Activity Report LNLS 2009 by Editora Cubo

LNLS ACTIVITY REPORT 2009 Editor Management Proofreader

Angelo Malachias Claudia Izique 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

Telephone Fax e-mail

Giuseppe Máximo Scolfaro Street, 10.000 Campinas, São Paulo, Brazil P.O. Box 6192 Postal Code 13083-970 Campinas, São Paulo, Brazil +55 19 3512-1010 +55 19 3512-1004 secre@lnls.br

home page

www.lnls.br

Correspondence

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.

ABTLuS (Since May, 2009) Brazilian Association for Synchrotron Light Technology Director General: Antonio José Brum (january to may, 2009) Michal Gartenkraut (may to december, 2009) LNLS Brazilian Synchrotron Light Laboratory Director: Antonio José Roque da Silva LNBio Brazilian Biosciences National Laboratory Director: Kleber Gomes Franchini CTBE Bioethanol Science and Technology Center Director: Marco Aurélio Pinheiro Lima

Activity Report 2009: 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, 2010

Desktop publishing

Introduction

Science Highlights

Facility Report

Scientific Reports at www.lnls.br

126

Introduction

Welcome The year of 2009 was marked by a

After my official appointment in July

major transition in the organization of

of 2009, the first goal was to define the

LNLS. By the end of the year of 2008 the

team of people that would coordinate

Ministry of Science and Technology and

the Engineering and Accelerator Division

the Administration Board of ABTLuS had

(DEA), the Scientific Division and the project

decided that the complex of laboratories

of the new synchrotron light source. By

identified until then as LNLS should be

November of 2009 this team was complete:

restructured into three National Laboratories,

Ruy Hanazaki Farias is now the head of

the LNLS itself, the Laboratório Nacional

the DEA, Yves Petroff accepted to come

de Ciência e Tecnologia do Bioetanol

to LNLS as Scientific Director and Antonio

– CTBE (Brazilian Bioethanol Science

Ricardo D. Rodrigues also agreed to return

and Technology Laboratory) and the

to LNLS to coordinate the project of the

Laboratório Nacional de Biociências – LNBio

new ring. I would also like to thank them

(Brazilian Biosciences Laboratory). All

for accepting these positions and the

these National Laboratories comprise the

challenges that come with them.

Centro Nacional de Pesquisa em Energia

It was clear that the major difficulty to

e Materiais – CNPEM (National Research

be addressed is the lack of personnel in

Center in Energy and Materials), which is

the Scientific Division. By the end of the

managed by ABTLuS.

year of 2009, the number of people with

As a consequence of these changes, a

PhD per beamline got to a critical level

new Director General of ABTLuS was chosen

of approximately 0.6, putting at risk the

to replace José A. Brum, who served with

quality of operation of the laboratory to the

great enthusiasm and dedication from July

scientific community. It was also clear that

2001 to May 2009. I would like to take this

many beamlines needed refurbishment,

opportunity to sincerely thank Dr. Brum for

and the UV undulator-based beamline,

all his achievements as Director General

PGM, which was late in schedule by a

throughout these years, a period that was

couple of years, had to be finished with

fundamental for the growth and establishment

great priority. Actions were planned and

of LNLS as a National Lab in Brazil. With

initiated to address these issues, and we

the above mentioned restructuring, each

expect to have already some positive

one of the National Labs had appointed

results by 2010.

new Directors: Marco Aurélio Pinheiro Lima

Albeit these difficulties, the following

for the CTBE, Kleber G. Franchini for the

Report presents many results that clearly

LNBio, and myself for the LNLS.

indicate the high degree of achievements,

6 | Activity Report 2009

Introduction

both from the machine side as well as from the science and instrumentation results at LNLS. One example is the replacement of two thirds of the machine beam position monitors, concluding the procedure that started in 2008. This is part of the efforts that have been made through these past years to improve the machineÂ´s performance and reliability. Other important developments that were concluded in 2009 was the assembly of the first solid state amplifier, which will be commissioned and installed in 2010, the improvement in the thermal stability of the wiggler-based protein crystallography beamline, which will significantly enhance the conditions for MAD experiments, and the finalization of the upgrade of the SAXS1 beamiline. All these results would

with 1.7 nm.rad emittance, which will make the new Brazilian synchrotron light source extremely competitive worldwide. There is no doubt that all the efforts that Brazil has dedicated throughout these years to create and operate LNLS will be

not be possible without the dedication

lost if the project of a third generation

and high quality of LNLS staff.

synchrotron ring does not come to fruition

Regarding the project of the new ring,

in the coming years. This state-of-the-art

the focus was on the definition of its major

machine will provide the scientific and

parameters. As described in detail in this

technology national community with an

Report, the project evolved from the initial

infra-structure that will allow the country to

design of a 2.5 GeV machine with relatively

maintain its competitiveness in strategic

low field of 0.45 T bending magnets distributed in a 16 TBA configuration to a 3 GeV storage ring with 20 TBA cells. Moreover, the permanent magnet dipoles now combine low bending field of 0.5 T magnets with a high field dipole slice of 2.0 T. This latter element covers a very short longitudinal extent while at the same time

areas, such as nanoscience, structural molecular biology, advanced materials and alternative energy sources. This is even more fundamental considering the importance of knowledge and technology as drivers of productivity and economic growth, thus key ingredients for Brazil

allowing high energy photons with critical

as it continues its evolution as one of the

energy of 12 KeV to be produced from the

leading economies in the world.

dipole beamlines, keeping in this way the total radiated power still at low level. The

Antonio JosĂŠ Roque da Silva

basic lattice design will provide a beam

Director LNLS

Activity Report 2009 | 7

Observation of the Smallest Square Cross–section Metal Nanotube

Unveiling the Chemical and Morphological Features of Sb:SnO2 Nanocrystals by the Combined Use of HRTEM and Ab Initio Surface Energy Calculations

Controlled Deposition of Silver Nanoparticles in Mesoporous Thin Films: Towards New Metallic–oxide Nanocomposites

Uncovering Molecular Structural Mechanisms of Signaling Mediated by the Prion Protein

Single Electrode Electrochemical Detection in Hybrid Poly(dimethylsiloxane)/Glass Multichannel Microdevices

Benzene Molecule is Destroyed by Ultraviolet and Soft X–rays in Circumstellar Environment

The Effects of CeO2 on the Activity and Stability of Pt Supported Catalysts for Methane Reforming, as Addressed by In Situ Temperature Resolved XAFS and TEM Analysis

Controlled Swollen and Drug Release from Urea–Cross– Linked Polyether/Siloxane Hybrids

Correlation Between AO6 Polyhedral Distortion and Negative Thermal Expansion in the A2M3O12 Family

Structural Aspects of the Distinct Biochemical Properties of Glutaredoxin 1 and Glutaredoxin 2 from Saccharomyces cerevisiae

Structure and Calcium Binding Activity of LipL32, the Major Surface Antigen of Pathogenic Leptospira sp.

A Multi–technique Study of Structure and Dynamics of Polyfluorenes Cast Films and the Influence on Their Photoluminescent Properties

Observation of the Smallest Square Cross–section Metal Nanotube Maureen Joel Lagos,1,2 Fernando Sato,2 Jefferson Bettini,1 Varlei Rodrigues,2 Douglas Soares Galvão,2 Daniel Ugarte2

Laboratório Nacional de Luz Síncrotron, CP 6192, 13.084–971, Campinas, SP, Brazil 2

Instituto de Física “Gleb Wataghin”,

Universidade Estadual de Campinas – UNICAMP, CP 6165, 13.083–970, Campinas, SP, Brazil

The development of nanotechnology require en ensemble of new experimental and theoretical and tools to analyze the properties of nanostructured materials. Among many technical challenges, the understanding and prediction of mechanical properties of nanoscale systems show a serious lack of basic physical understanding. The arrangement of atoms in nanostructures is very different from macroscopic matter, mainly due to the relevant role of surface energy in structure with a high surface/volume ratio. During mechanical deformation, the applied stress induce structural changes that result from a complex interplay between elastic, electronic and surface contribution to the total energy of the system; this can lead to unexpected properties. For example, metastable structures such as suspended chains of atoms and helical nanowires wires have already been observed. In this work, we report the formation of the smallest possible silver nanotube with a square cross–section (just one–lattice‑parameter width) during the stretching of silver nanocontacts. This wire was observed during in situ elongation experiments in an atomic resolution transmission electron microscope. Theoretical ab initio calculations and simulations reveal that the hollow wire is spontaneously formed because this structure minimized surface at the same time that creates a very soft wire capable of absorbing a huge tensile deformation.

Facility: C2nano Publication: Nature Nanotechnology, 4: 149–152 (2009) Funding: FAPESP, CNPq.

Science Highlights

A deep comprehension of the

point resolution); the dynamical process

mechanical properties of tiny volume

has been recorded with a high sensitive

materials is essential for the development

TV camera. Initially, holes are opened in

nanotechnology. In fact, there are still

a self–supported metal film by focusing

a huge set of open issues associated

the electron beam and, nanowires are

with nanomechanics, nanoindentation

formed between neighboring holes.3 The

and nanotribology. The relevance of this

dynamic observations have been realized

topic has received special attention in the

both at room (~300 K) and low temperature

Report on challenges for Instrumentation

(~150 K).4 Figure 1 shows the elongation

and Metrology for Nanotechnology

of a silver atomic–size wire along [001]

published in 2006 by the US National

direction. Initially, the wire shows a rod–like

Nanotechnology Initiative.1 In particular, it

morphology and, gradually thin to finally

is emphasized the existence of a serious

form a linear atom chain; finally, the wire

lack of basic understanding of mechanical

rupture occurs (not shown). As {100}–like

properties of nanosystems. Most of available

facets are favored in silver nanocrystals,

knowledge on mechanical properties

we would expect that nanorods generated

of nanomaterials has been derived by

along the [100] direction would display

computational simulations, which can not

square cross–section ({010} and {001}

be supported by experimental validation

facets form the lateral surfaces).5 The

and, consequently the basic physics is

atomically resolved image in Figure 1a

not understood. Atomic–size metal wires

shows a flattened hexagonal pattern, what

represent an excellent experimental

agrees with a square face centered cubic

and theoretical case to analyze the

(i.e. the macroscopic crystal structure)

deformation of matter at nanoscale, then this field concentrates a very intense scientific activity.2 Many theoretical and experimental studies have analyzed a wealth of possible metal structures generated during the wire stretching, what has led to the discovery of helical wires and one–atom–thick ones, anomalous structures generated during stretching. In this size range, these anomalous atomic arrangements arise from the interplay between surface, elastic and electronic energy of nanosystems. In this work, we have studied the structural evolution during the elongation and rupture of silver nanowires by in situ experiments

Figure 1.

Snapshots taken during the stretching of a silver nanowire along the [001] axis. The wire initially shows a rod–like morphology (0 s) (a), which becomes thinnes to finally form na atomic chain (10.3 s) (c) before breaking. At 3.6 s (b) the wire shows a bamboo–like contrast

in atomic resolution electron microscope

pattern (see text for explanations).

HRTEM (JEM–3010 URP 300 kV, 0.17 nm

image.

Atomic positions appear dark in the

Activity Report 2009 | 11

Observation of the Smallest Square Cross-section Metal Nanotube

Ag rod with one–lattice–parameter width (a0 = 4.09 Å). Subsequently, the image changes to a bamboo–like pattern; this contrast is formed by squares of side a0 and a rather bright center (Figure 1b). We must emphasize that fcc atomic arrangement (Figure 2a) can not explain the bamboo–like contrast. To explain the unexpected contrast pattern, we must simply remove the atoms at the wire axis (red colored atoms in Figure 2b), what generates a hollow square cross–section nanowire (Figure 2b). A more detailed analysis of HRTEM images can be realized by compared intensity profiles6 extracted from the experimental and simulated images for the hollow square Ag pillar (Figure 2c), what results in an excellent agreement. To gather additional understanding on the formation of the anomalous silver tube, we have analyzed the structural stability by total energy calculations using ab initio Density Functional Theory (DFT) methodology.7–9 The calculations indicate that tubular nanowires (Figure 2b) are slightly less stable than fcc ones (Figure 2a), what implies that elastic energy due to the stretching is contributing for the formation and stabilization of silver nanotubes. Then, we performed molecular simulations to analyze how the structural evolution during stretching leads to a metastable Ag nanotube. In the calculations, the elongation was induced by increasing the distance between buffer layers at the wire extrema (elongation step 0.1 Å) and, subsequently, the atomic structures were optimized within the same

Figure 2.

a) Schema of the Expected atomic arrangement of fcc silver nanowire whose width is one lattice parameter; b) Analogous structure obtained by removing the red atoms located at nanowire axis, what generates a square

ab–initio framework. We studied the effects

nanotube; c) Schematic projection of

very different stress gradients on the

observed along [0100] direction.

