in contact with the developer 26 | ACTIVITY REPORT 2010 – LNLS

Figure 1.

Image

of

the

electrochemical

constructed upon polyester.

microcell

THE CONCEPTION OF A GOLD ELECTROCHEMICAL MICROCELL AND ITS APPLICATION ON A DISPOSABLE SALICYLATE BIOSENSOR

well-studied calomel reference electrode. The

of the biosensor it was verified that the complex

redox potential of Fe(CN)6 /Fe(CN)6 , a probe

blood matrix interferes in the performance of

molecule, shifts toward more negative values,

the biosensor. So, the standard addition method

about -172 (±1) mV vs. SCE. by performing cyclic

was applied to achieve a reliable determination of

voltammetric measurements under the same

salicylate content in blood.

4-

3-

experimental conditions but employing different

Capillary blood obtained from a finger was

reference systems. The potential stability of the

analyzed with the biosensor. The required sample

pseudo-reference gold electrode was attested by

needs to be no greater than 20 µL and did not

monitoring its potential over 1 hour in 0.1 mol.L

undergo any pre-treatment before the analysis. If

-1

KNO3, pH 7.0.

necessary, the samples may be diluted to a suitable

The magnitude of the electrochemical surface

concentration range. The analysis was performed

area (ESA) is an important attribute of a metallic

according to the following protocol: 20 µL of a blank

platform that is going to support an amperometric

buffer solution (containing 0.5 mmol.L-1 NADH) was

biosensor because ESA is proportional to the

dropped onto the biosensor and up to five minutes

microscopic roughness observed at gold interface

of amperometric signal was recorded. Subsequently,

and it relates to the immobilization of the recognition

5 µL of spiked blood was added and after one minute

layer. The ESA is the ratio between the charge of the

the amperometric signal was recorded. Next, 5 µL

gold oxide reduction upon the studied surface and the

of a standard solution of salicylate (2.00 mmol.L-1)

standard reference charge found for polycrystalline

was added and after one minute the amperometric

Au, 390 ± 10 µC.cm-2 [4]. The ESA of the working gold

signal was registered. The addition order of the

electrode is 3.70 ± 0.11 mm and is, on average, 2.5

standard solution and blood sample also influence

times greater than the geometric area.

the analytical performance of the biosensor. It is

2

The optimized biosensor working conditions

important to first add the blank buffer solution

were 0.1 mol.L phosphate buffer at pH 7.6 with

containing the cofactor, then the blood sample and,

0.5 mmol.L of NADH and 300 mV vs. Au as the

last, the standard solution of salicylate. That protocol

applied potential. During the analytical validation

is illustrated in Figure 2.

-1

-1

Figure 2.

Scheme of salicylate analysis with the developed disposable biosensor fragmented in steps 1 and 2. In step 2 is shown amperograms obtained during the salicylate determination in spiked blood sample. Legend: a) PBS 0.1 mol.L-1, pH 7.6 (buffer); b) Buffer + spiked blood with 0.1 mmol.L-1 sodium salicylate; and c) buffer + spiked blood + 2 mmol.L-1 standard solution of sodium salicylate.

ACTIVITY REPORT 2010 – LNLS | 27

SCIENCE HIGHLIGHTS

A calibration curve obtained for a freshly prepared biosensor showed a linear range of response for salicylate concentration from 0.125 mmol.L-1 to 1.00 mmol.L-1, keeping the [NADH]/[salicylate] ratio between 2 and 4. The analytical curve Equation 1 was: i(nA) = 97.4 (± 4.9) [salicylate, mmol.L-1] + 15.2 (± 2.9)

(1)

with a correlation coefficient of 0.997 for n = 5.

The salicylate determinations with the disposable biosensor

were

compared

with

the

Trinder

spectrophotometric method and it was also found

Conclusions

The use of a microcell made of plastic proved

to be well suited for the fabrication of inexpensive electrochemical devices that could be applied for the development of disposable biosensors. These devices can solve challenging analytical problems that usually require sophisticated instrumentation, technical staff and some hours to be accomplished.

In this paper we describe the development of a disposable biosensor for salicylate determination.

that the results obtained with the biosensor were not

The biosensor showed adequate sensitivity and

significantly different, according a paired t-test at

accuracy to quantitatively detect salicylate in human

the 95 % confidence level.

blood.

References

[1] Warsinke, A. Point-of-care Testing of Proteins. Anal. Bioanal. Chem. v. 393, p. 1393-1405, 2009.

[2] García-Gonzáles, R. et al. Electrochemical characterization of different screen-printed gold electrodes. Electrochim.

Acta. v. 53, n. 8, p. 3242-3249, 2008.

[3] Oliveira Neto, G. et al. Electrochemical Biosensors for Salicylate. Electroanalysis. v. 11, n. 8, p. 527- 533, 1999.

[4] Trasati, S. and Petrii, O. A. Real Surface Area Measurements in Electrochemistry. Pure Appl. Chem. v. 5, n.(1-2), p. 711-734, 1991.

28 | ACTIVITY REPORT 2010 – LNLS

STRUCTURAL AND BIOCHEMICAL CHARACTERIZATION OF PEROXIREDOXIN Q OF XYLELLA FASTIDIOSA

Bruno Brasil Horta1, Marco Antonio de Oliveira2, Karen Fulan Discola1, José Renato Rosa Cussiol1, Luis Eduardo Soares Netto1 1

Instituto de Biociências, Universidade de São Paulo – USP, São Paulo, SP, Brazil 2 Universidade Estadual Paulista – UNESP, São Vicente, SP, Brazil

Peroxiredoxin Q (PrxQ) of Xylella fastidiosa is a non-heme peroxidase whose activity is endowed by reactive cysteine residues. During the catalytic cycle of PrxQ an intramolecular disul�ide bond is generated between Cys-47 and Cys-83, as showed by site-speci�ic mutagenesis and mass spectrometry. This work is a comprehensive analysis of the catalysis performed by PrxQ that belongs to a peroxiredoxin class still poorly characterized and previously considered as moderately reactive towards hydroperoxides. Contrary to these assumptions, competitive kinetics studies have shown that the peroxidase activity of PrxQ is as fast as the most ef�icient peroxidases. Furthermore, we elucidated the crystal structure of PrxQ C47S in which Ser-47 and Cys-83 lie approximately 12.3 Å apart. Therefore, signi�icant conformational changes are required for disul�ide bond formation. In fact, circular dichroism data indicated that there was a signi�icant redox-dependent unfolding of alpha helices. Take into account our data as well data as from the literature, we proposed a model for the conformational changes occurring in the catalytic cycle of peroxiredoxins from the same class that PrxQ.

Facility: MX2 Publication: Journal of Biological Chemistry, 285, 16051-16065 (2010) Funding: FAPESP, CNPq Corresponding author: Luis Eduardo Soares Netto – nettoles@ib.usp.br

5

SCIENCE HIGHLIGHTS

Xylella fastidiosa is the causative agent of Citrus

and abolishment of peroxidase activity showed

Variegated Chlorosis (CVC) and others economically

that Cys-47 is the peroxidatic cysteine of PrxQ.

important plant diseases. During infection by

Unequivocal localization of resolving cysteine was

microorganisms, one of the first plant responses

obtained by HPLC-ESI-MS analyses. We detected a

is the production of oxidants, including hydrogen

peptide in the N-ethylmaleimide (NEM)-alkylated

peroxide, organic hydroperoxides and peroxynitrite.

PrxQ tryptic-digested mixture, with the mass

To protect themselves, microorganisms developed

corresponding to the expected peptide containing

defenses such as antioxidant enzymes. One of these

a disulfide bond between Cys-47 and Cys-83. In

proteins of X. fastidiosa is PrxQ (peroxiredoxin Q),

addition, we detected two masses that corresponded

a non-heme peroxidase whose activity is endowed by

to the peptide containing Cys-23 and the peptide

reactive cysteine residues.

containing Cys-101, both conjugated with NEM.

PrxQ catalysis involves the oxidation of a conserved reactive cysteine (called peroxidatic

Thus, the intramolecular disulfide bond is formed between Cys-47 and Cys-83.

cysteine) to a sulfenic acid intermediate (Cys-SOH)

Recently, PrxQ homologous proteins were

with reduction of the hydroperoxide to the

further categorized into two sub-families: PrxQα

correspondent alcohol. The sulfenic acid reacts with

proteins that have the two catalytic cysteine

a second C-terminal cysteine (resolving cysteine)

residues (peroxidatic and resolving cysteines)

resulting in an intramolecular disulfide bond.

with four-residue spacing and PrxQβ proteins that

Among peroxiredoxin proteins, the sulfenic acid

do not have a cysteine vicinal to the peroxidatic

intermediate can also have other fates. It can reacts

cysteine. According to this categorization, PrxQ of

with a second cysteine located in the C-terminus

X. fastidiosa belongs to the PrxQβ subfamily.

of other subunit, resulting in an intermolecular

Kinetic characterization of PrxQ – PrxQ

disulfide bond, or is stabilized by the active site

presented low DTT-dependent peroxidase activity,

micro-environment. Catalytic cycle is completed

when

when disulfide bond or sulfenic acid is reduced. For

Substantial activity was only observed when high

most peroxiredoxins, its reduction is carried out by

concentrations of the thiol compound were employed.

thioredoxin.

Addition of thioredoxin (TsnC) of X. fastidiosa

compared

with

other

peroxiredoxins.

for

greatly stimulated the peroxidase activity (Figure 1a)

peroxiredoxins. Recently, a distribution into four

suggesting that thioredoxin system as their probable

classes of peroxiredoxins based on both amino

biological reducing system. Steady-state bisubstrate

acid sequence and structural similarities was

kinetic analyzes suggested that PrxQ is moderately

proposed and provided insights on the evolution of

reactive towards hydroperoxides (k cat/Km in the

these proteins within the thioredoxin suprafamily

range of 103 to 104 M-1.s-1) with a slightly higher

(Copley et al., 2004). According to this classification,

specificity towards hydrogen peroxide and cumene

PrxQ from X. fastidiosa belongs to class 1, the

hydroperoxide compared to t-butyl hydroperoxide.

most ancestral, from which the other three classes

In contrast, competitive kinetic studies with heme-

arose. However, they are the least characterized

containing peroxidase (horseradish peroxidase),

class, with crystal structures being elucidated only

established that the second-order rate constants

very recently. Among all peroxiredoxins, the ones

of PrxQ were high for hydrogen peroxide (k in the

belonging to class 1 have been considered the least

107 M-1.s-1 range) and for peroxynitrite (k in the

reactive proteins toward hydroperoxides.

106 M-1.s-1 range). These are the first second-order

Several

classifications

were

suggested

Functional Cysteine Residues of PrxQ – Since PrxQ

rate constants determinations of the reaction of a

has four cysteine residues, the identification of the

class 1 peroxiredoxin with hydroperoxides, and the

two cysteines involved in disulfide bond formation

results have changed the common belief that class 1

was only possible by a series of biochemical assays

peroxiredoxins present moderate reactivities in

on wild-type and Cys→Ser mutant proteins. Thiol

comparison to other members of the peroxiredoxin

titration using DTNB (5,5'-dithio-bis(2-nitrobenzoic

family. Instead, these values demonstrate that

acid)) under oxidized and reduced proteins

class 1 peroxiredoxins are as reactive towards

30 | ACTIVITY REPORT 2010 – LNLS

STRUCTURAL AND BIOCHEMICAL CHARACTERIZATION OF PEROXIREDOXIN Q OF XYLELLA FASTIDIOSA

hydroperoxides as class 3 and class 4 peroxiredoxins,

efforts to obtain structures for the wild-type protein,

glutathione peroxidases and catalases. The apparent

we could only obtain crystals of PrxQ C47S, which is

ambiguity between steady-state and competitive

probably representative of the reduced enzyme state

kinetics can be explained by the proposal that

of the wild-type protein. PrxQ C47S crystallized in

reduction of peroxiredoxins by thioredoxin is the

0.1 M HEPES-HCl (pH 7.5) and 20% PEG 8000 at

rate-limiting step of the catalytic cycle.

293 K, and in space group P212121 (orthorhombic) with

The reactivity of cysteine residues towards

one molecule per asymmetric unit. As expected, the

hydroperoxides is in part given by the pKa of its side

structure of PrxQ C47S is composed by a canonical

chain, since the thiolate is a stronger nucleophile than

thioredoxin fold with insertions and extensions

the protonated counterpart. The kinetic competitive

that form a five-stranded mixed β-sheet (in the

approach with horseradish peroxidase at different

order β3↑-β4↑-β5↑-β8↓-β9↑) surrounded by six

pHs was used to determine the pKa of the PrxQ

α-helices and four additional β-strands (Figure 2a).

reactive cysteine, showing a single inflexion point at

According to structural comparisons with known

6.2 (Figure 1b). This value corresponds to the pKa of

peroxiredoxin structures, we confirmed that PrxQ

the peroxidatic cysteine residue of PrxQ and it is in

of X. fastidiosa is a class 1 peroxiredoxin. To date,

agreement with the low pKa thiols of peroxiredoxins

a small number of structural coordinates of class 1

characterized so far. However, the second-order rate

enzymes is available in the RCSB Protein Data Bank.

constant determined for the protonated thiol form of

Besides, only three of seven structures available are

Cys-47 is also very high (in the range of 106 M-1.s-1)

structures of members of the PrxQβ subfamily. All

indicating that stabilization of thiolate alone is not

of them are structures of the same protein, Bcp from

sufficient to confer reactivity. Several aspects of

Xanthomonas campestris (PDB ID: 3GKK, 3GKN

peroxiredoxins reactivity remain elusive, such as the

and 3GKM). Furthermore, the four other structures

identification of residues responsible for the removal

refer to members of the PrxQα subfamily (PDB ID:

of the proton from the sulfur atom of the peroxidatic

2CX3, 2CX4, 2YWN and 3DRN).

cysteine; protonation of the RO leaving group and −

stabilization of the transition state.

The Ser-47, which replaces the peroxidatic cysteine in PrxQ C47S, is located at the N-terminus

Structural characterization of PrxQ – We

of helix α3. Electron density maps of Ser-47

attempted to obtain PrxQ structure in the reduced

indicated that the side chain can adopt two distinct

and oxidized forms to perform structural and

conformations. In one configuration, Oγ of Ser-47

functional relationship experiments. In spite of the

can make hydrogen bonds with O of Lys-41, Oγ of

Figure 1.

Peroxidase Activity of PrxQ. a) Removal of cumene hydroperoxide by DTT-dependent peroxidase assay in the presence of: 5 µM PrxQ (closed squares); 10 µM TsnC (open triangles); and 5 µM PrxQ plus 10 µM TsnC (open squares).

Peroxidase reactions were carried out in a reaction mixture containing 200 µM cumene hydroperoxide and 0.5 mM DTT, at 37 °C. b) Variation of the second-order rate constant of the reaction between PrxQ and hydrogen peroxide as a function of the pH. The reaction mixtures containing 8 µM HRP and reduced PrxQ in various concentrations were incubated with 8 µM hydrogen peroxide. After incubation at 37 °C, formation of HRP compound I was measured at 403 nm.

ACTIVITY REPORT 2010 – LNLS | 31

SCIENCE HIGHLIGHTS

Figure 2.

Structural features of the PrxQ C47S protein. a) Cartoon representation of the PrxQ C47S structure. The five-stranded mixed β-sheet of the thioredoxin fold is colored in orange. Side-chains of Ser-47 and Cys-83 are shown in ball and stick mode. b) Interaction network in the active site of PrxQ C47S. Residues are represented as balls and sticks and atoms are colored following the CPK color scheme (carbon, green; oxygen, red; nitrogen, blue; and sulfur, yellow).

The magenta ball represents water-290. Hydrogen bonds and salt bridges are indicated by dashed lines. c) PrxQ C47S mapped by electrostatic surface potentials (red, negatively charged; blue, positively charged), as calculated with the APBS program. The white circle demarcates the surface in the vicinity of the active site.

Thr-44 and Nη1 of Arg-122, probably corresponding

Arg-122 is fully conserved among peroxiredoxin

to interactions that stabilizes reactive cysteine in the

enzymes and is postulated to affect the pKa of the

thiolate form (R–S ) (Figure 2b). One water molecule

peroxidatic cysteine. The low pKa of the peroxidatic

(H2O-290) interacts with Oγ of Ser-47, with O and N

cysteine could be attributed (at least partially) to

−

of Lys-41 and with Oγ of Thr-44. Furthermore, Oε1 of Glu-50 makes a polar interaction with Nη1 of Arg-122 that appears to orient the Arg-122 and, thereby, allows the interaction between Arg-122 and Ser-47.

Ser-47 is also exposed to the surface of the protein, allowing interaction with substrate. Their side chain is located in a shallow cavity with a surface that is made up of the side chains of Pro-40, Lys-41, Thr-44, Gly-46 and Arg-122, and occupies 0.3 Å 2 of solvent accessible surface. This shape suggests that it could accommodate substrates of various forms and sizes, which is in agreement with the low hydroperoxide specificity of PrxQ. 32 | ACTIVITY REPORT 2010 – LNLS

the nearby guanidino group of Arg-122. Indeed, mutation of this Arg in other Prxs abolishes or diminishes peroxidase activity. The stabilization of this negative charge on Cys-47 could also arise from the influence of electrostatic interactions between the thiolate anion and other positively charged residues in the active site region. Finally, the positive electrostatic potential of the PrxQ surface where the peroxidatic cysteine is located and the localization of the peroxidatic cysteine in the N-terminus of helix α2 can also be correlated with the low pKa value of Cys-47 (Figure 2c).

The resolving cysteine Cys-83 is located at the middle of helix α4 and is 12.26 to 14.07 Å away from

STRUCTURAL AND BIOCHEMICAL CHARACTERIZATION OF PEROXIREDOXIN Q OF XYLELLA FASTIDIOSA

the peroxidatic Cys-47 (Figure 2a). Therefore, to

assays as well as information from the literature, we

produce distances within 2 Å (the idealized distance

elaborate a model in which crystal structures of PrxQβ

between Sγ atoms in disulfide bonds), substantial

proteins represent snapshots along the coordinate of

backbone

be

the enzyme-catalyzed process (Figure 5). Because

required. Therefore, conformational changes in

oxidation takes place in the peroxidatic cysteine

PrxQ structure were analyzed by CD spectroscopy in

(Cys-47 in PrxQ) of the reduced protein (Figure 5a),

different oxidation states. In fact, the CD spectrum

structural changes in the proteins probably begin

of oxidized wild-type PrxQ in the far-UV region

with the oxidation to a sulfenic acid derivative by

conformational

changes

would

displayed a decrease in the signal intensity at 222 nm relative to the reduced protein (Figure 3a), which is consistent with a smaller α helical content. A similar redox-dependent structural change occurred in the PrxQ C83S (Figure 3c) protein but not in the PrxQ C47S protein (Figure 3b). Estimating α helical content of these enzymes by the molar ellipticity at 222 nm, we found that oxidation of PrxQ wildtype and C83S proteins resulted in a 4.7% and 4.0% reduction in α helical content, respectively. Because helices α3 and/or α4 are 6.7% and 6.1% of the PrxQ α helical content, respectively, CD estimation indicates that at least part of helices α3 and α4 underwent a structural unfolding due to the redox state change of PrxQ during its catalytic cycle.

Some insights on the mechanism for this conformational change might be obtained from the comparison of PrxQ from X. fastidiosa with the recently described structures of Bcp from X. campestris as well as structures from Aeropyrum pernix. Peroxidatic and resolving cysteines of putative reduced form of Bcp from X. campestris are also in distinct α helices, whereas only helix α4 that holds its resolving Cys-84 is unfolded in the disulfide-containing structure of the same protein (PDB ID: 3GKK) (Figure 4a and 4b). In an apparent contrast, when structures of reduced and oxidized forms of Bcp from A. pernix K1 are compared (PDB ID: 2CX4 and 2CX3, respectively), only helix α2 (equivalent to helix α3 in X. fastidiosa and X. campestris) and not helix α3 (equivalent to helix α4 in X. fastidiosa and X. campestris) is unfolded, with an intramolecular disulfide bond in a loop (Figure 4c and 4d). Bcp from A. pernix K1 is a member of the PrxQα subfamily, and active cysteines are vicinal to each other (Cys-49 and Cys-54) and belong to the same helix α2.

Taking

into

consideration

all

available

crystallographic structures of class 1 peroxiredoxins, our CD spectra, mass spectra and other biochemical

Figure 3.

Conformational analysis of PrxQ. CD spectra in the reduced form (solid line) and treated with 1.2 equivalents of hydrogen peroxide (dashed line) of: a) wild-type PrxQ; b) PrxQ C47S; and c) PrxQ C83S proteins. Spectra were recorded at 20 °C using a protein concentration of 10 µM in 20 mM sodium phosphate buffer (pH 7.4).

ACTIVITY REPORT 2010 – LNLS | 33

SCIENCE HIGHLIGHTS

Figure 4.

Conformational changes in Bcp of X. campestris and A. pernix K1. a) Cartoon representation of Bcp C48S C84S of X. campestris (PDB ID: 3GKM). Helixes that suffer conformational changes are colored in cyan and orange. The superposition of this structure with PrxQ C47S of X. fastidiosa has a RMSD of 0.873 Å. b) Cartoon representation of Bcp of X. campestris in the intramolecular disulfide bond form (PDB ID: 3GKK). c) Cartoon representation of Bcp of A. pernix K1 in the reduced form (PDB ID: 2CX4). Helix that suffers conformational change is colored in magenta. The superposition of this structure with PrxQ C47S of X. fastidiosa has a RMSD of 1.785 Å. d) Cartoon representation of Bcp of A. pernix K1 in the intramolecular disulfide bond form (PDB ID: 2CX3).

34 | ACTIVITY REPORT 2010 – LNLS

STRUCTURAL AND BIOCHEMICAL CHARACTERIZATION OF PEROXIREDOXIN Q OF XYLELLA FASTIDIOSA

Figure 5.

Structurally detailed model of conformational changes in the PrxQβ catalytic cycle. Proposed sequence of structure snapshots along the catalytic cycle of PrxQ subfamily β proteins. Each panel represents a different species of the proposed model. a) Reduced species based on the determined crystal structure of PrxQ C47S of X. fastidiosa. b,c) These species in dashed boxes represent intermediates conformation hypothesized based on CD data presented here. d) Oxidized species based on the determined crystal structure of Bcp of X. campestris (PDB ID: 3GKK).

Peroxidatic and resolving cysteines are indicated as CysP and CysR, respectively.

the hydroperoxide. Because sulfenic acid is bulkier

acid to helix α4 where resolving cysteine is

and more electronegative than the corresponding

located (Figure 5b) and, finally, formation of the

thiol, electrostatic interactions that stabilize thiolate

intramolecular disulfide bond (Figure 5c). It is

in Cys-47 (Figure 2b) might be lost, triggering the

possible that the formation of the disulfide bond

unfolding of helix α3 (Figure 5b).

provoke partial unfolding of helix α4, followed by

In the next step, the local unfolding of helix

the full refolding of helix α3 and restructuration of

α3 might lead to the approximation of the sulfenic

the active site (Figure 5d). Interestingly, this feature ACTIVITY REPORT 2010 – LNLS | 35

SCIENCE HIGHLIGHTS

is unique to class 1 peroxiredoxins because the active site is fully unfolded in the disulfide configuration in the other three classes of peroxiredoxins, which may suggest these proteins as targets for the development of drugs against bacterial pathogens.

In conclusion, we have shown that class 1

Acknowledgments This work was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, as part of Projeto

catalytical

Milênio Redoxoma) and the Brazilian Synchrotron

mechanism among Cys-based peroxidases, although

Light Laboratory (LNLS) under proposal D03B-MX1

they are also very reactive towards hydroperoxides.

7568 (performed on the beamline W01B-MX2).

peroxiredoxins

References

present

a

distinct

[1] Horta et al. (2010) The Journal of Biological Chemistry, 285(21): 16051-16065.

[2] Copley et al. (2004) Biochemistry, 43(44): 13981-13995.

36 | ACTIVITY REPORT 2010 – LNLS

NANOSTRUCTURAL REORGANIZATION OF BACTERIAL CELLULOSE

BY ULTRASONIC TREATMENT

Paula Cristina de Sousa Faria Tischer1, Harry Westfahl Junior2, Cesar Augusto Tischer1, Maria Rita Sierakowski1

Laboratório de Biopolímeros - BioPol, Departamento de Química, Universidade Federal do Paraná - UFPR, CP 19081, CEP 81531-990, Curitiba, PR, Brazil 2 Laboratório Nacional de Luz Síncrotron – LNLS, Centro Nacional de Pesquisa em Energia e Materiais - CNPEM, CP 6192, CEP 13083-970, Campinas, SP, Brazil 1

Bacterial cellulose was subjected to a high-power ultrasonic treatment for different time intervals. The morphological analys revealed that this treatment changed the width and height of ribbons and roughness of their surface, originating �ilms with new nanostructures and higher thermal stability. The SAXS experiments demonstrated an increase of the thickness of the ribbons and WAXS showed that the average crystallite dimension and the degree of crystallinity also increased. We proposed the fusion of neighboring ribbons due to cavitation effects.

Facility: SAXS Publication: Biomacromolecules, 11, 1217-1224 (2010) Funding: FAPESP, CNPq Corresponding author: Paula Cristina de Sousa Faria Tischer – paula.tischer@pq.cnpq.br Harry Westfahl Junior – westfahl@lnls.br

6

SCIENCE HIGHLIGHTS

Introduction

Cellulose and starch are the most abundant

is organized (or cell-directed) to promote the

polymers in the nature. Taking into account the

ordered self-assembly of parallel glucan chains 4,5.

structural organization in the first level, both

In this process the coupling of polymerization and

biopolymers are constituted only by units of glucose

crystallization is suggested6.

linked by glycosidic bonds. In cellulose structure the

As a basic structural characteristic of the

pyranose rings are in the chair conformation C1,

supermolecular level, crystallinity is one of the

with the hydroxyl groups in an equatorial position,

most important parameter of cellulose for chemical

for better accommodation of hydroxyl groups all

and physical processes, and for properties like

alternate glucose units in the same cellulose chain are

derivatisation, solubility and sorption process. As

rotated 180°. In the second level of organization the

cited before, cellulose is a polycrystalline material.

presence of multiple hydroxyl groups are responsible

The cellulose crystals are aligned along the

by a diversity of hydrogen bonds that with van der

microfibrils so that the polymer chain axis is also

Walls interactions stabilize the molecular structure

the microfibril axis. The microfibrils can be oriented

of these biopolymers.

more or less parallel to the direction of the fibril or

4

Both polysaccharides, cellulose and starch, are

fibril bundle according to the species of origin, which

partially crystalline in nature but crystallites are

gives typical fibril diagrams in X-ray or electron

imperfect and presents regions not so organized,

diff raction experiments. The degree of crystallinity

called amorphous phase. The linearity of chains of

and the quality of the cellulose crystals vary

cellulose permits several and different positions of

extensively from one cellulosic material to another,

intra- and intermolecular hydrogen bonds giving rise

for example, the cell wall of Valonia ventricosa gives

crystals much more regular, for this reason cellulose

a cellulosic material with the highest known degree

is much more crystalline. Starch undergoes a

of crystallinity, near 100%[7].

crystalline to amorphous transition beyond 60-70 °C

The crystalline arrangement of cellulose can be

in water while cellulose requires 320 °C and 25 MPa

interconverted generating six different allomorphs,

to become amorphous in water . In a third level

as shown in the Scheme 1.

1

of organization (spatial organization) the distinct

The native crystalline structure of cellulose was

molecular organization confers profound differences

proposed based on results obtained by solid state

in these polymers reflected in their physical-

NMR experiments8 and further support by Raman

chemical properties, and in their functions in nature,

spectroscopy 9 and infrared spectroscopy10. Cellulose

nutritional for starch and structural for cellulose.

In bacteria the most extensively studied is

I is the native form and it occurs as Iα and Iβ and cellulose II is thermodynamically the most stable

Acetobacter xylinus formerly known as A. xylinum2

crystalline form11. Different allomorphs can coexist

reclassified as the genus Gluconacetobacter. Selecting

in the same ribbon of cellulose.

the substrates, culture conditions, additives, and

The morphology of cellulose is different for each

the bacterial strain, it is possible to control the

allomorph and the determination of morphology

molar mass and supramolecular structure of

of this biopolymer is very important to predict

cellulose produced. Thus is possible to control

some surface properties. The need for surface

important cellulose properties, and also the course

characterization of cellulose membranes is essential

of biosynthesis (kinetics, yield, and other metabolic

once the surface skills differ considerably from

products) .

that of the bulk12, while the surface properties

3

Bacterial cellulose biogenesis was described as a hierarchical, cell-directed self-assembly process

determine the behavior of the material in a number of applications.

in which chain aggregates crystallize into 3-4-nm

The scanning (SEM) and transmition (TEM)

microfibrils that combine into bundles, and bundles

electron microscopy are extensively used for this

of microfibrils are associated to form the composite

characterization and are useful because brings

ribbon.

different information about the morphology of

The

38 | ACTIVITY REPORT 2010 – LNLS

cellulose-synthesizing

apparatus

NANOSTRUCTURAL REORGANIZATION OF BACTERIAL CELLULOSE BY ULTRASONIC TREATMENT

longer efficiently absorb energy from the sound field to sustain itself. This size is determined by the frequency of the ultrasound. For instance, the critical size in water is around 170 µm in diameter at 20 kHz. The difference is that in contact with a solid, also, the surface energy becomes relevant and the liquid flow is asymmetric16.

Scheme 1. Relationship between differents allomorphos of cellulose17.

Although the search for new polymers with improved properties continues to attract great research interest, the possibility of use this “green” tool for the formation of new surfaces and nanometer-

cellulose.

Informations

about

ribbons

width,

sized materials aroused our interest. For this reason

presence and size of porous, the morphology of

the current work was focused in the analysis the

the ribbons are revealed 100 nm range, while with

effect of ultrasonic treatment during different times

TEM is possible to observe the microfibrils in 10 nm

(15, 30, 60, and 75 minutes), on the reorganization

range, with specific preparation of material (negative

of bacterial cellulose (BC) microfibrils using suitable

staining) and also determinate the crystal structure

and eco-friendly conditions (aqueous medium,

by diff raction of electrons (without coloration). The

without acid or heating treatment), looking for

nanostructure characterization can be improved by

develop an easy and economic method to obtain

AFM (Atomic Force Microscopy) analyses which

membranes with different nanostructures and new

bring important information about roughness

surface characteristics.

of surface, thickness of the fi lm, the wide of the ribbons and eventually the microfibrils, and there are methods to determine the elasticity of surfaces

by AFM.

Results and Discussion

The first point that we observed, after ultrasound

treatment, was the morphology of the fi lms. The

Due to the tight hydrogen bond systems

morphological analysis observed after scanning

within the crystallites, for obtain different forms

electron microscopy and atomic force microscopy

of cellulose as microfibrillated cellulose (MFC) or

revealed that the treatment changed the width and

whiskers, also called nanocellulose, different process

height of the microfibrillar ribbons and roughness

are used, but all of them imposing high controlled

of their surface, originating fi lms with new

conditions as shearing forces13 or acid treatment14.

nanostructures. The ribbons of bacterial cellulose are

These traditional ways are characterized by long

composed by microfibrils as represented in Figure 1b.

process time, high temperatures, high water usage

The AFM images of the native bacterial cellulose

and hazardous chemistry.

showed bands of microfibrils (ribbons) with widths

The feasibility to convert sound into chemistry

of 110–140 nm (Figure 1a). After ultrasonication,

has been demonstrated more than eighty years

there was, apparently, a reduction in the width of the

ago, but sonochemistry at solid surfaces are poorly

ribbons (51–70 nm) and the surface of membrane

understood. Acoustic cavitation (the formation,

was modified (Figure 1c). Apparently, the ultrasonic

growth, and collapse of bubbles) provides the

treatment changes the microfibrillar arrangement

primary mechanism for sonochemical effects15.

leading to a fi lm with a different nanostructure.

Bubbles are created by high pressure gradients

Increasing the time of ultrasonic application to

and large flow rates in liquids near a solid surface.

60 minutes or more causes a reduction of thickness

The collapse creates locally extreme pressures and

of the ribbons. After 75 minutes, individual ribbons

temperatures as well as shock waves and a liquid

with widths of 40-70 nm could be observed.

impinging on the surface. With high-intensity

These changes in nanostructured fibrillar

low frequency ultrasound (20 kHz), cavitations

arrangement of cellulose suggested that some

nuclei may grow rapidly through inertia effects.

modification in crystal and or amorphous structure

The cavity can reach a critical size where it can no

of cellulose occurred which implies in different ACTIVITY REPORT 2010 – LNLS | 39

SCIENCE HIGHLIGHTS

physic-chemical properties. For this reason we

in crystallites of native cellulose is well described

analysed the thermal decomposition of these

by X-ray, electron and neutron scattering crystal

different fi lms after ultrasound treatment. The

structure analysis. In this work the analysis of SAXS

results obtained from differential thermal analysis

and WAXS revealed very important modifications in

showed us the onset temperature of the pyrolysis was

nanostructure of bacterial cellulose.