12 | Activity Report 2009

the hollow square silver nanowire when

Science Highlights

structures formed during stretching. Our simulations revealed that the elongation of a one–lattice–parameter–wide fcc Ag rod does not evolve to form the hollow wires. As the size and shape of the basis affect the stress redistribution during the elongation process, we analyzed the next thicker square–section Ag nanowire, which is expect to form due to surface energy minimization. 5 This wire is 1.5 lattice parameter wide and, it should be formed by the stacking of two different planes containing 8 atoms (8A/8B stacking, see Figure 3, Inset). It is important to not

Figure 3.

Molecular simulation of the elongation of a slightly thicker silver wire generated by the stacking of two planes

that both atomic planes can be easily

containing eight atoms each (8A/8B stacking, see Inset).

decomposed in 2 squares containing

stacking required to generate the tubular structure (see

4 atoms. This means that each of these

Under high stress regime, the wire evolves to a 4/4 text for explanations); to help the interpretation of atomic planes formed by 4 atoms are highlighted in black.

planes can easily split into the 4/4 stacking required to form the tubular wire observed in the experiments. Further simulations, revealed that under conditions of high stress regime (elongation step 0.5 Å) and, the 8/8 silver rod spontaneously evolved to hollow structures (4/4 stacking), generating an atomic arrangement fully consistent with the ones experimentally revealed.

minimum basis size and high gradient stress. The tubular structure represents an atomic arrangement that to both minimize surface energy and generate a very deformable structure. This extremely soft hollow nanowire allows the absorption of a huge elongation with a minimal

In summary, we have unraveled the

energy cost. From the point of view of

spontaneous formation of the smallest

nanomechanics, these results demonstrate

possible, just one–lattice–parameter–wide,

that the modeling of mechanical deformation

square metal nanotube during Ag nanowire

at nanoscale must take into account

stretching. Our theoretical calculations

anomalous metastable structures of the

indicate that the formation of a silver

high symmetry that provide lower energy

nanotube requires a combination of

pathways during stretching.

Activity Report 2009 | 13

Observation of the Smallest Square Cross-section Metal Nanotube

References 1. Alloca, C.; Smith, D. Instrumentation and metrology for nanomechanics. In: INSTRUMENTATION AND METROLOGY FOR NANOTECHNOLOGY. REPORT OF THE NATIONAL NANOTECHNOLOGY INITIATIVE WORKSHOP, 2004, Gaithesburg. Proceedings… Gaithesburg, NIST/NNCO, 2004. Disponível em < http://www.nano.gov/NNI_Instrumentation_Metrology_rpt.pdf>. 2. Agraït, N.; Yeyati, A. L.; van Ruitenbeek, J. M. Quantum properties of atomic-sized conductors. Physics Reports, v. 377, n. 2–3, p. 81–279, Q13, 2003. 3. Kondo, Y.; Takayanagi, K. Gold nanobridge stabilized by surface structure. Physica l Review Let ters, v. 79, n. 18, p. 3455–3458, 1997. 4. Lagos, M. J. et al. Observation of the smallest metal nanotubewith a square cross-section. Nat ure Nanotechnology, v. 4, n. 3, p. 149-152, 2009. 5. Marks, L. D. Experimental studies of small-particle structures. Reports on Progress in Physics, v. 57, n. 6, p. 603–649, 1994. 6. Bettini, J. et al. Experimental realization of suspended atomic chains composed of different atomic species. Nat u re Nanotechnology, v. 1, n. 3, p. 182-185, 2006. 7. Sanchez-Portal, D. et al. Density-functional method for very large systems with LCAO basis sets. Internationa l Jou rna l of Quant um Chemistr y, v. 65, n. 5, p. 453–461, 1997. 8. Soler, J. M. et al. The SIESTA method for ab initio order-N materials simulation. Jou rna l of Physics: Condensed Matter, v. 14, n. 11, p. 2745–2779, 2002. 9. Rodrigues et al. Size limit of defect formation in pyramidal Pt nanocontacts. Physica l Review Let ters, v. 99, n. 25, 255501, 2007.

14 | Activity Report 2009

Unveiling the Chemical and Morphological Features of Sb:SnO2 Nanocrystals by the Combined Use of HRTEM and Ab Initio Surface Energy Calculations Daniel G. Stroppa,1 Luciano A. Montoro,1 Armando Beltrán,2 Tiago G. Conti,3 Rafael O. da Silva,3 Juan Andrés,2 Elson Longo,3 Edson R. Leite,3 Antonio J. Ramirez1

Brazilian Synchrotron Light Laboratory, 13.083-970, Campinas, SP, Brazil

Departament de Química Física i Analítica, Universitat Jaume I, 12071,

Castellón de la Plana, Spain Department of Chemistry, Federal University of São Carlos – UFSCar,

13.565-905, São Carlos, SP, Brazil

Modeling of nanocrystals supported by advanced morphological and chemical characterization is a unique tool for the development of reliable nanostructured devices, which depends on the ability to synthesize and characterize materials on the atomic scale. Among the most significant challenges in nanostructural characterization is the evaluation of crystal growth mechanisms and their dependence on the shape of nanoparticles and the distribution of doping elements. This work presents a new strategy to characterize nanocrystals, applied here to antimony‑doped tin oxide (Sb‑SnO2) (ATO) by the combined use of experimental and simulated high‑resolution transmission electron microscopy (HRTEM) images and surface energy ab initio calculations. The results show that the Wulff construction can not only describe the shape of nanocrystals as a function of surface energy distribution but also retrieve quantitative information on dopant distribution by the dimensional analysis of nanoparticle shapes. In addition, a novel three-dimensional evaluation of an oriented attachment growth mechanism is provided in the proposed methodology. This procedure is a useful approach for faceted nanocrystal shape modeling and indirect quantitative evaluation of dopant spatial distribution, which are difficult to evaluate by other techniques.

Facility: C2nano Publication: Journal of the American Chemical Society, 131: 14544–14548 (2009) Funding: Fapesp, CNPq, Finep

Unveiling the Chemical and Morphological Features of Sb:SnO2 Nanocrystals by the Combined Use of HRTEM and Ab Initio Surface Energy Calculations

Modeling of nanocrystals supported by

a novel three–dimensional evaluation of an

advanced morphological and chemical

oriented attachment growth mechanism

characterization is a unique tool for the

is provided in the proposed methodology.

development of reliable nanostructured

This procedure is a useful approach for

devices, which depends on the ability to

faceted nanocrystal shape modeling and

synthesize and characterize materials

indirect quantitative evaluation of dopant

on the atomic scale. Among the most

spatial distribution, which are difficult to

significant challenges in nanostructural

evaluate by other techniques.

characterization is the evaluation of crystal

The Antimony–doped Tin Oxide (Sb:SnO2)

growth mechanisms and their dependence

(ATO) nanocrystalline system was chosen

on the shape of nanoparticles and the

for this work because of the limitations

distribution of doping elements.

for its comprehensive characterization by

In recent years, advanced tools have been

conventional and advanced techniques. 6

developed for nanocrystal characterization

These limitations are due to the reduced

in order to obtain accurate chemical,

dimensions, small difference between

structural and morphological information,

the atomic weight of Sn and Sb, and the

such as crystallographic habit, surface

structural and chemical instability of these

chemistry, and growth mechanisms

nanoparticles, which preclude long–duration

from self–assembled arrangements.

TEM and/or STEM analyses, for example.

Although a number of techniques based

However, the proposed methodology

on X–ray,1 scanning probe microscopy,2

should not be seen as exclusive to the

and transmission electron microscopy

3–5

study of ATO system, for it can also be

have been successfully applied to retrieve

applied to other faceted–nanostructured

compositional and morphological

crystalline systems.

information about nanostructures, several

The ATO nanocrystals were synthesized

challenges still remain, especially with

in a glovebox under a controlled atmosphere

regard to three–dimensional reconstruction

by the benzyl alcohol method. 7 TEM

and chemical mapping.

samples were prepared by dripping

This paper presents a new strategy to

diluted ATO solution onto copper grids

characterize nanocrystals, applied here

covered with a thin amorphous carbon

to Antimony–doped Tin Oxide (ATO) by

film (~ 5 nm). HRTEM characterization

the combined use of experimental and

was performed using a JEM–3010 URP

simulated high–resolution transmission

TEM at 300 kV with a LaB 6 electron

electron microscopy (HRTEM) images and

gun and equipped with a 1024 × 1024

surface energy ab initio calculations. The

thermoelectrically cooled CCD camera

results show that the Wulff construction can

and a XEDS detector. Wulff construction 8

not only describe the shape of nanocrystals

was applied to build theoretical crystals

as a function of surface energy distribution

by using the ab initio calculated surface

but also retrieve quantitative information

energies and the SnO2 P42/mnm crystal

on dopant distribution by the dimensional

structure. HRTEM multislice simulated

analysis of nanoparticle shapes. In addition,

images of theoretical ATO nanocrystals

16 | Activity Report 2009

Science Highlights

were obtained using JEMS software. 9

with a mean length of 4.2 nm, mean width

Surface energy calculations

for ATO

of 3.2 nm and mean aspect ratio of 1.3.

nanocrystals were performed with the

The HRTEM analysis of ATO samples

CRYSTAL06 program package.

indicated the formation of faceted

A preliminar y cr ystallographic

nanocrystals for a significant number

characterization by XRD and Electron

of particles, as illustrated in Figure 1a–b.

Diffraction showed that ATO samples were

Figure 1c shows a representative HRTEM

constituted of highly crystalline nanocrystals

image of ATO samples and the Fast–Fourier

with SnO2 cassiterite tetragonal structure.

Transform (FFT), which indicates the

The presence of broad XRD peaks indicate

particle orientation along the [111] zone

small crystalline domains with dimensions

axis. An HRTEM multislice simulation of

of approximately 5 and 4 nm for (110) and

SnO2 P42/mnm crystal structure under the

(101) planes, respectively, as evaluated

experimental image conditions is shown

by Scherrer’s equation, suggesting the

in Figure 1c (dashed box). It is important to

presence of elongated crystals.

point out that the morphological features of

HRTEM images show that the nonaqueous synthesis route produces

the ATO nanocrystals are directly related to the distribution of Sb dopant.

highly dispersed and crystalline ATO

A hypothetical nanocrystal shape

nanoparticles, as presented in Figure 1a.

was proposed based on projected

The evaluation of size distribution shown

two–dimensional HRTEM image of ATO

in Figure 1b reveals elongated particles

nanocrystals observed along the [111] zone

Figure 1.

Typical HRTEM image of ATO nanocrystals and size distribution histogram. a) HRTEM image of representative ATO (Sb:SnO2) nanocrystals, where the inset shows the electron diffraction pattern and the dashed lines exemplify the measured length and width; and b) Size distribution histogram. The inset text indicates the mean sizes with their respective standard deviations and the aspect ratio for a total count of 200 particles.

Activity Report 2009 | 17

Unveiling the Chemical and Morphological Features of Sb:SnO2 Nanocrystals by the Combined Use of HRTEM and Ab Initio Surface Energy Calculations

Figure 2.

HRTEM images of ATO nanocrystals. a–b) HRTEM images of faceted ATO (Sb:SnO2) nanocrystals, showing oriented attachment growth. The red dashed lines highlight the projected facet boundaries; and c) HRTEM image of faceted ATO nanocrystal. The dashed box indicates the superimposed image of the simulated HRTEM multislice. The inset shows the Fast–Fourier Transform, which indicates the particle alignment along the [111] zone–axis.

axis. The actual HRTEM images provide a

the exact number of atomic columns on the oriented ATO nanocrystals, and hence provide precise information regarding their projected dimensions. In this specific case, the exposed (100), (110), (111) and (101) facets were successfully reconstructed based on the HRTEM image of the particles

due to the tetragonal crystalline structure symmetry on the [111] zone axis. Only the possibly exposed (001) facet could not be directly evaluated because it does not substantially modify the projected dimensions of the ATO nanoparticles HRTEM image when observed along the [111] zone axis. However, simulated HRTEM

Figure 3.

Proposed and actual ATO nanocrystals observed along the [111] zone axis. a) proposed ATO (Sb:SnO2) nanocrystal habit

images of the proposed nanocrystals atomic

superimposed on its Wulff construction; b) Multislice simulated

arrangements provided information about

HRTEM image obtained from the proposed nanocrystal habit;

all the facets considered. Figures 3a–b

c) Comparison of the nanocrystal multislice simulated HRTEM nanocrystal image; and d) the experimental HRTEM image.

18 | Activity Report 2009

present the proposed ATO nanocrystal

Science Highlights

atomic arrangement with a superimposed Wulff construction and the multislice simulated HRTEM image, respectively. Figure 3c and d compares the nanocrystal multislice simulated HRTEM image (left inset) and the experimental image (right). The remarkable agreement between the images supports the proposed nanocrystal habit. The remarkable agreement between the images supports the proposed nanocrystal habit. According to Wulffâ&#x20AC;&#x2122;s rule, 8 which determines the equilibrium crystal shape by minimizing surface energy for a given

Figure 4.