208, 250, and 268 °C for the native BC and the BC

The SAXS analyses showed that rc (cross

ultrasonicated for 15 and 30 minutes, respectively.

sectional radius of gyration) increased with

These analyses also indicated that the ultrasonic

ultrasonic treatment. Although the dimensions of

process did not change the cellulose chemically; but,

the native microfibril bands obtained were similar

apparently, only structural changes occurred.

to the ones reported previously25 the SAXS data

In particular for cellulose, due to the tight

analysis suggested the treatment with ultrasound

hydrogen bond systems within the crystallites, only

increased the thickness of the ribbons, resulting in

the amorphous phase is accessible for solvents, dyes

a modification of the nanostructure of the BC. The

and reactants Therefore, the determination of the

crystallite dimensions and crystalline fractions of

degree of crystallinity is one of the first parameters

the samples were determined from the WAXS data

to be assessed in the phase structure analysis. The

analysis (Table 1).

two most important methods for determining

Apparently, due to the ultrasonic treatment, the

crystallinity in polysaccharides, as well as crystal

average crystallite dimension increases in the (010)

structure changes are wide angle X-ray scattering

direction but shrinks in the other. These changes

(WAXS) and solid state NMR. The two dimensional

in crystalline dimensions were compatible with the

crystallographic symmetry (triclinic or monoclinic)

increase in the ribbon dimensions obtained from the

Figure 1.

a) AFM images of bacterial cellulose native; and c) ultrasonicated 60 minutes. In the right box, ribbons (110-140 nm) and microfibrils (7 nm) of bacterial cellulose are represented.

Table 1. Crystallinity (xc), and widths of the crystallites in the directions normal to the corresponding Bragg planes.

Native BC 15 BC 30

40 | ACTIVITY REPORT 2010 – LNLS

xc

D010

D001

D011

D-411

0.44 0.55 0.63

3.4 6.4 5.4

10.1 9.6 8.5

7.5 6.5 6.0

10.9 19.4 17.6

NANOSTRUCTURAL REORGANIZATION OF BACTERIAL CELLULOSE BY ULTRASONIC TREATMENT

SAXS analysis. Other important data from SAXS

enough to disrupt hydrogen bonds in the amorphous

analyses was the crystallinity of these samples.

regions. As the polymerization and crystallization

The samples ultrasonically treated had higher

are coupled process in Acetobacter xylinum, the

crystallinity; samples treated 15 and 30 minutes,

crystalline material formed is of type I but the shape

0.55 and 0.63, respectively, compared to native

of crystallites was changed, the width of ribbon was

cellulose which was 0.44.

increased reflecting in the production of membranes

Conclusion

Membranes

roughness

and

with higher crystallinity and different surface with

different

crystallinity

morphology,

were

produced

after modification of bacterial cellulose under

properties.

Acknowledgments

CNPq, FINEP, LAMIR, Prof. Paulo Cesar

ultrasonication process in mild conditions. The

Camargo (AFM) and for Mateus B. Cardoso for

energy release during cavitation processes was

insightful discussions.

References

[1] Deguchi, S.; Tsujii, K.; Horikoshi, K.. Cooking cellulose in hot and compressed water. Chemical Communications, v. 31, p. 3293-3295, 2006.

[2] Ross, P.; Mayer, R.; Benziman, M. Cellulose biosynthesis and function in bacteria. Microbiology and Molecular Biology Reviews, v. 55, n. 1, p. 35-58, 1991.

[3] Klemm, D.; Heublein, B.; Fink, H.-P.; Bohn, A.. Cellulose: Fascinating Biopolymer and Sustainable Raw Material.

Angewandte Chemie International Edition., v. 44, p. 3358-3393, 2005.

[4] Brown, R. M. Jr.; Willison, J. H. M.; Richardson, C. L. Cellulose biosynthesis in Acetobacter xylinum: Visualization of the site of synthesis and direct measurement of the in vivo process. Proceedings of the National Academy of Sciences USA, v. 73, p. 4565-4569, 1976.

[5] Zaar, K. J. Visualization of pores (export sites) correlated with cellulose production in the envelope of the gram negative bacterium Acetobacter xylinum. Journal of Cell Biology. v. 80, p. 773-777, 1979.

[6] Benziman, M.; Haigler, C. H.; Brown, M. R.; White, R. A.; Cooper, M. K. Cellulose biogenesis: polymerization and crystallization are coupled processes in Acetobacter xylinum. Proceedings of the National Academy of Sciences USA., v. 77, p. 6678–6682, 1980.

[7] Finkendstadt, V. L.; Millane, R. P. Crystal Structure of Valonia Cellulose Ib. Macromolecules, v. 31, p. 7776-7783, 1998.

[8] Atalla, R. H.; VanderHart, D. L. Native cellulose: a composite of two distinct crystalline forms. Science, v. 223, p. 283-285, 1984.

[9] Wiley, J. H.; Atalla, R. H. The Structures of Cellulose. ACS Symposium Series, v. 340, p. 151-168, 1987.

[10] Michell, A. J. Second-derivative F.t.-i.r. spectra of native celluloses. Carbohydrate Research, v. 173, p. 185-195, 1988.

[11] Langan, P.; Nishiyama, Y.; Chanzy, H. J. A Revised Structure and Hydrogen-Bonding System in Cellulose II from a Neutron Fiber Diffraction Analysis. American Chemistry Society, v. 121, p. 9940-9946, 1999.

[12] Laine, J.; Stenius, P.; Carlsson, G.; Ström, G. Surface characterization of unbleached kraft pulps by means of ESCA. Cellulose, v. 1, n. 2, p. 145-160, 1994.

[13] Turbak, A. F.; Snyder, F. W.; Sandberg, K. R. J. Microfibrillated cellulose, a new cellulose product: properties, uses, and commercial potential. Journal of applied polymer science (Applied polymer symposium), v. 37, p. 815-827, 1983.

[14] Revol, J-F.; Bradford, H.; Giasson, J.; Marchessault, R. H. ; Gray D. G. Helicoidal self-ordering of cellulose microfibrils in aqueous suspension. International Journal of Biological Macromolecules, v. 14, p. 170-172, 1992.

[15] Leighton, T. G. The Acoustic Bubble. London: Academic Press, 1994, 439 p.

[16] Shchukin, D. G.; Skorb, E.; Belova, V.; Möhwald, H. Ultrasonic Cavitation at Solid Surfaces. Advanced Materials, n/a. doi: 10.1002/adma.201004494.

[17] Kroon-Batenburg, L.M.J.; Bouma, B.; Kroon, J. Stability of cellulose structures studied by MD simulations. Could mercerized cellulose II be parallel? Macromolecules, v. 29 p. 5695- 5699,1996

ACTIVITY REPORT 2010 – LNLS | 41

7

A NOVEL APPROACH FOR HIGH RESOLUTION ELASTIC BEHAVIOR ASSESSMENT OF ALLOYED STRAINED NANOSTRUCTURES Luciano A. Montoro1, Antonio J. Ramirez1, Gilberto Medeiros-Ribeiro2

Brazilian Synchrotron Light Laboratory, CP 6192, CEP 13083-970, Campinas, SP, Brazil Hewlett-Packard Laboratories, P.O. Box 10350, 94303-0867, Palo Alto, California, USA

1

2

The quanti�ication of the strain/stress state with high spatial resolution of nanostructured materials is essential for several applications and recent technologies. Several methods have been proposed and applied to address the strain state of such materials. For example, the traditional strain state analysis from high resolution transmission electron microscopy (HRTEM) images. However, most of these methods fail when dealing with alloyed strained nanostructured materials. Such systems presents both intrinsic (due to chemical variations) and extrinsic (due to externally imposed stresses) strain which dif�icult the proper analysis.

Here, is presented a new methodology for high resolution elastic behavior assessment of alloyed strained nanostructures based on quantitative high resolution transmission electron microscopy. The application of this technique to quantify the elastic behavior of the model system Si-Ge:Si(001) shows that this methodology arises as a remarkable tool for accurate chemical and elastic state evaluation, which can be applied to several strained alloyed nanostructures, such as epitaxial islands, nanowires, nanocrystals, and thin �ilms.

Facility: LME Publication: Journal of Physical Chemistry C, 114, 12409-12415 (2010) Funding: FAPESP, CNPq, HP Brazil Corresponding author: Luciano A. Montoro – lmontoro@lnls.br

A NOVEL APPROACH FOR HIGH RESOLUTION ELASTIC BEHAVIOR ASSESSMENT OF ALLOYED STRAINED NANOSTRUCTURES

In recent years the advent of nanotechnology

powerful tool for chemical and electronic properties

has awaked a great interest on the nanostructures

evaluation with high spatial resolution9. Convergent

elastic behavior. This fact arise from that almost

beam electron diff raction (CBED) and electron back

all physical properties of materials can be affected

scatter diff raction (EBSD) performed in electron

by elastic strain or stress state, such as band-

microscopes provides excellent sensitivity for strain

gaps, vibrational and spectroscopic properties,

measurement but lack the required spatial resolution

mass transport by diff usion (which affects the

for small islands and thin-fi lm analysis10,11.

components intermixing or dopant distribution),

In recent years, high-resolution transmission

thermal and electrical transport, and several other .

electron microscopy (HRTEM) has become a

Thus, the knowledge of the strain and stress state at

powerful tool for strain analysis at the nanoscale

the nanoscale is of great importance for applications

with the development of advanced quantitative

ranging from semiconductor nanostructures and

methodologies for image analysis12, such as the

devices to structural engineering components.

digital analysis of lattice images (DALI)13, the

For example heteroepitaxial nanostructures have

geometric phase analysis (GPA)14, and the peak-

opened up development paths for semiconductor

pairs

devices that exploit band gap engineering through

been applied to study a wide variety of materials

control of strain/stress state and composition4.

and systems, such as multilayers, nanocrystals,

Hence, the investigation and development of zero-

nanowires, heteroepitaxial fi lms and dots. Strain

dimensional (quantum dots), one-dimensional

analysis combined with Vegard´s law has been

(wires), and two-dimensional (thin layers) strained

used for the chemical composition determination

epitaxial heterostructures has been a very active

in alloyed materials. However, this method can

area of research mainly due to their electronic and

provide accurate results only when the crystal lattice

optoelectronic applications.

is relaxed, unstrained. This method lacks when

1-3

procedure15.

These

methodologies

have

The physical and chemical properties of

the analyzed sample is submitted to both extrinsic

heteroepitaxial self-assembled islands, as well

and intrinsic strain, which means that the crystal

as their formation and evolution mechanisms

lattice is distorted by both external forces and

has been related to thermodynamic and kinetic

compositional changes.

factors that are directly related to the elastic

In a recent work16 we demonstrate the use of GPA

energy minimization5,6. Therefore, the knowledge

to obtain projected 2D quantitative chemical maps

of elastic state and compositional fields may

of self-assembled Si1-xGex:Si(001) strained alloyed

provide insights for understanding and control

epitaxial islands. This self-consistent methodology

both the growth processes and physical-chemical

allows

properties

strained

nanostructures, differentiating the extrinsic and

nanostructures. Hence, these requirements further

intrinsic strain. The combination of projected 2D

call for advanced experimental techniques that

chemical information obtained from two different

allow accurate measurement and mapping of elastic/

zone axis, [100] and [110], with iterative simulation

chemical properties with high spatial resolution.

made possible the reconstruction of the three-

However, only selected techniques are likely to

dimensional (3D) chemical arrangement inside

meet these requirements. For strain determination

the islands. Here, we go one step further using the

at the nanoscale, the grazing-incidence anomalous

Si1-xGex:Si(001) strain state information to evaluate

X-ray

the elastic properties at the nanoscale.

of

these

diff raction

heteroepitaxial

(GIXRD)

and

transmission

the

evaluation

of

strained

alloyed

electron microscopy (TEM) techniques have been

Si-Ge islands were grown on Si (001)-oriented

predominantly used. The GIXRD can provide high

substrate by a Chemical Vapor Deposition (CVD)

depth resolution regarding the strain state and

technique. The Ge was deposited at 605 °C using GeH4

composition ; however its results are an average

at 0.065 Pa in a H2 carrier gas for 120 seconds, resulting

over a statistical ensemble of nanostructures. TEM

in a final thickness of ~ 12 eq-ML (1 equivalent-

associated with spectroscopic techniques such

monolayer = 6.27∙1014 Ge atoms/cm2). TEM cross-

as electron energy loss spectroscopy (EELS) and

section specimens oriented at [110] and [100] zone

energy dispersive X-ray spectroscopy (XEDS) is a

axis were prepared using ion-beam thinning and a

7,8

ACTIVITY REPORT 2010 – LNLS | 43

SCIENCE HIGHLIGHTS

JEM-3010 URP TEM with a LaB6 - 300 kV was used

spatial resolution. The precision of the performed

for analyses. The images were processed by focal

mappings was estimated for each map based on the

series reconstruction technique (FTSR from HREM

standard deviation of the measured values in a Ge-

Research Inc.) for spherical aberration correction and

free region of the silicon substrate.

by the geometric phase analysis (GPA from HREM Research Inc.) to calculate the lattice distortion maps.

For the GPA processing a Lorentzian mask was used with a half-width of 1/4*d111 in reciprocal space, resulting in 2D chemical and strain maps with 1.6 nm

Our novel approach is performed by using the geometrical phase analysis (GPA) technique that describes how the spatial frequency components of the HRTEM image vary across the field of view.

Thus, GPA method allows the determination of the lattice displacement field u(r) at specific directions, which can be used to calculate the lattice distortion tensor (eij)14.

The strain can be defined as the ratio of total deformation to the initial dimension of the material body in which forces are being applied. However, because the Si1-xGex:Si(001) strained alloyed islands are submitted to both compressive external forces (due to the lattice mismatch between the Si1-xGex islands with the Si Substrate) and internal volumetric expansion (due to the Si-Ge intermixing), the deformation maps obtained by GPA do not correspond to strain tensors, but distortion tensors related to an undistorted Si reference lattice.

Therefore, the GPA method provides the lattice distortion maps (e|| and e⊥) from a Si reference lattice.

These distortion maps were used to calculate the chemical composition maps of the Si1-xGex (where 0 ≥ x ≥ 1) islands through the Vegard’s law. This empirical law establishes that the distortion of the Si1-xGex lattice parameter a(x) is related to a Si and aGe by the equation: a( x ) = aSi (1 − x ) + aGe x

(1)

Thus, using the lattice distortion maps (eij) and the Vegard’s law it is possible to obtain the chemical composition (i.e. the x value) in a self-consistent manner. This relationship was deduced from the Figure 1.

generalized Hooke´s law for cubic crystals σ i = C∙εi, Two-dimensional chemical maps and three-dimensional chemical model of representative Si1-xGex:Si(001) dome shape islands. a,b) are projected chemical maps through the [110] and [100] crystallographic directions, respectively. These maps show the

where σ i and εi are the normal stresses and strains, respectively and C corresponds to the stiff ness matrix17. Considering that an epitaxial cubic system

average Ge content (%atom) at the projected directions. The color

oriented along the 〈100〉 directions implies in a

code indicates the Ge content, and all maps are superposed

symmetric in-plane stress/strain, and assuming the

to the original HRTEM images of the Si-Ge strained islands on

islands in a plane-stress condition (a thin epitaxial

the Si(001) substrate. c) Perspective top-view of the modeled chemical distribution within the island. The line boundaries show the faceted dome, where are indicated the facets families (braces) and the directions (brackets). The numbers attributed to each region group refer to specific Ge content (%atom), as indicated by the scale bar.

44 | ACTIVITY REPORT 2010 – LNLS

system with a free surface, σ⊥ = 0), a quadratic expression for the composition (x) was deduced: Si  Ge   aSi ( e⊥ + 1)  −  aGe x + aSi (1 − x )  + 2 C12 x + C12 (1 − x )  = 0 Ge Si  aSi e|| + 1  −  aGe x + aSi (1 − x )  C11 x + C11 (1 − x )       

(

)

(2)

A NOVEL APPROACH FOR HIGH RESOLUTION ELASTIC BEHAVIOR ASSESSMENT OF ALLOYED STRAINED NANOSTRUCTURES

Here, Vergard´s law was applied to correct

the projected averaged composition. These maps are

the composition dependent parameters (a(x) and

representative results, such that a careful analysis

Cij(x)), where the stiff ness coefficients (Cij) and the

of several maps obtained from different islands

lattice parameters (aGe and aSi) are know values .

revealed a good reproducibility. The [100] chemical

In addition, the Si-Ge alloy presents a high elastic

map presents nearly monotonic compositional

anisotropy. Thus, in order to calculate the corrected

gradients. Otherwise, [110] map suggests a non-

stiff ness coefficients for an arbitrary crystal

monotonic behavior; where both maps emerge from

orientation was performed a transformation by

a non-uniform compositional distribution, as show

using rotation matrixes18.

in the 3D discretized model on Figure 1c[16].

18

Therefore, from the distortion maps (eij) provided

First, the GPA method allows the distortion

by GPA method, the stiff ness coefficients calculated

tensor mapping against an undistorted reference

for each observed direction ([100] and [110]), and

region. This means that from pure element samples

considering aSi = 0.5430 nm and aGe = 0.5657 nm,

the GPA provides the strain tensor maps. Otherwise,

the Ge content x was calculated. Thus, the

for alloyed structures these distortion tensor maps

chemical composition maps can be obtained using

correspond to the lattice parameter mismatching

a self-consistent methodology assuming that the

between the reference region (i.e. substrate) and

anisotropic elastic theory could be applied to such

the epitaxial alloyed nanostructure. Figures 2a,b

nanostructures. The value of composition obtained

respectively shows these parallel and perpendicular

for each atomic column of the HRTEM image

distortion tensor maps obtained for [110] direction.

represents the mean chemical composition along the corresponding direction averaged along a 1.6 nm diameter region. Thus, projected 2D maps with 1.6 nm spatial resolution are obtained.

Furthermore, the chemical composition map (x) can be applied to Vegard´s law equation and

Figure 2a shows that the central area of island presents just about 2.8 ± 0.4% a|| lattice distortion. On the other hand, the island edges parallel distortion shows that the a|| lattice component on these regions is better commensurate with the substrate. Unlike

classical elasticity to calculate the strain tensor components, ε|| and ε⊥ which correspond to the extrinsic strain. The assumption of a planestress condition (σ⊥ = 0) applied to the Hooke’s law allowed the calculation of the parallel stress:

σ || = ( C11 + C12 ) ε || + C12ε ⊥ . In addition, the elastic

strain energy density E strain (elastic strain energy per unity volume) could be calculated by the product Estrain = σ ||ε || , where the resulting unity given in GPa (from stress) can be directly converted to energy per volume (1 GPa = 6.24 eV/nm3).

Therefore, from this methodology it is possible to calculate the chemical composition map, the strain tensors components, the parallel stress tensor and the elastic strain energy, shedding light over the island elastic behavior.

In our previous work16 we demonstrate that using the GPA results combined with a self-consistent methodology for chemical composition calculation it is possible to obtain an accurate quantification for strained alloyed islands. Figures 1a and 1b respectively show the chemical maps obtained along both directions [110] and [100], which represents

Figure 2.

Two-dimensional

distortion

maps

of

representative

Si1-xGex:Si(001) dome shape island at [110] direction. a,b) show the distortion tensor maps of parallel and perpendicular components, respectively. These maps represent the distortion components calculated against an undistorted pure Si region of the substrate. The colors differentiate the distortion level (% ± 0.4%), where positives values correspond to lattice expansion and negative values to contraction.

ACTIVITY REPORT 2010 – LNLS | 45

SCIENCE HIGHLIGHTS

of the parallel component, the perpendicular one

of this here presented approach is calculate in a

(Figure 2b) presents a non-monotone distortion

self-consistent way the strain components maps of

profi le. This result suggest that the a⊥ lattice

alloyed nanostructures from a distortion mapping

component is more substantially modified along the

obtained by a strain state analysis method, such as

growth direction; either by chemical composition

the GPA, DALI or peak-pairs algorithm.

changes (intrinsic strain) or by substrate imposed

Figure 3 shows the projected strain components

stress (extrinsic strain). Furthermore, alike to [110]

and the parallel stress maps, averaged through the

projected chemical maps, this non-monotonic

3D island. The strain maps (Figure 3a and 3b) are

behavior can be attributed to the projected profi le

in agreement with epitaxial growth and the strain

through the non-uniform chemically distributed

relaxation expected for these islands size and

3D island (Figure 1c). It is important emphasize that in the case of alloyed structures these distortion maps do not represent the strain behavior. These distortion maps ought to be converted to strain maps by considering the local chemical composition and its lattice parameter in a relaxed state. The goal

geometry, which are predominantly ε|| < 0 and ε⊥ > 0.

Figure 3c shows the parallel stress behavior through the islands, where positive sign indicates tensile stress, and the negative one, compressive stress.

Hence, parallel stresses are overridingly compressive, which results from the substrate imposed stress due to the lattice mismatching between the substrate and the island Ge-rich regions.

In order to perform a more thorough data analysis, on Figure 4 are depicted dispersion curves of the strain components (from Figure 3) as a function of their respective lattice parameters components.

These figures were constructed from the strain and lattice parameters values of whole island maps.

These graphs are internally delimited by a set of lines which correspond to the zero strain (horizontal dashed line), Si and Ge lattice parameters (vertical dashed lines) and by iso-compositional diagonal lines of pure Ge (lower red line) and pure Si (upper blue line). These last ones also correspond to the pure Ge and Si strain behavior. The color code region indicates the chemical composition, alike as assigned on Figure 1, which can be subdivided in three regions indicated as (a), (b) and (c). This representation is useful for a more quantitative analysis of the strain data. One can see that the parallel strain predominantly belongs to the (b) region which is in a compressive state. Just a small fraction of the island is within the (a) region bounds, which is under tensile strain. This parallel component behavior is offsetted

Figure 3.

Two-dimensional strain and stress maps of representative Si1-xGex:Si(001) dome shape island at [110] direction. a,b) show

by the perpendicular one, according to the elasticity theory (Poisson effect). However, it is worth noting

the strain tensor maps of parallel and perpendicular components,

the (c) region behavior, which indicates a tensile

respectively. The colors differentiate the strain level (% ± 0.4%),

region of the island where the perpendicular lattice

where positives values correspond to lattice expansion and

parameters are beyond to the pure Ge (aGe). These

negative values to contraction. c) Parallel stress map, where the color code indicates the stress level (GPa ± 0.4 GPa) with positive

points on the (c) region correspond to the island

values indicating tensile stress and negative values, compressive

surface, at the top and edges. Such regions present a

stress.

free-surface in plane stress condition, which means

46 | ACTIVITY REPORT 2010 – LNLS

A NOVEL APPROACH FOR HIGH RESOLUTION ELASTIC BEHAVIOR ASSESSMENT OF ALLOYED STRAINED NANOSTRUCTURES

that it can be relaxed along the direction normal to the surface. Hence, these Ge-rich regions submitted to a compressive parallel stress are freely expanded leading to large perpendicular lattice parameters.

To finalize this discussion, relevant aspects related to the assessments of this new approach to strain state evaluation must be considered. First, the accuracy and precision of this approach is directly related to the used strain state analysis method and the chemical/elastic modeling assumptions.

In order to perform a displacement mapping with high precision the GPA method looks like as the better choice. Several works claims that this method presents a resolution down to 0.001 nm19. This capability leads to a 0.2% of strain measurement resolution (for compounds with typical 0.5 nm lattice parameter), which consequently results in a quantification limit of 4.5% Ge for the Si-Ge alloyed system. Other aspects to be considered are the validities of Vegard’s law and the planestress condition on the analyzed system. Due to the Vegard’s law requirement this procedure only can be applied to binary (A1-xBx) and pseudobinary (A1-xBxC) alloys, such as semiconductor materials from III-V and II-VI groups (GaAs-InAs, GaP-InP, GaAs-AlAs, CdTe, CdS, CdSe, ZnSe) and metallic

Figure 4.

alloys (Co-Ni, Cr-Mo, Ir-Pd, Ir-Pt, Pt-Rh, Ni-Cu, Ni-

Dispersion curves for the strain tensor components as a function of the respective lattice parameter component. The horizontal dashed lines correspond to the zero strain level. The vertical dashed lines correspond to the Si and Ge lattice parameters.

Zn). Rigorous analysis of Vegard´s law conducted in

The diagonal dashed lines correspond to strain behavior of pure

a thermodynamic framework shows that the linear

Si (upper blue line) and pure Ge (lower red line). The green-red

approximation is valid for ideal solutions when the

region is keyed to the chemical composition from pure Si (green) to pure Ge (red).

lattice parameters of the pure components differ by less than 5%20. This requirement is fulfi lled by a large number of systems due to the typical lattice parameter difference between the elements/compounds, where are included several technologically important materials/systems, such as a) quantum wells, wires and dots, b) colloidal core-shell nanocrystals, c) heterostructured free-standing nanowires and d) partially relaxed heterostructures, where some residual stress may be present. Concerning to the spatial resolution, it is directly related to the GPA mathematical processing. The size of the employed

space peak-finding procedures, such as the DALI and the peak-pairs algorithm.

These

results

show

that

the

presented

methodology can be highlighted as a powerful technique for an accurate chemical and elastic behavior assessment of specific strained alloyed nanostructures. Indeed, this technique arises as a remarkable tool to provide useful clues for shed light to the nanocrystals growth, evolution and chemical/ electronic/optical properties.

mask to select reciprocal space regions determines the effective lateral resolution of the technique, resulting in typical 1-2 nm averaging values.

Acknowledgements

The authors acknowledge LNLS, FAPESP

However, this spatial resolution can be improved

(2002/04151-9; 2007/05165-7) and CNPq for the

by using strain state analysis methods based in real

financial support.

ACTIVITY REPORT 2010 – LNLS | 47

SCIENCE HIGHLIGHTS

References

[1] Jacobsen, R. S.; Andersen, K. N.; Borel, P. I.; Fage-Pedersen, J.; Frandsen, L. H.; Hansen, O.; et al. Nature, 2006, 441, 199-202.

[2] Lee, M. L.; Fitzgerald, E. A.; Bulsara, M. T.; Currie, M. T.; Lochtefeld, A. J. Appl. Phys, 2005, 97, 011101.

[3] Smith, A. M.; Mohs, A. M.; Nie, S. Nature Nanotech, 2009, 4, 56-63.

[4] Bimberg, D.; Grundmann, M.; Ledentsov, N. N. Quantun Dot Heterostructures. John Wiley & Sons: Chichester, U.K., 1999.

[5] Lang, C.; Cockayne, D. J. H.; Nguyen-Manh, D. Phys. Rev. B, 2005, 72, 155328.

[6] Medeiros-Ribeiro, G.; Stanley-Williams, R. Nano Letters 2007, 7, 223-226.

[7] Malachias, A.; Kycia, S.; Medeiros-Ribeiro, G.; Magalhães-Paniago, R.; Kamins, T. I.; Williams, R. S. Phys. Rev. Lett. 2003, 91, 176101.

[8] Schülli, T. U.; Stangl, J.; Zhong, Z.; Lechner, R. T.; Sztucki, M.; Metzger, T. H.; Bauer, G. Phys. Rev. Lett. 2003, 90, 066105.

[9] Schade, M.; Heyroth, F.; Syrowatka, F.; Leipner, H. S.; Boeck, T.; Hanke, M. Appl. Phys. Lett. 2007, 90, 263101.

[10] Houdelier, F.; Roucau, C.; Casanove, M.-J. Microelectronic Eng. 2007, 84, 464-467.

[11] Wilkinson, A. J.; Meaden, G.; Dingley, D. J. Superlattices and Microstructures 2009, 45, 285-294.

[12] Rosenauer, A. Transmission Electron Microscopy of Semiconductor Nanostructures: Analysis of Composition and Strain State; Springer-Verlag: Berlin, Germany, 2003.

[13] Rosenauer, A.; Kaiser S.; Reisinger T.; Zweck, J.; Gebhardt W. Optik 1996, 102, 63-69.

[14] Hÿtch, M. J.; Snoeck, E.; Kilaas, R. Ultramicroscopy 1998, 74, 131-146.

[15] Galindo, P.L.; Kret, S.; Sanchez, A.M.; Laval, J.Y.; Yanez, A.; Pizarro, J.; Guerrero, E.; Bem, T.; Molina, S.I. Ultramicroscopy 2007, 107, 1186-1193.

[16] Montoro, L. A.; Leite, M. S.; Biggemann, D.; Peternella, F. G.; Batenburg, K. J.; Medeiros-Ribeiro, G.; Ramirez, A. J. J. Phys. Chem. C 2009, 113, 9018-9022.

[17] Tsao, J. Y. Materials Fundamentals of Molecular Beam Epitaxy; Academic Press: London, 1993.

[18] Wortman, J. J.; Evans, R. A. J. Appl. Phys. 1965, 36, 153-156.

[19] Hÿtch, M.J.; Putaux, J.L.; Pennison, J.M. Nature 2003, 423, 270-273.

[20] Jacob, K.T.; Raj, S.; Rannesh, L. Inter. J. Mater. Res. 2007, 98, 776-779.

48 | ACTIVITY REPORT 2010 – LNLS

X-RAY BRAGG-SURFACE DIFFRACTION: A SENSITIVE TOOL FOR STUDYING IN-PLANE STRAIN ANISOTROPY IN Fe+ ION IMPLANTATION IN Si(001)

Alan S. de Menezes1, Rossano Lang2,3, Adenilson O. dos Santos1,4, Shay Reboh2,3, Eliermes A. Meneses1, Livio Amaral3, Lisandro P. Cardoso1 1

Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas – UNICAMP, CEP 13083-859, Campinas, SP, Brazil 2 Programa de Pós-graduação em Ciências dos Materiais – PGCIMAT, Universidade Federal do Rio Grande do Sul – UFRGS Porto Alegre, RS, Brazil 3 Instituto de Física, Universidade Federal do Rio Grande do Sul – UFRGS, CEP 191501-970, Porto Alegre, RS, Brazil 4 Centro de Ciências Sociais, Saúde e Tecnologia – CCSST, Universidade Federal do Maranhão – UFMA, CEP 65900-410, Imperatriz, MA, Brazil

X-ray Bragg-Surface Diffraction (BSD) is presented as a high resolution probe to study surface effects in semiconductors that crucially in�luence their performance, as the striking in-plane strain anisotropy that occurs in the recrystallized lattice of a Fe+ implanted Si(001) layer.

Metallic spherical and plate-like γ-FeSi2 nanoparticles observed by High Resolution Transmission Electron Microscopy synthesized by ion-beaminduced epitaxial (re)crystallization (IBIEC) process appear within the recrystallized region. They are responsible (mainly the plate-like ones) for the noticeable in-plane strain anisotropy detected by rocking curves measured at exact two (111) BSD peak positions along two perpendicular directions on the sample surface and also by BSD peaks mappings.

Facilities: XRD1, LME Publication: Crystal Growth & Design, 10, 4363-4369 (2010) Funding: FAPESP, CNPq, CAPES Corresponding author: Lisandro Cardoso – cardoso@ifi.unicamp.br

8

SCIENCE HIGHLIGHTS

Bragg-Surface Diff raction (BSD)1 is a special

recently4, Fe+ ions was implanted in Si(001) at room

diff raction case of the X-ray multiple diff raction

temperature followed by IBIEC aiming to analyze the

(XRMD) technique which has become a very useful

synthesized metastable metallic γ-FeSi2 phase. Then,

and high resolution probe to study in-plane effects in

the BSD was able to provide the strain distribution

single crystals in general, and with very interesting

in the Si matrix surrounding the cubic metallic

contributions to semiconductor epitaxial systems.

phase that presents striking strain anisotropy on the

In the XRMD geometry, an incident X-ray beam

surface plane.

is simultaneously diff racted by planes normally

Figure

2

exhibits

representative

bright-

parallel to the crystal surface (primary) and by other

field Transmission Electron Microscopy (TEM)

inclined planes (secondaries) as the crystal suffers

micrographs

an azimuthal rotation (φ−axis) around the crystal

sample. In Figure 2a), it is possible to identify three

of

the

as-recrystallized

(IBIEC)

surface normal.

However, special diff raction geometry appears for the secondary diff racted beam propagated along the crystal surface, under an extreme asymmetric geometry, representing the BSD case occurrence as shown in Figure 1. Furthermore, BSD diff raction condition can also be tailored through the analysis of the ω:φ mapping2 which provides simultaneously in-plane (φ) and in-depth (ω) information on the crystalline quality. The primary reflection plot as an angular function of ω and φ is the abovementioned mapping represented as an isointensity mapping, which also provides a strain distribution on the crystal surface plane.

In a recent work 3, BSD has been applied in the study of Fe+ ions implantation in Si(001) at 90 k followed by ion-beam-induced epitaxial crystallization (IBIEC) and post thermal annealing to discuss the effects of the semiconductor β-FeSi 2 nanoparticles formation in the Si lattice. More

Figure 1.

BSD scheme using its consecutive scattering model with H01(primary), H02(secondary) and H21 (coupling) vectors. The

Figure 2.

IBIEC a)

sample

[110]Si

bright-field

cross-sectional

TEM

images.

revealing

two

nanoparticle regions in depth; high resolution

coupling planes rescatter the secondary beam towards the

TEM of γ-FeSi2 clearly showing; b) spherical-

primary direction.

like; and c) plate-like nanoparticles.

50 | ACTIVITY REPORT 2010 – LNLS

X-RAY BRAGG-SURFACE DIFFRACTION: A SENSITIVE TOOL FOR STUDYING IN-PLANE STRAIN ANISOTROPY IN FE+ ION IMPLANTATION IN SI(001)

regions regarding the nanoparticles distribution in

Figure 4 shows the measured ω:φ mappings for a

the cross-section image taken at [110]Si zone axis: a

Si matrix (pristine) and IBIEC sample for comparison

thin region a few nanometers thick which is closer

purposes to provide a better visualization and

to the surface; a Si region about 5 nm with small

characterization of the detected anisotropy. The exact

concentration of nanoparticles (R1); and a layer

BSD reflection is tailored in both ω and φ-directions

(≈ 40 nm wide) with a higher concentration of nanoparticles (R2). High-resolution cross-sectional

for each of the two above mentioned BSD secondary _ reflections: (111) Si pristine in Figure 4a and IBIEC

images (HRTEM) of the deeper layer (R2) are shown

sample in 4b and, for (111) Si pristine in 4c and

in Figures 2b and 2c. Two morphological variants

IBIEC one in 4d. A more complete view of the BSD

of the γ-FeSi2 metastable phase were observed and

reflection condition complements the HRRC results

recognized: spherical-like nanoparticles epitaxially

obtained from Figure 3. Furthermore, the mappings

formed in the substrate with a fully aligned

allow for the lattice parameters and 2D strain

orientation regarding the Si matrix (Figure 2b) and

determination of the distorted regions (R1 and R2).

plate-like nanoparticles rotated with respect to Si

The mappings obtained for the Si matrix (pristine)

matrix (Figure 2c), as previously reported .

along the two in-plane perpendicular directions as

5

Measurements of the (004) high resolution rocking curves (HRRC) are shown in Figure 3 at two perpendicular orientations on the sample surface: φ = 0º (Figure 3a) and 90º (Figure 3b). Both patterns present practically the same result with two distinct peaks corresponding to R1 and R2 regions, clearly seen in each pattern, with smaller perpendicular lattice parameters in comparison to the matrix peak (stronger). Also, (002) HRRC were measured at _ (111) and (111) BSD reflections then, at two azimuth angles on the recrystallized Si sample (φ = - 6.04º and 83.96º), since the main interest in this work is to detect in-plane anisotropy. The results are shown in Figures 3c and 3d. As (002) is a forbidden reflection of the Si space group, no primary intensity can be observed out of the BSD secondary peaks. The rocking obtained at φ = -6.04º shows three different contributions: the stronger peak due to the Si matrix; the broad peak to the right (higher angles), due to the R1 and R2 convoluted peaks; and a distinct peak to the left (lower angle), probably associated only with the R2 region. It should be noticed that the rocking at φ = 83.96º exhibits a meaningful profi le difference, that is, the peak to the left (lower angles) does not appear as discriminated as in the previous measurement (φ = -6.04º), it means, a noticeable confirmation of the anisotropic behavior. This _ anisotropy, observed between the [110] and [110] inplane directions, could be associated with the platelike nanoparticles (Figure 2c) since the shape and orientation of these ordered nanoparticles should introduce different strains in both perpendicular directions.

Figure 3.

High resolution rocking curves of IBIEC sample for (004) reflection at: a) φ = 0º; b) φ = 90º; c) (002) reflection at two BSD peaks: -6.04º; and d) 83.96º. Si pristine (blue) is also added for comparison purposes.

ACTIVITY REPORT 2010 – LNLS | 51

SCIENCE HIGHLIGHTS

Figure 4.

_ Strain anisotropy in MBSD: a) Si matrix (pristine); b) IBIEC sample at (111) BSD (φ ~ -6.04º); c) Si matrix; and d) IBIEC at (111) BSD (φ ~ 83.96º).

depicted in 4a and 4c, exhibit only the BSD matrix

to the plate-like ones. In turn, for the lower-side

peak at ω = 16.578º and, as expected, no difference

peak, one observes that ε⊥ and ε|| values are distinct _ ε⊥ = 5.4(6)x10 -4 and ε|| = 3.1(7)x10-4 for (111) BSD peak

is observed.

In turn, the recrystallization process (IBIEC) induces FeSi2 nanoparticles nucleation within the matrix and then, a huge broadening as well as a striking difference is clearly observed in Figure 4b and 4d mappings. Besides the BSD matrix peak in Figure 4b, two other peaks are also detected: one upper-side (ω ~ 16.59º) and one lower-side (ω ~ 16.57º) with respect to the matrix peak whereas, in Figure 4d just the matrix and the upper-side peak are clearly seen since the lower-side peak appears as a shoulder of the matrix one. This result confirms the one obtained in Figures 3c,d.

Perpendicular and in-plane lattice parameters as well as strain values were obtained from the _ IBIEC sample ω:φ mappings for φ ~ -6.04º (111) and 83.96º (111). The perpendicular strain obtained with _ the upper-side peak of the BSD (111) and (111) ω:φ mappings are ε⊥ = -5.8(6)x10 -4 whereas, the in-plane strains are ε|| = 0. Then, as no anisotropy strain is

and ε⊥ = 2.4(8)x10 -4 and ε|| = 1.3(9)x10-4 for (111) and then, an analogous behavior happens for a⊥ and a||.

Thus, one concludes there is anisotropy in the lattice parameters and strain in both sample directions: out-of-plane and in-plane. This anisotropy is attributed to the shape and distortion along the (111) _ and (111) crystallographic planes of the plate-like nanoparticles.

Summing up, Bragg Surface Diff raction has been used as a very useful and 3D high-resolution tool for studying the structural effects of ion implantation and irradiation in Si(001). The sensitivity, usefulness and versatility of the BSD mapping method provided the discrimination between the out-of-plane and inplane strain effects in implanted semiconductors.

Then, when BSD with its unique scattering condition is adequately used in-plane strain anisotropy is directly observed and it has been successfully

detected from this upper-side peak (ω = 16.588º), one

applied in the study of the ion-beam-induced

can assume that most of this result can be assigned

epitaxial crystallization (IBIEC process) in case of

to the spherical-like nanoparticles rather than

Fe+-implanted Si.

52 | ACTIVITY REPORT 2010 – LNLS

X-RAY BRAGG-SURFACE DIFFRACTION: A SENSITIVE TOOL FOR STUDYING IN-PLANE STRAIN ANISOTROPY IN FE+ ION IMPLANTATION IN SI(001)

References

[1] Chang, S. L. X-ray multiple-wave diffraction: theory and applications; Solid State Sciences, Springer-Verlag, Berlin: 2004; vol. 143.

[2] Morelhão, S. L.; Cardoso, L. P. J. Appl. Cryst. (1996) 29, 446.

[3] dos Santos, A. O.; Lang, R.; de Menezes, A. S.; Meneses, E. A.; Amaral, L.; Reboh, S.; Cardoso, L. P. J. Phys. D: Appl. Phys. (2009) 42, 195401.

[4] Lang, R.; de Menezes, A S.; dos Santos, A O; Reboh, S.; Meneses, E A.; Amaral, L.; Cardoso, L P. Crystal Growth & Design (2010) 10 (10), 4363.

[5] Lin, X. W.; Washburn, J.; Liliental-Weber, Z.; Bernas, H. J. Appl. Phys. (1994) 75, 4686.

ACTIVITY REPORT 2010 – LNLS | 53

9

SELF-ORGANIZATION OF DIBLOCK COPOLYMER SOLUTIONS IN MIXED SOLVENTS

Petr Štěpánek1, Zdeněk Tuzar1, Petr Kadlec1, Frédéric Nallet2, Nádya Pesce da Silveira3

Institute of Macromolecular Chemistry, Heyrovský Sq. 2, 16206 Prague 6, Czech Republic 2 Centre National de la Recherche Scientifique – CNRS, Centre de recherche Paul-Pascal – CNPP, Université de Bordeaux, 115 avenue du Docteur-Schweitzer, 33600 Pessac, France 3 Instituto de Química, Universidade Federal do Rio Grande do Sul - UFRGS, CP 15003, CEP 91501-970, Porto Alegre, RS, Brazil

1

A diblock copolymer dissolved in a mixture of partially miscible solvents creates a self-organized microemulsion with a morphology that depends on the numerous parameters of the system. We discuss one particular case of spherical particles (containing the minority solvent) forming a hard gel with cubic structure and demonstrate using high-resolution synchrotron scattering experiments that the self-organized solution has a BCC structure. After �itting one- and two-dimensional form factors we extract from the data the one- and two-dimensional structure factors, S(q) and S(q,φ). The experimental S(q) corresponds almost quantitatively, up to the 9th order Bragg peak, to that calculated numerically for a randomlyoriented, �inite-size BCC crystal. S(q,φ) contains a large number of re�lections that allow the structure to be identi�ied more exactly as a twin BCC morphology with some imperfections.

Facility: SAXS1 Publication: Physical Chemistry Chemical Physics (PCCP), 12, 2944-2949 (2010) Funding: EUROCORES-SONS Corresponding author: Petr Stepanek – stepanek@imc.cas.cz

SELF-ORGANIZATION OF DIBLOCK COPOLYMER SOLUTIONS IN MIXED SOLVENTS

When a diblock copolymer A-B is dissolved

through a chamber containing the sample, under

in a partially miscible mixture of solvents a and b,

vacuum. Afterwards the beam was diff racted on

where a is a solvent selective for block A and b is a

a CCD area detector placed at 1706 mm from the

solvent selective for block B (and a precipitant for

sample covering the momentum transfer range (q)

the block A), locally anisotropic nanostructures are

of 0.06 – 2.0 nm-1. Measurements were performed

formed, often consisting of periodically arranged

at 25 oC with an exposure time of 5 minutes.

regions of the solvents a and b, that are stabilized by

Calibration of the q-scale was obtained by means

the diblock copolymer forming a double brush on

of silver behenate4. Data obtained from the detector

the a/b interface .

were corrected by taking into account the flat field

1

We have previously described organization

properties

of

a

the self-

model

system

consisting of a mixture of two liquids immiscible

and the dark current. Finally, the data were corrected for sample transmission and background scattering using an empty cell as reference.

at room temperature, cyclohexane (solvent a) and

The block copolymer solution was injected

dimethyl-formamide (solvent b) and several diblock

laterally into a vacuum tight sample cell using a

copolymers A-B satisfying the conditions mentioned

syringe. The sample fi lls a 1 mm thickness gap sealed

above,

on both sides by two thin parallel mica windows

in

particular

polystyrene-polyisoprene, polystyrene-

(volume 300 µl)5. The measurement cell consists

poly(ethylene propylene). We have shown, using

of two aluminum blocks attached together with a

small-angle neutron scattering (SANS), that in

0.3 mm Teflon spacer; 3 mm openings in the center

such systems microphase-segregated structures

of these blocks are covered with mica windows to

are formed at temperatures below the coexistence

allow the passage of the X-ray beam.

polystyrene-polybutadiene

and

curve with a-rich and b-rich regions separated by

A number of measurements have been performed

interfaces covered with the diblock copolymer.

for solutions of the PS-PEP copolymer at polymer

The solutions appear as hard gels even though

concentrations ϕP ranging from 3 to 10 % and at

the polymer concentration remains rather small,

solvent composition CX/12% DMF. Besides the first

typically below 10% (w/w).

scattering maximum located at a position q 0 and scattering

visible on all curves, the solutions with concentration

experiments and have shown that the material

larger than 4 % show also higher-order maxima on

consists of randomly oriented grains of typical

the scattering curves. A detailed analysis of these

size approximately 2 µm. Long-range order should

curves is shown below using as example the curve for

Ultra

small

angle

neutron 2

exist inside each grain but the individual grains are oriented randomly in space as schematically depicted in Figure 1. This figure also shows (in panel c) a scheme of the spherical particles making up the body-centered cubic (BCC) structure, as determined below in this paper.

The mixture of the partially miscible solvents3 consists of cyclohexane (CX) and dimethylformamide (DMF). This mixture has a UCST temperature of 51.4 oC at a volume fraction φDMF = 0.327. The diblock copolymer is polystyrene-b-poly(ethyleneco-propylene) (PS-PEP) with a molecular weights MPS = 45 000 g.mol–1 and MPEP = 135 000 g.mol–1.

Figure 1.

Schematic representation of the nano and microstructure of the self-organized solution of diblock copolymers in immiscible solvents. a) Large scale structure made of randomly oriented

The measurements were carried out at the

grains of typical size 2 µm; b) the inner structure of each grain

“Laboratório Nacional de Luz Síncrotron – LNLS”

is long-range ordered and is shown here with a typical body-

(Campinas, Brazil), on the beamline D11A-SAXS, the wavelength of the X-rays being 0.148 nm. A collimated X-ray beam was passed horizontally

centered cubic (BCC) morphology; and c) the BCC cell is made of spherical objects containing the minority solvent that are embedded in the majority solvent, and the interface is covered with the diblock copolymer (PS-PEP).

ACTIVITY REPORT 2010 – LNLS | 55

SCIENCE HIGHLIGHTS

the solution with polymer concentration 5% (w/w), reproduced in enlarged form in Figure 2.

A structure factor with the sequence q0, √2q0 and √3q0 as observed here is characteristic of primitive

In the low q region, the data clearly displays

cubic (PC) or BCC structures, and cannot be

sharp and intense Bragg peaks, with a first-order

found with face-centered cubic systems that were

peak located at q0 = 0.0915 nm , and two secondary

occasionally observed6 in micellar dispersions. As

maxima at √2q0 and √3q0. There is still a significant,

known generally for PC and BCC structures it is the

though much less intense, scattering in the high

presence or absence of the 7th order peak that makes

q region, with a broad hump at about 0.4 nm-1 and

the difference between these morphologies.

-1

an asymptotic decrease of the signal that closely follows the q-4 Porod law. The latter feature (“form factor”, F(q)) is associated to the presence of objects with a well-defined shape and size at microscopic scales, while the former (“structure factor”, S(q))

In

the

one-dimensional

representation

appropriate for “powder” spectra, the scattered intensity is usually expressed as I (q ) ∝ F (q ) S (q )

(1)

corresponds to their periodic stacking at mesoscopic scales, as schematically depicted in Figure 1b and

where F(q) stands for the form factor of the individual

1c. The large-q end of the scattering curve with the

objects (i.e. the DMF-rich regions at the scale

characteristic q decrease comes from the scattering

investigated here), S(q) is the isotropically-averaged

from randomly oriented, locally planar interfaces.

structure factor accounting for periodic stacking,

Referring to Figure 1c, such interfaces are found

and an implicit proportionality constant ensures

between the minority and majority solvent regions,

proper account of contrast, irradiated volume, solid

respectively inside and outside of the particles.

angle and efficiency of the detector, etc.

-4

Thus, as the shapes of the polymer-covered DMF regions are, presumably, close to spherical, the form factor F(q) is easily obtained by fitting the high-q 10000

part of the data to the simple geometrical model of

q 0 √2 √3

spheres. The experimentally observed slope of -4 in the large-q region of the scattering curve in Figure 2

1000

represents the Porod law of randomly oriented

I(q)

interfaces and thus confirms that the scattering 100

objects can be modeled as spheres with sharp

FF

interfaces, in spite of their polymer coverage. This allows to get the structure factor S(q) in the whole

10

q range as –4

S (q ) = I (q ) / F (q )

1

with, as required, S(q)→1 in the large q limit.

0.1 0.05

0.1

0.2

0.5

1.0

2.0

q (nm –1) Figure 2.

(2)

Azimuthally averaged scattering curve (arbitrary intensity units) obtained after background subtraction for a solution of the diblock copolymer PS-PEP with concentration 5% (w/w) and solvent composition CX/12% DMF. The first order Bragg peak

Referring to the data in Figure 2, we have fitted the scattering curve I(q) in the range 0.2 nm-1 < q < 2 nm-1 with a model of spheres with radius R and a lognormal distribution of sizes characterized by a (dimensionless) width σ, using the program7 WFISPD3B. We found a distribution centered at

is at q0 = 0.0915 nm . Two higher-order peaks of the structure

R = 14.7 nm, and a width σ = 0.132 corresponding to

factor are identified by √2 and √3 from their relative positions with

a full-width at half-maximum of the distribution of

-1

respect to q0, and FF marks the position of the characteristic hump in the form factor. The full line represents the fitted form

4.5 nm. The model form factor displayed in Figure 2

factor (see text); for q > 0.2 nm-1 the fitted line missing in Figure 4

obviously gives a satisfactory description of the data

compared to my original.

in the large q limit.

56 | ACTIVITY REPORT 2010 – LNLS

SELF-ORGANIZATION OF DIBLOCK COPOLYMER SOLUTIONS IN MIXED SOLVENTS

Dividing the experimental scattering curve I(q) by the form factor F(q) derived from the same curve, we obtain the experimental structure factor S(q) shown in Figure 3 (fi lled symbols).

Characteristic peaks are observed for all the positions expected for a BCC structure up to q = √9q0 = 3q0, except the peak at √8q0. In particular, the peak at q = √7q0 (= 2.65 q0), though not especially sharp, is now clearly visible. The absence of the peak at √8q0 (= 2.83 q0), buried below the high-q wing of the √7q0 peak, is the probable consequence of its very low intensity.

In order to definitely confirm the structure, we have also calculated the isotropically-averaged structure factor of a finite-size BCC crystal comprising 63 primitive cells (with 6 primitive cells along each of the 3 principal axes), i.e. 216 scattering centers, using a MAPLE procedure. The calculated data, shown also in Figure 3, correspond very closely

Figure 3.

Structure factor S(q) experimentally obtained for a solution of the PS-PEP diblock copolymer with polymer concentration 5% (w/w) and solvent composition CX/12% DMF (filled symbols), and calculated structure

to the experimental results.

factor (solid line) obtained by isotropically averaging

The conclusion from Figure 3 is straightforward:

scattering from a finite-size crystal with BCC structure

The polymer solution has indeed a BCC structure so

and 6 scattering centers per principal axis.

that the schematic structure of the ordered solution in Figure 1b is correct.

In a procedure similar to that used above, and using polar coordinates for detector pixels, the effective 2-dimensional structure factor Seff (q,φ) is given by Seff (q,ϕ ) = I (q,ϕ ) / F (q )

(3)

The original 2-dimensional spectrum I(q,φ) was then according to this equation divided pixel-by-pixel by the form factor F(q) to yield the 2-dimensional structure factor Seff (q,φ). A typical resulting image is shown in Figure 4.

This isolation of the structure factor enhances and renders visible a large number of diff raction spots with |q| > √3q0 which is quite remarkable considering that the investigated system is a polymer solution with a low concentration (5%) and in equilibrium state—no shear being applied.

Indexation of these spots and determination

Figure 4.

Two-dimensional structure factor Seff(q,φ) obtained by dividing the measured 2-dimensional SAXS diffractogram I(q,φ) with the calculated form factor F(q). The intensity scale is identical to that

of the exact structure is not immediately obvious

of Figure 3, i.e., linear and goes from 0 to 6. The full and dotted

because the positions of the reflections are not

lines represent the reciprocal lattice for a twinned BCC structure _ → with common <111> axis parallel to the flow direction V and the _ → <112> axis parallel to the neutral direction e. The indexing is given

compatible with the positions expected for a single BCC lattice8,9. It was however shown previously that, quite commonly, dispersions of micelles, latex

for the grid marked by full lines and refers to lattice points to the left of the index.

ACTIVITY REPORT 2010 – LNLS | 57

SCIENCE HIGHLIGHTS

spheres or other spherical nanoobjects subjected to a

both in the one-dimensional, azimuthally-averaged

shear self-orient into a twin BCC structure

. Close

scattering curve and in the original two-dimensional

examination of Figure 4 reveals that in the present

scattering pattern. The obtained one-dimensional

case the data can be described as well by a twin BCC

structure factor corresponds almost quantitatively

10,11

structure, in a way very similar to that observed earlier in a shear-oriented diblock copolymer melt12.

In conclusion, we have shown that, to the contrary of the micellar solutions self-organized under shear8, in the present case we have a polymer solution that is anisotropically self-organized in an equilibrium state, without shear, into a network of micelles with twin BCC structure. The anisotropic orientation has been induced by the initial flow of the viscous

to the isotropically-averaged corresponding quantity, calculated semi-analytically using a MAPLE procedure. The isolated two-dimensional structure factor contains reflections that allow the structure to be identified as being close to a twin BCC.

Acknowledgements

The authors gratefully acknowledge support

solution into the scattering cell and maintained by

by the Grant Agency of the Czech Republic

surface effects in the very thin cell. We have shown

(202/09/2078).

that the form factor of the spherical scattering

Luz Sincrotron (LNLS), Campinas, Brazil, is

objects can be separated from the scattered signal

acknowledged for the SAXS measurements.

The

Laboratorio

Nacional

de

References

[1] P. Štěpánek, Z. Tuzar, F. Nallet, L. Noirez, Macromolecules 2005, 38, 3426-3431.

[2] V. Ryukhtin, P.Štěpánek, Z. Tuzar, K.Pranzas, D. Bellmann, Physica B 2006, 762, 385-386 [3] P. Štěpánek, Z. Tuzar, P. Kadlec, P. Černoch, J. Kříž, Int. J. Polym. Anal. Charact. 2007 12, 3-12.

[4] T.C. Huang, H. Toraya, T.N. Blanton, Y. Wu, J. Appl. Cryst. 1993 26, 180 [5] L. P. Cavalcanti, I. L. Torriani, T. S. Plivelic, C. L. P. Oliveira, G. Kellermann, R. Neuenschwander, Review of Scientific Instruments 2004, 75, 4541-4546.

[6] G.A. McConnell, A.P. Gast, J.S. Huang, S.D. Smith, Phys. Rev. Lett. 1992, 71, 2102 [7] courtesy R. Ober, Collège de France, Paris [8] S. Foerster, A. Timmann, C. Schellbach, A. Froemsdorf, A. Kornowski, H. Weller, S. V. Roth, P. Lindner,. Nature Materials 2007, 6, 888-893.

[9] C. Perreur, J.-P. Habas, J. François, J. Peyrelasse, A. Lapp, Phys. Rev. E 2002, 65, 041802.

[10] B. J. Ackerson, N. A. Clark, Phys. Rev. A 1984, 30, 906-918.

[11] K. Mortensen, E. Theunisses, R. Kleppinger, K. Almdal, H. Reynaers, Macromolecules 2002, 35, 7773-7781.

[12] C. M. Papadakis, F. Rittig, K. Almdal, K. Mortensen, P. Štěpánek, Eur. Phys. J. E 2004 15, 359-370.

[13] I. W. Hamley, J. A. Pople, J. P. A. Fairclough, A. J. Ryan, C. Booth, Y. W. Yang, Macromolecules 1998, 31, 39063911.

58 | ACTIVITY REPORT 2010 – LNLS

OBSERVATION OF FERROMAGNETISM IN PdCo ALLOY NANOPARTICLES ENCAPSULATED IN CARBON NANOTUBES

Roa, D. B.1, Barcelos, I. D.1, Siervo, A. de2, Pirota, K. R.2, Lacerda, R. G.1, Rogério Magalhães-Paniago1

Departamento de Fisica, Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, MG, Brazil Instituto de Fisica, Universidade Estadual de Campinas - UNICAMP, Campinas, SP, Brazil

1 2

The synthesis of carbon nanotubes (CNTs) has opened up the possibility of production of several devices taking advantage of the geometry and size of these nanostructures. One of the challenges in their production is the encapsulation of metals inside these nanotubes, which could be used in several applications where a conductive and/or magnetic end is necessary.

Usually 3d transition metals (e.g., Fe, Ni and Co) are used as catalysts for the formation of CNTs by Plasma-Enhanced Chemical Vapor Deposition (PECVD). However, the oxidation of these particles or formation of carbides may degrade their properties over time. Therefore, the incorporation of noble metals in these nanoparticles would be very interesting for application purposes. In this work, CNTs terminated by PdCo catalyst nanoparticles were grown by PECVD. Transmission Electron Microscopy (TEM) reveals that these nanoparticles have a droplike shape and are completely encapsulated inside multiwalled CNTs. Magnetization measurements showed the existence of a permanent magnetization with a small shape anisotropy effect. The magnetization of both cobalt and palladium was con�irmed by X-ray Magnetic Circular Dichroism (XMCD). These results show that nanotubes ended by magnetic PdCo nanoparticles can be grown and could be used in magnetic storage media and electrical spin injection.

Facilities: SXS, LME Publication: Applied Physics Letters, 96, 253114-1-3 (2010) Funding: FAPEMIG, CNPq, FAPESP Corresponding author: Rogério Magalhães-Paniago– rogerio@fisica.ufmg.br

10

SCIENCE HIGHLIGHTS

Since the 90´s, with the Carbon Nanotube´s

which was grounded, acting as an anode for the

(CNTs) advent, we have a “gold rush” in science

plasma discharge. The plasma was generated by a

looking toward new materials in nanometer

dc power supply. The chamber was maintained at

scale. The controlled synthesis of CNTs reached

vacuum using a rotary pump, with a base pressure

an appreciable degree and we can think now in

of 8 × 10-2 mbar. The substrate was sequentially

metals encapsulated inside them, which could be

coated by thermal evaporation of a double layer of

used in applications where we need a condutive or

metal catalysts [Pd(5 nm)/Co(5 nm)/Si]. Our CNT

magnetic end 2. Unfortunally, there is no possibility

growth procedure consisted of loading this Pd/Co/Si

to get a homogeneous growth of CNTs by Plasma

fi lm onto the graphite stage and heating to 500 °C in

Enhanced Chemical Vapour Deposition (PECVD)

NH3 [200 SCCM (SCCM denotes cubic centimeter

using an aleatory metal and a 3d transition metal

per minute at STP) flow rate, achieving a pressure of

(e.g., Fe, Ni and Co) is usually used to catalyze CNTs

2.5 mbar]. At these conditions, the thin fi lm PdCo

in this process . The oxidation of these particles or

catalyst agglomerates into nanoparticles suitable for

formation of carbides may degrade their properties

seeding nanotube growth. The dc plasma was then

over time and the incorporation of noble metals

immediately initiated, and C2H2 was added into the

in these nanoparticles would be very interesting

gas flow as the carbon feedstock for the growth of

for application purposes. Several groups have

multiwalled nanotubes7. The plasma dc bias was

already accomplished the growth of CNTs ended by

maintained at 600 V, with a current of typically

bimetallic nanoparticles (e.g., FePt and PdCo)3,4.

100 mA. The gas flow rates were 200 SCCM for NH3

1

2,3

Bimetalic nanoparticles with palladium are

and 60 SCCM for C2H2. The heater temperature

ideal candidates, since Pd is chemically stable and

was regulated to maintain the temperature stably at

it can become ferromagnetic . The introduction of

600 °C throughout the deposition (~30 min). After

small amounts of 3d transition metals such as Fe, Ni,

this process a forest of vertically aligned nanotubes

and Co in palladium stabilizes its ferromagnetism6.

was formed all over the substrate(see the detail in the

Fujita et al. have recently reported the growth of

Figure 3).

5,8

4

CNTs terminated by PdCo nanocomposites. They

The nanoparticles were analyzed with a 300 kV

have observed, however, a composition separation

JEM transmission electron microscope. In Figure 1a

which resulted in inhomogeneous nanoparticles.

one can see several nanotubes distributed over a

In the present work, we have grown CNTs with

transmission grating with a Lacey-type carbon

homogeneous PdCo nanoparticles starting from a

fi lm deposited on top. The size distribution of both

Pd(5nm)/Co(5nm)/Si fi lm. Transmission Electron

nanotubes and nanoparticles is quite uniform

Microscopy (TEM) confirmed the formation of

and the average diameter of the nanoparticles

CNTs terminated by drop-shaped nanoparticles,

was determined to be (79 ± 30) nm. The length

with an aspect ratio of 3:1. Vibrating sample

and density of our CNTs are (3.1 ± 0.7) μm and

magnetometry (VSM) measurements at room

(6.9 ± 0.9) × 10 -9cm-2, respectively. It should be

temperature confirmed their ferromagnetism. To

noted that all nanotubes are perfectly terminated by

prove that an alloy magnetic nanostructure was

homogeneous droplike PdCo nanoparticles, which

formed, the separate magnetization of both cobalt

explains the response to magnetic fields applied

and Pd was confirmed by X-ray Magnetic Circular

parallel and perpendicular to them. In Figure 1b a

Dichroism (XMCD).

TEM micrograph of an isolated PdCo nanoparticle

CNTs were grown using a home built PECVD

is shown, where one can see that the nanoparticles

setup with the substrate located on a resistively

are completely encapsulated inside the CNTs. The

heated graphite stage. The substrate temperature

image was taken with the particle center oriented

was measured using a thermocouple attached

along the [001] zone axis. No fringes due to

directly to the upper surface of the stage. Gas

oriented planes can be seen due to the thickness

flow rates were controlled independently using

of the nanoparticle of approximately 60 nm. All

mass flow controllers and the combined gases

particles have the same 3:1 aspect ratio and exhibit

were fed into the chamber through a metal pipe

a spherical core and a conical (crystalline) tail,

60 | ACTIVITY REPORT 2010 – LNLS

OBSERVATION OF FERROMAGNETISM IN PDCO ALLOY NANOPARTICLES ENCAPSULATED IN CARBON NANOTUBES

Figure 1.

a) Composition of 16 TEM micrographs of approximately 3 × 3 µm2 producing an overview of the distribution of several CNTs, which

Figure 2.

a) Electron diffraction pattern (taken at the particle center) aligned along [301] zone axis identifying a strucuture close to Palladium fcc.

all have encapsulated PdCo nanoparticles.

b) EDS spectrum of three different regions of

b) High Resolution TEM of a single drop-

the particle, showing the signal from Pd and

shaped PdCo nanoparticle. The nanoparticle

Co. The signal for Si, C and Cu Is from the

are composed of a spherical core followed by

detector, lacey Carbon film and transmission

a conical tail.

grating respectively.

where several stacking faults are visible8*. There is

[close to pure palladium, face-centered cubic (fcc)

probably a defi ned crystallographic orientation

with a = 0.389 nm], with the possible presence of

between the core and the conical extension, since

stacking faults in between them. Analysis by Energy

once we orient the core along one zone axis several

Dispersive X-ray Spectroscopy [EDS, Figure 2b] of

fringes due to oriented planes are visible. Selected

three different regions of the particle indicated that

area electron diff raction [Figure 2a] showed that the

the concentration of Pd and Co is nearly constant.

structure of the particle core is the same of the tail

No residual content of oxygen and nitrogen was

* Although the magnetism in Pd was previously ascribed to the presence of stacking faults, (Ref. 9) the alloying with Co is clearly the most important factor for the magnetization of Pd (see, e.g., Ref. 6).

observed.

To analyze the global magnetic properties and possible magnetization reversal mechanisms, VSM ACTIVITY REPORT 2010 – LNLS | 61

SCIENCE HIGHLIGHTS

measurements were done at room temperature for

XMCD measurements of this sample. The XMCD

magnetic fields applied parallel and perpendicular

experiments were done at beamlines SGM (near

to the CNTs axis. As seen in Figure 3, the PdCo

the cobalt L2 and L3 edges) and SXS (Pd L2 and L3

nanoparticles exhibit a typical ferromagnetic

edges) at the Brazilian Synchrotron Light Source

hysteresis curve, at room temperature, with a

(LNLS, Campinas, SP) in total electron yield mode.

saturation net magnetic moment of 3.5 × 10 -4 emu

Measurements were performed with fi xed circular

and a coercive field of about 100 Oe for both orientations. A slight difference in shape can be seen for fields applied parallel and perpendicular to the tubes axes, which can be ascribed to a uniaxial magnetic anisotropy, desired for magnetic storage media, with contributions from crystalline and shape anisotropy of the PdCo nanoparticles. For a better determination of the saturation field, the second derivative (d 2m/dH2) of the magnetization (inset of Figure 2) shows that for fields above 1500 Oe no change in curvature is seen, which reveals that field is due to residual paramagnetic material. It should be also pointed out that in remanence the nanoparticles retain only about 25% of the total magnetization in both directions, not expected for a single domain nanoparticle with perfect uniaxial anisotropy. This fact could have origin in a magnetic domain structure favored by the nanoparticles size

Figure 3.

polarization and alternating the magnetic field of 8000 Oe for each x-ray photon energy measured9.

Circular polarization was obtained by collecting the synchrotron light below the electron orbit planet, obtaining thereby a beam with 65% of circular polarization.

In Figures 4a,b both the absorption spectra as well as the XMCD difference are shown for both atomic L edges. The separate magnetization state of cobalt and palladium can be determined following the XMCD sum rules9,10, which allow us to infer directly the orbital and spin momentum of the atoms. According to these rules for L2,3 edges,11 the orbital and spin momentum can be obtained from morb = −4q(10−n)/3r and mspin = −(6p−4q)(10−n)/r, where q is the integrated area of the XMCD signal over the two (L3 and L2)

(~100 nm) or in magnetic dipolar interactions (not

edges, p the integrated area of the XMCD signal

considered in this work).

over the L3 edge, and r the sum of the integrated

Simple magnetization measurements always

areas of the absorption spectrum for positive

give us the global behavior of the sample. In order

and negative magnetic fields. n is the occupation

to confirm the contributions of both cobalt and

number in the 3d band for cobalt and the 4d band

palladium to the total magnetization, we have

for palladium.

Magnetization as a function of magnetic field for PdCo nanoparticles is noticeable as the slight difference in lineshape for applied perpendicular and parallel to the CNT axis. A small hysteresis of ~100 Oe is also observed. The inset shows the second derivative of parallel magnetization, from which a saturation field of ~1500 Oe was inferred. Above one can see a schematic diagram of the parallel VSM measurement.