Surface energies for different Sb contents and Wulff constructed nanocrystals for each dopant content considering

enclosed volume, the crystal morphology

a homogeneous Sb distribution. The

can be thermodynamically predicted using

surface energies for the selected crystalline

the surface energy of different facets. Thus, the crystal shape can be derived

Figure shows the ab initio calculated planes with different Sb contents. The facets on the constructed Wulff crystals are indicated by a color code.

from a geometrical construction where the distance of the facet from an arbitrary

systems. Therefore, both qualitative and

origin is proportional to the respective

quantitative information can be extracted

crystallographic plane surface energy.

from HRTEM images of faceted and

The ab initio calculated surface energies

crystalline nanosystems by evaluating

for different crystalline planes and Sb

the aspect ratio for different crystalline

concentrations are presented in Figure 4, as

planes within the Wulff construction.

well as the Wulff construction for different

The dimensional analysis of the

Sb contents. Due to the substitutional

proposed ATO nanocrystal indicates the

character of Sb in the ATO structure,

surface energy ratio for the different exposed

the dopant concentration is quantized

crystallographic planes of the experimental

according to available exposed sites.

ATO nanocrystals. Therefore, a comparison

The results of the calculations shown

of these surface energy values and the

in Figure 4 indicate that the surface

ab initio calculated ones provides the

energy for different exposed crystalline

dopant content on those exposed facets.

planes is highly dependent on the Sb

Table 1 presents the absolute distances of

concentration, leading to the dependence

the proposed Wulff-constructed facets of

of the nanocrystal habit on the dopant

the ATO nanocrystal, the surface energy

content. In addition, preferential segregation

values, and the estimated Sb content

towards different exposed crystalline

for the exposed crystalline planes. Both

planes can be inferred due to modifications

surface energy and dopant content of

of the nanocrystal habit as a function of

each facet were evaluated using the Wulff

dopant content, especially in highly doped

construction dimensions, the mean Sb

Activity Report 2009 | 19

Unveiling the Chemical and Morphological Features of Sb:SnO2 Nanocrystals by the Combined Use of HRTEM and Ab Initio Surface Energy Calculations

Table 1.

Evaluation of surface energy and Sb content for the proposed ATO nanocrystal habit

Exposed Plane

Distance (nm)

Surface Energy (J/m2)

%AtomSb

(001)

1.73

4.65

8.0

(101)

2.08

5.54

14.2

(100)

1.90

5.18

15.3

(110)

2.50

6.87

16.1

(110) facets and a dopant depletion at the (001) facets of the ATO nanocrystals. As previously shown, the ATO nanocrystal self–assembling process occurs through oriented attachment (OA) growth.11 OA is a statistical process related to the collision rate among nanocrystals in suspension and to the reduction of surface energy driven by the area minimization of high–energy

facets. It has been recently reported as the predominant growth mechanism for an increasing number of materials and has called the attention of scientists as a suitable technique for processing mesocrystals and anisotropic nanomaterials.12 Figure 2b shows a pair of coalesced ATO nanocrystals, self–organized through

OA growth. This oriented ensemble was evaluated using the previously proposed nanocrystal model and simulated HRTEM images in order to investigate the OA growth mechanism. Figures 5a–b present the atomic arrangement of an ATO nanocrystal ensemble superimposed with its Wulff construction and the results

Figure 5.

Proposed ATO nanocrystal ensemble and its simulated HRTEM image. a) Atomic arrangement of the ATO

of HRTEM multislice image simulation,

(Sb:SnO 2) nanocrystal ensemble superimposed on its

respectively. Figure 5c compares the

Wulff construction. b) Multislice simulated HRTEM image obtained from the proposed nanocr ystal ensemble. c) Comparison of the simulated nanocrystal image and d) the experimental image.

multislice simulated HRTEM image of the ensemble (left inset) and the experimental image (right). The remarkable agreement between

content retrieved by XEDS measurements,

the experimental HRTEM image and the

and ab initio calculated surface energies.

simulated image of the proposed ATO

Finally, the estimated Sb concentrations

nanocrystal assembly allows for an

of the exposed facets of the proposed

accurate evaluation of the OA mechanism.

ATO nanocrystal were quantized based

The [100] and [101] were observed as the

on the available Sn atomic sites on these

preferential growth directions for the ATO

crystallographic planes. This evaluation

nanoparticles. Figure 5c corresponds to an

of the Sb content on the exposed facets,

example of (100) facet oriented attachment.

presented in Table 1, indicates a preferential

The OA growth process along the [100]

segregation of Sb towards the (100) and

and [101] directions is congruent with the

20 | Activity Report 2009

Science Highlights

predicted attachment configurations and

effort and/or would be restricted by

with the higher expected collision rate

system dimensions and/or small atomic

for the (100) and (101) facets as a result

weight differences between the material

of their larger exposed facet area. In the

elements.10

proposed nanocrystal habit, more than 78% of the total surface area corresponds to (100) and (101) facets. The combined use of HRTEM characterization, HRTEM image multislice simulation and ab initio calculations provided information on the 3D habit and surface chemical composition of faceted nanocrystals by correlation of the crystal

In addition, the combined use of surface energy ab initio calculations and Wulff construction applied to nanocrystal modeling was applied successfully to study the oriented attachment growth mechanism in ATO nanocrystals, and can be used to carry out such studies in a number of nanostructured systems.

faceting and the dopant–dependent surface

Modeling hypothetical nanocrystals as

energy of exposed facets.

building blocks with known surface

Conclusion Remarks. Based on

energy distribution and faceting enables

indirect quantitative measurements, this

one to produce a three–dimensional

methodology is a novel approach for the

description of the oriented attachment

evaluation of surface dopant distribution

growth mechanism, which can be further

on nanoparticles. It is a powerful tool for

investigated by HRTEM imaging and

the analysis of nanocrystals, where usual

HRTEM multislice image simulation.

quantitative techniques such as X–ray Photoelectron Spectroscopy (XPS), X–ray Energy Dispersive Spectroscopy (XEDS),

Acknowledgements

High Angle Annular Dark Field (HAADF),

The authors acknowledge the financial

and Electron Energy Loss Spectroscopy

support of the Brazilian research funding

(EELS) would require a much greater

agencies FAPESP, CNPq, and FINEP.

Activity Report 2009 | 21

Unveiling the Chemical and Morphological Features of Sb:SnO2 Nanocrystals by the Combined Use of HRTEM and Ab Initio Surface Energy Calculations

References 1. Renaud, G. et al. Real-time monitoring of growing nanoparticles. Science, v. 300, n. 5624, p. 1416‑1419, 2003. 2. Morales, E. H. et al. Surface structure of Sn-doped In2O3 (111) thin films by STM. New Journa l of Physics, v. 10, n. 12, 125030, 2008. 3. Ferrer, D. et al. Three-layer core/shell structure in Au−Pd bimetallic nanoparticles. Nano Let ters, v. 7, n. 6, p. 1701-1705, 2007. 4. Muller, D. A. et al. Atomic-scale chemical imaging of composition and bonding by aberrationcorrected microscopy. Science, v. 319, n. 5866, p. 1073-1076, 2008. 5. Jia, C. L.; Urban, K. Atomic-resolution measurement of oxygen concentration in oxide materials. Science, v. 303, n. 5666, p. 2001-2004, 2004. 6. Sun, K.; Liu, J.; Browning, N. D. Correlated atomic resolution microscopy and spectroscopy studies of Sn (Sb)O2 nanophase catalysts. Jou rna l of Cataysis, v. 205, n. 2, p. 266-277, 2002. 7. Niederberger, M.; Gartweitner, G. Organic reaction pathways in the nonaqueous synthesis of metal oxide nanoparticles. Chemistr y: A European Journal, v. 12, n. 28, p. 7282-7302, 2006. 8. Herring, C. Some theorems on the free energies of crystal surfaces. Physica l Review, v. 82, n.1, p. 87-93,1951. 9. Stadelmann, P. A. EMS - a software package for electron diffraction analysis and HREM image simulation in materials science. Ultramicroscopy, v. 21, n. 2, p.131-145, 1987. 10. Beltrán, A. et al. Thermodynamic argument about SnO2 nanoribbon growth Applied Physics Let ters, v. 83, n. 4, p. 635-637, 2003. 11. Penn, R. L.; Banfield, J. F. Imperfect oriented attachment: dislocation generation in defect-free nanocrystals. Science, v. 281, n. 5379, p. 969-971,1998. 12. Meldrum, F. C.; Colfen, H. Controlling mineral morphologies and structures in biological and synthetic systems. Chemica l Reviews, v. 108, n. 11, p. 4332-4432, 2008.

22 | Activity Report 2009

Controlled Deposition of Silver Nanoparticles in Mesoporous Thin Films: Towards New Metallic–oxide Nanocomposites

María Cecilia Fuertes,1 Martín Marchena,1 Alejandro Wolosiuk,1,2 Galo Juan de Avila Arturo Soler-Illia1,2

Gerencia de Química, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica,

Av. Gral Paz 1499 (B1650KNA) San Martín, Buenos Aires, Argentina 2

Departamento de Química Inorgánica, Analítica y Química Física – DQIAQF,

Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria Pab. II, C1428EHA, Buenos Aires, Argentina

Metal–oxide nanocomposites made up of Ag nanoparticle (NP) assemblies embedded within mesoporous oxide thin films were produced by mild reduction of Ag + adsorbed onto the pore surface. The nanocomposites were characterized by Small Angle X–ray Scattering (2D SAXS, D03A SAXS2) and X–ray Reflectometry (XRR, D10A XRD2). A quantitative method based in XRR was developed in order to assess pore filling. Inclusion of Ag NP assemblies in mesoporous SiO2 or TiO2 requires different processing conditions. The difference of reactivity of both oxide matrices towards Ag+ reduction is exploited to selectively synthesize NPs in a pre–determined layer of a multilayered mesoporous stack. This leads to highly controlled 1D ordered multilayers with precise spatial location of nanometric objects.

Facility: XRD2, SAXS2, C2nano Publication: Small, 5: 272–280 (2009) Funding: CONICET, ANPCyT, MCT

Controlled Deposition of Silver Nanoparticles in Mesoporous Thin Films: Towards New Metallic-oxide Nanocomposites

The synthesis of controlled film–

MOTF were deposited by dip–coating

supported nanocomposite systems

glass substrates using water/ethanol

constitutes one of the most active fields

acidic solutions containing an inorganic

in nanotechnology. The rational design

precursor (TiCl4 or Si(OEt)4) and a pore

of these materials holds a promise for

template (cationic surfactant CTAB or

obtaining integrated devices for a diversity

block–copolymers: Brij58 and Pluronics

of applications. Mesoporous Oxide Thin

F127). Each surfactant provides a different

Films (MOTF) represent attractive template

pore size and pore ordering. 3 After

matrices for the inclusion of isolated

deposition, films were stabilized and

or interacting metal nanoparticles (NP),

calcined at 350 °C for 2 hours. Ag NPs

permitting to fully exploit their optical,

were deposited within single MOTF or

electronic or catalytic properties. The

multilayered stacks through an electroless

nano–derived properties are due to the metal

deposition reaction, using a 1:1 (mass ratio)

NP dimensions, confinement, interfacial

water:ethanol mixture of AgNO3 0.05 M

effects and the possibility to combine the

and a formaldehyde (HCHO) solution.

accessibility of the mesopore system and

Film thickness and electronic density

the protective properties of the matrix. A

were obtained from XRR measurements

variety of metallic or semiconductor NP

(λ = 1.5498 Å); film mesostructure was

have been embedded in mesoporous

analyzed using Small Angle X–ray Scattering

powders or thin films.1,2 An accurate control

with 2D detection (λ = 1.608 Å). Both

of NP size and pore filling is needed in

techniques were performed at LNLS.

order to control size–derived effects such

Transmission Electron Microscopy (TEM)

as electron transfer, surface plasmon

images were obtained with a Philips EM

resonance, fluorescence enhancement

301 microscope operating at 60 kV.

or surface–enhanced Raman scattering.

Figure 1a shows a TEM image of an

Consequently, non–destructive methods

F127–templated TiO 2 film where both

that permit to evaluate the actual metal

the mesostructure and uniform pore

loading inside the film are needed to

size can be clearly observed. The inset

better characterize these systems, and

shows the characteristic Im3m 2D–SAXS

understand their formation paths.

pattern from the same sample evidencing

In this work, we present a straightforward

the remarkable long range pore order.

approach for quantifying the filling of

Figure 1b shows a TEM micrograph of

mesoporous films with metallic NP using

Ag NPs synthesized within the TiO2 layer

X–ray reflectometry (XRR). This method

using HCHO as the reducing agent. The

permits to monitor the formation of Ag NP

NPs are 8–10 nm diameter, which is in

within a mesopore network, and hence to

good agreement with the known pore

control the pore fraction occupied by the NP.

dimensions of the F127 templated films

In addition, we demonstrate the possibility to

along the xy plane. The mesoporous matrix

determine the spatial localization of metallic

permits an homogeneous distribution of

NP inside a multilayer structure composed

NP with controlled maximum size inside

of different mesoporous oxides.

the MOTF.