62 | ACTIVITY REPORT 2010 – LNLS

OBSERVATION OF FERROMAGNETISM IN PDCO ALLOY NANOPARTICLES ENCAPSULATED IN CARBON NANOTUBES

Figure 4.

Normalized X-ray absortion spectra at: a) the L2,3 edges of Cobalt; and b) Palladium of PdCo nanoparticles in CNTs. In all spectra a linear background was subtracted. At the bottom, the difference curves normalized by the degree of circurlar polarization are shown, from which the magnetization of both atoms was determined.

Considering that it was extremely difficult to measure r reliably, we could only determine the ratio morb/mspin=2q/(9p−6q), which can be inferred directly from p and q. We found morb/mspin = (0.12 ± 0.05) for Cobalt and (0.07 ± 0.05) for Palladium. These values

shape anisotropy, while maintaining the magnetic properties.

Acknowledgements

This work was financed by Instituto Nacional de

should be compared with 0.099 for bulk cobalt and

Ciência e Tecnologia (INCT—NanoCarbono). The

up to 0.09 for palladium fi lms12, which indicates

technical assistance of F. Vicentim (beamline SGM),

that magnetic nanoparticles with properties close to

and P. de Tarso (SXS) and the staff of the Microscopy

bulk PdCo were formed. Future studies will focus on

Center (LME) of LNLS is gratefully acknowledged.

minimizing the Co content of these nanoparticles

The authors also gratefully acknowledge the financial

(to control the chemical reactivity) and changing its

support from CNPq, FAPESP, and FAPEMIG.

11

References

[1] S. Iijima, Nature (London) 354, 56 (1991).

[2] See, e.g., T. Fujita, Y. Hayashi, T. Tokunaga, and K. Yamamoto, Appl. Phys. Lett. 88, 243118 (2006).

[3] F. Schäffel, C. Täschner, M. H. Rümmeli, V. Neu, U. Wolff, U. Queitsch, D. Pohl, R. Kaltofen, A. Leonhardt, B. Rellinghaus, B. Büchner, and L. Schultz, Appl. Phys. Lett. 94, 193107 (2009).

[4] T. Fujita, Y. Hayashi, T. Tokunaga, T. Butler, N. L. Rupesinghe, K. B. K.Teo, and G. A. J. Amaratunga, Appl. Phys.

Lett. 90, 133116 (2007).

[5] See, e.g., T. Taniyama, E. Ohta, and T. Sato, Europhys. Lett. 38, 195 (1997); T. Shinohara, T. Sato, and T. Taniyama, Phys. Rev. Lett. 91,197201 (2003).

[6] J. Crangle and W. R. Scott, J. Appl. Phys. 36, 921 (1965); G. J. Nieuwenhuys,Adv. Phys. 24, 515 (1975).

[7] M. S. Bell, R. G. Lacerda, K. B. K. Teo, N. L. Rupesinghe, G. A. J. Amaratunga, W. I. Milne, and M. Chhowalla, Appl. Phys. Lett. 85, 1137 (2004).

ACTIVITY REPORT 2010 – LNLS | 63

SCIENCE HIGHLIGHTS

[8] B. Sampedro, P. Crespo, A. Hernando, R. Litrán, J. C. Sánchez López, C. López Cartes, A. Fernandez, J. Ramírez, J. González Calbet, and M. Vallet, Phys. Rev. Lett. 91, 237203 (2003).

[9] J. J. S. Figueiredo, R. Basílio, R. Landers, F. Garcia, and A. de Siervo, J. Synchrotron Radiat. 16, 346 (2009).

[10] P. Carra, B. T. Thole, M. Altarelli, and X. Wang, Phys. Rev. Lett. 70, 694 (1993); B. T. Thole, P. Carra, F. Sette, and G. van der Laan, ibid. 68, 1943 (1992).

[11] C. T. Chen, Y. U. Idzerda, H.-J. Lin, N. V. Smith, G. Meigs, E. Chaban, G. H. Ho, E. Pellegrin, and F. Sette, Phys.

Rev. Lett. 75, 152 (1995).

[12] J. Vogel, A. Fontaine, V. Cros, F. Petroff, J.-P. Kappler, G. Krill, A. Rogalev and J. Goulon, Phys. Rev. B 55, 3663 (1997).

64 | ACTIVITY REPORT 2010 – LNLS

THE ROLE OF Lys122 AND Ca2+-BINDING LOOP REGION FOR THE CATALYTICALLY INACTIVE Lys49PHOSPHOLIPASES A2 FROM SNAKE VENOMS Carlos A. H. Fernandes, Daniela P. Marchi-Salvador, Guilherme H. M. Salvador, Mabel C.O. Silva, Tássia R. Costa, Andreimar M. Soares, Marcos R. M. Fontes Departamento de Física e Biofísica, Instituto de Biociências, Universidade Estadual Paulista – UNESP, Botucatu, SP, Brasil

Envenoming resulting from snake bites is an important public health problem in rural areas of tropical and subtropical countries situated in Asia, Africa, Oceania and Latin America being considered as neglected tropical diseases by the World Health Organization. Lys49-PLA2s are a class of phospholipases A2 (PLA2s) present in several snake venoms which does not show catalytic activity but can exert a pronounced local myotoxic effect that is not neutralized by serum therapy. Here, we report �ive structures of Lys49-PLA2s from snakes of the Bothrops genus in apo form, complexed with PEG molecules and chemically modi�ied by p-bromofenacil bromide (BPB), a classic inhibitor of PLA2. We present herein an extensive structural analysis including: (i) the function of hydrophobic long-chain molecules as Lys49-PLA2s inhibitors, (ii) the role of Lys122, previously indicated as being responsible for Lys49-PLA2s catalytic inactivity and,

(iii) a structural comparison of the Ca2+-binding loop region between Lys49 and Asp49-PLA2s.

Facilities: MX1, MX2 Publication: Journal of Structural Biology, 171, 31-43 (2010) Funding: FAPESP, CNPq and INCTTox. Corresponding author: Marcos Fontes – fontes@ibb.unesp.br

11

SCIENCE HIGHLIGHTS

In this study we present five crystal structures

The absence of catalytic activity in Lys49-

of bothropstoxin I (BthTX-I), a Lys49-PLA 2 isolated

PLA 2s is explained due to their incapacity to bind

from Bothrops jararacussu venom: two of them

the cofactor Ca 2+ since the ε-amino group of Lys49

in native form, each with a different number of

occupies exactly the position of the coordinated

molecules in the asymmetric unit; two chemically

Ca 2+ ion in catalytic active phospholipases

modified by p-bromophenacyl bromide (BPB), a well-

A2

known inhibitor of snake venom PLA2s, each with a different number of molecules in the asymmetric unit; and, finally, one structure co-crystallized with PEG 4000 (Figure 1).

(Asp49-PLA 2s)1.

However,

site-directed

mutagenesis with a Lys49-PLA 2 showed that a Lys49Asp mutant remained catalytically inactive, demonstrating that not only the single Asp49Lys replacement but also other possible structural changes are responsible for the lack of enzymatic activity3. In order to understand the reasons for the catalytic inactivity of Lys49-PLA 2s, we performed a structural comparison of Ca 2+ binding loop regions from Lys49-PLA 2s, Asp49-PLA 2s and lowcatalytic-activity Asp49-PLA-2s which also display myotoxic activity as Lys49-PLA 2s (BthTX-II and PrTX-III). Figure 2 shows the C α superposition between the Ca 2+ binding loop regions (residues 27-35) from several snake venom PLA 2s. Th is comparison reveals that this loop adopts a similar conformation within Lys49-PLA 2s and within

Figure 1.

Dimeric

structures

of:

a)

apo-dBthTX-I;

b) dBthTX-I/BPB; and c) BthTX-I/PEG4K show as a cartoon representation. The BPB and PEG molecules (yellow) are showed by sticks.

66 | ACTIVITY REPORT 2010 – LNLS

Figure 2.

Cα superposition of Ca2+-binding loop region of Lys49-PLA2s (red) and Asp49-PLA2s (green) and low-catalytic-activity Asp49-PLA2s (blue) structures.

THE ROLE OF LYS122 AND CA2+-BINDING LOOP REGION FOR THE CATALYTICALLY INACTIVE LYS49-PHOSPHOLIPASES A2 FROM SNAKE VENOMS

Figure 3.

Figure 4.

Tyr28 (Asp49-PLA2s) and Asn28 (Lys49-PLA2s) side chain residues are shown in the Ca2+-binding loop region superposition of: a) Asp49-PLA2s (green) and Lys49-PLA2s (red) structures; and b) Asp49-PLA2s (green) and low-catalytic-activity Asp49-PLA2s (blue) structures.

Interaction between Oγ atom between Tyr28 residue and Gly35 amino group that stabilizes the Ca2+-binding loop region of Asp49-PLA2s structures.

ACTIVITY REPORT 2010 – LNLS | 67

SCIENCE HIGHLIGHTS

Asp49-PLA 2s, but when these two classes are

is also structurally conserved in Asp49-PLA 2s,

compared the conformation becomes very different.

with the exception of low-catalytic Asp49-PLA-2s

Amino acid sequence alignment of Ca -binding

(Figure 3). The structural analysis of Tyr28 of Asp49-

loop region of Lys49-PLA 2s and Asp49-PLA 2s from

PLA 2s reveals an important stability feature of the

several snakes, showed that Tyr28 is conserved

Ca 2+-binding loop region. All Asp49-PLA 2s (except

2+

for all Asp49-PLA 2s while Asn28 is conserved for

low-catalytic Asp49-PLA-2s) present a conserved

Lys49-PLA 2s. Furthermore, the Tyr28 side chain

interaction between Oγ atom of Tyr28 and Gly35 amino group in the range from 3.1 to 3.5 Å (Figure 4)

Table 1. Values of d distance between Cα atoms of Tyr28 and Gly33 reflecting the aperture of Ca2+binding loop in Asp49-PLA2s and Lys49-PLA2s structures.

Protein

d

apo-dBthTX-I

6.05

PrTX-I

6.22

BnSP-7

6.46

Anum-II

6.30

godMT-II

5.06

BthA-I-PLA2s

4.20

Acid-PLA2s

4.41

DPLA2

4.58

β2-Bungarotoxin

4.33

PLA2s pancreatic bovine

3.91

Asp49-PLA2s

Lys49-PLA2s

Class

which is also present in other catalytic PLA2s, including pancreatic bovine PLA 2. This Tyr28-Gly35 interaction may provide more structural stability for the Ca 2+-binding loop which may be verified by the conservation of the distance d that reflects the aperture of this loop. Table 1 shows that the distance d between Cα atoms of Tyr28 and Gly33 in Asp49PLA 2s (except low-catalytic-activity Asp49-PLA 2s) is approximately 4.3Å. In contrast, for Lys49-PLA 2s, due to the natural mutation Tyr28Asn, the distance d becomes greater than 6.3 Å. This open configuration of Ca 2+-binding loop may be one of the factors responsible for the inability of Ca 2+ ion to bind to Lys49-PLA 2, even when the Lys49Asp mutation is performed by site-directed mutagenesis.

Table 2. The role of Lys122 residue for Apo and complexed Lys49-PLA2s. B-factor side chains, electron density and polarization of Cys29-Gly30 analyses.

Complexed

Apo

B-factor average of all protein atoms (Å2)

#

B-factor average of Lys122 side chain atoms (Å2)

Eletron density for Lys122 side chain (cut-off 1.2σ)

Polarization of Cys29-Gly30 peptide bond

Monomer A Monomer B

Monomer A Monomer B

Monomer A Monomer B

dBthTX-I

41.1

62.9

31.7

Yes

Yes

No

Yes

mBthTX-I

27.8

60.0

–

Yes

–

No

–

PrTX-I

34.1

42.4

31.2

Yes

Yes

No

Yes

BaspTX-II

12.1

27.1

23.0

#

#

Yes

No

BnSP-7

30.5

51.7

55.4

Yes

Yes

No

No

BnSP-6

38.3

47.5

68.9

Yes

Yes

Yes

No

dBthTX-I/BPB

48.7

–

–

No

No

No

No

mBthTX-I/BPB

29.2

26.1

–

Yes

–

Yes

–

BthTX-I-PEG4K

27.8

37.5

45.0

Yes

Yes

Yes

No

BthTX-I/αT

30.4

–

47.2

No

Yes

No

No

PrTX-I/BPB

48.9

66.9

65.1

Yes

Yes

No

No

PrTX-I/αT

22.7

37.7

38.1

Yes

Yes

No

No

PrTX-II/fatty acid

31.1

32.8

32.7

#

#

Yes

Yes

MjTX-II/stearic acid

33.6

39.1

36.0

Yes

Yes

Yes

Yes

BaspTX-II/suramin

24.0

32.5

48.1

Yes

Yes

Yes

No

BthTX-I/PEG 400

41.1

60.4

51.2

Yes

Yes

No

Yes

Structure factors values not available in PDB Data Bank.

68 | ACTIVITY REPORT 2010 – LNLS

THE ROLE OF LYS122 AND CA2+-BINDING LOOP REGION FOR THE CATALYTICALLY INACTIVE LYS49-PHOSPHOLIPASES A2 FROM SNAKE VENOMS

A classical crystallographic study of a Lys49-

of the catalytic cycle. However, since this study,

PLA 2 from Bothrops pirajai venom (PrTX-II)

a large number of structures of Lys49-PLA 2s, in

complexed with fatty acid, proposed that Lys122

native or complexed forms, have been solved, thus

(conserved in all Lys49-PLA 2s but rare in Asp49-

necessitating a revision of the position of Lys122

PLA 2s) interacts with the carbonyl of Cys29

in these new structures. Table 2 summarizes

hyperpolarizing the peptide bond between Cys29

different structural data of Lys122 for 30 different

and Gly30 . Th is strong interaction causes an

monomers for apo and complexed Lys49-PLA 2

increased affi nity for the fatty acid, precluding

whose coordinates are available in the PDB data

the release of free fatty acid produced after an

bank. There are 12 monomers in which Lys122

initial phospholipid hydrolysis and interruption

interacts with the Cys29 versus 18 monomers where

[2]

Figure 5.

Interactions of Lys122 with several residues in different Lys49-PLA2s structures. The distances between the atoms are shown. a) apo-mBthTX-I; b) mBthTX-I/BPB; c) BaspTX-II/Suramin; d) apo-BaspTX-II; e) BnSP-7; and f) BnSP-6.

ACTIVITY REPORT 2010 – LNLS | 69

SCIENCE HIGHLIGHTS

this interaction does not occur. In some cases,

residue that may adopt random configurations,

Lys122 side chains lack electron density above 1.2 σ,

interacting with different sites of negative charges

probably due to their high flexibility, not interacting

(Figure 5). Then, we can hypothesize that the affi nity

with Cys29 or any other residue. Table 2 also shows

of the hydrophobic channel by fatty acids are related

our analysis of the B-factors for Lys122 side chains.

to membrane anchorage rather than Lys49-PLA 2s

It can be observed that only seven Lys122 residues

catalytic inactivity, which may, eventually, be aided

present B-factor values compatible with the average

by hyperpolarization caused by Lys122.

of their respective proteins, while all others present

The hypotheses raised in this work may be

very high values (in most cases the values are 50%

useful for guiding new biophysical and biochemical

higher). These results indicate the high flexibility of

experiments that may definitively clarify the action

these residues in the majority of the structures which

mechanism of intriguing snake venom PLA 2s and

is not compatible with the polarization process.

lead to the design of structure-based inhibitors to

Furthermore, besides Cys29, this residue can also

complement the serum therapy, thus preventing the

interact with a carboxyl group from the several

permanent injuries still caused by these proteins in

other residues. Therefore, Lys 122 is a very flexible

snakebite victims around the world.

References

[1] Holland, D.R., L.L. Clancy, S.W. Muchmore, T.J. Ryde, H.M. Einspahr, B.C. Finzel, R.L. Heinrikson, and K.D. Watenpaugh, 1990. The crystal structure of a lysine 49 phospholipase A2 from the venom of the cottonmouth snake at 2.0-A resolution. J Biol Chem 265: 17649-56.

[2] Lee, W.H., M.T. da Silva Giotto, S. Marangoni, M.H. Toyama, I. Polikarpov, and R.C. Garratt, 2001. Structural basis for low catalytic activity in Lys49 phospholipases A2--a hypothesis: the crystal structure of piratoxin II complexed to fatty acid. Biochemistry 40: 28-36.

[3] Ward, R.J., L. Chioato, A.H.C. de Oliveira, R. Ruller, and J.M. Sa, 2002. Active-site mutagenesis of a Lys(49)phospholipase A2: biological and membrane-disrupting activities in the absence of catalysis. Biochemical Journal 362: 89-96.

70 | ACTIVITY REPORT 2010 – LNLS

EFFECTS OF ADDING La AND Ce TO Ni/Mg/ Al HYDROTALCITE CATALYST PRECURSORS ON ETHANOL STEAM REFORMING REACTIONS

Alessandra Fonseca Lucrédio1, Jorge David Alguiar Bellido2, Elisabete Moreira Assaf1*

Instituto de Química de São Carlos, Universidade de São Paulo - USP, Av. Trabalhador São Carlense, 400, CEP 13560-970, São Carlos, SP, Brazil 2 Universidade Federal de São João Del Rei - UFSJ, Campus Alto Paraopeba, Rodovia MG-443, Km 07, Fazenda do Cadete, Ouro Branco, MG, Brazil 1

Catalyst precursors composed of Ni/Mg/Al oxides with added La and Ce were tested in ethanol steam reforming (ESR) reactions. The catalysts were studied by X-ray diffraction (XRD), Temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and X-ray absorption nearedge structure (XANES), which showed that catalyst precursors consist of a mixture of oxides, with the nickel in the form of NiO strongly interacting with the support Mg/Al. The XPS analysis showed a lanthanum-support interaction, but no interaction of Ce species with the support. The reaction data obtained with the active catalysts showed that the addition of Ce and La resulted in better H2 production at 550 °C. The CeNi catalyst provided the higher ethanol conversion, with lower acetaldehyde production, possibly due to a favoring of water adsorption on the weakly interacting clusters of CeO2 on the surface.

Facility: DXAS Publication: Applied Catalysis A, 388: 77/85 (2010) Funding: CNPq, FAPESP, CAPES Corresponding author: E. M. Assaf – eassaf@iqsc.usp.br

12

SCIENCE HIGHLIGHTS

about

properties, high surface area and thermal stability;

environmental degradation and the exhaustion of

moreover, after calcination, the double-layered

finite resources there is a need to develop new means of

structure of hydrotalcites is known to lead to a

power generation from renewable fuels. Ethanol steam

homogenous dispersion of the active phase2. This

reforming (ESR, CH3CH2OH + 3H2O→ 6H2 + 2CO2)

article describes a study of catalysts derived from

has been suggested as an efficient way to generate

Ni/Mg/Al hydrotalcite –type precursors modified

H2 for application in fuel cells. Nickel catalysts are

by La and Ce. The catalysts were analyzed by ex situ

promising for ESR, showing high activity, but favor

techniques, to understand the mixed oxide structure,

carbon deposition. Among the various oxides used

and also by in situ techniques to monitor the changes

as supports, Al2O3 is widely used in reforming

in the catalysts during the activation with H2. The

catalysts, but this material, in ESR, promotes carbon

results were correlated with the performance of the

deposition, as it favors the formation of ethylene,

catalysts in the ESR reaction.

Owing

to

the

growing

concern

an intermediate produced by ethanol dehydration

The hydrotalcite-type precursors were prepared

on the Al2O3 acid sites. The rate of coking can be

in two ways: the standard Ni-LDH (layered

reduced by additives or promoters, which can favor

double hydroxide) was prepared by the traditional

the adsorption of H2O and the mobility of –OH on

technique of precipitation with carbonate, while

the surface. Lanthanide oxides (CeO2, La 2O3) are

the promoted catalysts LaNi-LDH and CeNi-

added to improve the stability of Ni-based catalysts .

LDH were prepared from a Mg/Al/Ni hydrotalcite

The use of calcined Mg-Al hydrotalcites as supports

produced by precipitation with NaOH. This

for ESR catalysts seems promising, given their basic

hydrotalcite was subjected to anion-exchange with

1

Figure 1.

In situ XANES spectra: a) All samples at 20 °C; b) Ni; c) LaNi; and d) CeNi; under reducing conditions.

72 | ACTIVITY REPORT 2010 – LNLS

EFFECTS OF ADDING LA AND CE TO NI/MG/AL HYDROTALCITE CATALYST PRECURSORS ON ETHANOL STEAM REFORMING REACTIONS

Table 1. Ethanol conversion and liquid effluents after 6 hours of ESR and mean H2 and CO yields.

Temperature (°C)

550

650

Catalyst

Liquid effluents (mmol)

Acetaldehyde

Ethanol

Ethanol conversion (%)

H2 yield

CO yield

Ni

13.5

28.8

78.5

1.7

0.15

LaNi

10.1

25.1

81.1

2.5

0.22

CeNi

0.9

6.1

95.5

2.8

0.35

Ni

0.3

1.8

98.7

4.2

1.2

LaNi

0.2

1.5

98.8

4.4

1.2

CeNi

0.2

2.3

98.3

4.3

1.2

Feed molar ratio H2O:C2H5OH = 3:1; feed rate 2.5 mL/h; mass of catalyst 150 mg.

chelation complexes of La and Ce, to introduce them inside the hydrotalcite layers and thus ensure a better dispersion of these cations. The resulting hydrotalcites were calcined at 500 °C in air for 15 hours, and denominated Ni, LaNi and CeNi. XRD analysis indicated the formation of a (Ni, Mg)O solid solution doped with Al3+ cations and, for the promoted catalysts, CeO2 and La 2O3 phases were observed, indicating a low interaction of these species with the support. TPR-H2 analysis, for all catalysts, showed a small peak around 450 °C corresponding to NiO interacting weakly with the support, and an intense peak above 900 °C, confirming the formation of the thermally stable phase Mg(Ni,Al)O. In XPS analysis, the binding energy (BE) found for the Ni2p3/2 peak was around 855.5 eV (Ni = 855.4; LaNi = 856; CeNi = 855.4), this value being higher than that given in the literature for free NiO (854.5 eV), but similar to that observed for Ni2O3 (856 eV) and NiAl2O4 (856 eV)[5]. Also, for this core-level, satellite lines are visible, at BEs about 6 eV higher than the main peak (Ni = 861.4; LaNi = 861.8; CeNi = 861.7). These satellite lines are related to Ni+2 species, suggesting the presence of these ions. Electron transfer from Ni to Mg or Al in neighboring positions in the structure could cause the shift to a higher binding energy than that of free NiO[5]. These XPS results are consistent with those of XRD and TPR, which showed a strong interaction between Ni and the Mg-Al support. The value of the binding energy of La3d peak was 835.7 eV, which is higher than the literature value for La 2O3 (834.6 eV) and closer to that for LaAlO3 (836.5 eV), indicating a possible interaction of the La3+ species with the support in sample LaNi5. For the sample promoted

Figure 2.

Comparison of XANES spectra before and after heat treatment under an atmosphere of H2.

ACTIVITY REPORT 2010 – LNLS | 73

SCIENCE HIGHLIGHTS

with Ce (CeNi), the BEs for Ce3d peaks were 882.3 eV

According to the XANES-TPR-H2 profi les

and 885.1 eV; these correspond closely to CeO2

(Figures 1b,c,d) the intensity of the peak referred to

(882 eV) and Ce2O3(885 eV), suggesting the presence of species of Ce and Ce interacting weakly with 4+

3+

the support.

To investigate the changes in the catalysts under the conditions of activation, the electronic properties of the Ni atoms were monitored by in situ XANES-TPR- H2 at the Ni K-edge. The pre-edge peak intensity and white line intensity are considered the main characteristics for monitoring the reduction of the nickel species6. For the purpose of comparison, Figure 1a shows the XANES spectra of all the samples at 20 °C, plotted together with spectra of

as the white line (8350 eV) did not fall appreciably during the activation with H2 up to 700 °C, indicating that only a small fraction of the nickel in these species was reduced up to 700 °C. Figure 2 clarifies this observation by comparing the spectra at the starting temperature (20 °C) and at the final temperature (700 °C) with the NiO and Ni foil spectra; it is then possible to see that the white line showed almost change between the initial and final temperatures.

These results agree with the TPR results reported previously3. Before the catalytic tests, the catalysts were activated by reduction in situ in flowing H2 at 550 °C for 1 hour. The XANES results suggest that,

reference materials, Ni foil and NiO, representing

after activation, the catalyst consists of a few Ni0

the Ni0 and Ni2+ oxidation states, respectively. The

species anchored on a solid solution of (Ni, Mg)AlO,

Ni experimental spectrum shows a weak pre-edge

which acts as a support.

0

peak (1), which arises from the 1s–3d transition,

Table 1 presents the total ethanol conversion

forbidden in the case of Oh symmetry around a Ni

obtained on each catalyst, during 6 hours on

atom. The samples did not show this peak and their patterns are similar to the NiO pattern, suggesting the presence of Ni2+. The position of the white line (2) at 8350 eV is similar to that of the NiO standard in the spectra of all the samples. Among these spectra, only the intensity of the white line varies, indicating the presence of NiO in all the samples.

stream at 550 °C and at 650 °C, along with the amounts of liquid effluents collected and yield of H2 and CO (number of moles of H2 and CO produced per mole of ethanol in the ESR reaction feed). The results indicated that at 550 °C, ethanol conversion increased with the addition of the rareearth metals in the following order: Ni < LaNi < CeNi. The opposite was observed for production of acetaldehyde, an undesirable by-product. Carbon deposition was observed only in trace amounts on all catalysts, showing the stability of these catalysts.

The CeNi catalyst led to the lowest acetaldehyde production, indicating that the presence of Ce favored acetaldehyde conversion. The XPS results indicated that Ce interacted little with the support and, according to the literature7, the presence of Ce (as CeO2) promotes steam reforming reactions due to an improvement in the adsorption and dissociation of water molecules associated with CeO2. This hypothesis agrees with the results obtained here, as the lower acetaldehyde formation can be explained by promotion of acetaldehyde steam reforming (CH3CHO + H2O → CO2 + CH4 + H2)[6]. At 550 °C, it is observed that H2 production increased with the

Figure 3.

Conversion of ethanol and production of H2 and other gases by

addition of the rare earths to the catalysts and this

the catalyst CeNi during a 50 hours stability test at 650 °C and a

effect was more pronounced on the CeNi catalyst,

flow rate of 2.5 mL/h.

which also showed the highest CO production.

74 | ACTIVITY REPORT 2010 – LNLS

EFFECTS OF ADDING LA AND CE TO NI/MG/AL HYDROTALCITE CATALYST PRECURSORS ON ETHANOL STEAM REFORMING REACTIONS

This higher H2 and CO production may be due

In sum, the addition of Ce or La resulted in

to better ethanol and acetaldehyde conversion on

better H2 production. The CeNi catalyst afforded

the CeNi catalyst. At 650 °C, all catalysts achieved

the highest ethanol and acetaldehyde conversion

ethanol conversions close to 100% and acetaldehyde

rates at 550 °C and the better performance may be

production was suppressed. Also, an increase

related to the low interaction of the Ce species with

occurred in both the H2 and CO production rates, which were similar on all catalysts. The CeNi catalyst was also monitored for 50 hours on stream at 650 °C. The results are shown in Figure 3 It can be seen that the ethanol conversion did not vary significantly throughout the time on stream and also that the H2 production was constant, proving the stability of this catalyst. The carbon deposition rate was measured and found to be 0.001 molCdeposited/molCinlet on CeNi,

the support, with enhanced water adsorption on CeO2. The physical/chemical characterization of the catalysts was essential to understand their improved performance on being modified by La and Ce, especially by Ce.

Acknowledgements

The authors are grateful to the Brazilian state

a value close to that observed at 6 hours, again

and federal research funding agencies, FAPESP,

showing the stability of the catalyst during the test.

CNPq and CAPES, for financial support.

References

[1] M.C. Sánchez-Sánchez et al., Ethanol steam reforming over Ni/MxOy–Al2O3 (M = Ce, La, Zr and Mg) catalysts: Influence of support on the hydrogen production. International Journal of Hydrogen Energy, v. 32, n. 10-11, p. 1462-1471, 2007.

[2] A.Vaccari, Preparation and catalytic properties of cationic and anionic clays. Catalysis Today, v. 41, n. 1-3, p. 53-71, 1998.

[3] A.F. Lucrédio et al., Nickel catalysts promoted with cerium and lanthanum to reduce carbon formation in partial oxidation of methane reactions. Applied Catalysis A, v. 333, n. 1, p. 90-95, 2007.

[4] J. F. Moulder et al. Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer Co., Minnesota, 1992.

[5] L.P.R. Profeti et al. Hydrogen production by steam reforming of ethanol over Ni-based catalysts promoted with noble metals. Journal of Power Sources, v. 190, n. 2, p. 525-533, 2009.

[6] R.M. Navarro et al., Hydrogen production by oxidative reforming of hexadecane over Ni and Pt catalysts supported on Ce/La-doped Al2O3. Applied Catalysis A, v. 297, n. 1, p. 60-72, 2006.

[7] J. Comas et al., Bio-ethanol steam reforming on Ni/Al2O3 catalyst. Chemical Engineering Journal, v. 98, n. 1-2, p. 61-68, 2004.

ACTIVITY REPORT 2010 – LNLS | 75

13

PHASE FORMATION IN RDE GROWN IRON SILICIDE NANODOTS

J. C. González*, M. V. B. Moreira, D. R. Miquita, M. I. N. da Silva, R. Magalhães-Paniago, A. G. de Oliveira

Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais - UFMG, CP 702, CEP 30123-970, Belo Horizonte, MG, Brazil

The epitaxial growth by reactive deposition of ε-FeSi and β-FeSi2 nanodots on Si (111) is studied as a function of Fe coverage. The nanodots density, size, aspect ratio, and strain were analyzed by atomic force microscopy and X-ray diffraction. Almost single phase ε-FeSi and β-FeSi2 were formed at low and high iron coverage, respectively. A ε-FeSi to β-FeSi 2 change in phase formation is observed at Fe coverage of 5.5 nm, which is coincident with the coalescence of the nanodots, the relaxation of the strain in both phases and a discontinuous increase of the grain size of the β-FeSi2 phase. A direct comparison of the diffraction and microscopy data shows that nanodots of different phases also exhibit different shapes, being the ε-FeSi (β-FeSi2) nanodots smaller (larger) and with a low (high) aspect ratio.

Facility: XRD1 Publication: Physical Review B, 81, 113403-1-4 (2010) Funding: CNPq, FAPEMIG, CAPES Corresponding author: J. C. González – gonzalez@fisica.ufmg.br

PHASE FORMATION IN RDE GROWN IRON SILICIDE NANODOTS

In recent years, there has been a trend in materials

chamber and heated at 400 °C for 30 minutes for

science and engineering towards the development

degassing. The temperature of the substrates was

of new and environmental-friendly materials.

then raised to 700 °C and an iron fi lm (99.999% of

Iron silicides are composed of non-toxic and

purity) with a nominal thickness θFe was deposited

abundant elements. In particular, semiconducting

at a rate of 0.06 nm/s, as measured by a quartz

β-FeSi2 presents a number of advantages for

crystal oscillator. After deposition, the samples

industrial applications due to its excellent physical

were annealed at 700 °C for 2 hours in UHV. Twelve

properties such as a band gap of ~0.85 eV , large

different samples where grown with iron coverages

optical absorption coefficients , and high Seebeck

between θFe = 2.0 nm and θFe = 12.0 nm. The

coefficient 2. This material is a promising material for

morphological evolution of the samples as a function

Si-based optoelectronic devices and solar cells , and

of θFe, was examined by AFM using TappingModeTM

can be epitaxially grown on Si substrates by reactive

in a Veeco MultiMode scanning probe microscope

deposition epitaxy (RDE) and solid phase epitaxy

with a NanoScope IV controller. The structural

(SPE) . However, thin fi lms grown using these

properties of the samples were also investigated by

techniques have many defects in the form of misfit

XRD. The diff raction experiments were carried out

[1]

2

4

5

6,7

dislocations and Si vacancies and exhibit an indirect

at beamline XRD1 of the Brazilian Synchrotron

band gap1, which are important limiting factors for

Light Laboratory (LNLS, Campinas, SP) at 10.0 keV

high performance optoelectronic devices and solar

X-ray photon energy (λ = 1.24 Å).