24 | Activity Report 2009

Science Highlights

Figure 1.

Scheme of NP production within mesopores. a) TEM before and b) after Ag NP production inside mesoporous TiO2. Inset in (a) shows 2D SAXS (3° incidence) data typical of an Im3m cubic mesophase.

Despite the ample literature regarding metallic infiltration in mesostructured

volume fraction of mesopores, Fp, can be estimated as:

ordered films, no rigorous quantification of the metal loading in these systems has been informed. Analytical techniques

FP = 1−

ρfilm ρframework

(2)

such as EDS give an overall idea of film

where ρfilm is the electronic density of the

composition, but no details about NPs

mesoporous film and ρframework the electronic

location. In this context, XRR allows the

density of a non–mesoporous film with

simultaneous and direct determination of

the same composition.

density, thickness and interfacial roughness

Figure 2 shows the evolution of XRR

of thin films from the reflectivity intensity

data along reaction time for TiO2 or SiO2

variations with the X–ray incident angle.4

mesoporous films in contact with aqueous

The reflectivity critical angle θc measured

Ag+/HCHO solutions. Figure 2a shows a

allows determining the electronic density of the film, ρel, using:

ρel =

π 2 θc λ re 2

significant and continuous increase in the measured θc for Brij 58–templated TiO2 films along reaction time. This implies that

(1)

the electronic density of the TiO2 porous film increases as Ag NPs are formed

where λ is the X–ray wavelength and re

inside the film. The θc values are close to

is the classical radius of the electron.

the porous titania values, and significantly

From the calculation of the ρel for both a

lower than those corresponding to pure

mesoporous and a non–porous film, the

Ag (θ c ~ 0.44°). In addition, no change Activity Report 2009 | 25

Controlled Deposition of Silver Nanoparticles in Mesoporous Thin Films: Towards New Metallic-oxide Nanocomposites

in the Kiessig interference spacing is a

observed, albeit the fringe amplitude decreases. These features imply that silver NP are continuously incorporated

within the mesopores, rather than forming a continuous film on top of the TiO2 film. The incorporation of Ag can be tracked by assessing the evolution of film density by following the changes in the θc with the Ag infiltration time. Figure 2d shows the time evolution of the reflectivity (θc region) for a CTAB–templated

SiO 2 mesoporous film in contact with the Ag+/HCHO solution. As opposed to TiO2 films, no significant changes in the SiO2–θc are observed, showing that the

film density remains almost unaltered within the reduction reaction time. Figure 2b shows a 2D–SAXS image at 90° incidence of TiO 2 mesoporous film before the silver infiltration process. The ring observed corresponds to the [110] in–plane pores of an Im3m cubic structure. After reaction in the Ag+/HCHO solution, the signal diminishes (Figure 2c) and, as the Ag+ concentration and time reduction increases, finally disappears. This effect is due to the random NP formation within the TiO2 pores, disrupting the periodic electronic density long–order structure, which is the origin of the diffraction signal. In addition, the signal intensity increases at low q values, probably due to

Figure 2.

Low–angle XRR patterns of mesoporous a) titania, and b) silica thin films exposed to Ag reduction for increasing periods. The arrows indicate the change in the critical angle θc. 2D SAXS patterns (90° incidence) of mesoporous TiO2 b) before and c) after silver infiltration. 2D SAXS patterns of mesoporous SiO2 e) before and f) after silver infiltration. g) Volume fraction of the pore system occupied by silver for each oxide, calculated from Equation 4. Dotted lines were added for eye guiding. Please note that the θc observed at 2θ =0.468° in (b) corresponds to the glass substrate.

26 | Activity Report 2009

the low–angle X–ray scattering produced by the Ag NPs. On the other hand, the signal intensity for the SiO2 layer does not change after the reduction reaction (Figures 2e–f), confirming that the Ag NP formation is strongly dependent of the inorganic framework.

Science Highlights

XRR can also be used to fully quantify

deposit Ag NP preferentially in the TiO2

the amount of silver present inside the

mesopores of a bilayered or multilayered

pores. Considering that the increase in

system composed of TiO 2 and SiO 2

film density is only due to the presence

layers. Figure 3a shows the XRR data

of metal, the silver volume fraction FAg

of a substrate/TiO2/SiO 2 mesoporous

within the film can be determined from

bilayer at different Ag reduction times.

the measured electronic densities:

No changes are observed for the θ c of the silica layer along reduction; however,

FAg =

ρfilm + Ag − ρfilm ρAg

(3)

already observed in TiO2 single layer

where ρfilm+Ag is the electronic density of Ag–filled film, ρfilm is the electronic density of the empty mesoporous film and ρAg is the silver electronic density. The mesopore filling fraction at each infiltration time can be defined as the ratio between the silver volume fraction and the pore volume fraction:

R Ag (t) =

the TiO2–θc increases in a similar way as films. The preferential deposition of Ag NP within the titania mesopores alters dramatically the electronic density of the TiO2 film inside the bilayered stack (scheme in Figure 3e). Additional XRR experiments performed in the presence of water vapors confirm accessibility of the pore systems after Ag infiltration. The 2D SAXS signal from the bilayer

FAg (t) FP

(4)

before the infiltration is shown in Figure 3b. Two distinctive rings are observed, corresponding to the [110] in–plane pores

Figure 2g shows the evolution of the

of two different Im3m cubic structures. The

mesopore filling fraction with Ag+ reduction

lower–angle diffraction signal reflects the

time calculated using Equation 4 for

F127–SiO2 mesostructure (cubic parameter

the systems described above. It can be

a = 18.5 nm) and the outer circle corresponds

observed that a plateau is reached by

to the Brij58–TiO2 characteristic mesoporous

50–55% relative volume filling for TiO2

distance (a = 9.1 nm). After reaction in

films, while SiO2 shows filling fractions

the Ag+/HCHO solution (Figure 3c), the

well below 5%. This limit might be due to

TiO2 mesoporous signal disappears but

partial pore blocking by silver NP. The

the intensity for the SiO2 layer does not

silver–loaded titania films present remaining

change, confirming the clear different

accessible porosity, as confirmed with

behaviors of both oxide layers with

additional XRR experiments (not shown) in

respect to Ag NPs synthesis. The same

which the Ag–filled films were submitted

effect was observed by transmission 2D

to water vapor, and an increase in the

SAXS in photonic multilayered structures

critical angle was observed due to water

built using alternating TiO 2 and SiO 2

condensation.

mesoporous films.

The different reactivity of silica and

Figure 3d shows the time evolution

titania systems towards the Ag+/HCHO

of the silver filling in both oxides of the

systems can be exploited in order to

mesoporous bilayer. No production of Ag

Activity Report 2009 | 27

Controlled Deposition of Silver Nanoparticles in Mesoporous Thin Films: Towards New Metallic-oxide Nanocomposites

nanoparticles occurs in the SiO2 layer, but the TiO2 layer presents a plateau again, at approximately the same values obtained for the TiO2 single layer. Therefore, we

can conclude that each layer presents an independent chemical behavior in this particular bilayer system. The topmost SiO2 non reacting film is fully accessible and allows the diffusion of reactants to the TiO2 layer underneath, suggesting the possibility to design a “smart” coating for

an integrated nanodevice5,6. In conclusion, this work describes a chemical method to control the production of Ag/MOTF nanocomposites presenting spatially defined arrays of homogeneously distributed monodisperse nanoparticles. XRR and SAXS methods afford quantitative information about the Ag NP formation process in single and multilayered stacks. Formaldehyde oxidation proceeds at different rates in different MOTF matrices; this different reactivity on different oxide surfaces can be exploited in order to control the selective deposition of Ag NP within the titania layers in bilayered

Figure 3.

a) Low–angle XRR patterns of mesoporous TiO 2/SiO 2 bilayer exposed to Ag reduction for increasing periods.

or multilayered MOTF stacks in a single

The arrows indicate the change in the critical angle θc. 2D

and mild chemical step. We envision the

SAXS patterns (90° incidence) of mesoporous TiO2/SiO2

design of tailored multilayers with varying

bilayer b) before and c) after silver infiltration. d) Volume fraction of the pore system occupied by silver for each oxide, calculated from Equation 4. The dotted lines were added for eye guiding. e) Scheme of NP production only within the TiO2 mesoporous film.

28 | Activity Report 2009

and controlled Ag NP fractions and empty responsive layers for advanced optical devices and sensors.

Science Highlights

References 1. (a) Zhang, S. B. et al. One-pot synthesis of Ni-nanoparticle-embedded mesoporous titania/silica catalyst and its application for CO2-reforming of methane. Catalalysis Communications, v. 9, n. 6, p. 995-1000, 2008.

(b) Pérez, M. D. et al. Growth of gold nanoparticle arrays in TiO2 mesoporous matrixes. Langmuir, v. 20, n. 16, p. 6879-6886, 2004.

2. (a) Besson, S. et al. 3D quantum dot lattice inside mesoporous silica films. Nano Let ters, v. 2, n. 4, p. 409-414, 2002.

(b) Buso, D. et al. PbS-doped mesostructured silica films with high optical nonlinearity. Chemistr y of Materia ls, v. 17, n. 20, p. 4965-4970, 2005.

(c) Fukuoka, A. et al. Preferential oxidation of carbon monoxide catalyzed by platinum nanoparticles in mesoporous silica. Journal of the A merican Chemical Societ y, v. 12, n. 33, p. 10120‑10125, 2007.

(d) Wang, H. W. et al. Synthesis and photocatalysis of mesoporous anatase TiO2 powders incorporated Ag nanoparticles. Jou rna l of Physics and Chemistr y of Solids, v. 6, n. 2-3, p. 633-636, 2008.

(e) Wang, L. C. et al. Formation of Pd nanoparticles in surfactant-mesoporous silica composites and surfactant solutions. Microporous and Mesoporous Materia ls, v. 110, n. 2-3, p. 451‑460, 2008.

3. Fuertes, M. C. et al. Photonic crystals from ordered mesoporous thin-film functional building blocks. Advanced F unc tiona l Materia ls, v. 17, n. 8, p. 1247-1254, 2007. 4. Daillant, J.; Gibaud, A. (Eds.). X-ray and neutron ref lectivit y: principles and applications. Berlin: Springer, 2009. 348 p. 5. Angelome, P. C.; Fuertes; M. C.; Soler-Illia, G. J. A. A. Multifunctional, multilayer, multiscale: integrative synthesis of complex macroporous and mesoporous thin films with spatial separation of porosity and function. Advanced Materia ls, v. 18, n. 18, p. 2397-2402, 2006. 6. Martínez, E. D.; Bellino, M. G.; Soler-Illia, G. J. A. A. Patterned production of silver−mesoporous titania nanocomposite thin films using lithography-assisted metal reduction. ACS Applied Materia ls & Interfaces, v. 1, n. 4, p. 746-749, 2009.

Activity Report 2009 | 29

Uncovering Molecular Structural Mechanisms of Signaling Mediated by the Prion Protein

Sebastián A. Romano,1 Yraima Cordeiro,2 Luis M. T. da Rocha e Lima,2 Marilene H. Lopes,3 Jerson L. Silva,4 Débora Foguel,4 Rafael Linden1

Instituto de Biofísica, Universidade Federal do Rio de Janeiro – UFRJ, Rio de Janeiro, RJ, Brazil

Faculdade de Farmácia, Universidade Federal do Rio de Janeiro – UFRJ, Rio de Janeiro, RJ, Brazil 3

Instituto Ludwig de Pesquisa de Câncer, São Paulo, SP, Brazil

Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro – UFRJ, Rio de Janeiro, RJ, Brazil

The glycosylphosphatidylinositol (GPI)–anchored prion protein (PrPC), usually associated with neurodegenerative diseases, modulates various cellular responses and may scaffold multiprotein cell surface signaling complexes. Engagement of PrPC with the secretable cochaperone hop/ STI1 induces neurotrophic transmembrane signals through unknown molecular mechanisms. We addressed whether interaction of PrPC and hop/STI1 entails structural rearrangements relevant for signaling. Circular dichroism and fluorescence spectroscopy showed that PrPC:hop/ STI1 interaction triggers loss of PrP helical structures, involving at least a perturbation of the PrPC143–153 α–helix. Novel SAXS models revealed a significant C–terminal compaction of hop/STI1 when bound to PrPC. Differing from a recent dimeric model of human hop/STI1, both size exclusion chromatography and SAXS data support a monomeric form of free murine hop/STI1. Changes in the PrPC143–153 α–helix may engage the transmembrane signaling proteins laminin receptor precursor and neural cell adhesion molecule, both of which bind that domain of PrPC, and further ligands may be engaged by the tertiary structural changes of hop/STI1. These reciprocal structural modifications indicate a versatile mechanism for signaling mediated by PrPC:hop/STI1 interaction, consistent with the hypothesis that PrPC scaffolds multiprotein signaling complexes at the cell surface.

Facilities: SAXS1, SAXS2 Publication: FASEB Journal, 23: 4308-4316 (2009) Funding: CNPq, FAPERJ, CAPES and FAPESP

Science Highlights

Prion diseases are transmissible

a flexible random coil, whereas the

spongiform encephalopathies (TSEs), such

globular C–terminal half contains 3

as human Creutzfeldt–Jakob disease and

α–helices corresponding to aminoacid

bovine ‘mad cow disease’, that course with

residues 144–154, 173–194 and 200–228,

neurological symptoms and that, despite

interspersed with an antiparallel β–pleated

their low prevalence, are incurable and

sheet formed by β–strands at residues

invariably fatal. Histopathological analysis

128–131 and 161–164. A single disulfide

shows neurodegeneration, vacuolization

bond is found between cysteine residues 179

of brain tissue and deposits of insoluble,

and 214.2 PrPC modulates various functions

protease–resistant aggregates dubbed

of the nervous and immune systems,

‘prions’, for ‘proteinaceous–only infectious

including memory and inflammation;

particle’. The prions contain an abnormal

the proliferation, differentiation, and

form of an evolutionary conserved

sensitivity to programmed cell death

protein called ‘prion protein’ (PrPC), which

in various cell types; and the activity of

is particularly abundant in the brain.

numerous signal transduction pathways.

Conversion of the α–helix dominated PrP

In addition, PrPC trafficks both laterally

into a β–sheet enriched conformer leads,

between distinct plasma membrane

either by itself or combined with other still

domains, and along endocytic pathways,

unresolved molecules, to the formation of

on top of continuous, rapid recycling. Its

the pathogenic prions. Current hypothesis

trafficking is affected by several ligands

has it that the latter are responsible both

and, conversely, affects PrPC–mediated

for the neurodegeneration and for the

events. Such an extensive, and often

progression and transmission of the TSEs,

contradictory, data suggest that, rather than

because prions coerce into conformational

playing a specific role in a straightforward

conversion the normal PrP molecules of

signaling pathway, PrPC inserts as a wild

either the same or, through infection, of

card in a variety of functional processes.

a distinct subject.1 Nevertheless, major

We, therefore, proposed that PrPC may

unresolved issues in prion diseases

serve as a scaffolding protein in multiple

include the functions of PrP , as well as

sets of interactors at the cell surface.

the role of presumptive loss–of–function

Combined with its extensive trafficking,

pathogenic events due to conformational

the data indicate that PrPC is a dynamic

conversion of the normal protein.

cell surface platform for the assembly

Our group aims primarily at uncovering

of signaling modules, based on which

physiological functions of PrPC, which,

selective interactions with many ligands

apart from its role in disease, is an

and transmembrane signaling pathways

abundant component of the cell

translate into wide–range consequences

surface of several cell types besides

upon both physiology and behavior.3

nerve cells. PrPC is an N–glycosylated,

Several dozen putative ligands of the

glycophosphatidylinositol (GPI)–anchored

prion protein have been identified with

protein of 208–209 aminoacids (Figure 1a),

variable degrees of confidence. One of

the N–terminal half of which composes

the ligands with the strongest supporting

Activity Report 2009 | 31

Uncovering Molecular Structural Mechanisms of Signaling Mediated by the Prion Protein

evidence is the 66 kDa cochaperone hop/

secreted to the extracellular medium. When

STI1, which contains 9 tetratricopeptide

extracellular hop/STI1 engages the cell

repeats (TPRs), grouped in 3 globular

surface PrPC, various signal transduction

domains TPR1, TPR2a (the PrPC–binding

pathways are activated with robust

domain), and TPR2b, as well as 2 small

biological consequences. A major question

DP domains rich in aspartate–proline

in this context is how the engagement

repeats (Figure 1a). TPR1 and TPR2a

of the GPI–anchored PrPC, which lacks

had their structure resolved and contain

an intracellular domain, leads to signal

highly α–helical globular structures that

transduction (Figure 1b). The simplest

line a canal where binding sequences

explanation requires transmembrane

can lie in an extended form. Hop/STI1

partners of either PrPC or its ligand, or both,

has a well known intracellular function

thus forming higher order multiprotein

among the chaperone machinery that

signaling complexes at the cell surface.

controls the maturation and activation

The assembly of such complexes likely

of glucocorticoid receptors, but it is also

entails and depends on orchestrated

Figure 1.

a) Diagram of the sequences of PrPC and hop/STI1. Major domains are indicated together with relevant residue numbers: PrPC N–term = flexible random coil, C–term = globular domain; hop/STI1 TPR = tetratricopeptide repeats; DP = dipeptide repeats; b) The problem of PrP C–mediated signaling. The GPI–anchored PrPC does not have an intracellular domain to convey through the plasma membrane (PM) signals initiated by its binding to soluble extracellular hop/STI1; c) CD spectra of measured (light green line) and predicted (grey line) equimolar sample of hop/STI1:PrPC113–132, shown along with the measured (green line) and predicted (red line) spectra of an equimolar sample of PrPC:hop/STI1230–245. d) CD spectra of measured (grey line) and predicted (green line) equimolar sample of PrPC:hop/STI1, along with the spectrum predicted for an equimolar mixture of PrPC and hop/STI1 in the peptide–bound conformations (light green line). The spectra for the latter were obtained by subtracting the respective peptide contributions from the spectra shown in (a).

32 | Activity Report 2009

Science Highlights

cooperative allosteric structural changes

shows an allosteric effect of hop/STI1

that may propagate in the various partner

upon the region of the PrPC molecule that

proteins. To help examine the hypothesis

contains the binding sites for N–CAM and

that PrPC may scaffold cell surface signaling

LRP/LR (Figure 2e, f), both of which are

complexes, we addressed whether

well know transmembrane proteins that

interaction of PrP and hop/STI1 involves

are capable of signal transduction.6, 7

structural rearrangements relevant for

Data from small angle X–ray scattering

signaling, using recombinant wild–type

data for either hop/STI1 alone or the

and mutant mouse proteins, as well as

PrPC: hop/STI1 complex led to estimates

synthetic peptides PrP C113–128 and hop/

of both the molecular radius of gyration

STI1230–245, which contain the cognate

and the maximum molecular diameter of

binding sites of each protein.

PrPC: hop/STI1 which were smaller than

A combination of circular dichroism (CD)

those of hop/STI1 alone (Figure 3a, b).

and fluorescence spectroscopy showed

Results of size exclusion HPLC were also

changes in PrP induced by binding to

consistent with compaction of the binary

hop/STI1. Thus, when comparing the

complex as compared with hop/STI1

far‑ultraviolet CD spectrum of a 1:1 PrPC–hop/

alone. The data indicated that, despite the

STI1 mixture with the expected residue

presence of the flexible N–terminal tail of

number–weighted sum of the spectra

PrPC, the binding of PrPC to hop/STI1 entails

of the individual proteins, a reduction in

significant structural compaction.

CD peak deflection suggested a loss of

Averaged low resolution ab initio

α–helical structure (Figure 1d). There was a

models were produced with the GASBOR

large change in the spectrum of PrP C when

software, followed by rigid body modeling

mixed with its cognate hop/STI1 peptide,

of the full–length molecules using the

whereas little if any change was seen in

BUNCH software. As an approximation

the spectrum of hop/STI1 when mixed

in the absence of high resolution models

with its cognate PrPC peptide (Figure 1c).

of the full hop/STI1 protein, we used the

These data suggested a rearrangement

resolved structures of TPR1, TPR2a, and

of secondary structure in PrP

upon

the C–terminal globular domain of PrPC,

binding its ligand hop/STI1. Furthermore,

together with homology models for TPR2b,

titration of PrPC with the hop/STI1 peptide

DP1, and DP2 domains obtained using

led to to a decay of the intensity of the

the structure prediction server Lomets.

intrinsic fluorescence spectrum of up to

The domains were linked with dummy

80% at a 1:1 Molar ratio (Figure 2a, c). The

residue flexible chains. For the complex,

fluorescence spectrum of a construct

a proximity constraint was imposed

of PrPC containing only one Trp residue

between the binding sites of the proteins.

(Figure 2b), mixed with the cognate hop/

The volumetric and the full–length rigid

STI1 peptide, indicated that binding of the

body models agreed well (Figure 3c–f).

two proteins leads to structural changes

Aligning the model of hop/STI1 in the

in the first α–helix of PrPC (Figure 2d). This

PrP C–binding conformation with that

is of particular significance, because it

of free hop/STI1 indicates clustering

Activity Report 2009 | 33

Uncovering Molecular Structural Mechanisms of Signaling Mediated by the Prion Protein

Figure 2.

a) Diagram of pre–processed prion protein highlighting recognized functional and/or structural domains, showing the location of its 8 triptophan residues (W), and the location of sequences of residues containing the binding sites for hop/STI1, N–CAM and LRP/LR; b) A construction made for testing changes in the first α–helix of PrPC by intrinsic fluorescence measurements; c) Emission spectra of 2 µM free PrPC (black solid line), and PrPC: hop/STI1230–245 samples at 2:0.5 (orange solid line), 2:1 (green solid line), and 2:2 (red solid line) µM concentrations. Spectrum of 2 µM free hop/STI1230–245 (cyan solid line) is also shown. To demonstrate the saturation of the effect, we also show the spectra obtained by subtracting the spectral emission of 2 µM free hop/STI1230–245 from the emission of a 2:4 µM PrP C: hop/STI1230–245 sample to subtract the contribution from the excess peptide (blue solid line). All spectra were normalized by the maximum intensity of the free PrPC spectrum, i.e., 71230. Excitation was set at 280 nm. Inset: relative area of the spectra obtained during this hop/STI1230–245 titration, as a function of the STI1230–245: PrPC molar ratio; d) Same as in (c), but replacing PrPC (a) with PrPC95–231W98F (b) at a 5.5 µM concentration, exciting at 295 nm, and normalizing by the maximum intensity of the free PrPC95–231W98F spectrum, i.e., 32940. a.u. = arbitrary units; e, f) PYMOL depictions of the globular C–terminal of PrPC (residues 121–231), highlighting the binding domains of hop/STI1, N–CAM and LRP/LR as shown in (a).

34 | Activity Report 2009

Science Highlights

Figure 3.

a, b) SAXS data suggesting structural compaction as a consequence of hop/STI1:PrP C complex formation. a) Measured scattered intensity for hop/STI1 (red dots) and an equimolar sample of PrPC:hop/STI1 (blue dots), along with the corresponding GNOM fits (green lines) and BUNCH fits (black lines). Inset: linear fits to Guinier plots. Red dots, hop/STI1; blue dots, PrPC:hop/STI1; b) Pair distance distribution, p(r), calculated by GNOM, for hop/STI1 (red line) and the PrPC:hop/STI1 complex (blue line). Inset: Kratky plots for hop/STI1 (red dots) and PrPC:hop/STI1 (blue dots). Scattering intensities at 0 angle of both samples were matched before calculation of the Kratky plot to allow comparisons; c–f) BUNCH rigid body models (d, f) and superposition of these models with GASBOR volumetric models represented as gray spheres (c, e), for free hop/STI1 (c, d) and for the PrP C:hop/STI1 complex (e, f). Domain and flexible linker colors are as in Figure 1a. Binding sites PrPC113–132 and hop/STI1230–245 are highlighted in red. g) Alignment of free hop/STI1 (blue) and hop/STI1 in the PrPC–bound conformation (red), BUNCH models (PrPC omitted for clarity).

of the C–terminal portion of hop/STI1,

that has since been supported by other

which contains the TPR2a, TPR2b, and

investigators.8

DP2 domains. This is the result of the

The overall data show that binding

approximation of DP2 and TPR2a (the

of PrPC to its ligand hop/STI1 induces

PrPC–binding domain) to TPR2b, which

remodeling of both proteins. The structural

are otherwise outward oriented in the

rearrangement of PrPC involves at least

model of hop/STI1 alone (Figure 3g).

the domain containing binding sites for

In addition, and differing from a recent

two transmembrane proteins that underlie

dimeric model of human hop/STI1, both

PrP C–mediated signal transduction. In

size exclusion chromatography and SAXS

turn, the changes in the structure of the

data are consistent with a monomeric form

extracellular partner hop/STI1 may engage

of free murine hop/STI1, a conclusion

other signaling molecules among a large

Activity Report 2009 | 35

Uncovering Molecular Structural Mechanisms of Signaling Mediated by the Prion Protein

number of putative candidates identified

shown are consistent with both the idea

in an ongoing phage display screening

that PrPC dynamically scaffolds multiprotein

(T.A. Americo, M.H. Magdesian and R.

functional complexes composed of

Linden, unpublished). The identification of higherâ&#x20AC;&#x201C;order ligands of a cell surface molecular complex based on PrP :

various, cell type specific combinations of ligands,3 as well as with the possibility

hop/STI1 interaction may lead to an explanation of the variety of signals mediated by the prion protein. Furthermore, the approach taken in this study serves

that such multiprotein complexes may be involved in the pathogenesis of prion diseases, perhaps by imparting distinct pathological characteristics depending

as a paradigm to provide structural insight

on specific combinations of ligands of

into PrPCâ&#x20AC;&#x2018;mediated signal transduction

either normal or pathogenic forms of the

triggered by other ligands of PrPC. The data

prion protein.