8

cells. Nevertheless, the lattice mismatch between

Figure 1 shows the morphology of three

Si and iron silicides can be used as a driving force

samples with a) θFe = 2.4 nm, b) θFe = 3.8 nm, and

to produce coherent nanostructures with no misfit

c) θFe = 5.5 nm. At low θFe hemispherical iron silicide

dislocations, lattice mismatch strain and direct

nanodots are formed, increasing in size and density

band gap. Therefore, iron silicide self-assembled

as θFe increases. At θFe ~ 5.5 nm the iron silicide

nanostructures not only solve part of the issues

nanodots completely cover the surface of the sample

presented by thin fi lms, but also have great potential

and their areal density reaches a maximum value of

for new and improved optoelectronic devices.

approximately 1011 cm-2 before nanodots coalescence

A variety of fabrication methods

9-14

has been

applied to synthesize iron silicides thin fi lms. In

begins to set in. At larger θFe the density of nanodots decreases and large iron silicide islands are created.

the present study, we show that high quality self-

A closer look at the AFM images of Figure 1a,b

assembled iron silicide nanodots can be fabricated by

and 1c shows two families of nanodots present in the

reactive deposition epitaxy on Si(111) substrates. We

samples. The first family is formed by small and low

should additionally note that this approach provides

volume to base area ratio (aspect ratio) nanodots,

reliable control the areal density, size and crystalline

while the second family consist of larger nanodots

phase of the nanodots, avoiding metastable phases

with high aspect ratio. This behavior can be observed

commonly observed in iron silicide nanostructures

in Figure 1d, 1e and 1f where a statistical analysis of

and thin fi lms15,16. In particular, a change in phase

nanodots volume versus base area is presented. At

formation from ε-FeSi to β-FeSi 2 nanodots as a

low θFe most of the nanodots are small and present

function of the deposited amount of iron (θFe) was

a low aspect ratio. However, as θFe increases the

examined by atomic force microscopy (AFM) and

population of larger and high aspect ratio nanodots

X-ray diff raction (XRD).

also increases. At θFe = 5.5 nm almost all nanodots

The samples were prepared in an ultra-high

have a high aspect ratio. The mean aspect ratio of

vacuum (UHV) evaporation system at a base

the low and high aspect ratio families of nanodots

pressure of about 1 × 10-9 Torr by RDE. Prior to the

is 0.7 nm and 3.5 nm, respectively. Therefore, for

growth process, the Si(111) substrates were hydrogen

a more intuitive interpretation of the aspect ratio

passivated to assure an atomically flat and clean

plots, and without introducing any significant

silicon surface terminated by hydrogen atoms. The

distortion, an aspect ratio threshold of 1 nm was

substrates were then introduced into the UHV

chosen to differentiate the two families of nanodots.

14

ACTIVITY REPORT 2010 – LNLS | 77

SCIENCE HIGHLIGHTS

Figure 1.

(Color online). AFM images of samples with: a) θFe = 2.4 nm; b) 3.8 nm; and c) 5.5 nm. Statistical analysis of the AFM images of the samples with: d) θFe = 2.4 nm; e) 3.8 nm; and f) 5.5 nm. The nanodots with aspect ratio lower than 1 nm were denoted by open blue squares, while the nanodots with aspect ratio larger than 1 nm have been denoted by open red circles.

78 | ACTIVITY REPORT 2010 – LNLS

PHASE FORMATION IN RDE GROWN IRON SILICIDE NANODOTS

The mean volume as well as the standard deviation of the volume of the nanodots of each phase is also shown in Figure 1d,e,f.

In order to understand the shape transition presented in Figure 1 the structural properties of selected samples were studied by XRD measurements in reflection geometry. Figure 2 shows two typical difractograms of low and high iron coverage samples. Both samples are polycrystalline with a mixture of ε-FeSi and β-FeSi2 phases. However, a strong texture was observed in all samples with the ε-FeSi(111)/Si(111), β-FeSi2(220)/Si(111) and β-FeSi2 (202)/Si(111) heteroepitaxial relationships. Due to the small difference between the b and c lattice constant of the orthorhombic β-FeSi2 and to the shift and broadening of the Bragg peaks caused by the strain

Figure 2.

(Color online). Typical XRD difractograms of a) low and b) high iron coverage samples. The measurements were performed in reflection geometry, and a small beam divergence of 0.0050 was used to avoid an overlap of the substrate signal. Therefore, all

and small size of the nanodots, it is very difficult to

linewidths of peaks stemming from the nanodots can be inferred

distinguish between the two heteroepitaxial β-FeSi 2/

directly from the diffraction data, without the need of instrumental

Si relationships in our difractograms. Therefore we

deconvolution.

use a β-FeSi2 (220)/(202) notation in the following to indicate that fact. In addition to the ε-FeSi and β-FeSi2 phases no other iron silicide phases were observed. This result contrasts with common observations of the formation of metastable iron silicide phases prior to β-Fesi215,16.

The XRD data were analyzed to infer the concentration of each phase in the samples, as well as the average grain size and strain of the crystallites along the growth direction. The concentration of each phase was calculated following the stardard procedure described in17. It was considered that only the ε-FeSi and β-FeSi 2 phases were present in the samples. The effects of absorption, texture, multiplicity and Lorentz-polarization factor in the intensity of the Bragg peaks were also taken into account. The strain in the dots was estimated by comparing the lattice distance of the ε-FeSi (111) and β-FeSi2 (220)/(202) reflections with the respective bulk values. The Scherrer equation17 was used to infer the evolution of the grain size along the growth direction as a function of θFe. Figure 3 shows the results of the analysis of the XRD data. The relative concentration of the iron silicide phases are shown in Figure 3a as a function of θFe. The most striking feature of this graph is a clear phase transition from the ε-FeSi to β-FeSi 2 at approximately θFe = 5.5 nm, coinciding

Figure 3.

(Color online). Analysis of the XRD data as a function of θFe: a) relative concentration of the ε-FeSi and β-FeSi2 phases, b) strain along the growth direction, and c) grain size along the growth direction.

ACTIVITY REPORT 2010 – LNLS | 79

SCIENCE HIGHLIGHTS

with the coalescence process observed in the AFM

decrease of the island energy due to elastic relaxation

images. A clear relaxation of the strain can also

determines not only a thermal energy barrier for the

be observed at θFe = 5.5 nm followed by a sharp

island nucleation but also the transition to lower

rise of the β-FeSi 2 grain size. Th is coverage is also

energy shapes. However, in our case of non-wetting

the optimum value to obtain samples with a large

nanodots the increase in surface energy due to the

density of almost single phase (95% of the material

nanodot-substrate interface has to be considered.

in the β phase) and small (mean size around 30 nm) β-FeSi 2 nanodots. The grain size analysis also show that both phases present different mean crystallites sizes, being the ε-FeSi smaller than the β-FeSi 2 crystallites. These results show that the two families of nanodots observed in the AFM images not only correspond to nanodots of different shape and sizes, but also of different crystallographic phases and chemical composition. Based on the evolution of the ε-FeSi and β-FeSi 2 phase concentrations and grain sizes as θFe increases, it

Considering a simple model of pyramidal shaped islands the energy excess necessary to create a faceted island is22-24: 1

1

3 ∆E = 2[ cot(α )]3 V 3 [γ l cos(α ) − γ s ] – 2 σ 2 (1 −ν 2 ) V tan(α ) −6 xx πE

(1)

Were V is the volume of the island, α is the angle between the island facets and the substrate surface, E is the Young’s modulus of the island, ν is

is possible to identify the family of smaller and low

the Poisson’s ratio of the island, σxx is in-plane stress

aspect ratio nanodots as being of the ε-FeSi phase

of the island due to the lattice mismatch with the

and the family of larger and high aspect ratio ones

substrate, γl is the elastic energy per unit area of the

as being of the β-FeSi 2 phase.

island facet, and s is the interface energy per unit area

The AFM and XRD results indicate that for

of the island interface with the substrate.

small nanodots the relaxation of the strain in the

The first term of the right side of the above

nanodots should be the driving force for the phase

equation refers to the increase in surface and

transition. It is interesting to note that the phase

interface energy due to the creation of the island and

transition sequence ε-FeSi α-FeSi 2  β-FeSi 2,

the second term refers to the elastic energy relaxation

sometimes intercalated by several metaestabble phases, frequently observed as a function of the increasing iron coverage for high annealing temperatures

(>500-700 °C)

in

iron

silicide

thin fi lms18,19 is not present in our samples. The availability of Si adatoms from the substrate to form Si-rich iron silicide phases, usually invoked to explain phase transitions in iron silicide thin fi lms19, is also not an issue here since the growth and annealing temperatures are high enough to sustain a large Si and Fe diff usion and the β-FeSi 2 (Si-rich phase) was observed to be formed mostly in the thicker samples. Our phase transition follows more closely the iron-silicon bulk phase diagram 20 with a direct ε-FeSi β-FeSi 2 transition.

in the island. As the volume of the island increases the excess energy increases reaching a maximum that corresponds to the energy barrier for nucleation of the island at a critical volume Vc. For V > Vc the excess energy decreases due to the elastic relaxation.

As θFe increases the elastic relaxation of the high aspect ratio and lower lattice mismatch (δ = 1.4% along the b axis of the orthorhombic unit cell and δ = 1.95% along the c axis) β-FeSi 2 nanodots must be more effective in lowering the nanodots excess energy that in the case of the low aspect ratio and higher lattice mismatch (δ = 4.3%) ε-FeSi nanodots.

At some particular volume, larger than Vc for each phase, the excess energy of the ε-FeSi island will

From the thermodynamic point of view the

be equal to the excess energy of the β-FeSi island.

ε-FeSi β-FeSi2 transition can be qualitatively

At this cross point there is a discontinuity in the

understood in a similar way to the shape transitions

chemical potential22 promoting from this point up

observed in self-assembled strained islands21-24,

the growth of the β-FeSi 2 nanodots at the expense of

where a competition between the increase in surface

the ε-FeSi nanodots. The volume VT of the islands at

energy due to the creation of a wetting layer and the

this transition point is:

80 | ACTIVITY REPORT 2010 – LNLS

PHASE FORMATION IN RDE GROWN IRON SILICIDE NANODOTS

of approximately the same volume reinforces this

1

3 [ cot(α 2 )]3 [γ l 2 cos(α 2 ) − γ s 2 ] – 2 1 )]3 [γ

3 3 −[ cot(α1 l1 cos(α1 ) − γ s1 ] )2 VT = ( 2 2 2 σ (1 −ν 2 ) 3 xx 2 tan(α 2 ) – π E2 −3

2 2 σ xx 1 (1 − ν 1 )

π E1

conclusion.

(2)

tan(α1 )

Were the sub-index 1 and 2 correspond to the ε-FeSi and β-FeSi2 islands, respectively. The transition volume corresponds to the largest possible volume of the ε-FeSi islands at the equivalent iron coverage of aproximatelly 5.5 nm. A direct look to the AFM data presented in Figure 1 reveals that the maximum volume of the ε-FeSi islands in our

In summary, it is shown that almost single phase ε-FeSi and β-FeSi 2 iron silicide nanodots can be formed by Reactive Deposition Epitaxy on Si(111).

The density, size and shape of the nanodots can be controlled by the amount of deposited iron. However, low iron coverage leads to ε-FeSi reach samples with small isands, while high iron coverage leads to β-FeSi2 reach samples with large ones. A direct comparison of the diff raction and microscopy data shows that nanodots of each phase exhibit different shapes, being the ε-FeSi (β-FeSi2) nanodots of a low (high) aspect ratio. The ε-FeSi to β-FeSi 2 transition is observed at iron coverage of 5.5 nm and is coincident

samples is approximately 2000 nm3. Unfortunately,

with the coalescence of the nanodots, the relaxation

a further comparison of the model with the

of the strain in both phases and a steep increase of

experimental results needs values for γl, γs, E,

the grain size of the β-FeSi2 phase. This coverage was

and ν, for both phases, that are not well known.

This process can be further accelerated by the introduction of dislocations in the β-FeSi2 nanodots

found to be the optimum to obtain almost single phase samples with a large density of small β-FeSi 2 nanodots. A thermodynamic qualitative model to

that will reduce, even more, the excess energy of the

explain the phase and shape transitions was also

nanodots. Regardless of other kinetics aspects, in

discussed. Several kinetics issues and facts that can

this coarsening, large β-FeSi 2 nanodot grow while

play an important role in the transitions were also

ε-FeSi nanodots shrink and disappear. Furthermore,

pointed out.

since the phase transition is largely accelerated at the onset of nanodots coalescence and of large elastic relaxation kinetics aspects and interaction

Acknowlegements

We would like to thank the Brazilian National

between the nanodots could also play also and

Light Synchrotron Laboratory, CNPq, CAPES and

important role in the transitions. The observation

FAPEMIG for the financial and technical support of

of a variety of different morphologies for nanodots

this work.

References

[1] A. Vantomme, M. A. Nicolet, G. Bai, and D. Fraser, Appl. Phys. Lett. 62, 243 (1993).

[2] K. Lefki and P. Muret, J. Appl. Phys. 74, 1138 (1993).

[3] M. Takeda, M. Kuramitsu, and M. Yoshio, Thin Solid Films 461, 179 (2004).

[4] D. Leong, M. Harry, K. J. Reeson, and K. P. Homewood, Nature 387, 686 (1997).

[5] Z. Liu, S. Wang, N. Otogawa, Y. Suzuki, M. Osamura, Y. Fukuzawa, T. Ootsuka, Y. Nakayama, H. Tanoue, and Y. Makita, Solar Energy Mater. Solar Cells 90, 276 (2006).

[6] A. Rizzi, B. N. E. Rösen, D. Freundt, C. Dieker, H. Lüth, and D. Gerthsen, Phys. Rev. B 51, 17780 (1995).

[7] J. E. Mahan, V. L. Thanh, J. Chevrier, I. Berberzier, J. Derrien, and R. G. Long, J. Appl. Phys. 74, 1747 (1993).

[8] T. Miki, Y. Matsui, K. Matsubara, and K. Kishimoto, J. Appl. Phys. 75, 1693 (1994).

[9] Q. Zhang, M. Tanaka, M. Takeguchi, M. Han, and K. Furuya, Jpn. J. Appl. Phys., Part 1 42, 4667 (2003).

[10]

Y. Ozawa, T. Ohtsuka, C. Li, T. Suemasu, and F. Hasegawa, J. Appl. Phys. 95, 5183 (2004).

ACTIVITY REPORT 2010 – LNLS | 81

SCIENCE HIGHLIGHTS

[11] A. Wohllebe, B. Hollander, S. Mesters, C. Dieker, G. Crecelius, W. Michelsen, and S. Mantl, Thin Solid Films 287, 93 (1996).

[12]

T. Suemasu, Y. Negishi, K. Takakura, F. Hasegawa, and T. Chikyow, Appl. Phys. Lett. 79, 1804 (2001).

[13] D. R. Miquita, R. Paniago, W. N. Rodrigues, M. V. B. Moreira, H. D. Pfannes, A. G. de Oliveira, Thin Solid Films 493, 30 (2005).

[14] D. R. Miquita, J. C. González, M. I. N. da Silva, W. N. Rodrigues, M. V. B. Moreira, R. Paniago, R. RibeiroAndrade, R. Magalhães-Paniago, H. D. Pfannes, A. G. de Oliveira, J. Vac. Sci. Technol. A 26, 1138 (2008).

[15] J. Won, A. Kovács, M. Naito, M. Ishimaru, Y. Hirotsu, J. Appl. Phys. 102, 103512 (2007), and references cited therein.

[16] I. Dézsi, Cs. Fetzer, I. Szücs, J. Dekoster, A. Vantomme, M. Caymax, Surface Science 599, 122 (2005), and references therein.

[17] Thin Film Analysis by X-Ray Scattering, Mario Birkholz, Paul F. Fewster, Chistoph Genzel. Wiley-VCH Verlag GmbH & Co. KGaA 2006.

[18]

H. Nakano, K. Maetani, K. Hattori, H. Daimon, Surface Science 601, 5088 (2007).

[19]

K. Kataoka, K. Hattori, Y. Miyatake, H. Daimon, Phys. Rev. B 74, 155406 (2006), and references therein.

[20]

M. Hansen, Constitution of Binary Alloys (McGraw–Hill, New. York, 1958).

[21]

I. Daruka, J. Tersoff, and A. L. Barabasi, Phys. Rev. Lett. 82, 2753 (1999), and references therein.

[22]

F. M. Ross, J. Tersoff, R. M. Tromp, Phys. Rev. Lett. 80, 984 (1998).

[23]

J. Tersoff, and F.K. LeGoues, Phys. Rev. Lett. 72, 3570 (1994).

[24]

K. Brunner, Rep. Prog. Phys. 65, 27 (2002).

82 | ACTIVITY REPORT 2010 – LNLS

CITRUS GREENING DISEASE INVESTIGATION USING MICRO SYNCHROTRON RADIATION X-RAY FLUORESCENCE IN ASSOCIATION WITH SOFT INDEPENDENT MODELLING OF CLASS ANALOGY (SIMCA) Fabíola Manhas Verbi Pereira*, Débora Marcondes Bastos Pereira Milori Embrapa Instrumentação Agropecuária, CP 741, CEP 13561-206, São Carlos, SP, Brazil

This study describes the use of micro synchrotron radiation X-ray �luorescence (µSR-XRF) to investigate citrus greening disease in sweet orange (Citrus sinensis) plants. An experiment using healthy plants as control and plants of the same variety infected with Candidatus Liberibacter asiaticus (CLas) was performed to verify variations of the mineral composition of citrus leaves. A µSR-XRF system using the D09B X-ray �luorescence beam line at the Brazilian Synchrotron Light Source (LNLS, Campinas, São Paulo State) was employed for this purpose. The data were analyzed using a chemometric tool called soft independent modelling of class analogy (SIMCA). The promising results from SIMCA models reinforce the evidence that plants infected by citrus greening (both asymptomatic and symptomatic) undergo alterations in their micro- and macronutrient compositions.

Facility: XRF Publication: Journal of Analytical Atomic Spectrometry, 25: 351-355 (2010) Funding: CNPq, FAPESP Corresponding author: Fabíola Manhas Verbi Pereira – fmverbi@uol.com.br

14

SCIENCE HIGHLIGHTS

The detection of citrus greening or huanglongbing

The measurements were performed with the

(HLB) in plants prior to the onset of visual

D09B X-ray fluorescence beam line at the Brazilian

symptoms is a challenging task. Expeditious and

Synchrotron Light Source (LNLS, Campinas,

reliable methods are urgently needed because citrus

São Paulo State). The setup configuration used a

greening contamination occurs very rapidly1,2. This

monochromatic beam with a 200 x 200 µm cross

spread of disease leads to the progressive reduction

section. The multilayer monochromator consisted of

of orchards, resulting in economic damage to citrus

75 d-periods of W/C layers. The maximum photon

producers and related industries . Currently,

energy was 12 keV, and the tests were executed in an

the development of methods for early diagnosis

air atmosphere. The active total area of the detector

would result in important tools for citrus greening

was 30 mm2. The 4 mm circular collimator was

management and control.

used in the detector to improve the signal-to-noise

3,4

Nowadays, visual inspection is one of the most

ratio of the XRF spectra and to avoid decreasing of

applied methods to diagnose citrus greening;

resolution at higher count rates. The distances from

however, visual inspection is highly influenced by

the sample (citrus leaf) to the source and to the

subjective interpretation, and diagnostic errors can

detector were 120 and 20 mm, respectively. An Si(Li)

be higher than 30% . Additionally, plants may be

detector with an 8 µm Be window was used; this

infected for up to several months (between 6 and

detector has an energy resolution of 165 eV for the

36 months) before visual symptoms are detected .

Mn Kα line. The samples were positioned at an angle

Another common method for diagnosis is to use

of 45o with respect to both the incident beam and the

polymerase chain reaction (PCR) to test for the

detector. The measurement positions on the leaves

bacterial deoxyribonucleic acid (DNA).7 The main

were marked with computer-controlled X, Y, Z, θz

5

6

drawback to PCR assays is the fact that these

stages and an optical microscope. The scanning of

methods are time consuming and expensive8.

the leaves was divided into three regions: midrib and

The purpose of this study was to investigate

two lateral sides, where nine spectra were obtained

the mineral composition of citrus leaves infected

per leaf. The vertical and horizontal distances

by citrus greening using spectra obtained by

between points were 1 mm. The irradiation time per

micro synchrotron radiation X-ray fluorescence

point was 100 s and the dead time was approximately

(µSR-XRF); due to the ability of this technique to

2%. The diagram of µSR-XRF configuration setup

scan samples in different positions with adequate

was shown in Figure 1.

sensitivity, repeatability and reproducibility, without pre-treatment of the samples.

The evaluation of the mineral composition using µSR-XRF and soft independent modelling of class analogy (SIMCA) was suitable for understanding the effects of the citrus greening disease and proposing

Figure 1.

Diagram of micro synchrotron radiation X-ray fluorescence (µSR-XRF) configuration setup for measurements of citrus leaves.

84 | ACTIVITY REPORT 2010 – LNLS

Figure 2.

Values of correct predictions obtained from soft independent modelling of class analogy (SIMCA) models.

CITRUS GREENING DISEASE INVESTIGATION USING MICRO SYNCHROTRON RADIATION X-RAY FLUORESCENCE IN ASSOCIATION WITH SOFT INDEPENDENT MODELLING OF CLASS ANALOGY (SIMCA)

the classification models, as shown in Figure 2. The

The monitoring of the mineral compositions

elements K, Ca, Fe, Cu and Zn and the region of coherent

of the plants was qualitative but could generate

and incoherent scatterings were very important for the

responses about the infected samples, mainly those

differentiation of these three conditions.

in the asymptomatic stage.

References

[1] Ploetz, R. C. Diseases of tropical perennial crops: challenging problems in diverse environments. Plant Disease, v. 91, n. 6, p. 644-663, 2007.

[2] Nava, D. E. et al. The effects of host, geographic origin, and gender on the thermal requirements of Diaphorina citri (Hemiptera: Psyllidae). Environmental Entomology, v. 39, n. 2, p. 678-684, 2010.

[3] Vojnov A. A. et al. Bacteria causing important diseases of citrus utilise distinct modes of pathogenesis to attack a common host. Applied Microbiology and Biotechnology, v. 87, n. 2, p. 467-477, 2010.

[4] Gottwald, T. R. Current Epidemiological Understanding of Citrus Huanglongbing. Annual Review of Phytopathology, v. 48, p. 119-139, 2010.

[5] Belasque Junior, J., et al. Base científica para a erradicação de plantas sintomáticas e assintomáticas de Huanglongbing (HLB, Greening) visando o controle efetivo da doença. Tropical Plant Pathology, v. 34, n. 3, p. 137-145, 2009.

[6] Bové, J. M. Huanglongbing: a destructive, newly-emerging, century-old disease of citrus. Journal of Plant Pathology, v. 88, n. 1, p. 7-37, 2006.

[7] Schmittgen, T. D. Quantitative gene expression by real-time PCR: a complete protocol. In: Dorak MT, ed. Real-time PCR (BIOS Advanced Methods). New York, USA: Taylor and Francis, p. 127-137, 2006.

[8] Li, W. et al. Evaluation of DNA amplification methods for improved detection of “Candidatus Liberibacter Species” associated with Citrus Huanglongbing. Plant Disease, v. 91, n. 1, p. 51-58, 2007.t

ACTIVITY REPORT 2010 – LNLS | 85

FACILITY REPORT 88 Accelerator Development and Operation 95 Industrial Research Activities

100 Beamlines

104 Nanoscience and Nanotechnology 109 Sirius Project 114 Main Events

118 Facts and Figures

1

ACCELERATOR DEVELOPMENT AND OPERATION

The main improvement made to the storage ring in 2010 was the installation of new solid state RF ampli�iers. These ampli�iers, which replaced the original klystron-based system that was in operation since 1996, represent the culmination of ten years of developments in solid state ampli�iers at the LNLS, a project carried out in close collaboration with Synchrotron Soleil. After Soleil, the LNLS synchrotron light source is the second facility to adopt this type of technology to drive the storage ring RF cavities. Another important achievement was the completion of the PGM beamline: a milestone in terms of the LNLS team’s ability to work under the pressure of a tight schedule. The beamline is under commissioning since October 2010 and is showing very good performance. From the operational standpoint, 2010 was an excellent year in terms of reliability and mean time between failures of the light source.

ACCELERATOR DEVELOPMENT AND OPERATION

Introduction

Upgrades and improvements have been part of

The replacement of two thirds of the BPMs in

the LNLS synchrotron light source’s operational

2009 led to the replacement of an equivalent portion

scenario since it started operating as an open

of the vacuum chamber. This extensive vacuum

facility in 1997. These upgrades have considerably improved the range of applicability of the source, either by extending the range of photon energies made available for users or by increasing the quality of the photon beam delivered to the beamlines. The most comprehensive upgrade of the storage ring was undoubtedly the installation of the booster synchrotron in 2002 and the overall replacement of the storage ring beam position monitors (BPM) in the machine shutdowns in 2008 and 2009. The installation of insertion devices required modifying the machine’s magnetic optics to keep beam lifetime at the same level and simplify operating procedures.

Several other small scale improvements have been implemented along these 13 years, the last one being the replacement of the entire klystron-based RF amplification chain by a set of new solid-state amplifiers built in the lab during the last three years.

intervention, together with the installation of the superconducting wiggler (SCW) and its 14 mm wide vertical vacuum chamber, strongly impacted the operation of the machine in the first two months of 2010. Injection, in particular the accumulation and ramping processes, was specially affected, leading to lower initial currents in the first weeks of operation.

In mid-February 2010, the SCW was removed from the storage ring for a complete check-up to identify and solve the problem of Helium overconsumption detected after its installation. Several hours of machine studies led to the improvement of injection conditions. However, overall, the average injection time in 2010 was 5 minutes longer than in 2009.

As for the performance of the light source, the main achievement was the increase in the machine’s reliability compared to 2009. In addition, the

Another major achievement was the construction

number of beam losses during user shifts plummeted

of the PGM beamline, a challenging undertaking

compared to previous years. Preventive maintenance

that involved several groups of the Accelerator and

procedures have been focused on the main causes

Engineering Division and highlighted the importance

of beam losses in the previous year. As a result,

of tight resource management to carry out complex

roughly half of the events in 2010 involved sags and

projects. The same management procedures have

faults in the electrical power supply to the campus.

been applied successfully to other activities and have

Studies were conducted to investigate the possibility

become a standard procedure at the LNLS. During the long shutdown of 2010, an unpredicted vacuum intervention had to be scheduled to replace a cooled mask and a set of photon shutters. This event forced the venting of one third of the storage ring vacuum chamber.

The installation of a ceramic vacuum chamber for injection tests using a pulsed sextupole led to the venting of a long straight section. The long recovery time required for these activities affected the beam lifetime at the beginning of the users run in 2011.

Finally, it should be noted that the preparations for the installation of the superconducting wiggler beamline and its initial testing are on schedule.

In recent years, considerable efforts have been devoted to improve the performance and reliability of the light source, with specific focus on orbit stability.

In 2010, the main activities related to this important

of reducing the vertical beam size, which resulted in the installation of two new skew quadrupoles in the storage ring magnetic lattice. The installation of the insertion devices introduced an extra coupling between the transverse emittances, leading to an increase of the vertical emittance. To compensate for this effect, new magnets were installed which reduced the coupling from 1.5 to 0.3%. The reduced vertical beam size had an extremely positive effect on the photon flux in the beamlines, particularly for the experimental setups using very narrow slits.

Conversely, however, this reduced beam size affected the beam lifetime, slightly reducing the average beam lifetime and beam current in the user shifts compared to the situation in 2009.

As in 2009, the activities of the engineering and accelerator groups were organized considering the

issue were the installation of fans to homogenize

studies and developments for SIRIUS. The current

the temperature inside the storage ring tunnel and

light source may benefit from the new developments,

to provide it some thermal insulation by sealing the

since the new source has much tighter specifications

open vaults with thick movable plastic strips.

than those of the current machine.

ACTIVITY REPORT 2010 – LNLS | 89

FACILITY REPORT

On average, thirteen beamlines were available

environment, a standard adopted at an increasing

for the user community during 2010. The control

number of scientific facilities around the world. The

and data acquisition systems of the XAFS1 beamline

construction of the PGM beamline was completed

were thoroughly rebuilt in the second half of

and its commissioning started in September. The

the year, and will serve as a model for an overall

beamline is now fully operational and is yielding

upgrade of the existing beamlines. The system was

extremely good results so far. The preparations for

remodelled to comply with the EPICS soft ware

the installation of the SCW beamline are also on schedule and the assembly of the complete line will begin in February 2011.

Accelerator Operations

The operation of the synchrotron light source

for users followed the same pattern as in previous years, with operations for users 24 hours a day from Monday through Saturday morning. The 2010 user run began in mid-January and lasted until the end of October, followed by a 7-week shutdown for upgrades and new installations in the storage ring.

The last two weeks of the user run were scheduled for single bunch operation, dedicated to time-resolved Figure 1.

Total beam time delivered to users since 1997.

experiments in the UV and soft X-ray beamlines. A total of 4,203 hours of beam time were delivered to users (Figure 1) and the reliability of the light source increased to 97.8% (Figure 2). Reliability accounts for the fraction of the scheduled beam time that was effectively implemented on time.

As a result of the slow recovery after the major vacuum venting allied to the operation with shorter vertical beam size, the average beam lifetime dropped to about 20 hours (Figure 3). This also had a negative impact on the integrated beam charge, reducing it by 10% compared to the previous two years (Figure 4), and on the average beam current in user shifts (Figure 5). The mean time between

Figure 2.

Machine reliability in user shifts since 1997.

failures reached 97 hours, the best result in recent years, and the mean recovery time after failure was 1.1 hours. Failures in the electricity supply were the cause of 60% of all beam losses during user shifts.

In 2010, maintenance stoppages were scheduled for Fridays (once a month) with machine studies on the subsequent Mondays. This allowed for more comprehensive maintenance procedures and reduced the risk of affecting subsequent user shifts by recovery misfire after maintenance.

Problems involving accumulation efficiency and ramping increased the average injection time by approximately five minutes compared to 2009 (Figure 6). Accumulation was slower due to the lower booster to storage ring injection efficiency

Figure 3.

Average beam lifetime in user shifts since 1997.

90 | ACTIVITY REPORT 2010 – LNLS

following the replacement of the BPMs of the

ACCELERATOR DEVELOPMENT AND OPERATION

machine’s injection section. The partial loss of

federal funding agency FINEP approved a project to

accumulated beam during the ramping process was

design and build two solid state amplifiers capable of

the main cause of delays whenever the machine was

delivering the 100 kW of power at 476 MHz required

left without stored beam even for short periods of

to drive the current storage ring RF system. In 2008,

time. The problem, which involves the low level RF system, is currently under investigation. Finally, the longer standardization procedure for the magnets in the low vertical betatron operation mode increased the machine’s recovery time after failures and after interventions that required turning off the main magnet power supplies also played a role in increasing the mean injection time. The low vertical betatron mode has been the standard operating mode since 2009.

Solid State RF Ampli�iers

LNLS started working with solid state RF

amplifiers in 1999 as the chosen technology for the RF booster system. At that time, the French laboratory LURE was developing an innovative high power

Figure 4.

Total beam charge per year delivered to users since 1997.

Figure 5.

Average beam current in user shifts since 1997.

Figure 6.

Distribution of injection times in 2010 compared to 2009. Most of

solid state RF amplifier for the new synchrotron light source SOLEIL. In close collaboration with LURE’s RF group, LNLS built a 900 W solid state amplifier operating at 476 MHz to drive the RF booster cavity.

The system has been in successful operation since it started working in 2001.

The original LNLS storage ring RF system was based on commercial UHF klystron tubes. It is a reliable and established technology adopted at almost all synchrotron facilities worldwide.

However, electron tubes are becoming increasingly expensive to purchase and operate. For the operating conditions of the LNLS storage ring, the system’s electrical efficiency is very poor. In addition, it is very expensive to keep spare tubes for the two klystron sets. Therefore, solid state amplifiers are an effective alternative to electron tubes. They have the distinct advantage of being modular. The amplifier’s high output power is achieved by the optimal combination of the output signals of an ensemble of individual lowpower amplifier modules. These modules are cheap and can be repaired in-house, and the amplifier can operate even if some of the modules fail. In terms of electrical efficiency, the solid state amplifier is at least twice as efficient as the klystron system for the LNLS storage ring operating conditions.

Reliability and reduction of electricity costs, allied to its interest in keeping pace with the development of solid state technology, motivated LNLS to replace the klystron system. In 2007, the

the injections where performed in less than 20 minutes.

ACTIVITY REPORT 2010 – LNLS | 91

FACILITY REPORT

in close collaboration with the SOLEIL RF group, the

limitation emerged. In order to operate at a very low

amplifiers were designed and the main components

He consumption setting of the SCW without the risk

were prototyped, specified and ordered. The heart of

of quenching, the maximum field would have to be

the system is the MOSFET-based amplifier module,

limited to 3.9 T. A higher field is possible with an

with integrated circulator and individual power

open relief valve, but at the cost of a higher Helium

supply, each with a power delivery capacity of more

consumption.

than 330 W at 476 MHz. More than four hundred of these amplifier modules were specified and ordered, as well as cables, combiners, dividers, and power

Beam Stability

Since 2004, a program has been under way to

supplies, all of them checked and characterized at

improve the stability of the electron beam orbit

the RF laboratory before assembly.

and, hence, that of the photon beam delivered to the

The two amplifiers, each built by combining 162

experimental stations at the beam lines. The program

amplifier modules, were fully assembled in the test

involves several activities to improve the beam

area in early 2010. The nominal maximum output

position measurement and orbit correction systems,

power of each amplifier is 50 kW. The amplifiers were

modify the vacuum chamber to reduce the beamâ&#x20AC;&#x2122;s

commissioned and passed a series of short and long-

thermo mechanical effects, and improve the control

term tests. A team from SOLEIL visited the lab for

of ambient temperature. After lengthy and careful

two weeks and helped with the characterization of

sets of measurements, all the machine beam position

the first amplifier. After extensive tests, the amplifiers

monitors were replaced with a new model which is

were approved for installation in the storage ring.

less sensitive to thermal variations, mechanically

The installation took place in November 2010, with

decoupled from the vacuum chamber and water

the solid state amplifiers replacing the old klystron system. The new amplifiers were commissioned in the storage ring in December.