References 1. Aguzzi, A.; Calella, A. M. Prions: protein aggregation and infectious diseases. Physiolog ica l Reviews, v. 89, n. 4, p. 1105-1152, 2009. 2. Zahn, R. et al. NMR solution structure of the human prion protein. Proceedings of the Nationa l Academy of Sciences of the United States of A merica, v. 97, n. 1, p. 145-50, 2000. 3. Linden, R. et al. Physiology of the prion protein. Physiologica l Reviews, v. 88, n. 2, p. 673-728, 2008. 4. Zanata, S. M. et al. Stress-inducible protein 1 is a cell surface ligand for cellular prion that triggers neuroprotection. EMBO Jou rna l, v. 21, n. 13, p. 3307-3316, 2002. 5. Romano, S. A. et al. Reciprocal remodeling upon binding of the prion protein to its signaling partner hop/STI1. FASEB Jou rna l, 23, n. 12, p. 4308-4316, 2009. 6. Hundt, C. et al. Identification of interaction domains of the prion protein with its 37-kDa/67-kDa laminin receptor. EMBO Jou rna l, v. 20, n. 21, p. 5876-5886, 2001. 7. Schmitt-Ulms, G. et al. Binding of neural cell adhesion molecules (N-CAMs) to the cellular prion protein. Jou rna l of Molec u lar Biology, v. 314, n. 5, p. 1209-1225, 2001. 8. Yi, F.; Doudevski, I.; Regan, L. HOP is a monomer: investigation of the oligomeric state of the co-chaperone HOP. Protein Science, v. 19, n.1, p.19-25, 2010.

36 | Activity Report 2009

Single Electrode Electrochemical Detection in Hybrid Poly(dimethylsiloxane)/Glass Multichannel Microdevices

Ney Henrique Moreira,1 André Luis de Jesus de Almeida,1 Maria Helena de Oliveira Piazzeta,1 Dosil Pereira de Jesus,2 Ariane Deblire, 3 Angelo Luiz Gobbia,1 José Alberto Fracassi da Silva3

Laboratório de Microfabricação, Laboratório Nacional de Luz Síncrotron,

Campinas, SP, Brazil 2

Instituto Nacional de Ciência e Tecnologia em Bioanalítica – INCTBio,

Campinas, SP, Brazil 3

Instituto de Química, Universidade Estadual de Campinas – UNICAMP,

Campinas, SP, Brazil

The fabrication process of a novel multichannel µTAS based on PDMS and glass materials and with fully–integrated electrodes for amperometric detection has been described. Using the Facilities of the Microfabrication Laboratory (LMF) at Brazilian Synchrotron Light Laboratory (LNLS), soft–lithography, lift–off and O2 plasma surface activation sealing techniques were employed for rapid prototyping of cost effective PDMS/glass microchips. Fast calibration procedures were possible for the electrooxidation of hydroquinone, thiocyanate, and acetaminophen using Au and Cu electrodes.

Facility: Lab. Microfabricação Publication: Lab on a Chip, 9: 115–121 (2009) Funding: CNPq, FAPESP

Single Electrode Electrochemical Detection in Hybrid Poly(dimethylsiloxane) / Glass Multichannel Microdevices

Introduction

substrates of few square centimeters.

This work describes the fabrication

The protocol of microfabrication depends

and characterization of a PDMS/glass

on the choice of the substrate and

multichannel microfluidic chip, with

resolution required. For example, silicon

fully–integrated electrodes for amperometric

microdevices can be produced using the

detection.

same photolithographic methods employed

In the last two decades, the Micro Total

in microelectronics and microchannels

Analysis Systems (µTAS or Lab–on–a–Chip)

can be grooved in most polymers using

have revolutionized the field of Analytical

infrared or ultraviolet laser radiation. In

Chemistry. 1–4 The concept of µTAS,

general, µTAS show some advantages

introduced by Manz and colleagues in 1990,

such as reduced consumption of samples

involves the coupling of many analytical

and reagents, reduced analysis time, high

steps into a single substrate. These steps

portability (suitable for hostile environments

relates to sample pretreatment and injection,

and for point–of–care applications), and

flow control, dilution, separation, detection,

high throughput achieved by parallel

fraction collection, and so on. Many materials

processing.5

have been used in the construction of

Electrochemical detection (ED), 6 in

µTAS, such as quartz, different types of

particular amperometric detection, is very

glasses, silicon, ceramics, and polymers.5

suitable for µTAS, because the response is

Typically, channels varying from 1 to

not dependent of the detected volume – the

hundreds micrometers are produced in

volume at the detection point can reach 10 –9 to 10–11 L and detection schemes based on radiation absorption suffer of low sensitivity. Moreover, the deposition of thin conductor films is relatively easy and can be included in the fabrication process. As a non–absolute method, amperometric detection often requires a calibration step for the quantification of analytes. However, calibration may contribute significantly to an increase in analysis time.

Experimental Figure 1.

Steps for the fabrication of hybrid PDMS/glass microchips. a) Clean glass substrates; b) Photoresist deposition; c) Photoresist exposition; d) Photoresist development; e) Ti

The fabrication of the devices were completely performed using the facilities

and Au (or copper) thin–film deposition (additional layers

of the Laboratory of Microfabrication (LMF/

of Ti and SiO2 were deposited in some devices); f) Lift-off

LNLS) and consisted of the following

(photoresist removal); g) Support for PDMS casting; h) PDMS curing; and i) The cured PDMS is detached from the master.

steps: 1) Preparation of a glass substrate

The final step is the sealing of PDMS containing microchannels

containing gold or copper deposited

against the glass substrate containing the electrodes (access holes are made in the PDMS prior the sealing).

38 | Activity Report 2009

electrodes, 2) Preparation of a master in

Science Highlights

Figure 2.

Microchip designs. a) Design 1: Single outlet reservoir where auxiliary and reference electrodes are placed; and b) Design 2: Five independent channels–all three electrodes are positioned on–channel. Electrode and channel widths are 50 µm and 100 µm, respectively, and the channel height is 50 µm. WE, RE, and CE stands for working, reference, and auxiliary electrodes, respectively.

SU–8 photoresist, 3) Replication of the master in poly(dimethylsiloxane) (PDMS), 4) Sealing the PDMS replica against the glass substrate (Figure 1). Two designs were evaluated, one containing a common auxiliary and reference electrodes reservoir (Figure 2a). In the second design, all three electrodes were shared by five channels (Figure 2b). In Figure 3 are shown details of one device using the design 1. The electrodes were connected to a potentiostat (PAR model 400) interfaced to a microcomputer for data acquisition.

Figure 3.

Photograph of a device constructed using the design 1. C: Microfluidic channels; WE, RE, and CE stands for working, reference, and auxiliary electrodes, respectively.

Results and Discussion The operation of the microdevice is quite simple and is exemplified in Figure 4. Before analysis, all channels and the reservoir are filled with supporting electrolyte and the potentiostat is turned

a mini vacuum pump while the current is monitored. Keeping the first standard solution in channel 1, the supporting electrolyte is now replaced by the second standard solution in channel 2, and so

on (Figure 4a). Under this condition,

on up to the last channel. If one or more

no electron transfer takes place at the

solutions inserted in the microchannels

electrode. In the next step, the supporting

were standard solutions, a calibration can

electrolyte in channel 1 is replaced by

be performed. During the process, one or

the standard solution (Figure 4b) using

more channels can also be filled with sample

Activity Report 2009 | 39

Single Electrode Electrochemical Detection in Hybrid Poly(dimethylsiloxane) / Glass Multichannel Microdevices

Figure 4.

Scheme for analysis using a single working electrode and the multiple channels design. a) All channels are filled with supporting electrolyte and the potentiostat is turned on; b) The electrolyte solution in the first channel is replaced by a solution containing an electroative analyte. A rise in current is observed; and c) The electrolyte solution in the second channel is replaced and a new increase in current is observed.

solutions, in order to perform quantitative a

determinations. Figure 5 exemplifies a representative amperogram obtained for the oxidation of hydroquinone (HQ) at +0.80 V and using Au electrode. The plot of the current plateau vs. concentration gives a linear relationship. During the experiments, we observed

solution leakage over the Au electrodes. These leakages occur due to the lack of adhesion between Au surfaces and PDMS. To overcome this drawback, we deposit additional layers of Ti and SiO2 over the Au layer. Also, after sealing the devices, a hydrofluoric acid solution was used to attack the Ti/SiO 2 layers in order to expose the Au surface, only

Figure 5.

a) Representative current response for the oxidation of 1.0 mmol L

–1

HQ in

0.1 mol L-1 NaNO3 using a microchip with design 1. b) Current differences between injections (quadruplicate), measured at the diffusion condition, present a linear relationship in the range of 1.0 to 4.0 mmol L

–1

of HQ. Other conditions:

three Au electrode cell; Potential: +0.80 V against Au pseudo–reference.

40 | Activity Report 2009

in the regions delimited by the fluidic microchannels. This procedure significantly enhanced the microchip performance. Other species, such as thiocyanate and acetaminophen were also successfully detected using the multichannel–single electrode approach.

Science Highlights

Conclusions

experimental conditions, the sensitivity of

The concept of amperometric

the devices ranged from 19 (thiocyanate)

measurements with a single shared

to 78 µA mol–1 L and the selectivity could

working electrode has been demonstrated to

be improved by the modification of the

be functional, leading to fast calibration and

electrodes or by the use of a separation

reliable analytical procedures. Our results

technique coupled to the detector. Moreover,

suggest that the complete independent

different modifications could be made in

channel design (design 2) is more suitable

each of the active areas in order to promote

due to the absence of back–flow problems

specific responses per channel.

associated with devices with a common outlet reservoir. In addition, the results

Acknowledgements

indicate that the performance of the

Authors would like to thank the

device is affected by the sealing quality,

Fundação de Amparo à Pesquisa do

and that O 2 plasma sealing efficiency

Estado de São Paulo (FAPESP) and the

can be strongly enhanced by covering

Conselho Nacional de Desenvolvimento

electrodes with thin–films of SiO2. Under the

Científico e Tecnológico (CNPq).

References 1. Vilkner, T.; Janasek, D.; Manz, A. Micro total analysis systems: recent developments. A na ly tica l Chemistr y, v. 76, n. 12, p. 3373-3386, 2004. 2. Dittrich, P. S.; Tachikawa, K.; Manz, A. Micro total analysis systems: latest advancements and trends. A na ly tica l Chemistr y, v. 78, n. 12, p. 3887-3907, 2006. 3. Ohno, K.; Tachikawa, K.; Manz, A. Microfluidics: applications for analytical purposes in chemistry and biochemistry. Elec trophoresis, v. 29, n. 22, p. 4443-4453, 2008. 4. West, J. et al. Micro total analysis systems: latest achievements. A na ly tica l Chemistr y, v. 80, n. 12, p. 4403-4419, 2008. 5. Coltro, W. K. T. et al. Micro chemical analysis systems: introduction, fabrication technologies, instrumentation and applications. Química Nova, v. 30, n. 8, p. 1986-2000, 2007. 6. Kuban, P.; Hauser, P.C. Fundamentals of electrochemical detection techniques for CE and MCE. Elec trophoresis, v. 30, n. 19, p. 3305-3314, 2009.

Activity Report 2009 | 41

Benzene Molecule is Destroyed by Ultraviolet and Soft X–rays in Circumstellar Environment Heloisa Maria Boechat-Roberty,1 Rosicler Neves,1 Sergio Pilling,2 Alexsandre F. Lago,3 Gerardo Gerson Bezerra de Souza4

Observatório do Valongo, Universidade Federal do Rio de Janeiro – UFRJ 2

Pontifícia Universidade Católica do Rio de Janeiro – PUC–Rio Universidade Federal do ABC – UFABC

3 4

Instituto de Química, Universidade Federal do Rio de Janeiro – UFRJ

Benzene molecules, present in the proto–planetary nebula CRL 618, are ionized and dissociated by ultraviolet (UV) and X–ray photons originated from the hot central star and by its fast wind. Ionic species and free radicals produced by these processes can lead to the formation of new organic molecules. The aim of this work is to study the photoionization and photodissociation processes of the benzene molecule, using synchrotron radiation and time–of–flight mass spectrometry. Mass spectra were recorded at different energies corresponding to the vacuum UV (21.21 eV) and soft X–ray (282–310 eV) spectral regions. The production of ions from the benzene dissociative photoionization is here quantified, indicating that C6H6 is more efficiently fragmented by soft X–ray than UV radiation, where 50% of the ionized benzene molecules survive to UV dissociation while only about 4% resist to X–rays. Partial ion yields of H+ and small hydrocarbons, such as C2H2+, C3H3+, C4H2+, are determined as a function of photon energy. Absolute photoionization and dissociative photoionization cross–sections have also been determined. From these values, half–life of benzene molecule due to UV and X–ray photon fluxes in CRL 618 was obtained.

Facility: TGM Publication: Monthly Notices of the Royal Astronomical Society, 394: 810–817 (2009) Funding: CNPq, CAPES, FAPESP, FAPERJ

Science Highlights

Benzene, C6H6, may be taken as the

X–rays are more effective ionizing agents

basic unit for the polycyclic aromatic

as compared to UV radiation because they

hydrocarbons (PAHs), which are believed

penetrate more deeply in the envelope

to play an important role in the chemistry

and heat up the gas more efficiently

of the interstellar medium. It is known

than UV. The present work is concerned

that PAHs are mainly formed in the

with the experimental investigation of

circumstellar envelopes of stars in the late

the photoionization and dissociative

stages of stellar evolution of asymptotic

photoionization of the benzene molecule

giant branch type carbon–rich stars.

upon interaction with UV and soft X–ray

Subsequent to the ejection of its C–rich

(in the vicinity of the carbon K shell).

envelope into the interstellar medium, these

The experiment was performed at the

stars become a proto–planetary nebula

Brazilian Synchrotron Light Laboratory

(Figure 1a), which evolves to planetary

using UV and soft X–ray photons from a

nebulae (Figure 1b).

toroidal grating monochromator (TGM)

The detection of benzene, C4H2, C6H2,

beamline (12–310 eV) perpendicularly

methyl acetylene (CH3C2H) and methyl

intersect the gas sample inside a high

diacetylene (CH3C4H) in the direction of the

vacuum chamber. The emergent photon

proto–planetary nebula CRL 618 (Figure 1c)

beam flux was recorded by a light–sensitive

was reported by Cernicharo et al.1. The soft

diode. Conventional time–of–flight mass

F1/Fc

Synthetic spectrum

1.0

0.8 Ne[II] 0.6

C 6H 6

0.4

C 2H 2

HC3N

HCN HCCH

HC3N

C 6H 2 C 4H 2

λ (µm)

Figure 1.

a) Proto–planetary nebula CRL 618 is created at the end of the life of a Sun–like star when its carbon rich envelope is ejected into the interstellar medium, having fast bipolar outflows, up to 200.km s–1. The hot central star (30.000 K) is obscured by dense envelope constituted by molecular gas and grains of dust. b) The detection of benzene, C4H2, C6H2, methyl acetylene (CH3C2H) and methyl diacetylene (CH3C4H) in the direction of the proto–planetary nebula CRL 618 c) Planetary Nebula Helix. The chemistry in circumstellar regions is strongly modified by the UV photons emitted from the hot central star and by the X–rays associated with its high–velocity winds. Several molecules are detected in these objects.

Activity Report 2009 | 43

Benzene Molecule is Destroyed by Ultraviolet and Soft X-rays in Circumstellar Environment

spectra (TOF–MS) were obtained the

Mass spectra of benzene were obtained at

technique photoelectron – photoion

the UV energy of 21.21 eV that corresponds

coincidence (PEPICO).The ionized recoil

to the photon energy emitted by helium atom

fragments produced by the interaction

(HeI) and at energies 282, 285, 289 and

with the photon beam were accelerated

301 eV, around the C1s → π∗ resonance at

by a two–stage electric field and detected

285.2 eV. The mass spectra obtained at

by two micro–channel plate detectors in a

21.21 and 289 eV are shown in Figure 2.

chevron configuration, after mass–to–charge

Clearly, X–rays produce much more types of

(m/q) analysis by a time–of flight mass

ions than UV photons. The most abundant

spectrometer (297–mm long). They

ion at 21.21 eV corresponds to the parent

produced the stop signals to a time–to–digital

ion C6H6+, confirming the relatively high

converter (TDC). Photoelectrons, accelerated

stability of the benzene molecule at the

in an opposite direction with respect to

UV energy range, whereas at 289 eV the

the positive ions, are recorded without

molecule is highly destroyed giving rise to

energy analysis by two micro–channel

several fragments like C4H2+(diacetylene)

plate detectors and provide the start

and to an enhancement of the H+ proton

signal to the TDC

production.

Figure 2.

The mass spectra of the benzene molecule obtained at 21.21 eV and 289 eV. We can see that 70 eV electrons produce, as a first approximation, the same ionic dissociation as created by UV photons. The molecular ion C6H6+ is clearly more destroyed by soft X–rays than by UV photons, or only 3% survive to X–rays while 50% resist to UV, as expected.

44 | Activity Report 2009

Science Highlights

The radical C6H2+ is the second most abundant ionic species in this mass range

X–ray (289 eV) photons are compared in Figure 3a–c, respectively.

formed by hydrogen loss due to X–ray

Assuming a negligible fluorescence yield

interaction and its yield increases with

due to the low–carbon atomic number and

the photon energy, particularly near the C1s resonance. Our data show that UV photons do not produce this radical from benzene (or PAHs) dissociation, and as the C6H2 was observed in the CRL 618, its abundance in this environment might have a part due to the PAH fragmentation by X–rays.

discarding anionic fragments in the present X–ray photon energy range, we assumed that all absorbed X–ray photons lead to cationic ionizing process. Therefore, the precise determination of non–dissociative single–ionization cross–section (σ ph−i) and the dissociative single ionization

The partial ion yields (PIY) as a function of

(photodissociation) cross–section (σph−d)

the photon energy of ions are determined as

of benzene can be determined by PIY

a function of photon energy. A comparison

values. The absolute photodissociation

between the mass spectra recorded

(σph−d ) and photoionization (σph−i ) cross

with 70 eV electrons, 21.21 eV and soft

sections determined as a function of the

Figure 3.

Comparison between PIY of C 6H 6 molecule obtained and a) 70 eV electrons from NIST, b) 21.21 eV photons and c) 289 eV photons.

Activity Report 2009 | 45

Benzene Molecule is Destroyed by Ultraviolet and Soft X-rays in Circumstellar Environment

X–ray photon energy of benzene can be

integrated photodissociation cross–sections

seen in Figure 4.

are σUV = 1.5 × 10−18 cm2. However, the half–life

The determination of photodissociation

of gas phase benzene due to photolysis

cross–section (σph−d) of molecules is very

in diffuse clouds is 27 yr that corresponds

important to estimate the molecular

to σUV = 8.1 × 10−18 cm2. Therefore, this latter

abundance in the interstellar environments

cross–section is 5.4 times higher than the

that depends on the formation and destruction

dissociation by acetylene loss only.

rates. The destruction of a given molecule

Employing electron energy–loss

is proportional to the photodissociation

spectroscopy, we have determined

rate kpd (s ) that is given by the product of

photoabsorption cross–sections (σ ph−abs) at

the σph−d (E) (cm ) by the photon flux f(E)

the UV region (3–45 eV) for the benzene

(photons cm−2 eV−1 s−1), integrated in the

molecule.3 Integrating these σabs (E) values

energy range from E2 to E1. Consequently,

from 6 to 13.6 eV, we obtained σUV = 4.93 ×

it is also possible to determine its half–life,

10−16 cm−2, which corresponds to 61.1 times

t1/2 (s) that is equal to ln2/kpd.

the photodissociation cross section.

−1

In the UV interstellar radiation field

In the X–ray range, the integrating of

(ISRF), a benzene molecule is destroyed

our photodissociation cross–section

by acetylene loss at a rate of 1.5 × 10−10 s−1

values from 280 to 310 eV gives the

which corresponds to a survival time of

value of 3.8 × 10−17 cm2 and integrating the

around 200 years.2 Taking into account

photoionization cross–section values at the

that the integrated interstellar UV flux from

same range, we found 1.2 × 10−18 cm2.

6 to 13.6 eV is 10 photons cm .s , the 8

−2

−1

In spite of the fact that X–rays have not been detected in CRL 618 yet, for future observations, it was proposed4 an X–ray emission spectrum for CRL 618 in the 0.2–1.5 keV energy range derived from a model flux. This spectrum was used to estimate the soft X–ray photon flux at 280–310 eV range impinging on benzene molecules located at about 8.9 × 1015 cm or 595 AU (astronomical unit is equal to the mean Sun–Earth distance) from the central star, where the majority of species are more abundant. It was also considered that CRL 618 is distant 1500 pc from the Earth. The integrated photon flux from 280 to 310 eV, is equal to 7.6 × 104 (photons

Figure 4.

Non–dissociative single–ionization (photoionization) cross

cm−2 s−1), which corresponds to a half–life

section, σph−i and dissociative ionization (photodissociation)

of the benzene of 7.6 × 103 yr. As the X–ray

cross section, σph−d of benzene as a function of photon

extinction was not taken into account in this

energy. The photoabsorption cross–section, σph−abs (solid line) taken from literature.

46 | Activity Report 2009

calculation, the actual photon flux will be

Science Highlights

consequently smaller than the presented value. For comparison, the X–ray photon flux (280–310 eV) from the Sun at 1 AU is about 8 × 107 photons cm−2 s−1 whose half–life is only 7.2 yr. The half–life of the benzene molecule as a function of UV and X–ray photon fluxes is shown in Figure 5. In conclusion, it was observed that the benzene molecules are more efficiently fragmented by soft X–rays, producing many more ions, than UV photons. 50% of the C 6H 6+ molecules survive to UV dissociation while only about 4% resist to X–ray destruction. PIY of H+ and small

Figure 5.

Half–life of the benzene molecule as a function of UV and X–ray integrated photon fluxes, FUV (from 6 to 13.6 eV) and FX (from 280 to 310 eV).

hydrocarbons are determined as a function of photon energy. The abundance of

in general, the stellar UV photon flux is

the hydrocarbons detected in the CRL

higher than X–ray one. For the Sun, UV

618 could also be associated with the

flux is about 104 times X–ray flux. In the

photodissociation of benzene, PAHs and

CRL 618, the UV radiation field emitted

their methyl derivatives that might undergo

from the central star type B is about 2

the radiative recombination. Moreover, the

× 105 times the ISRF (2 × 1013 photons

X-ray destruction cross–section is 4.7 times

cm−2 s−1), at a distance of 1 × 1016 cm or

higher than the UV cross section. However,

668.5 AU.

References 1. Cernicharo, J. et al. Infrared space observatory’s discovery of C4H2, C6H2, and benzene in CRL 618. Astrophysica l Jou rna l, v. 546, p. L123–L126, 2001. 2. Woods, P. M.; Willacy K. Benzene formation in the inner regions of protostellar disks. Astrophysical Jou rna l, v. 655, p. L49–L58, 2007. 3. Lee, C.-F.; Sahai, R. Shaping proto–planetary and young planetary nebulae with collimated fast winds. Astrophysica l Jou rna l, v. 586, n. 1, p. 319, 2003. 4. Boechat-Roberty, H. M. et al. Absolute differential cross sections for elastic and inelastic electron scattering from benzene with 1 keV impact energy, Jou rna l of Physics B: At. Mol. Opt. Fis., v. 37, p. 1467, 2004.

Activity Report 2009 | 47

The Effects of CeO2 on the Activity and Stability of Pt Supported Catalysts for Methane Reforming, as Addressed by In Situ Temperature Resolved XAFS and TEM Analysis

Adriana de Paula Ferreira,1 Daniela Zanchet,2 Jesuína Cassia Santiago Araujo,1 Janete Werle de Camargo Liberatori,1 Eduardo Falabella Sousa-Aguiar,4 Fabio Bellot Noronha,3 José Maria Correa Bueno 1

Universidade Federal de São Carlos – UFSCar, CP 676, São Carlos, SP, Brazil Laboratório Nacional de Luz Síncrotron – LNLS, CP 6192, 13.083–970,

Campinas, SP, Brazil Laboratório de Catálise, Instituto Nacional de Tecnologia,

Av. Venezuela, 82/518, Centro, 21.081–312, Rio de Janeiro, RJ, Brazil Universidade Federal do Rio de Janeiro – UFRJ, CENPES/PETROBRAS,

Rio de Janeiro, RJ, Brazil

The effects of Ce as a promoter on the activity and stability of Pt/Al2O3 and Pt/CeO2‑Al2O3 catalysts for autothermal reforming and partial oxidation of methane were investigated. The Pt/CeO2-Al2O3 catalyst exhibited higher activity and stability than the Pt/Al2O3 catalyst that showed strong Pt agglomeration with time on stream. The higher stability of the Pt/CeO2-Al2O3 catalyst was attributed to a combination of different properties: (i) hindrance of carbon deposition on the Pt surface; (ii) interaction of Pt-O‑Ce species in the presence of oxygen, inhibiting vapour and diffusion transport of PtO2 and mainly, (iii) thermal stability of the support, which prevents the loss of surface area, and consequently the sintering of the Pt. X-ray absorption fine structure spectroscopy and transmission electron microscopy were used to support these conclusions.