Superconducting Wiggler for Materials Sciences

The superconducting wiggler dedicated to

materials science research was reinstalled in the

cooled. Moreover, a set of cooling masks was added to the vacuum chamber to prevent synchrotron light from reaching non cooled parts of the chamber. These modifications were highly effective in reducing the sensitivity of the orbit correction system to thermal drifts and to mechanical deformations caused by the heating of parts of the vacuum chamber due to the incidence of synchrotron light.

storage ring in November 2010. After its initial

The current activities now concentrate on

installation in 2009, the wiggler showed a higher

achieving better temperature control of the storage

than expected consumption of liquid helium.

ring tunnel and of the experimental hall, in order

Constant monitoring and analysis of the device

to reduce the effect of ambient temperature changes

was necessary to discover the possible source of

on the electron beam orbit and beam lines. The

the problem. Although the problem would not

focus now is on the daily and seasonal effects of

have jeopardized the wigglerâ&#x20AC;&#x2122;s operation, it would

temperature variations that are still measurable on

have increased the operating cost significantly by

the electron beam orbit. In 2010, a set of fans were

requiring several helium refi lling sessions during

installed in the storage ring tunnel to provide better

the year. To facilitate the diagnosis of the problem

temperature homogenization. A curtain of thick

and enable whatever intervention that might be

plastic strips was also installed to provide a closed

required to solve it, the device was removed from

environment for the storage ring tunnel and increase

the storage ring in February 2010. Several tests and

its thermal stability. Aiming at the same goal, the

measurements were performed under the guidance

control system of the air conditioning of the storage

of specialists from the Budker Institute during the

ring building is being upgraded for higher control

first half of the year. In the second half of 2010, a

flexibility. This will allow for performance tests that

team from Budker came to the LNLS to implement

may result in hardware upgrades, possibly leading

modifications in the internal cooling connections of

to greater control of the temperature of the entire

the wiggler. These modifications effectively corrected

experimental hall.

the high consumption problem. However, after the

Improvements are also in progress in the two

wiggler was reinstalled in the storage ring, another

beam diagnostic beamlines. A new mirror has been

92 | ACTIVITY REPORT 2010 â&#x20AC;&#x201C; LNLS

ACCELERATOR DEVELOPMENT AND OPERATION

installed in the visible light diagnostic beamline

refurbishment of the XAFS1 beamline, installation

(DFE beamline). Modifications are also underway

of the Gleeble thermo mechanical simulation

in the X-ray diagnostic beamline (DFX beamline).

device on the XRD1 beamline, and preparations for

A new X-ray CCD camera has been installed and

the installation of the SCW beamline. These and

new inertial concrete blocks have been built to better

many other activities to improve the quality of the

insulate the beamline elements from movements

experimental stations were part of the wide range of

of the floor. The aim is to provide better diagnostic

activities carried out by the technical support groups

tools for detecting problems with the photon beam.

in the experimental hall. The construction of the

Beam-based alignment procedures are now

PGM beamline was one of these multitask activities

performed weekly to check the BPMs and are

in which several technical groups of the LNLS were

determinant for the establishment of the reference orbit for the beamlines. The procedure was crucial to make machine recovery easier after the major vacuum intervention in late 2009. Machine studies related to improvements in the electron beam diagnostic system were performed throughout the year.

A transverse bunch-by-bunch feedback system was designed, bench tested and installed in the storage ring during the machine shutdown in November 2010. The system is based on a commercial digital bunch-by-bunch beam position monitor and uses the old stripline kicker of the tune measurement system to act on individual electron bunches in order to damp transverse oscillations of the beam. The system is now being commissioned and is yielding very promising preliminary results. A longitudinal feedback system is being designed and should be built in coming years.

A second feedback system, a fast orbit correction system, was also conceived, bench tested and installed in the storage ring in the same period.

This system is based on commercial data acquisition

engaged. After the overall assessment of the project in 2009, which carefully reviewed and rescheduled the whole technical project of the beamline, the main bottlenecks were identified and the main problems solved. All the critical components of the beamline had been built or were in the final stages of construction by mid-2010, particularly the monochromator (Figure 7) and the mirror chambers (Figure 8). By September, the beamline was completely assembled and ready for commissioning with beam. The beamline became fully operational in early 2011, with the undulator controlled from the beamline during user shifts.

Upgrade of the Control System

A new version of the low level control system is

being developed to replace the old system. The new system, which is based on single board computers, will replace both the communication (serial and Ethernet) and the CPU cards of the current system.

The plan is to adopt this solution for SIRIUS. The system is based on Ethernet (with high level control)

and control systems and is designed for fast orbit corrections at a rate of up to 3 kHz. The correction rate is currently limited by the response time of the steering magnet power supplies. A new power supply is being developed to meet the requirements for fast response. The new system can also synchronize the current adjustments of the steering magnets within a range of one hundred microseconds. These features will allow for smoother orbit correction and prevent drifts of a few micrometers between corrections that occur in the current system. These feedback systems will be crucial for SIRIUS due to the extremely low emittance of the electron beam in the new machine.

Conclusion of the PGM Beamline

In 2010, the technical groups of the Engineering

and Accelerator Division implemented several improvements in the beamlines, including a complete

Figure 7.

Mirror and mechanical parts of the PGM Monochromator during installation on the beamline.

ACTIVITY REPORT 2010 â&#x20AC;&#x201C; LNLS | 93

FACILITY REPORT

Figure 9.

Figure 8.

Project of a pulsed sextupole for injection tests in the storage ring.

Second mirror chamber being prepared for installation on the PGM beamline.

and RS485 (with equipment) communication protocols. Since it is planned as a rapid solution for problems that intensified in 2009, mainly involving communication and CPU cards, the objective is to replace these cards gradually, keeping the same local controller crates with minimum changes in the topology of the control network. Four SBC cards are currently installed in the control network of the synchrotron light source. The communication soft ware is in an advanced stage of development and

Figure 10. Hexapod system holding the multilayer mirror

chamber during installation at the SAXS1 beamline.

will make the new card completely transparent for the high level control soft ware. The communication between SBC cards and equipment is based on the RS485 serial communication protocol. An AD/ DA conversion card was designed as a general purpose control card to be attached to the controlled equipment, providing the serial interface and doing away with cables for analogue data transmission.

The card is being tested and an operational version should be available soon.

Other Developments for the Light Source

A ceramic vacuum chamber was installed in the storage ring for injection experiments using a pulsed sextupole (Figure 9). The sextupole is in the design stage and the pulser has already been tested with a similar load. The main advantage of this method is that it eliminates the pulsed closed bump in the orbit of the stored beam which is necessary for injection with kicker magnets. A closed bump is critically dependent on the fine tuning of the injection kickers pulses, which is always very difficult to achieve. The method is an interesting option for SIRIUS since

The development of small modular power

the perturbation of the stored orbit is a problem

supplies for the magnets of the orbit correction

for machines operating with top-up injection. Tests

system has advanced to the phase of testing and

performed at the Photon Factory (Japan) have been

characterization of prototypes and will serve as

very successful, with very minor perturbation of the

a concept for the dc power supplies of the new

stored beam during top-up injection.

machine. A set of ten units is slated for installation

A hexapod system was designed and built

in the storage ring in 2011. The power system

for use as a support for critical beamline optical

comprises an AC/DC power module that feeds up to

components that require precise positioning and

four DC/DC power supplies. These DC/DC modules

alignment (Figure 10). This system allows objects to

can be independent or may be combined to provide a

be positioned and moved in space with six degrees of

higher output current. The device has digital setting,

freedom. The first device was installed on the SAXS1

no forced cooling and meets the requirements of the

beamline to support the chamber of the multilayer

fast orbit feedback system.

mirror.

94 | ACTIVITY REPORT 2010 â&#x20AC;&#x201C; LNLS

INDUSTRIAL RESEARCH ACTIVITIES

Premium screens: partnership with the Statoil Brazil Oil and Gas Ltd. to produce 14 prototypes in real dimensions

The industrial program of LNLS in 2010 focused on continuing and concluding projects and partnerships established previously, and on implementing new projects with important industries. This program is being revised to align it with the guidelines of the new administration of LNLS and CNPEM. The most relevant results achieved in 2010 are described below.

2

FACILITY REPORT

Introduction

The past year was very productive in terms of

2007-2009. The main purpose of the project was to

joint work the industrial sector. In 2010, the main

develop a diff usion bonding process for binding

highlights were an agreement signed with the

together several metal elements that comprise the

Norwegian oil company Statoil Brazil Oil & Gas

fi lter of the Premium screen. As a result of this

Ltd. for the development of Premium screen

partnership, LNLS will transfer the fi lter element

prototypes for the petroleum industry, and the

production technology to ADEST in exchange for

continuation of friction stir welding projects with

royalties to be reinvested in R&D.

Petrobras, as well as the possibility of a third

The prototypes will be characterized by

project in the same area. The goal of the LabWeb

mechanical, corrosion and sand retention testing.

is to design and supply the beam line remote

This required the identification of reference

access soft ware platform to improve the access of external users to the LNLS facilities. In the fi rst public demonstration of this system, a researcher performed remote SAXS and XRD experiments from an auditorium at the CBPF in Rio de Janeiro.

During 2010, the Scanning Tunneling and Atomic Force Microscopy Group (MTA) prioritized its

centers with the proper structure and expertise, including UNICAMP, USP and IPT-LAMEFUFRGS, to perform these tests. The photographs below show a sample of the fi lter element (Figure 1), its microstructure (Figure 2) and the welding equipment for diff usion bonding (Figure 3).

interaction with the industrial sector by resuming a scientific cooperation agreement with Hewlett Packard Computadores S/A and by providing consulting services on atomic force microscopy.

The LMF Group developed several projects of interaction with industry in 2010, with emphasis on process development for metal characterization in optical fibers, fabrication of resonant mesh fi lters and a project with Petrobras – MEMS Technology for Distributed Well Sensors. The latter project was initiated in September 2010 for the purpose of developing a new type of system for oil well monitoring applications.

Statoil – Filter Elements The

main

interaction

of

the

Materials

Group (MAT) with industry was the signing of

Figure 1.

Sample of filter element produced by the

Figure 2.

Microstructure of the sample.

diffusion bonding process.

a partnership with the Norwegian state-owned oil company Statoil Brazil Oil and Gas Ltd. in the amount of R$ 2.6 million in August 2010.

The purpose of this partnership is to produce 14 prototypes of Premium screens in real dimensions, using stainless steel fi lter elements joined by diff usion bonding, a process developed at LNLS. The

project

with

Statoil

motivated

the

nationalization of Premium screens through a FINEP-financed project between LNLS/ABTLuS and the company ADEST during the period of 96 | ACTIVITY REPORT 2010 – LNLS

INDUSTRIAL RESEARCH ACTIVITIES

Petrobras – Friction Stir Welding

LNLS continues to engage in major science and

technology projects linked to Brazilian companies.

The project co-funded by FINEP and Petrobras to study the possible application of friction stir welding technology in the oil and gas industry started on 2006. Another project was signed to continue research into the efficient and safe exploration and use of Brazilian fossil-based energy resources.

To enable the evaluation of fracture toughness of joints at low temperatures, the physical simulation capabilities of the laboratory will be expanded with the installation of a new dynamic testing system. The large Brazilian companies Usiminas and Tecnaris-Confab, the former manufacturing steel and the latter pipes, are also involved in this project. The significance of the results obtained so far for Brazil’s current and future oil and gas activities has led Petrobras-LNLS to propose a third project in this area.

Hewlett Packard – Metallic Oxides

During 2010, the MTA prioritized its interaction

activities with industry by resuming the scientific cooperation with Hewlett Packard Computadores force microscopy (e.g., to Nanocore Biotecnology S/A and WT Consultoria ME) were offered.

The aim of the LabWeb project of the Brazilian

Synchrotron Light Laboratory (LNLS) is to provide a soft ware platform for remote access to its beamlines to improve the access of external users to the LNLS facilities. The fi rst phase of this project involved the development of a hardware/soft ware prototype that enables access control, data acquisition and data storage on the beamline. Using a standard web browser, an external user can perform a full radiation

Equipment for diffusion bonding welding.

S/A. Furthermore, consulting services on atomic

Petrobras – Lab-Web: Remote Operation of LNLS Beamlines

synchrotron

Figure 3.

experiment,

including

sample changes, data acquisition and pre-analysis.

Two beamlines were targeted for the fi rst trials of the prototype, an X-ray Diff raction beamline (XRD1) and a Small Angle X-Ray Scattering (SAXS1) beamline. Most of the soft ware components used in the creation of the web browser interface were developed in JavaScript, local python scripts and

Investments to enable the AFM microscopes for biotechnological and metallurgical experiments were made to meet demands of the industry. The agreement with Hewlett Packard Computadores S/A enters now the 8th year of scientific cooperation between the two organizations, with investments by HP of up to R$ 2.8 million through the ‘Informatics Law’ since 2002, when the cooperation began.

In 2010, this agreement involved the MTA, LME (Electron Microscopy Laboratory Group) and DRX (X-ray Diff raction Group). The current project focus on studies of metallic oxides for application in electronic devices. The work plan for 2011 was approved in late 2010, confi rming the success and continuation of this cooperation.

BRLABS – Resonant Mesh Filters

The interest in THz photometric and imaging

APIs for the common beamline control soft ware

measurements led to the development of resonant

(Figure 4). In the fi rst public demonstration of this

band-pass fi lters to be coupled to multiple pixel

system, a researcher performed remote SAXS and

devices.

XRD experiments from an auditorium at the CBPF

This work involves the microfabrication of

in Rio de Janeiro. The LabWeb project is funded by

3D nickel mesh with different geometric patterns,

the nanotechnology network of PETROBRAS.

as indicated in Figure 5. These devices, known as ACTIVITY REPORT 2010 – LNLS | 97

FACILITY REPORT

resonant mesh fi lters, can act as band-pass, high-pass and low-pass fi lters in different frequency bands.

This project is aimed at improving the microfabrication technique to produce electroformed nickel plates with controlled dimensions, thereby ensuring the correct frequency for each specified filter.

Figure 4.

Web interfaces for XRD1 and SAXS1.

Figure 5.

3D electroformed nickel plates with different geometric patterns.

98 | ACTIVITY REPORT 2010 â&#x20AC;&#x201C; LNLS

Petrobras â&#x20AC;&#x201C; Distributed Well Sensors

The MEMS Technology for Distributed Well

Sensors project was initiated in September 2010 to develop a new type of oil well monitoring system.

The system consists of a temperature sensor and a pressure sensor that enable it to operate in conditions

INDUSTRIAL RESEARCH ACTIVITIES

of extremely high temperature (around 175 °C) and pressure (around 15000 psi). This requires the design of special electronic circuits, since conventional circuits are non-applicable. Moreover, the physical inaccessibility of the sensor in the well precludes the use of cables for delivering power or for telemetry, so wireless technology is also needed.

The energy to power the system must therefore be harvested from the environment. This project offers numerous challenges, for power consumption must be reduced, the telemetry must work in unfavorable environments and the sensors in severe conditions, all of which requires innovation in view of the current absence of commercial solutions.

Figure 6.

Fully operational Gleeble 3800® thermomechanical simulator

Figure 7.

Gleeble® synchrotron system, a thermomechanical simulator

installed at LNLS.

Petrobras – Advanced Physical Simulation

An advanced physical simulation laboratory

was set up and two thermomechanical simulators were installed and commissioned: a Gleeble® 3800 simulator for tension, compression and torsion simulation and a Gleeble Synchrotron simulator, which was co-designed and manufactured by DSI-LNLS engineers and is now installed on a dedicated hutch at a beamline to allow for in situ materials characterization by X-ray diff raction (Figures 6 and 7). In addition, a customized system has been ordered for residual stress mapping by X-ray diff raction.

designed specifically for state-of-the-art in situ experiments using synchrotron radiation. Installation and commissioning is underway.

ACTIVITY REPORT 2010 – LNLS | 99

3

BEAMLINES

The photo-electron spectroscopy endstation at the PGM beamline.

The LNLS beamlines serve a large community of academic and industrial users. The continuous improvement and upgrade of these facilities grants a competitive edge for its users in several areas of research. Presently, there are fourteen beamlines at LNLS in full-time operation for users and two beamlines in commissioning - a PGM based on a APPLE II undulator and the XDS (X-ray diffraction and Spectroscopy beamline) based on a 4 Tesla superconducting wiggler. The beamlines are organized in �ive groups, Macromolecular Crystallography, X-ray Absorption and Fluorescence, X-ray Diffraction, X-ray Scattering and Ultraviolet and Soft-X-ray Spectroscopies. Thanks to a management reorganization and budget recovery, during 2010 the laboratory showed signi�icant signs of recovery from the past years of understaff conditions and low budget. Several new scientists and technical staff members were hired, improving the work conditions and increasing the motivation on the beamlines which was evidenced in the latest the scienti�ic instrumentation developments that we describe in the following.

BEAMLINES

New insertion device beamlines

The two newest and most advanced beamlines

LNLS, who suffer with the relatively low flux in the

at LNLS are nearly finished. The soft x-ray PGM

hard x-ray region. Using different combinations of

beamline is based on a 2.7 m long EPU variable

optics (Table 1) the beamline will operate between

polarization

and

5 and 30 keV, and with a flux up to 1013 photons/s

characterised in-house. This beamline is currently

at 100 mA and energy resolution power of the order

being commissioned and covers the energy range

of 10000. The optical section of the beamline was

from 100 to 1200 eV with an energy resolution

purchased from Bruker ASC and is currently being

power above 8000. The first results (Figure 1) show

assembled at the LNLS site. The first commisioning

undulator

that

was

built

that the beamline is very stable and reliable, with easy access to change of gap and polarization of the undulator. Its main end-stations allow photoemission experiments in liquids, nano-sciences and magnetism. The Superconducting Wiggler Beamline for Materials Science, has been projected to simultaneously satisfy the needs of the x-ray diff raction and absorption user communities of

stages of the beamline will start in April 2011 and a first beam in the sample position is expected for August, 2011.

Macromolecular crystallography and spectroscopy

This group has two protein crystallography

beamlines, a MAD beamline (W01B:MX2) using a 2.0 T hybrid 30 pole wiggler source, and a fi xed energy beamline (D03B:MX1) based on a bending magnet source. The major improvement on the protein crystallography beamlines was the acquisition of a new automated end-station system from IRELEC which will be installed in 2011. This system will permit to change samples automatically without manual intervention, avoiding the typical loss of crystals by mishandling of samples.

X-ray Absorption and Fluorescence

Among the four beamline within this group,

two are dedicated to x-ray absorption D04B:XAFS1 Figure 1. First photoabsorption spectrum of Argon at

the L2,3 edge obtained at PGM, measured with

and D08B:XAF2 with conventional energy scanning and allow the realization of most conventional

a photoionization chamber. The exit slit width,

transmission and fluorescence experiments within

which determines the resolution, is 10 µm.

the energy range of 3-25 keV. A third one, the

Table 1. The possible operation modes for the Materials Science Beamline.

Collimating mirror

DCM

Focusing mirror

Crystal/shape

Mirror stripe coating / mirror angel (mrad) / shape

Mode

Energy range (keV)

Mirror stripe coating / mirror angel (mrad) / shape

1

4.8-10

Si / 2.75 / cylindrical

1. Si(111 / plan) 2. Si(111) / sagitally bent

2

9-20

Rh / 2.75 / cylindrical

1. Si(111 / plan) 2. Si(111 / plan)

Rh / 2.75 / toroidal

3

14-30

Pt / 2.75 / cylindrical

1. Si(111 / plan) 2. Si(111 / plan)

Pt / 2.75 / toroidal

4

9-20

Rh / 2.75 / cylindrical

1. Si(111 / plan) 2. Si(111) / sagitally bent

Rh / 2.75 / cylindrical

Rh / 2.75 / cylindrical

ACTIVITY REPORT 2010 – LNLS | 101

FACILITY REPORT

D06A:DXAS, is an energy dispersive beamline,

for the use of gases with redundant security system,

dedicated to time-resolved and extreme condition

implementation of gas flow controllers, matching

experiments and cover the range from 5-12 keV.

the line of exhaust gases. The detection system of

The x-ray fluorescence beamline D09B:XRF can

the fluorescence beamline was expanded by the

work with either a monochromatic or white beam

acquisition of two new single-element silicon drift

and attends a broad multi-disciplinary community

detectors to improve data collection from those

of users mainly involved in applications on

experiments demanding high count rate capability

environmental sciences, chemistry and biophysics.

and/or flexible arrangements. Important advances

A large community of users of the absorption

were done on the confocal microXRF/microXRD

catalysis

setup which involved testing with new home-made

experiments. Many of the improvements along this

policapillaries designs for the excitation channel

year were dedicated to this community, such as the

and testing with polymer x-ray refractive lenses

implementation of combined measurements of XAS-

manufactured by the Institute for Microstructure

mass spectrometer (for simultaneously analyzing

Technology (IMT) at the Research Centre Karlsruhe

XAS of catalysts and the residual gases of the

(FZK). Finally, the microXRF will be upgraded with

reaction), construction and commissioning of new

a Kirkpatrick-Baez (KB) system from ESRF in 2011.

beamlines

use

them

for

in-situ

furnaces, and improvements of the infrastructure

An important development in the XAFS1 beamline was the complete upgrade (soft ware and hardware) in the control and data acquisition system from an in-house component to a more commercial solution running on the EPICS control system which is used in many other synchrotrons. This was a test probe upgrade that will guide a general refurbishing of all beamlines in the next years.

X-ray Diffraction

This group includes three X-ray Diff raction

beamlines:

D10A:XRD2,

D10B:XPD

and

D12A:XRD1 working in a collaborative mode, with the users’ proposals distributed among them according the best possible use of the beamlines Figure 2.

The multi-analyzer system with 5 cyberstar detectors and Ge(111) analyzer crystals.

characteristics, their scientific instrumentation and time allocation.

There has been a continuous effort in the past years to improve detection systems. At the XPD station a multianalyzer system with 5 cyberstar detectors and Ge(111) analyzer crystals was developed and is currently in the final commissioning stage, with user operation planned for the second semester of 2011 (Figure 2). Two new Mythen 1K (from DECTRIS) were recently purchased for XPD and XRD1 beamlines, and will be available for the beamline users in the second semester of 2011 yielding an efficiency gain in measurements of the order of 100 times. Besides the crucial improvements in detection the scientific production of some communities pushed forward

Figure 3.

The

Gleeble

machine

simulation at XRD1.

102 | ACTIVITY REPORT 2010 – LNLS

endstation

for

thermo-mechanical

the development of different sample environments.

A setup with in-vacuum sample holder and

BEAMLINES

automated beamstopper is being implemented for the GISAXS community in XRD2, avoiding window scattering and allowing scattering and reflectivity measurements without stopping the operation for modifications inside the experimental hutch. In XRD1 the beamline remote access project, LabWeb, (see industrial activities section of the report) had a direct impact into the development of new sample holders for powder diff raction (up to 6 samples) and supported polycrystalline fi lms (up to 8 samples), that allow users to operate the system from home or run longer macros during night shifts. The furnaces used for catalysis experiments also received a new

Figure 4. The scattering flight path at SAXS1 beamline.

adaptation to XRD1 and are now compatible with all three beamlines. Finally, The installation of a Gleeble machine for thermo-mechanical tryouts at XRD1 is almost finished and a fraction of the beamtime of this facility (about 20%) will be dedicated to industrial projects (Figure 3).

X-ray Scattering

Since 2009, LNLS has two small angle scattering

beamlines operating for external users D01B:SAXS1 and D02A:SAXS2. The small-angle scattering beamline (SAXS1) optics was completely remodeled with a new multilayer toroidal mirror designed and optimized by ray-tracing simulation and constructed in collaboration with the Fraunhoffer Institut in Germany. The new optics resulted in a gain of almost two orders of magnitude in flux (~ 10¹² ph/s) compared with the previous silicon crystal, with a drawback of fi xing the beamline energy, in our

Figure 5. The hexapod support for the multilayer mirror chamber.

Ultraviolet and Soft-X-ray Spectroscopies

This group is responsible for four beamlines,

case it is 8 keV (Figure 4). This beamline will now

three in the UV range (the U11A:PGM, D05A:TGM

be specialized in time-resolved SAXS with rheo-

and D08A:SGM) and one in the soft-X-ray range

SAXS and stopped flow experiments. Measured flux,

(D04A:SXS).

bandwidth and beam size are comparable with the

In the TGM beamline, that covers the lowest energy

simulated values. A hexapod mount supports the

range available at LNLS (12-300 eV), a self-alignment

multilayer mirror and thus allows easy alignment

system to maximize flux after injections was developed

(Figure 5). The SAXS camera was also remodeled

to improve its operation. A gain on stability at this

with longer flight paths and a new PIN diode

beamline is also expected soon in this beamline due to

integrated beamstop. The wave vector range spanned

new set of mirrors in Silicon substrate that have been

on SAXS by the beamline goes from 0.03nm to

ordered and to replace the current ones in 2011. The

6nm-1, depending on the flight path configuration.

optical section of SGM was also remodeled with new

A Pilatus 300k is now used for SAXS measurements

mirrors in Silicon substrate and a longer focal distance

and a Pilatus 100k for WAXS data acquisition. The

that will improve its stability, flux and resolution. The

background scattering is strongly reduced thanks to

gain in space will also allow the installation of one more

two sets of scatterless slits purchased from XENOCS.

vacuum pump to improve the vaccum of the beamline.

-1

ACTIVITY REPORT 2010 – LNLS | 103

4

NANOSCIENCE AND NANOTECHNOLOGY

7 7 7 6

â&#x20AC;&#x201C;40% 2 nm

2 nm

Nanoscience and Nanotechnology are �ields that study atomic structures and their properties. Understanding these structures is crucial in the areas of medicine, computation, materials, pharmaceuticals and chemistry. Nanoscience and nanotechnology today are of global interest, which is why governments around the world invest heavily in them.

40%

NANOSCIENCE AND NANOTECHNOLOGY

Introduction

Brazil’s National Nanoscience and Nanotech-

494 papers published in indexed journals. In 2010

nology Laboratory (LNNano) is a national labora-

alone, approximately 6,505 hours of TEM and

tory of reference which operates as an open mul-

SEM were delivered to external users involved

tiuser facility. Its goals are to provide training for

in 193 research projects, resulting in 82 articles

Brazilian and foreign scientists, researchers and

in indexed journals. In addition to training

technicians, to develop microscopy techniques and

microscopists, several programs offer theoretical

instrumentation, to conduct competitive research in

and practical training, including specialized

different fields that exploit microscopy techniques,

graduate level courses offered at nearby universities

and to support the development of national industry

(UNICAMP and USP). These courses are also

in these areas. This laboratory is part of the Brazil-

available free of charge on the LNLS website. In

ian Synchrotron Light Laboratory (LNLS) located in

addition, a 3-week summer course is given every

Campinas, São Paulo.

other year to offer users living far away from the

The open facilities at the LNNano include an electron microscopy laboratory (LME), a scanning tunneling and atomic force microscopy laboratory (MTA), a microfabrication laboratory (LMF), and facilities for in-house research on the chemical synthesis of nanostructures and catalysis. In addition, the nanoscience and nanotechnology program is supported by the other national laboratories located at the National Energy and Materials Research Center (CNPEM), making it a unique site for scientific research in Brazil. the physical and chemical synthesis of 2D and 3D nanostructures, advanced microscopy (TEM, SEM, AFM, and STM), theoretical modeling, manipulation

of

nanostructures,

theoretical education and practical training in electron microscopy. The LME also interacts with industry through services, collaboration and partnership in materials sciences.

The LME installation is equipped with the following devices: • Jeol JEM-2100F – a 200 keV TEM–STEM–FEG microscope; • Jeol JEM 3010 – a 300 kV TEM–HR microscope (Figure 1);

The LNNano focuses its research efforts on

the

LNLS the opportunity to obtain a comprehensive

and

microfabrication of thin fi lms. These combined efforts help shed light on the unique behavior and properties of nanoscale materials, the development of new materials, precise control over the production

• Jeol JEM 2100 – a 200 kV TEM–STEM–MSC microscope (Figure 2); • Jeol JSM 6330F – a 30kV SEM–FEG microscope; • Jeol JSM 5900LV – a 30kV SEM–LV microscope; • A new laboratory for sample preparation for SEM with coarse and fine cutting machines, automated and manual grinding and polishing, automated mounting, electrochemical etching and polishing, sputter, optical microscope and

of these materials, and most importantly, the search

stereomicroscopes, microhardness indenter, and

for useful applications for new generations of

a microhardness mapping system;

materials and devices for the national industry.

• A TEM sample preparation laboratory with

An overview of the main activities and new

cutting, grinding, polishing, dimple grinder,

developments in this area during 2010 is presented

ion milling, disk punch, tripod, plasma cleaner,

below.

Electron Microscopy

The Electronic Microscopy Laboratory (LME)

was inaugurated in 1999 as an open facility for national and foreign users. Since it opened its doors, more than 65,000 hours of electron microscopy have been spent by 1484 users in the development of 1560 research projects, which resulted in

optical microscopes, evaporators, and cryoultramicrotomy; • A set of soft ware programs that include SAD indexing and SAD, CBED and HRTEM image simulation; crystallographic databases; quantitative TEM: GPA, FSR, deconvolution; an in-house developed Megacell, and strain mapping by DIC; and • A user room with PCs for image analysis and simulation.

ACTIVITY REPORT 2010 – LNLS | 105

FACILITY REPORT

The year 2010 saw the introduction of several improvements and developments, as follows: • The 3rd Advanced Course in Transmission Electron Microscopy was offered by LME/LNLS in January, involving theoretical classes and practical activities. The course was attended by 32 Brazilian and foreign graduate students and researchers; • A technical report was concluded on the study and evaluation of magnetic field effects on the LME installations; • A SEM equipped with a FEG on loan from Carl Zeiss Inc. was installed for use and evaluation in June. The FEG is still at LME and has been used by experienced researchers; • The purchasing process for LME infrastructural improvements was initiated, involving the

important tool for the study of structural molecular biology. The goal is to have a structural biology research group and a national open multiuser facility. The basic equipment is being purchased.

Scanning Tunneling and Atomic Force Microscopy Group (MTA)

The Scanning Tunneling Electron and Atomic

Force Microscopy Group continued its activities. The task force was recomposed with new hires and new openings, e.g., hiring of mid-level technicians (for user and instrumental support), trainee openings, e.g., mechatronic (UHV and MBE) and electrical engineers, a new PCI/DTI scholarship for a graduate chemistry student and a selection of researchers who should begin working at the laboratory in 2011. With

equipment for TEM sample preparation in

regard to facilities, the move to the new area in the

gentle ion milling conditions and a TEM sample

Cesar Lattes building was delayed due to hiring and

holder for studies involving high temperature

services, but is now slated for the second half of 2011.

conditions (up to 1200 oC);

With respect to the fostering of research activities,

• A new research line was started, the Single-

in 2010, CNPq renewed the 2010 ‘Rede SPM Brasil’

Particle Electron Cryo-Microscopy (Crio-ME), an

program for that year and for 2011. LNLS’s scientific partnership with Hewlett Packard Computadores S/A was resumed in 2010 and extended to 2011, with an increase in the budget. Amendments to the LNLS management agreement were also approved.

The resources obtained through these amendments will allow for continued investments in scientific instruments, the purchase of supplies and the maintenance of scholarship grants. The institutional project for the updating of scientific instrumentation submitted to FINEP was also approved, and is now awaiting the release of funds.

With

regard

to

scientific

instrumentation,

investments were made in a SolverPro AFM microscope for in-house projects. The microscope was reconfigured and became available to external users in October 2010. In response to user demands, investments were made in the Nanoscope llla AFM microscope to enable it to perform nanoindentation and measurements in liquid biological environments.

The microscope was equipped with a new station and data processing software, and a head was built and installed on this tool for STM measurements and X-ray induced photocurrent detection. New controllers for Figure 1.

Images of an InAs nanowire (grown by Juan Carlos-UFMG) in the

electron beam cells were acquired for the UHV VT-

light and dark field modes, clearly showing the nanowire’s cubic

STM microscope and MBE systems to increase the

and wurtzite structures.

quality of the in situ deposition of nanostructures.

106 | ACTIVITY REPORT 2010 – LNLS

NANOSCIENCE AND NANOTECHNOLOGY

The MTA laboratory operates in continuous mode, accepting research projects throughout the year, and is equipped with the following devices: a) VT UHV-STM microscope – Omicron Nanotechnology, Germany • Scanner: 12 × 12 × 1.5 um with Z resolution of about 0.01 nm. UHV chamber base pressure of about 1.0E-11T (with LN2 best of <5.4 E-12T), equipped with 4 e-beams, sample heating, optical pyrometers, and an introduction/preparation

b) AFM model Nanoscope IIIa imaging tool – Veeco Instruments, USA • Scanner: AS-12” E” 10 × 10 × 2.5 um • Scanner: AS-130” J” 125 × 125 × 5.5 um • Z resolution of about 0.3 nm • Microscope equipped with liquid cell for liquids and nanoindentation accessories; c) AFM model SolverPro microscope – NT MDT Nanotechnology, Russia

chamber to clean and prepare samples, allowing

• Smena Scanner: 100 × 100 × 3.5 um

for epitaxial deposition of materials;

• Conventional Scanner: 10 × 10 × 2.0 um.

Figure 2.

Nanoscientific research using Transmission Electron Microscopy – TEM. a) HRTEM image of a CeO2 nanocrystal obtained with a Jeol JEM-2010 TEM microscope at 200 kV. b) Model of a nanocrystal obtained from the analysis of an HRTEM image, considering the symmetry of the CeO2 crystalline structure. c) [110] Zone Axis projection from the nanocrystal model. d) Superimposition of the HRTEM image (red square inset) of the simulated nanocrystal model and the original HRTEM image.

ACTIVITY REPORT 2010 – LNLS | 107

FACILITY REPORT

Microfabrication Laboratory (LMF)

In 2010, the Microfabrication Laboratory carried

out numerous projects, some of them involving researches by federal universities, and contributed in the training of specialists in microfabrication techniques. The LMF also worked on in-house projects, especially those related with the beamlines and nanotechnology laboratory, and to meet the demand of service and industrial projects.

Cooperation with universities focused on the development of sensors for chemical and biological applications. A biosensor for salicylate has already been patented. Lactate sensors for the fi xation of reagents on metallic electrodes are in the test phase. A partnership was started to develop paperbased sensors, which have shown promising initial results. We successfully fi xed enzymes on the chipâ&#x20AC;&#x2122;s reservoirs and detected Fe II and Fe III in water with a good resolution. This procedure, which is based on color change, may represent an interesting solution

experimental setup for the characterization of these devices is completely operational.

Projects funded by FINEP and CNPq enabled the purchase of 3D profi lometers and sputtering with five targets. The laboratory is now awaiting the delivery of these devices, whose arrival is expected in the first half of 2011. A joint project was signed with Petrobras (SensorBR) to develop deep sea temperature and pressure sensors, as was an agreement with BRLabs to produce band passes. In addition, a project was initiated with the National Laboratory of Biosciences (LNBio) for the development of glass and/or polymer micropatterned plates for high throughput screening applications. The first plates have been produced and tested at LNBio. As can be seen, LNNano/LNLS continues to consolidate its position as a world class facility, concentrating major efforts on the education and training of human resources while simultaneously engaging in internationally competitive scientific production. However, to remain on this successful

for detecting iron contamination in rivers and

path requires the ongoing modernization of its

lakes. Chips on paper with amperometric detection

facilities and the expansion of its technical and

(metallic electrodes deposited on the paper)

scientific staff. Therefore, four researchers were hired

were developed and used to separate compounds

in 2010 and the search for new talents continues.

present in urine, such as uric and ascorbic acids.

In addition, several projects/proposals have been

The fabrication of multiplexer and demultiplexer

prepared and submitted to research funding agencies

devices, mixers, pumps and pneumatic valves based

and to private and government organizations to raise

on PDMS Soft Lithography was also concluded. The

much needed funds to modernize its facilities.

108 | ACTIVITY REPORT 2010 â&#x20AC;&#x201C; LNLS

SIRIUS PROJECT

LNLS is in the process of designing and building a new world-class synchrotron light source â&#x20AC;&#x201C; Sirius. This source will consist of a low emittance storage ring based on the use of permanent magnet technology for dipoles. In addition to contemplate a large number of insertion devices, as a third generation source, it will provide hard x-rays from bending magnets by means of an innovative approach in the magnetic lattice design. During 2010, most of the accelerator and engineering team efforts related to the Sirius Project focused on the reďż˝inement of this lattice design and the prototyping of magnets. Also, in preparation for the construction challenges of Sirius components, a major update was made of the physical infrastructure.

5

FACILITY REPORT

Magnetic Lattice

To meet the future demand for synchrotron

dipole radiation sources but would still maintain the

radiation in Brazil, a proposal for a new ring is being

benefits of low overall dipole radiation power. Th is

developed to replace the existing 1.37 GeV UVX light

idea consists of combining the low bending field

source, a facility that has been in operation for users

for the main beam deflection with a high magnetic

since July 1997. The proposed new source, Sirius, is a

field that extends over only a very short longitudinal

3 generation 3.0 GeV low emittance synchrotron light

length (a slice magnet, for 1° deflection), so that

source facility to be constructed on the same LNLS site.

the hard X-ray radiation is produced only at the

rd

The initial design was based on the use of low

beamline exit. Th is approach was implemented

field (0.45 T) permanent magnets for the storage ring

in the new lattice design and, together with

dipoles. The use of permanent magnets can reduce

further considerations about the need to produce

both the investment and operating costs of the

high brightness radiation of up to about 100 keV

project by significantly decreasing power supplies

(Figure 1), led to a 3.0 GeV electron storage ring

and cooling systems. The low dipole field also favors

with 20 TBA cells (Figure 2). The permanent magnet

reduced emittance by wigglers. However, there is the

dipoles now combine a low bending field of 0.5 T

drawback of excluding hard X-ray bending magnet

for the main beam deflection with a 2.0 T slice to

sources, which may be in considerable demand by

produce hard X-ray bending magnet spectrum with

users, since the beam size is naturally very small

12 keV critical energy. There are some attractive

at the dipole sources and some experiments do not

features in this proposal, including lower RF power

require the high brightness of the insertion devices.

consumption, less heating of the vacuum chambers,

A new idea was then introduced in the design

lower investments and operating costs for power

that preserves the implementation of hard X-ray

supply and cooling. In addition, the central

Figure 1.

Brightness expected from Sirius (with 0.5% coupling and 500 mA) compared with that of the ring (UVX) operating at LNLS. WSC60 is a superconducting wiggler with 17 periods of 60 mm; U20 is an undulator with 150 periods of 20 mm.

110 | ACTIVITY REPORT 2010 – LNLS

SIRIUS PROJECT

position of the high field dipole slice is optimal for reducing beam emittance and provides dipole radiation sources with axes equally spaced (± 9°) to neighboring insertion device beamlines. The general machine parameters are listed in Table 1.

Figure 2.

Layout of the modified TBA arc with the high

Table 1.

Storage ring main parameters.

field slice in the center of the middle dipole.

Energy GeV

3.0

Beam current mA

500

Circumference m

479.7

Nat. emittance nm.rad Number of cells / symmetry / structure

1.8 20 / 4 / TBA

Main dipole field Tesla

0.5

Slice dipole field Tesla

2.0

Total deflection by main dipoles

340°

Total deflection by slice dipoles

20°

Critical energy, main dip. keV

3.0

Critical energy, slice dip. keV

12.0

SR loss/turn, all dipoles keV

417.7

SR power, all dipoles kW

208.8

Betatron tune h/v

24.2 / 13.2

Synchrotron tune

0.01

Natural chromaticity h/v

-47.9 / -46.6

Natural energy spread %

0.08

Momentum compaction

7.5 x 10-4

Harmonic number

800

RF frequency MHz

500

RF voltage MV

3.2

Bunch length mm

4.4

Damping time (h/v/s) ms

Figure 4. New design of the low field dipoles in construction.

16.3 / 22.1 / 13.4

Straight sections (number * length)

4*9 m / 4*7 m / 12*5 m

Beam size @ slice (k = 0.5%) µm2

60 x 9

Beam size @ SS (k = 0.5%) µm2

Figure 3. Ferrite-based prototype of the 0.5 Tesla dipoles.

137 x 2 Figure 5.

Prototype for the 2-Tesla “slice”.

ACTIVITY REPORT 2010 – LNLS | 111

FACILITY REPORT

Figure 6.

Hybrid quadrupole prototype.

Prototypes

Storage ring magnets The first prototype for the low field dipoles

used permanent ferrite magnets (Figure 3). The dimensional and magnetic tolerances of such permanent magnets proved insufficient for this application.

Compared

to

NdFeB

magnets,

commercially available ferrite-based permanent magnets have the following disadvantages: the dimensional tolerances are an order of magnitude worse and the magnetization tolerance and the temperature stability of the magnetization are twice that of NdFeB magnets.

Although the price of NdFeB is higher than ferrite, taking into account its technical advantages and the lower necessary volume to build the dipoles,

Figure 7.

Combined function electromagnet prototype: sextupole, vertical and horizontal correctors and skew quadrupole.

we have decided to abandon ferrite. A prototype for the low field dipoles, based on NeFeB, is on the way

Figure 6 presents a preliminary design for the

(Figure 4). In both designs the field can be trimmed

quadrupoles. Coils are provided for ±15% adjustment

by an adjustable shunt of the return flux. This new

of the gradient produced by eight permanent magnet

design is also much more compact than the ferrite

cassettes. The built-in copper plates dissipate the

one.

heat produced by the coils and help stabilize the

The 2-Tesla slice prototype, also designed with permanent NdFeB magnets and 1006 steel, reached

temperature of the permanent magnets.

A

combined

function

electromagnet

was

fields higher than specified, which is also adjustable

designed, which includes a sextupole, vertical

by a trimming fi xture (Figure 5). The poles, tapered

and horizontal correctors and a skew quadrupole

in both directions, reach saturation but the resulting

(Figure 7). The magnet core is laminated to allow for

field is compatible with the calculated value within

fast orbit correction and uses cooled copper plates

the trimming range. The use of a better alloy for the

to extract the heat from the coils and stabilize the

poles is under study.

temperature of the carbon steel core.

112 | ACTIVITY REPORT 2010 – LNLS

SIRIUS PROJECT

Other Developments

local RS485 network of in-house built equipment.

The possibility of injection using a pulsed

A “universal” micro-controlled hardware interface

sextupole to replace the kickers is being studied.

was designed for this purpose. Commercial devices

Th is approach, already tried by Japan’s Photon

will be connected via Ethernet directly to operating

Factory, offers important advantages for top-up

computers or through the nodes (Ethernet, RS485,

injection since the transitory perturbation of the

USB, etc.). The control system of the existing storage

stored beam orbit is null for a perfect sextupole.

ring is being replaced gradually by the new system,

The control system under development is

serving both as a test bench for the new system and

based on ‘nodes’ using a standard Single Board

as an upgrade of the old control system. Currently

Computers, running Linux light distribution and

there are 4 fully operating nodes installed, each

“ANSI C” control soft ware. Each node controls a

controlling a variety of devices.

Figure 8.

Layout of the installations with beamlines up to 70 m long.

ACTIVITY REPORT 2010 – LNLS | 113

6

MAIN EVENTS

The Brazilian Minister of Science and Technology Sergio Machado Rezende (in the center of picture), meets the new synchrotron light source prototypes, in the company of by Jose Roque, LNLS director and Giancarlo Tosin.

In 2010, LNLS set up a Scienti�ic Committee to organize and promote an environment for discussion among users and to strengthen communication with managers and coordinators of the laboratory facilities. In the same year, LNLS hosted Hercules (Higher European Research Course for Users of Large Experimental Systems), a tranning course for doctoral and post-doctoral researches in the �ield of synchrotron radiation, designed in Grenoble, France. Also an agreement was signed with the Norwegian state-owned oil company Statoil and the metallurgical company ADEST to develop a �ilter element for petroleum extraction.

MAIN EVENTS

20th LNLS Annual Users Meeting

The 20th edition of the LNLS Annual Users

areas of Biology, Atomic and Molecular Science

Meeting (AUM), held on February 22 and 23,

and Materials Science, as well as an industrial

2010, brought together 450 researchers from Brazil

representative.

and other countries, who presented the results of 250 scientific researches conducted with synchrotron radiation (Figure 1). One of the highlights of the 20

th

edition of the AUM was the project of the second Brazilian synchrotron light source.

In addition to thematic sessions, plenary meetings were held with experts on research-related issues in the areas of microscopy, X-ray, advanced material spectromicroscopy, and new tools for characterizing macromolecular structures, among others.

Scienti�ic Committee

International Partnerships

LNLS, the Norwegian state-owned oil company

Statoil and the metallurgical company ADEST signed an agreement to develop a filter element for oil extraction. One part of the development will cover 14 months. This research and development project places Brazil among a select group of nations that already possess the technology to produce this type of screen. Only three companies worldwide build this type of equipment today. The filter element operates at great depths and requires special characteristics, such

LNLS set up a Scientific Committee to organize

as resistance to 370 times the average atmospheric

and promote an environment for discussion

pressure at sea level and pores with diameters of up to

among users of the Laboratory and to strengthen

18 thousandths of a millimeter.

communication with managers and coordinators

In June 2010, LNLS also resumed its partnership

of the laboratory facilities. Elected by peers, the

with Hewlett Packard to develop projects in the area

Committee comprised seven members from the

of information technology.

Figure 1.

The 20th RAU edition: 450 researchers from Brazil and others countries.

ACTIVITY REPORT 2010 – LNLS | 115

FACILITY REPORT

New Opportunities for International Cooperation

researchers in the field of synchrotron radiation,

of Science and Technology (MCT) visited

Light Laboratory (LNLS) (Figure 2).

The

Scientific

Advisory

Council

for

International Cooperation of Brazil’s Ministry the National Center for Research in Energy and

Materials

opportunities

(CNPEM) for

to

international

evaluate

new

cooperation.

The council aims to propose topics, evaluate

Figure 2.

celebrated its 20 th anniversary with a Latin American edition, the first one outside the European continent, at the Brazilian Synchrotron Held from July 12 to 30, 2010, the course was attended by 63 students from Brazil and other Latin American countries. Designed in Grenoble, France, the main objective of Hercules is to offer

programs and offer advice on the instruments of

training in synchrotron light applications to

cooperation proposed by the Ministry’s institutes

doctors, post-docs and senior scientists from

and agencies.

European and non-European universities.

Higher European Research Course for Users of Large Experimental Systems (Hercules)

LabWeb Project

LNLS successfully conducted its first remotely

operated experiment. In June 2010, a group of

Hercules (Higher European Research Course

researchers from Petrobras, LNLS and other

for Users of Large Experimental Systems), a

research institutes gathered together in the

training course for doctoral and post-doctoral

auditorium of the Brazilian Center for Physics

Hercules: training course for doctoral and post-doctoral researchers in the field of synchrotron radiation.

116 | ACTIVITY REPORT 2010 – LNLS

MAIN EVENTS

Figure 3.

Walter Colli (right), general director of the National Energy and Materials Research Center (CNPEM), and Rogério Cezar de Cerqueira Leite, president of the ABTLuS Board.

Research (CBPF) in Rio de Janeiro, where remote

magnets that will be used in the new synchrotron

experiments were conducted using synchrotron

light source. Mr. Rezende also co-signed an

light source beamlines located in Campinas.

agreement between BRASKEM and the Brazilian

The remote operation, called LabWeb, is being designed in partnership with the Petrobras

Biosciences National Laboratory (LNBio), which is located in the campus of CNPEM.

Nanotechnology Network.

New Director of CNPEM

The Board of the Brazilian Association

3rd Advanced Course in Transmission Electron Microscopy

The LME / LNLS conducted the 3rd Advanced

of Synchrotron Light Technology (ABTLuS)

Course in Transmission Electron Microscopy,

approved the nomination of Professor Walter

which was attended by 32 graduate students and

Colli for the post of director of the National

researchers from Brazil and abroad, who were

Energy and Materials Research Center (CNPEM).

selected from 125 course candidates. The classes

Dr. Colli took office on June 1, 2010 (Figure 3).

were taught by researchers at the LME and abroad,

Minister Rezende Visits LNLS

including Dr. Odile Stephan (Professor of the Université Paris-Sud, STEM Group – Laboratoire

On September 1, 2010, Mr. Sergio Rezende,

de Physique des Solid, France) and Dr. Antonio

Brazil’s Minister of Science and Technology, visited

Casares (Carl Zeiss NTS GmbH, Electron Optics

CNPEM where he was shown the prototypes of

Development).

ACTIVITY REPORT 2010 – LNLS | 117

7

FACTS AND FIGURES

In 2010, 2,716 users submitted 529 research proposals. Of this set of proposals, 432 were submitted by Brazilian researchers and 97 by foreign users, mainly from Argentina. Another 236 research proposals were developed at the facilities of the Cesar Lattes Center for Nanoscience and Nanotechnology (C2Nano). With regard to scienti�ic production, 253 scienti�ic papers were published in indexed journals, 23 of them with an impact factor higher than 5. During 10 months of operation, users and researchers used 3,994 hours of beam to conduct experiments on the 14 available beamlines. The source reliability index reached 97.8%, a percentage similar to that of previous years.

FACTS AND FIGURES

The Brazilian Association for Synchrotron Light

In 2010, ABTLuS comprised the Synchrotron

Technology (ABTLuS) is a non-profit organization

facility (LNLS), the National Biosciences Laboratory

that operates the LNLS through a management

(LNBio) and the Bioethanol Science and Technology

agreement signed with Brazil’s Ministry of Science

Center (CTBE). These three laboratories work

and Technology (MCT) and the National Council for

in synergy with all the laboratories operated by

Scientific and Technological Development (CNPq), in

ABTLuS to advance areas of knowledge that are

line with Executive Order 2405 of November 26, 1997.

strategic to Brazil.

2010

Shifts

2010

Proposals

Requested

2598

Requested

675

Accepted

1497

Accepted

554

Requested

Accepted

MX1/2

70

67

XAFS1/2

106

71

DXAS

24

23

XRF

50

44

SXS

37

29

TGM

31

25

SGM

15

13

XRD2

58

46

XRD1

47

44

XPD

88

52

SAXS1/2

149

140

Total

675

554

ACTIVITY REPORT 2010 – LNLS | 119

FACILITY REPORT

The project of the second Brazilian synchrotron

conduct experiments on the 14 available beamlines.

light source made considerable progress in 2010.

The source reliability index reached 97.8%, a

Most of the accelerator and engineering team

percentage similar to that of previous years.

efforts involving the Sirius Project focused on the

In 2010, 2,716 users submitted 529 research

refinement of this lattice design and on magnet

proposals and used the 14 synchrotron beamlines. Of

prototyping. Also, in preparation for the challenges

this set of proposals, 432 were submitted by Brazilian

of building components for Sirius, the physical

researchers and 97 by foreign users, mainly from

infrastructure underwent a major upgrade.

Argentina (74). Another 236 research proposals were

The current source operated from January to

developed at the facilities of the Cesar Lattes Center

October 2010, 24 hours a day, Monday through

for Nanoscience and Nanotechnology (C2Nano).

Saturday morning, with programmed one-day

With

regard

to

scientific

production,

shutdowns for maintenance and machine studies

253Â scientific papers were published in indexed

every two weeks. During 10 months of operation,

journals, 23 of them with an impact factor higher

users and researchers used 3,994 hours of beam to

than 5.

Proposals 2010

Submitted

Accepted

Executed

Canceled

MX1/MX2

70

67

63

4

XAFS1XAFS2

106

71

71

0

XRF

50

44

44

0

DXAS

24

23

24

0

SXS

37

29

28

1

TGM

31

25

21

4

SGM

15

13

14

0

XRD1

47

44

42

2

XRD2

58

46

44

2

XPD

88

52

52

0

SAXS1/2

149

140

126

14

Total

675

554

529

27

120 | ACTIVITY REPORT 2010 â&#x20AC;&#x201C; LNLS

FACTS AND FIGURES

Accepted 144

124

112

185

147

129

81

112

129

126

208

1497

Shifts Requested

Accepted

MX1MX2

168

144

DXAS

109

112

XAFS1/2

435

185

XRF

188

124

TGM

266

147

SGM

109

81

SXS

187

129

XRD2

254

129

XRD1

198

112

XPD

370

126

SAXS1/2

314

208

Total

2598

1497

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

São Paulo State (%)

65

62

60

62

57

51

51

44

46

39

42

Other States (%)

20

23

25

23

28

32

33

39

36

42

40

Other Countries (%)

15

15

15

15

15

17

16

17

18

19

18

Proposals executed in other opens facilities Other laboratories

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

Microfabrication laboratory

7

18

18

20

27

19

34

33

28

Atomic force and scaning tunnelins microscopes

6

6

16

16

16

14

25

19

17

ACTIVITY REPORT 2010 – LNLS | 121

FACILITY REPORT

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

226

169

142

181

231

358

379

423

434

466

438

455

529

74

86

112

96

150

138

161

143

125

160

197

Synchrotron Electron microscopy

122 | ACTIVITY REPORT 2010 – LNLS

MX2

SAXS1

SAXS2

MX1

SXS

XAFS1

TGM

DXAS

SGM

XAFS2

XDS

XPD

PGM

Small-Angle X-ray Scattering

Small-Angle X-ray Scattering

Macromolecular Crystallography

Soft X-ray Spectroscopy

X-ray Absorption Fine Structure

Toroidal Grating Monochromator

Dispersive X-ray Absorption Spectroscopy

Spherical Grating Monochromator

X-ray Absorption Fine Structure

Superconducting Wiggler BeamLine

X-ray Fluorescence

X-ray Diffraction

X-ray Powder Diffraction

High Resolution VUV Spectroscopy

X-ray Diffraction

W01B

D01B

D02A

D03B

D04A

D04B

D05A

D06A

D08A

D08B

W09B

D09B

D10A

D10B

U11A

D12A

XRD1

XRD2

XRF

Acronym

Name

Macromolecular Crystallography

Dipole

Applications

Reference

Single crystal diffraction, Multiple Beam Diffraction

Power Diffraction Studies in Materials Science

Focusing Double crystal 5-15 keV

Focusing Double crystal 5-15 keV

Magnetic Scattering, Grazing Incidence, Nanostructures

Focusing Double crystal 5-15 keV

Surface and Interfaces. Atomic and Molecular Physics, X-ray Magnetic Dichroism

Environment and Geochemistry, Biophysics and Agriculture

White beam or double crystal 5-25 keV

Planar Grating 100-1200 eV

Materials Science

Materials Science, thin films and diluted systems

Surface and Interfaces. Atomic and Molecular Physics

Materials Science, In-situ Studies, Magnetic Dichroism

Surface, Atomic and Molecular Physics; Time-of-Flight

Materials Science, thin films and diluted systems

Photoabsorption and photoemission spectroscopy

Structural Molecular Biology

Glasses and Nanocrystals, Polymers and Molecular Biology

Glasses and Nanocrystals, Polymers and Molecular Biology

Structural Molecular Biology using MAD technique

Doble Cystal 5-30 KeV

Focusing Double crystal 4-17 keV

Spherical Grating 100-1200 eV

One single-bent crystal 5-12 keV

Toroidal Grating 12-300 eV

Channel cut 3-25 keV

Double crystal 1500-5500 eV

One single-bent crystal 6-12 keV

One single-bent crystal 6-12 keV

One single-bent crystal 6-12 keV

Focusing Double crystal 5-15 keV

Monochromator

A

A

A

A

A

Detectors

Sample enviroment

Operational

Construction

Operational

Operational

Operational

Construction

Operational

Operational

Operational

Operational

Operational

Operational

Operational

Operational

Operational

Operational

Status

FACTS AND FIGURES

ACTIVITY REPORT 2010 â&#x20AC;&#x201C; LNLS | 123

SCIENTIFIC REPORTS

SCIENTIFIC REPORTS IN

www.lnls.br

1. Biology

Crystalline changes of dental hard tissues after high-intensity laser irradiation aimed at caries prevention

Ana, P.A., Benetti, C., Bachmann, L., and Zezell D. M.

Deglycosylation effect on the structure and stability of ovorubin, a protease inhibitor from the eggs of pomacea canaliculata M.S.Dreon, Ituarte, S., Ceolin M., and H.Heras

Effect of the antimicrobial protein rBPI on biomembrane model systems studied by small angle X-ray scattering

Domingues, M.M., Santiago, P.S., Tabak, M., Itri, R., and Santos, N. C.

Atomic signature of human stem cells under neural differentiation

Cardoso, S.C., Stelling, M.P., B Paulsen, and Rehen, S

Assessment of as incorporation in larvae of Argentinian toad (Rhinella arenarum) developed in as-contaminated medium by SR-TXRF Mardirosian M.N., Pérez, C. A., Venturino,A., and Bongiovanni, G.A.

Chemical speciation of bioaccumulated arsenic by SR-TXRF-XANES Pérez, C. A., Martins,B.S., and Bongiovanni, G.A.

2. Chemistry

Structural effect of thionaphtho-quinones and -hydroquinones on model membranes Funari, S.S., Marzorati, L., and di Vitta, C.

XAS investigation of Ni(II)-glyphosate complexes in the solid state Fonseca, N.F. and Herbst, M.H.

Effect of an anionic surfactant (SDS) on the Glossoscolex paulistus hemoglobin (HbGp) thermostability: small angle X-ray scattering (SAXS) studies Batista, T., Santiago, P.S., Carvalho, P. J. W., and Tabak, M.

Effect of a cationic surfactant (CTAC) on the Glossoscolex paulistus hemoglobin (HbGp) thermostability: small angle X-ray scattering (SAXS) studies.

Batista, T., Santiago, P.S., Carvalho, P. J. W., and Tabak, M.

124 | ACTIVITY REPORT 2010 – LNLS

The effect of sol-gel route on the microstructure of acid-base sensors

Capeletti, L.B., Cardoso, M.B., and Dos Santos, J. H. Z.

Structural changes of carbon supported PtV nanoparticles promoted by heat treatment Gentil, R. and Villullas, H.M.

The effect of metal-support interactions on the electronic properties of Pt and PtSn catalysts for ethanol oxidation Souza, N., Godoi, D. R. M., and Villullas, H.M.

XAFS studies of gold supported on silica modi�ied with organosilanes L.M. Rossi, Zanchet, D., and Oliveira, R.L.

Fragmentation dynamic of chlorobenzene and toluene induced by synchrotron radiation Guerra, A. C. O., Turci, C. C., Fernandes, D.H.L., Ferreira, G. B., and A.L.F. de Barros

Electronic properties and activity of PdNi/C catalysts for oxygen reduction Pires, F.I. and Villullas, H.M.

Study of the electronic properties of carbon supported PtV nanoparticles at different temperatures Gentil, R. and Villullas, H.M.

Electronic and structural properties of ZnO �ilms grown on aluminum Bürger, T. S., Bernardi, F., Morais, J., and Alves, M.C.M.

Characterization of the chemical stability of DNA-Psoralens

de Castilho, R.B., Ricardo, W., Rocco, M.L.M., and C. Lage

Electronic and structural characterization of Pt layers deposited on Au (111) Mauricio J. Prieto and Tremiliosi-Filho,G.

Complex salts of anionic polyelectrolytes and cationic surfactants. Structural characterization

by SAXS

Percebom, A. M., Alves, F. R., Vitorazi, L., and Loh, W.

XANES investigation of the enhanced chemical stability of Pd in supported Pd-Mo catalysts Cónsul, J.M.D., baibich, i.m., and Alves, M.C.M.

SCIENTIFIC REPORTS

Effect ofwater inwater-in-oil nanoemulsions formation prepared by the method of self-emulsi�ication

Santos, L.M., Santana, M. H. A., and d´Avila, M. A.

Synthesis of highly dispersed spheroidal metallic silver nanoparticles in surfactant-free N,N-dimethylacetamide da Costa L. P., Formiga, A. L. B., Sigoli, F.A., and Mazali, I. O.

Metalloproteomic study of manganese and zinc in plasma sample of nile tilapia (oreochromis niloticus) using D PAGE and SR XRF

Santos, F.A., Neves, R.C.F., Lima, P. M., Moraes, P. M., Pérez, C. A., Castro, G. R, and Padilha, P. M.

Study of the particle size distribution of suported M-MSx/C prepared with diferent concentrations of thiourea Carbonio, E. A., Mauricio J. Prieto, and Tremiliosi-Filho,G.

Fragmentation dynamic of benzene, aniline and nitrobenzene induced by synchrotron radiation

Guerra, A. C. O., Fernandes, D.H.L., Paschoal, R. C., Ferreira, G. B., A.L.F. de Barros, and Turci, C. C.

Spectroscopic evidence of photodegradation by ultraviolet exposure of Tris(-hydroxyquinoline) aluminum (Alq) thin �ilms Ricardo, W., Araujo,G.S, Quirino, W., M. Cremona, and Rocco, M.L.M.

In situ studies of sulphur poisoning in zeolite supported Pt and PdPt catalysts Rodrigues, V. O., Lopes, C. C., Sá, C.F., Licea, Y., and Faro Jr., A. C.

Electronic and structural characterization of Pt layers deposited on polycrystalline Au Mauricio J. Prieto and Tremiliosi-Filho,G.

Formation of catalytic silver nanoparticles supported on branched polyethylene imine derivatives

Signori, A., Santos, Kelly de O., Albuquerque, Brunno L., Giacomelli, F. C., and Domingos, Josiel B.

SAXS studies of �ilms based on diblock copolymer Porto, L. C., Melo, A., and Soldi, V.

Ionization, dissociation and desorption of pyrimidine ice due to X-ray interaction

Mendoza, E. F., Almeida,G.C., Andrade, D. P. P., W. Wolff, Rocco, M.L.M., and Boechat-Roberty , H.M.

X-ray absorption near-edge spectroscopy study of copper nanoparticles in chitosan membrane GODOI, F. C., Rabelo, B. R., and Beppu, M. M.

Structural changes in the zirconium-iron mixed oxide system during the thermal treatments

Alconchel, S. A., Pierini, B. T., Lamas, D. G., and A. F. Craievich

Photocatalytic degradation of methylene blue by TiO-Cu thin �ilms: theoretical and experimental study Ramalho, TC and Carvalho, H.W.P

Sulfur in�luence in polyaniline modi�ied by nucleophilic addition of arenesulphinic acids Andrini, L. and Requejo, F. G.

Small angle X-ray scattering (SAXS) studies of the effects of urea upon Glossoscolex paulistus hemoglobin (HbGp) in the oxy- and cyanometforms: denaturant concentration Santiago, P.S., Carvalho, P. J. W., Carvalho, F. A. O, Batista, T., and Tabak, M.

Ni@Pt core-shell and M-MSx (M = Pt,Rh) nanostructures investigated by X-ray absorption spectroscopy for Fuel Cells applications Carbonio, E. A., Cantane, D.A., Lima, F. H. B., and Gonzalez, E. R.

Effect of the structural properties of the MnyOx /C on oxygen reduction reaction in alkaline electrolyte Garcia, Amanda Cristina and Ticianelli, E. A.

Characterization of PtRh supported nanoparticles prepared with different concentrations of thiourea Carbonio, E. A. and Gonzalez, E. R.

Mesoporous silica for biocompatibility study (in vitro) by hydroxyapatite post-precipitation

Mendes, L. S., Jorge, J., Silveira, R. M., Castro, G. R, and Martines, M. A. U.

Characterization of H-Si(111) substrates Carbonio, E. A. and Gonzalez, E. R.

In situ time resolved XRD study of NiO-MgO-ZrO catalysts during the combination of dry reforming and partial oxidation of methane Asencios Y.J.O, Lucredio, A.F., and Assaf, E.M.

ACTIVITY REPORT 2010 – LNLS | 125

SCIENTIFIC REPORTS

In-situ monitoring of the structure of a goethite based catalyst during methane oxidation by XANES spectroscopy assisted by chemometric methods Nunes, C. A., Resende, E.C., Guimaraes, I.R., Anastacio, A. S., and Guerreiro, M.C.

SAXS evaluation of Renex-based self-assembly for nanostructured mullite preparation: in�luence of precursors Garcia, R. B. R., QUEIROZ, HIURE A. A. S, Gonçalves, R. F. B., and Kawachi, E. Y.

Asencios Y.J.O, Lucredio, A.F., and Assaf, E.M.

Mesoporous silica SBA- structural characterization

Ionic photofragmentation of CISO2NCO in the S p, Cl p and S s regions

Lago, A. F., dos Santos, L.C.R., and Davalos, J.Z.

In situ time-resolved XANES study of NiO-MgO-ZrO catalysts in the partial oxidation of methane

Angelica Moreno Betancourt, Rodriguez Pirani, Lucas, Geronés, Mariana, Erben, Mauricio F., Cavasso Filho, R. L., Della Védova, Carlos O., and Romano, Rosana M.

Characterization of bulk sul�ides hydrotreating catalysts using synchrotron radiation x-ray diffraction and xas techniques Licea, Y., Palacio L., Rodrigues, V. O., Eon J-G., and Faro Jr., A. C.

Pires, C. T. G. V. M. T., Badshah, S., and Airoldi. C

Photodissociation study of -imidazolidinone molecule by electron-ion coincidence -TOF-MS and synchrotron radiation

3. Environment and geoscience

Elemental quanti�ication of atmospheric aerosols

by SR-XRF in Córdoba City, Argentina López, M.L., Ceppi, S., Palancar, G. G., Olcese L.E., Tirao G., and TOSELLI B. M.

Novel selective surface functionalization of poly(butadiene) and poly(propylene) by coreshell excitation and oxygen exposure

Hyper�ine structure of Fe57 in iron-bearing minerals from a mangnese ore deposit

On the thermal stability of the extracellular Glossoscolex paulistus hemoglobin (HbGp), in the presence of urea: small angle X-ray scattering (SAXS) studies

Harguinteguy, C.A., Wannaz, E.D., Pignata, M. L., and Pérez, C. A.

Kessler, F., Rajajeyaganthan.R, and Weibel, D. E. or Weibel, D.

Carvalho, P. J. W., Carvalho, F. A. O, Santiago, P.S., Batista, T., and Tabak, M.

Characterization of bulk sul�ides hydrotreating (HDT) catalysts using HR-TEM Licea, Y. and Faro Jr., A. C.

In situ time–resolved XANES study of CuO/CeO catalysts during the reduction process and the preferential oxidation of CO Maciel, C. G., Profeti, L. P. R., Assaf,E.M., and Assaf, J. M.

Microwave-assisted synthesis of metal-organic framework evaluated by rietveld re�inement Wanderley, K. A., Rodrigues, M. O., Antonio, S.G., Paiva-Santos C. O., De Simone,C.A., and Alves, S.

Electronic excitation and ionic dissociation of core-excited sulfur compounds related with the ocean-atmosphere cycle: DMS and DMDS Bernini, R.B., Rodrigues, F. N., Grangeiro,L.B., Coutinho, L. H., and de Souza, G.G.B.

Nascimento, C. K., Couceiro, P.R.C., and Fabris, J. D.

Assessment of two species of macrophytes as biomomitors of heavy metals in rivers of Córdoba, Argentina Quanti�ication of heavy metals in particulate matter in Limeira city (SP) by SR-TXRF Canteras, F. B. and Moreira, S.

Study of the in situ reduction of Pt2+ and Ni2+ cations supported on Zeolite Beta

Oliveira, K. D., Barsi, F. V., Lima, P. M., Araújo, J., Cardoso, D.

4. Instrumentation

Self organization of magnetic nanoparticles in Ferro�luids Mendoza Zélis P., M. B. Fernández van Raap, Coral, D.F., T.E.Torres, G.F. Goya, S.J. Stewart, and F.H.Sánchez

Feasibility of pump and probe X-ray diffraction measurements at LNLS Giles, C., Gomez L.F., C.S.B. Dias, Vescovi, R. F., and Faria, G. A.

Crystallinity degree evaluation on three components (Mg-Co-Al) and (Mg-Ni-Al) layer double hydroxides

Development of standard reference materials for powder diffraction

Sales, E.M., Damalio, J.C.P., Barbosa, L.R.S., Araújo, A.P.U., and Itri, R.

Souza, T. D., Girardelli, D., Gomez L.F., Mardegan, J. R. L., Vescovi, R. F., Faria, G. A., and Giles, C.

Diniz, R., Chagas, L. H., and Bandeira, S

Temperature and concentration effects on the septin G aggregation process

126 | ACTIVITY REPORT 2010 – LNLS

Martinez, L. G., Galvão, A. S. A., Rossi, J. L., Orlando, M. T. D., Corrêa, H. P. S., and X. Turrillas

Study of cartilage and joints by phase contrast radiography with a Pilatus detector at the LNLS

SCIENTIFIC REPORTS

5. Materials Science

Microchannel fabrication in an e-tongue system Part 1 Dantas, C.A.R., Piazzetta,O.M.H, Gobbi, A. L., and Riul Jr, A.

Microchannel fabrication in an e-tongue system Part 2 Dantas, C.A.R., Piazzetta,O.M.H, Gobbi, A. L., and Riul Jr, A.

Reduction behaviour of novel nanostructured Pd/gadolinia-doped ceria catalysts with tubular morphology Muñoz, F.F., Acuña, L. M., and Fuentes, R. O.

Understanding the stability of cobalt supported catalysts for reforming of ethanol as addressed by operando temperature and spatial resolved XANES analysis de Ávila, C. N., Zanchet, D., and Bueno, J.M.C.

X-ray diffraction study of the microstructural evolution of the PbTiO3 system doped with rare earths Penton-Madrigal, A., A. Pelaiz-Barranco, B. Concepcion-Rosabal, and Y. Méndez-González

Development of silver clusters in hybrid organicinorganic sol-gel coatings Procaccini, R.A., Cere, S, and Pellice, S. A.

Structural properties and reduction behavior of novel ZrO-CeO solid solutions with tubular nanostructure by incorporation of Pd Acuña, L. M., Muñoz, F.F., Fantini, M. C. A., Lamas, D. G., and Fuentes, R. O.

Structural stability of T(bipy)[Ni(CN)4].xbipy with T = Mn, Fe, Co, Ni; bipy = 4,´4-bipyridine under vacuum and cryogenic conditions

Small-angle x-ray scattering studies in colloidal silica/pmma nanocomposites

Characterization of polymer-layered silicate nanocomposites

Persistence length, mass fractal and branching in the aggregating of vtes-derived organic/silica hybrids

Phase stability and structural distortions of nanostructured iron-cobaltite Mixed Conductor

Temperature induced spin transition in Ni[Ni(CN)4].2Pyrazine

Structure description of relaxor ferroelectric materials by an alternative structural re�inement protocol

Peruzzo, P. J., Anbinder, P. S., Plivelic, T.S., and Amalvy, J. I.

Vollet, D. R., Awano, C.M., w.chiappim junior, De Vicente, F. S., A. Ibañez Ruiz, and Donatti, D.A.

M. Gonzalez-Montiel, Lemus-Santana A. A., RodriguezHernandez, J., O. Hernández, M. Avila, Knobel, M., and E. Reguera*

Speciation of metals in a nanostructured ironcobaltite Mixed Conductor used for SOFC design Soldati, A.L., Baqué, L., Serquis, A, Lamas, D. G., Napolitano, F. R., and A. Caneiro

Charge density study of the high pressure phase of the CoSb3 skutterudite Perottoni, C. A., Miotto, F., Amorim, C.L.G., Gallas, M. R., and Figueirêdo, C.A.

Decomposition of sucrose at high pressure and high temperature

K.S.Trentin, Pereira, A. S., Perottoni, C. A., Balzaretti, N. M., and Jornada, J. A. H.

Structural modi�ication of Fe[Co(CN) ] at high pressure 6

Catafesta, J., Pereira, A. S., Perottoni, C. A., and F. Garcia

Porous molecular solids with tunable pore functionality for hydrogen storage

Reguera, L., J.Roque, J. Hernández, O. Hernández, and E. Reguera

Microstructure and properties of TEOS derived silica hydrogels synthesized by the alcohol-free route

Perullini, M., Jobbagy, M., Sara A. Bilmes, Torriani, I.L., and Candal, R.J.

M. Avila, O. Hernández, Lemus-Santana A. A., L., J. Roque, and E. Reguera*

Bianchi, A.E., Punte, G., Torriani, I.L., Eisenberg, P., Botana, A., Mollo, M., and R.M. Torres Sanchez

Baqué, L., Napolitano, F. R., Soldati, A.L., Lamas, D. G., A. Caneiro, and Serquis, A

Botero, E. R. and Garcia D.

Synthesis and characterization of heavy metal iodide nanoparticles L. Fornaro, I. Aguiar, and M. Pérez

Morphological study of Na�ion applied on electroactive composites in different levels of hydration Hirano, L. A., Rey, J. F. Q., Mantovani, G. L., and Scuracchio, C. H.

Mn-Ce catalysts suitable for the removal of organic pollutants in water. Ce L3 XANES study Andrini, L.

XANES studies in colloidal nanocrystals with molecular metallic ligands Requejo, F. G. and Andrini, L.

Structure of nanocomposite cathode for thin �ilm solid oxide fuel cells Casanova, J. R., Napolitano, F. R., A. F. Craievich, Lamas, D. G., and Serquis, A

SAXS study of cardanol-furfuraldehyde magnetic nanocomposites Varela, A., Oliveira, G. E., and Souza Jr, F. G.

Grazing incidence X-ray diffraction studies of nanoparticle-based calcium phosphate substrates Bapat, P. V. and Camata, R. P.

ACTIVITY REPORT 2010 – LNLS | 127

SCIENTIFIC REPORTS

Recrystallization of amorphous zirconium tungstate

Perottoni, C. A., Zorzi, J. E., Catafesta, J., Pereira, A. S., and Ramos, G. R.

Characterization of heterostructured TiO2-WO3 core-shell nanoparticles Santos, E. B. and Mazali, I. O.

Structure and microstructure evolution of Ce doped BiFeO3 as function of temperature

Penton-Madrigal, A., J.P.Sinnecker, de Oliveira, L. A. S., B. Concepcion-Rosabal, and E. Estevez-Rams

Evaluation of clavulanic acid adsorption in MgAllayered double hydroxides Forte, M. B. S, Elias, E.C.L., Pastore, H. O., Maugeri, F., and Rodrigues, M.I.

Morphological and crystalline behavior of PHBV nanocomposites evaluated by small angle X-ray scattering Carli, L. N., Bianchi, O., Machado, G, Crespo, J. S., and Mauler RS

Morphology of nanocomposites of cellulose acetate and organic montmorillonite prepared with different plasticizers de Lima, J. A., Pinotti, C. A., Felisberti, M. I., and Gonçalves, M. C.

Study of formation of nanometric ceria highly dispersed inside SBA-15 Silva, J.M.D.E., Pastorello, M., Strauss, M., Maroneze, C. M., Gushikem, Y., Sigoli, F.A., and Mazali, I. O.

Ce doping in BiFeO3 studied by EXAFS spectroscopy

Penton-Madrigal, A., de Oliveira, L. A. S., J.P.Sinnecker, B. Concepcion-Rosabal, and E. Estevez-Rams

EXAFS study of Fe-doped TiO2 and a-Fe2O3/TiO2 photocatalysts Santos, R. S., Oliveira, B.H., Silva, E. T. S. G., H. G. Oliveira, Leite, C.A.P., Giles, C., and Longo, C.

Residual stress of Cr/CrN multilayer thin �ilms using X-ray diffraction method

SAXS study of polyurethane/poly(2-(diethyl amino)ethyl methacrylate) blends for drug delivery applications Echeverria, M.G., Pardini, O. R., Peruzzo, P. J., and Amalvy, J. I.

X-ray diffraction characterization of Pb1-xBaxZr0:40Ti0:60O3 ferroelectric materials as a function of the temperature Mastelaro, V.R., Mesquita, A., and Michalowicz, A.

Combined XANES and GIXRF studies applied to study Zn ferrites F. Golmar, A.M. Mudarra Navarro, S. P. Heluani, Esquinazi, P., Ziese, M., and Rodríguez Torres, C. E.

XAS study of the local environment around Fe in SnO2 and ZnO doped with Fe and/or Sb or Nb

Barrero, C.A., C.E. Rodríguez Torres, and GARCIA, K.E.

XAS study of the local environment around Fe in SnO2 doped with Fe and/or Sb or Nb: part I Barrero, C.A. and C.E. Rodríguez Torres

Magnetic and structural characterization of ascast and annealed melt spun Fe80-xSi20Crx Penton-Madrigal, A. and E. Estevez-Rams

Characterization of a biomimetic coating on dense and porous titanium substrates Balestra, R. M., Ribeiro, A.A., Andrade, M. C., Rossi A. M., L. C. Pereira, and Oliveira, M. V.

Morphological properties of Sn:Fe:Sb:O Barrero, C.A.

SAXS study of lignin-CNSL-formol magnetic nanocomposites

Grance, E.O., Varela, A., Pereira, E.D., Oliveira, G. E., and Souza Jr, F. G.

Microchannels with the polymer polyvinylidene �luoride (PVDF) Sinézio, J.C.C. and Ricchi Jr. R.A

XANES and EXAFS characterization of zinc-doped magnetite nanoparticles for hyperthermia applications

Arias, D. F., Gómez, A. G., Souza, R. M., and Velez, R. J. M

Pasquevich, G. A., S.J. Stewart, F.H.Sánchez, Pianciola B. N., Mendoza Zélis P., M. B. Fernández van Raap, S. Jacobo, and J. Aphesteguy

Synthesis and characterization of TiO2 nanoparticles supported in SBA-15 mesopores Silva, J.M.D.E., Pastorello, M., Strauss, M., Maroneze, C. M., Gushikem, Y., and Mazali, I. O.

Microchannel fabrication in an e-tongue system - part 3

Morphological and chemical analysis of silicon etched by low pressure constricted plasma jet

Study of Ag nanocrystals distribution supported on natural clinoptilolite

Wakavaiachi, S. M., Fraga, M. A., Tezani, L. L., Pessoa, R.S., and Maciel, H. S.

Interpretation of SAXS and TEM data for analyses of the mesophase structures in hybrids silica-P(N-iPAAm) Andrade, G. F., A. Sousa, and E.M.B. Sousa

W,N-Codoped TiO2-Anatase: electronic and structural XANES-EXAFS study Andrini, L. and Requejo, F. G.

128 | ACTIVITY REPORT 2010 – LNLS

Dantas, C.A.R., Piazzetta,O.M.H, Gobbi, A. L., and Riul Jr, A.

B. Concepcion-Rosabal, E. Estevez-Rams, and Penton-Madrigal, A.

Synthesis and characterization of α-Fe2O3 nanoparticles obtained using sucrose

Jesus, J. R., Lima, R. J. S., Duque J.G.S., and Meneses, C. T.

Study of the adsorption of organometallic compounds on supported metallic catalysts M. Mizrahi, Ruggera, J. F., Casella, M.L., and Ramallo-López, J. M.

SCIENTIFIC REPORTS

Reduction of Cu2+ in the presence of Ag+ in natural clinoptilolite: structural characterization B. Concepcion-Rosabal, Penton-Madrigal, A., and I. Rodríguez Iznaga

Temperature dependence of disorder in Cobalt E. Estevez-Rams, Penton-Madrigal, A., and Somarriba-Jarque, J.C.

Characterization of the morphotropic phase boundary of the 0:6BiFeO3-0:4PbTiO3 compound

by HR-TEM Santos, I. A., Freitas, V. F., and Radovanovic, E.

Structural and micro-structural analysis of two Cu-Ni-Cr alloys with high electrical conductivity using synchrotron radiation Carrio, J. A. G., Carvalhal, M. A., Marques, I. M., and W. A. Monteiro

Study of the structure/properties relations in BiFeO3-PbTiO3 compounds by HR-TEM Santos, I. A., Freitas, V. F., and Radovanovic, E.

WAXS study of maghemite / polyaniline hybrid material Souza Jr., F. G., Cerruti, R., Pinto, J.C., and Oliveira, G. E.

SAXS study of maghemite / polyaniline hybrid material

Souza Jr, F. G., Varela, A., Pinto, J.C., Oliveira, G. E., and Lima, L. M. T. R.

AFM study of maghemite / polyaniline hybrid material

Souza Jr, F. G., Cerruti, R., Manzini R., C. H., Oliveira, G. E., and Pinto, J.C.

Stainless alloys process by rapidly solidi�ied

Bernardi, H.H., Käfer, K.A, Coelho, A. A., and J. Otubo

Preparation of conducting bacterial cellulosepolyaniline nanocomposites Marins, J. A., Soares, B.G., and Dahmouche, K.

Structural distortions of nanostructured ironcobaltite tubes

Napolitano, F. R., Granada, M, Troiani, H., and Serquis, A

Porous solids for hydrogen storage: behavior of some metal-organic frameworks under vacuum and on cooling René Cabrera, M. Avila, O. Hernández, C. Vargas, J.Roque, and E. Reguera*

Morphological behavior of PS/POSS hybrid nanocomposites Bianchi, O., Mauler R.S., Oliveira, R. V. B., Teixeira, S.R., and Machado, G.

Local structure of Pb(Fe1/2Nb1/2)O3 and Pb(Fe2/3W1/3)O3 multiferroic materials probed by X-ray absorption spectroscopy Mesquita, A., Mastelaro, V.R., Fraygola, B.M., Botero, E.R., and Eiras, J.A.

Optical spectroscopy and EXAFS characterization of Eu3+:LiLa(WO4)2 single crystal �ibers de Moraes, J.R., Baldochi, S.L., Soares, L.R.L., Courrol, L.C., Macedo, Z.S., Valerio, M.E.G., Mazzocchi, V.L., and Parente, C.B.R.

SAXS study of magnetic nanocomposites obtained from castor oil and glycerin Lopes, M. C., Oliveira, G. E., and Souza Jr, F. G.

Grain boundary analysis on the PrFeCoBNb sintered magnets with HR-TEM T. Mendes and Takiishi, H.

Hematite segregation dynamics in manganesezinc ferrite synthesis Martins, M. L. and Saeki, M. J.

Growth and characterization of thin �ilms of titanium, zirconium, and niobium oxides deposited on Si(111)

Tallarico, D.A., Gobbi, A. L., Paulin Filho, P.I., maia da costa, M. E. H., A. Galtayries, and Nascente, P. A. P.

XANES study of nanocrystalline ZrO2-CaO solid solutions: Zr L2 and L3 edges Fábregas, I. O., Andrini, L., and Lamas, D. G.

Microstructural characterization of Ni-based superalloys by analytical transmission electron microscopy Silva, C. C., Miranda, H. C., Farias, J. P., Afonso, C.R.M., and Ramirez, A.J.

Structural study of the LiCoO2 obtained by sol-gel method with starch Siqueira Jr, J.M., Resende, J. A. L. C., and Garrido, F.M.S.

Structural analysis of reactive hydride composites for hydrogen storage Ramallo-López, J. M. and Requejo, F. G.

Development and characterization of conductive nano�illers based on cellulose matrixes and polyaniline Picciani, P.H.S, Mendes,M.C, Medeiros, E. S., Souza Jr, F. G., Zaioncz, S., and Mattoso, Luiz Henrique Capparelli

Structural properties of LSC and BSCF for IT-SOFCs Acuña, L. M., Muñoz, F.F., Lamas, D. G., and Fuentes, R. O.

A simple method to synthesis α-Fe2O3 nanorods Lima, R. J. S., Jesus, J. R., Cunha, T. R., Duque J.G.S., and Meneses, C. T.

Magnetic structure of R2CoGa8 (R=Gd, Tb, Dy) investigated by X-Ray Magnetic Scattering Mardegan, J. R. L., C. Adriano, Faria, G. A., Vescovi, R. F., Veiga, L. S. I., C.S.B. Dias, L. N. Coelho, and Giles, C.

Microstructural characterization of Fe-Mn-SiCr-Ni-Co-Ti stainless SMA after equal channel angular extrusion Käfer, K.A, Bernardi, H.H., and J. Otubo

ACTIVITY REPORT 2010 – LNLS | 129

SCIENTIFIC REPORTS

Preparation of new peptide nanostructures via solid-vapor phase

In-situ DXAS study on the reduction behavior of Ce0:9Zr0:1O2 nanocatalysts

Ramallo-López, J. M., Giovanetti, L. J., P. S. Cappellari, Planes, G.A., A.F. Craievich, Requejo, F. G., and Barbero, C. A.

Synthesis and characterization of nanocomposite thin �ilms formed by barium titante and cobalt ferrite

Liberato, M.S., Oliveira Jr., V.X., and Alves, W. A.

Aqueous phase synthesis of gold nanoparticles capped by Cysteine studied by SAXS In¡Situ.

Spatial organization of peptide nanotubes for electrochemical devices Cipriano, T. C. and Alves, W. A.

AFM study of cardanol-furfuraldehyde magnetic nanocomposites Varela, A., Manzini R., C. H., Oliveira, G. E., and Souza Jr, F. G.

Physical characterization of High-k H fxAl1-xOy gate dielectrics prepared by ALD Christiano, V., C. Adelmann, Kellermann, G., Verdonck, P., and Santos, S.G.

XAS characterization of nanocrystalline Co(II) hydroxides Jobbagy, M., Fabregas, Ismael, and Oestreicher, V.

Study of formation of Co1-xTMx (TM=Fe, Cr and Mn) nanoparticles by organometallic synthesis Lima, R.J.S., Moura, K.O., Duque J.G.S., and Meneses, C.T.

Properties of TiO2 tubular nanostructure impregnated with CdSe quantum dots

Duarte, D. A., Milani, R., Menezes, F. D., Feil, A. F., J. Albino Aguiar, and Machado, G

Structural analysis of polyurethane nanocomposites by SAXS Pereira, I. and Orefice, R. L.

XANES studies on ZrO2-based materials for catalysis

Bacani, R., Fantini, M. C. A., Martins, T. S., Fuentes, R. O., Prado, R. J., Fábregas, I. O., Acuña, L. M., Andrini, L., Muñoz, F.F., and Lamas, D. G.

Zimicz, M.G., Larrondo, S.A., Prado, R.J., and Lamas, D.G.

Mohallem, N. D. S., Andrade, H. R. C. S., Seara, L. M., and Miquita, D.R.

Study of the in situ reduction of Ptx+2 and Nix+2 supported on Zeolite Beta Oliveira, K. D., Barsi, F., Lima, M. P., Araújo, and Cardoso, D.

Spectroscopic study of molecular packing on phenylene-vinylene/aliphatic multiblock copolymers

Bernardinelli, O. D., Cassemiro, S. M., Akcelrud, L., and de Azevedo, E.R.

Study of expanded austenitic formed in plasma nitrided AISI L samples using synchrotron radiation diffraction Olzon- Dionysio, M., Campos, M., de Souza, S.D., and Martinez, L. G.

6. Microscopy and Microfabrication Fabrication of electrodes on printed circuit boards for contactless conductivity detection in electrophoresis microchips Duarte Junior, G. F., Braga, L.E.P, Gabriel,E.F.M, Oliveira, K. A., Garcia, P.T., and Coltro, W. K. T.

Deposition of multi-walled CNT thin �ilms by SAWatomization O. V. Balachova

Rhodamine B encapsuled mesoporous silica channels Jorge, J., Renan G.C.S. Reis, Almeida, E.R., Queiroz, F.D, Castro, G.R, and Martines, M.A.U.

Synthesis of 2D and 3D superlattices of gold nanodisks and nanospheres by sputtering onto ionic liquid

Size distribution of cobalt ferrite nanoparticles

Cation distribution in Co ferrite nanoparticles

O. V. Balachova

Wender, H., Migowski, P, Feil, A.F., de Oliveira, L.F., J.Dupont, and Teixeira, S.R. Albuquerque, A.S., Azevedo, G.M., and W.A.A. Macedo

Structural characterization of TiO2/CeO2 mixed oxide by high resolution transmission electron microscopy Hewer, T.L.R. and Freire, R.S.

HRTEM study of defect type in CdTe/Si(111) thin �ilm Ospina, C. A., Ferreira, S. O., and Malachias, A.

Quenching of photoactivity in phthalocyanine copper(II) - titanate nanotube hybrid systems Alves, W. and Alves, W. A.

130 | ACTIVITY REPORT 2010 – LNLS

Chagas, E. F., Leite, G. C. P., Pereira, R., and Terezo, A. J.

Preparation of LiNbO3 and quartz wafers for their use in SAWsensors Evaluation of surface topography of a composite subjected to different polishing techniques Piementel, P.E.Z, Galvão, Y. F. S., Goyatá, F.R., and Cunha LG

SEM analysis of the deformation of blades of two types instrument according to the number of use Salum, G., Habitante S.M., Nohara E.L., Mansano, T.M., and Medeiros, J.M.F.

Evaluation of the super�icial characteristics of NiTi rotary instruments before and after used Arantes, W.B., Medeiros, J.M.F., and Lage-Marques, J.L.

SCIENTIFIC REPORTS

7. Physics

Characterization of ordinary chondrites from the Atacama Desert, Chile, by synchrotron x-ray diffraction and Mössbauer Spectroscopy de Avillez, R. R., Campos, J.B., R.B. Scorzelli, P. Munayco, and E. Santos Filho

Fragmentation of the CH2Cl2 molecule by attosecond proton beams and synchrotron radiation Alcantara, K.F de, Gomes, A. H. A., W. Wolff, Sigaud, L., and ACF Santos

Thermally driven core-shell formation on Pt-Pd nanoparticles Bernardi, F., Fecher, G. H., Alves, M.C.M., and Morais, J.

Photodissociation of methyl formate in circumstellar environment: stability under soft X-rays

Local structure study of Mn and V in spinel Mn(2-x)V(1+x)O4 series by high-resolution Kβ Emission Spectroscopy Ceppi, S., Tirao G., Pannunzio Miner, E. V., Pomiro, F., and Carbonio, R. E.

Reciprocal space maps of CdTe/Si(111) ultra-thin layers

Mello, J. O., Ferreira, S. O., and Malachias, A.

SAXS as a tool for studying of structural features of healthy and pathological human breast tissues Conceição, A. L. C., Antoniassi, M., Torriani, I., and Poletti, M. E.

Arsenic speciation by x-ray spectroscopy using Resonant Raman Scattering

H. J. Sánchez, Leani, J.J., Pérez, C. A., and R.D. Pérez

Fantuzzi, F., Pilling, S., A.C.F. Santos, Baptista, L., and Boechat-Roberty, H.M.

An XANES study on Eu doped calcium aluminosilicate glasses

High kinetic energy XPS and PED investigation of Pd/Cr2O3/Ag(111)

Resonant inelastic x-ray scattering by 2p electrons near the K absorption edge of Cu

Kilian, A. S., Bernardi, F., de Siervo A., Landers R., and Morais, J.

Comparison between Einstein and Debye models for an amorphous Ni46Ti54 alloy investigated using EXAFS and cumulant expansion K. D. Machado

Dependence of the sulfur reactivity of Pt-Pd bimetallic nanoparticles on the Pd concentration

Bernardi, F., A. Traverse, Alves, M.C.M., and Morais, J.

Monitoring the formation of Cu2(OH)3Cl particles by in situ DXAS and ex situ XPS

BOITA, Jocenir., KILIAN, A. S., Rodrigues, A, Bernardi, F., Alves, M.C.M., and Morais, J.

Investigation on vibrational and structural properties of amorphous Se1-xSx alloys by Raman Spectroscopy, XRD, EXAFS and RMC simulations

K. D. Machado, Dubiel A. S., Deflon, E.E, Sanchez, D. F., Kostrzepa, I. M., and Stolf, S. F.

Elemental quanti�ication by confocal micro-XRF

R.D. Pérez, V. Sbarato, Stoytschew, V., Kanngießer, B., H. J. Sánchez, Pérez, C. A., Sosa, C., and Rubio, M.

Determination of spatial distribution of trace and ultra trace elements in normal and neoplastic breast tissues Silva, M. P., Oliveira, M.A., and Poletti, M. E.

Correlation between spatial distribution of trace elements in normal and neoplastic breast tissues: preliminary results.

Silva, M. P. and Poletti, M. E.

Characterization of a ZnO/Si(111) �ilm prepared by chemical bath deposition Rodrigues, A., Boita, J., Kilian, A. S., Bernardi, F., Alves, M.C.M., and Morais, J.

Medina, A.N., Sampaio, J. A., dos Santos, D. R., Viana, J. R. M., and Rohling, J.H.

Stutz, G., Bianco, L., and Ceppi, S.

X-ray absorption characterization of Pb1-xRxZr0:40Ti0:60O3 (R=Ba or La) ferroelectric ceramics at the Zr LIII edge

Mesquita, A., Mastelaro, V.R., and Michalowicz, A.

Study of chemical environment of cerium in low silica calcium aluminosilicate glasses by Extended X-ray Absorption Fine Structure.

Sampaio, J. A., dos Santos, D. R., Peixoto, S. M. B., Medina, A.N., Rohling, J.H., and Baesso, M.L.

Amino acid alanine �ilms production by wet powder spraying

Silveira,T., E. M. Nascimento, Prudente, F. V., and Marinho, R. R. T.

Doping effect on the structural and magnetic properties of Cu1-x(Fe;Ni)xO. Part I: X-ray Diffraction Pedra, P. P., SANTOS,C.L, Lima, R. J. S., Duque J.G.S., and Meneses, C. T.

Morphology and local order structure of vanadium pentoxide D-nanostructures

Avansi, W., Maia, L. J. Q., Leite,E.R., Ribeiro, C., and Mastelaro, V.R.

Depth analysis of chemical environments using Resonant Raman Spectroscopy in total re�lection geometry

Leani, J.J., H. J. Sánchez, R.D. Pérez, and Pérez, C. A.

Photofragmentation of formic acid molecule using Synchroton Radiation Arruda, M. S., Marinho, R. R. T., MANIERO, A. M., Mundim, M. S. P., Mocellin,A., Pilling, S., Naves de Brito, A., and Prudente, F. V.

ACTIVITY REPORT 2010 – LNLS | 131

SCIENTIFIC REPORTS

8. Structural Molecular Biology

Structural characterization of Ohr (Organic Hydroperoxide Resistance Protein) from Xylella fastidiosa in oxidized state.

Alegria, T.G.P., Discola, K.F., Cussiol, J.R.R., and Netto, L.E.S.

Characterization of Thermomyces lanuginosus lipase by Small Angle X-ray Scattering

Gonçalves, K.M., de Souza, ROMA, and Cordeiro, Y.

Small Angle X-ray Scattering Analysis of NADE (p75NTR-Associated Death Executor), a new protein related to cancer Cordeiro, Y., Silva, V.S., and Almeida, M.S

Small Angle X-ray Scattering analysis of recombinant murine prion protein complexed with a mer RNA molecule Gomes, MPB, Silva, J. L., and Cordeiro, Y.

Structural basis for both pro- and anti-in�lammatory response induced by mannose-speci�ic legume lectin from Cymbosema roseum Rocha, B.A.M., Delatorre, P., Oliveira, T.M., Benevides, R. G., Pires, A.F., Sousa, A.A.S., Souza, L.A.G., Assreuy, A.M.S., Debray, H., Azevedo Jr., W. F., Sampaio, A.H., and Cavada, B.S.

Mass spectrometry and X-ray diffraction analysis of two crystal types of Dioclea virgata lectin: An antinociceptive protein candidate to structure/ function analysis Delatorre, P., Rocha, B.A.M., Simões, R.S., Pereira-Junior, F. N., Silva, H.C., Bezerra, E.H.S., Bezerra,M. J. B., Marinho, E.S., Gadelha, C. A. A., Santi-Gadelha, T., Farias, D.L., Assreuy, A.M.S., Marques-Domingos, G.F.O., Naganao, C.S., and Cavada, B.S.

132 | ACTIVITY REPORT 2010 – LNLS

Unraveling the most probable assembling of Na,K-ATPase α subunits induced by large amounts of C12E8: a Small Angle X-Ray Scattering study Barbosa, L.R.S., Rigos, C. F., Yoneda, J. S., Itri, R., and Ciancaglini, P.

Structural analysis of ConBr reveals molecular correlation between the carbohydrate recognition domain and endothelial NO synthase activation Bezerra, E.H.S., Rocha, B.A.M., Naganao, C.S., Bezerra, G.A., Moura TR, Bezerra,M. J. B., Benevides, R. G., Sampaio, A.H., Assreuy, A.M.S., Delatorre, P., and Cavada, B.S.

Expression, puri�ication, crystallization and data collection of the histidine kinase domain of LOV-HK from Brucella abortus Rinaldi, J., Klinke, S., Paris G, and Goldbaum, F.A.

Structural analysis of non-glucosylated and mutant rabbit glycogenins Carrizo, M.E., Issoglio, F.M., Romero, J.M., and Curtino, J.A.

DNA encapsulation by Lipid vesicles: Structural characterization by Small-Angle X-Ray Scattering Oliveira, C. L. P, Gerbelli, B. B., Bicev, R. N., Alves, C., and Oliveira, E. A.

Parcial x-ray structure of Azospirillum brasilense GlnB protein

Araújo, L. M., Kadowaki, M.A.S., Iulek, J., HUergo, L.F., chubatsu, L.S., Steffens, M.B.R., Pedrosa, F.O., and Souza, E. M.

ISSN 1518-0204

LNLS ACTIVITY REPORT 2010 Editor: Angelo Malachias Management: Claudia Izique Proofreader: Beatrice Allain The editors express their gratitude to the LNLS users and staff for their contributions, advice and patience DISCLAIMER This document was prepared as an account of work done by LNLS users and staff. Whilst the document is believed to contain correct information, neither LNLS nor any of its employees make any warranty, expresses, implies or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed within. As well, the use of this material does not infringe any privately owned copyrights.

LNLS Campus: Giuseppe Máximo Scolfaro Street, 10.000, Campinas, São Paulo, Brazil Correspondence: P.O. Box 6192 Postal Code 13083-970, Campinas, São Paulo, Brazil Telephone: +55 19 3512-1010 Fax: +55 19 3512-1004 e-mail: secre@lnls.br home page: www.lnls.br A non-profit organization Brazilian Association for Synchrotron Light Technology (ABTLuS) operate the Brazilian Syncrotron Light Laboratory (LNLS)for the Brazilian Ministry of Science and Technology.

AC T I V I T Y

Brazilian Synchrotron Light Laboratory

ABTLuS Brazilian Association for Synchrotron Light Technology Director General: Rogério Cezar de Cerqueira Leite (January to June, 2010 – pro tempore) Walter Colli (June to December, 2010) LNLS Brazilian Synchrotron Light Laboratory Director: Antonio José Roque da Silva LNBio Brazilian Biosciences National Laboratory Director: Kleber Gomes Franchini

CTBE Brazilian Bioethanol Science and Technology Laboratory Director: Marco Aurélio Pinheiro Lima

Activity Report 2010: LNLS / Brazilian Synchrotron Light Laboratory - Campinas, SP: Brazilian Ministry of Science and Technology / Brazilian Association for Synchrotron Light Technology, 2010.

Annual ISSN 1518-0204 1. Synchrotron accelerator. I. LNLS / Brazilian Synchrotron Light Laboratory CDD 539.735

This publication is available at the eletronic format in www.lnls.br/publicacoes Printed in December, 2011 Desktop publishing

R E P O RT

2 0 1 0

Bra z il ia n Sy nc h ro t ro n Ligh t La bo ra to r y

ISSN 1518-0204

AC T IV IT Y R E PO RT 2 0 1 0

w w w. l n l s . b r

AC T I V I T Y

R E P O RT

Brazilian Synchrotron Light Laboratory

2 0 1 0