Facility: DXAS, XAFS1, XAFS2, C2nano Publication: Journal of Catalysis, 263: 335–344 (2009) Funding: CNPq, Petrobras

Science Highlights

The effects of Ce as a promoter on

to produce sulphur–free synfuels. In this

the activity and stability of Pt/Al2O3 and

technology, the production of the synthesis

Pt/CeO2–Al2O3 catalysts for autothermal

gas (CO and H2) represents a step of major

reforming and partial oxidation of methane

importance and represents half of the capital

(POM) were investigated. The Pt/CeO2–Al2O3

cost of the GTL plant.1 Since methane is the

catalyst exhibited higher activity and stability

main component of the natural gas, a lot

than the Pt/Al2O3 catalyst. Analysis by in situ

of effort has been dedicated to understand

X–ray absorption spectroscopy (XAFS)

methane reforming reactions.2

under POM conditions reveals that Pt is

The activity and stability of catalysts for

reduced by heating the catalysts to about

methane reforming are strongly influenced

730 K. The overall first–shell coordination

by the support and metal dispersion. In a

numbers suggest changes in Pt cluster

previous study, we reported the effects of

morphology with increasing temperature and

CeO2 loading on the properties and catalytic

Transmission Electron Microscopy (TEM)

behaviour of CeO2–Al2O3–supported Pt

showed strong Pt agglomeration with time

catalysts on dry reforming and partial

on stream for the Pt/Al2O3 catalyst. These

oxidation of methane3,4 and showed that those

results suggest that the interaction of reduced

catalysts with 12 wt. % of CeO2 presented

Pt and Ce oxide in the presence of O2 inhibits

the highest catalytic activity and stability.

Pt sintering by surface diffusion and the

Figure 1 shows the stability test for Pt/Al2O3

high thermal stability of the Ce–containing

and Pt/CeO2–Al2O3 as a function of time on

support and its ability to anchor metallic Pt nanoparticles helps in the retention of

surface area, preventing the migration and coalescence of the metal crystallites.

Recently, the needs to reduce dependence on petroleum feedstock and the continuous increase of known natural gas reserves have

generated great interest in the conversion of natural gas to fuels and petrochemical products. Although in the near future there is

need to change towards bio– and renewable chemical sources, the dependence on fossil fuel will continue for many years. The development of new efficient catalytic

processes to produce cleaner fuels is a challenge to environmental requirements. The so–called Gas–To–Liquids (GTL) technology, which deals with the conversion of natural gas to fuels and petrochemical products, is a promising solution for the exploitation of stranded gas reserves and promises

Figure 1.

CH 4 conversion with time on stream for Pt/CeO 2–Al 2O 3 (a, b, c) and Pt/Al2O3 (d, e) for various reactant compositions at 1073 K. Reactant compositions are (H2O:O2:CH4): (a, d) 0.65:0.5:1.0; (b) 0.2:0.5:1.0; (c, e) 0.0:0.5:1.0.

Activity Report 2009 | 49

The Effects of CeO2 on the Activity and Stability of Pt Supported Catalysts for Methane Reforming, as Addressed by In Situ Temperature Resolved XAFS and TEM Analysis

stream, under reaction mixtures containing various compositions (H2O:O2:CH4). It is clear that CeO2–containing catalyst show higher stability (Figures 1a–c), while Pt/ Al2O3 catalyst showed strong deactivation under partial oxidation of methane (POM) conditions (CH4 conversion decreased from 64 to 27%) (Figure 1e). To elucidate the influence of Ce on the stability and activity of Pt supported catalysts for methane reforming, we present results obtained by in situ temperature–resolved X–ray absorption near–edge structure (XANES) spectroscopy under POM conditions, extended X–ray absorption fine–structure (EXAFS) of reduced catalysts and transmission electron microscopy Figure 2.

TEM images of Pt/Al 2O 3 before and after ATR reaction (above); and of Pt/CeO2–Al2O3 before and after the same reaction (below).

(TEM) of fresh and used catalysts. TEM images of the fresh and spent in autothermal reforming (ATR) reaction (H2O:O2:CH4 of 0.65:2:1 at 1073 K during 24 hours on stream) for Pt/Al2O 3 and Pt/CeO 2–Al 2O 3 catalysts are shown in Figure 2. The presence of the support, particularly for the Pt/CeO2–Al2O3 samples, makes it difficult to obtain a good estimate of the Pt size distribution, but it can be inferred from the TEM images that the particles are very small in both fresh catalysts (Figure 2a–c). This is in agreement with % of Pt dispersion (dPt) estimated from cyclohexane dehydrogenation (dPt = 66% for Pt/Al2O3 and dPt = 54% for Pt/CeO2–Al2O3). After ATR reaction, however, an extensive growth of the Pt nanoparticles can be easily identified in the case of the Pt/Al 2O3 sample (Figure 2b). High resolution TEM images are shown in Figure 3. It can be

Figure 3.

HRTEM images of Pt/Al2O3 before and after ATR reaction (above); and of Pt/CeO2–Al2O3 before and after the same reaction (below).

50 | Activity Report 2009

seen from the lattice fringes that both catalysts show well crystallized metallic

Science Highlights

Pt particles after reduction (Figures 3a–c).

occurs at similar temperatures for both

After ATR reaction, the nanoparticles

Pt/Al2O3 and Pt/CeO2–Al2O3 catalysts. At

in the spent Pt/Al2O3 catalyst grow and

773 K under POM conditions, the Pt is at

become facetted (Figures 3b). On the other

metallic state in both catalysts.

hand, the Pt nanoparticles do not show

The quantitative analysis of the EXAFS

significant modification in the case of the

oscillations for both catalysts after reduction

Pt/CeO2–Al2O3 catalyst (Figure 3d).

(Figure 5) showed reduction of the rPt–Pt

In addition, from TEM images there is

interatomic distance (rPt–Pt = 2.71 + 0.02 Å)

a clear change in the morphology of the

when compared to the bulk Pt values

Al2O3 support due to reaction (Figure 2b),

(rPt‑Pt =2.772 + 0.003 Å), decrease of average

whereas the Ce–containing support was

first shell coordination number, CN Pt–Pt

highly stable (Figure 2d). This effect

and increase of the Debye Waller factor,

should enhance significantly the mobility

in agreement with the formation of very

of Pt nanoparticles, contributing to the

small nanoparticles (< 2 nm).5 Interestingly,

strong coalescence of Pt in our Pt/Al2O3

the CNPt–Pt obtained from the analysis at

catalyst.

298 K and 773 K of Pt/CeO2–Al2O3 were

In situ temperature–resolved XANES–POM

7.2 + 1.1 and 5.1 + 0.8, respectively. This

spectra of Pt/CeO2–Al2O3 catalysts are

significant reduction of the CN Pt–Pt with

shown in Figure 4; similar profiles were

temperature suggests a change in particle

observed for Pt/Al2O3 (not shown). The

morphology (flattening), which was similar

samples were reduced in situ and cooled

for both catalysts. The flattening of the Pt

down to room temperature; the H2 flow

particles onto the support correspond to a

was then replaced by a mixture for POM reaction (CH4:O2 = 2:1 molar). Under POM atmosphere, even at 298 K, the white line (WL) increased, indicating partial

new surface energy balance, which could be caused either by desorption of the H* or by the increase of the temperature, and would supposedly be compensated by

oxidation of Pt. By heating the samples under the POM mixture, the WL slightly decreases at temperatures around 673 K (623 K for Pt/Al2O3 catalyst) and an abrupt change takes place around 725 K (735 K for Pt/Al2O3 catalyst). It is interesting to point out that: i) the thermal reduction of PtO2 is expected within the region of 820– 20 K; and ii) above 723 K, large CH 4 consumption was detected with formation of H 2 and CO. From these results, it is reasonable to propose that the abrupt decrease in the WL at 725 K is likely due to the decomposition of CH4 and reduction of the PtO2 species, which

Figure 4.

Temperature–resolved XANES–POM for the Pt/CeO 2–Al2O3 catalyst. Catalyst reduced and heated under POM mixture (CH4:O2 = 2:1 v:v) at 10 K.min–1 up to 973 K.

Activity Report 2009 | 51

The Effects of CeO2 on the Activity and Stability of Pt Supported Catalysts for Methane Reforming, as Addressed by In Situ Temperature Resolved XAFS and TEM Analysis

Figure 5.

EXAFS oscillations (first shell) and corresponding fits for Pt/Al2O3(a, c) and Pt/CeO2–Al2O3 (b, d) acquired at 773 K (a and b) at 298 K (c and d) under H2:He (5:95) flow.

the increase of the interaction between the Pt and the oxygen from the support.

1) The interaction of reduced Pt and Ce oxide in the presence of O 2 inhibits

The high stability of Pt in Ce–containing

Pt sintering by surface diffusion.

supports, under oxidizing conditions at

The high thermal stability of the

high temperature, have been assigned

Ce–containing support and its ability

to Pt–O–Ce bond, which act as an anchor

to anchor metallic Pt nanoparticles

and inhibit the sintering of Pt.6 EXAFS

helps in the retention of surface

results showed a slightly higher Pt–O

area and prevents the migration

scattering contribution for the Pt/CeO2–Al2O3

and coalescence of the metal

catalyst under H2 at 773 K and the FTIR of

crystallites.

adsorbed CO showed suppression of the

2) Pt is reduced by CH4 in the presence

CO linearly adsorbed on Pt/CeO2–Al2O3

of O2 in the ATR or POM reactions,

catalysts, which is in agreement with a

decreasing the PtO2 content. Pt is

strong Pt–O–Ce interaction.7

predominantly in a reduced state,

Based on the presented results, the

which suppresses sintering via the

main conclusions of the study are as

formation of mobile and volatile

follows.

PtO2.

52 | Activity Report 2009

Science Highlights

References 1. Bakkerud, P. K. Update on synthesis gas production for GTL. Catalysis Today, v. 106, n. 1-4, p. 30-33, 2005. 2. Wei, J.; Iglesia, E. Isotopic and kinetic assessment of the mechanism of reactions of CH4 with CO2 or H2O to form synthesis gas and carbon on nickel catalysts. Journal of Catalysis, v. 224, n. 2, p. 370-383, 2004. 3. A.C.S.F. Santos et al. The effect of ceria content on the performance of Pt/CeO2/Al2O3 catalysts in the partial oxidation of methane. Applied Cata lysis A , v. 290, n. 1-2, p. 123-132, 2005 4. Damyanova, S.; Bueno, J. M. C. Effect of CeO2 loading on the surface and catalytic behaviors of CeO2-Al2O3-supported Pt catalysts. Applied Cata lysis A , v. 253, n. 1, p. 135-150, 2003. 5. Frenkel, A. I.; Hills, C. W.; Nuzzo, R. G. A view from the inside: complexity in the atomic scale ordering of supported metal nanoparticles. Jou rna l of Physica l Chemistr y B, v. 105, n. 51, p. 12689-12703, 2001. 6. Nagai, Y. et al. Sintering inhibition mechanism of platinum supported on ceria-based oxide and Pt-oxide–support interaction. Jou rna l of Cata lysis, v. 242, n. 1, p. 103-109, 2006. 7. Riguetto, B. A. et al. Surface behavior of alumina-supported Pt catalysts modified with cerium as revealed by X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy of CO adsorption. Jou rna l of Physica l Chemistr y B, v. 108, n. 17, p. 5349‑5358, 2004.

Activity Report 2009 | 53

Controlled Swollen and Drug Release from Urea–Cross–Linked Polyether/Siloxane Hybrids

Celso V. Santilli, 1 Leila A. Chiavacci, 2 Leandro Lopes,1 Sandra H. Pulcinelli,1 Anselmo G. Oliveira2

Instituto de Química, Universidade Estadual Paulista – UNESP, CP 355, Araraquara, SP, Brazil

Faculdade Ciências Farmacêuticas, Universidade Estadual Paulista – UNESP, Araraquara, SP, Brazil

From a simple synthesis method we produced transparent ureasil cross–linked polyether (poly(ethylene oxide), PEO, or poly(propylene oxide), PPO) networks, whose designed inter cross–linking distance and tunable swellability was assessed by small angle X–ray scattering on the D11A–SAXS1 beamline of the LNLS. We demonstrated that the controlled drug release from swellable hydrophilic ureasil–PEO materials can be sustained during some days, while from the unswellable ureasil–PPO ones, during some weeks. This outstanding feature conjugated with the biomedically safe formulation of the ureasil cross–linked polyether/ siloxane hybrid widen their scope of application to include the domain of soft and implantable drug delivery devices.

Facility: SAXS1 Publication: Chemistry of Materials, 21: 463–467 (2009) Funding: CNPq, CAPES/COFECUB, Fapesp

Science Highlights

Controlled–release technology can be

rate during short (days) and prolonged

applied to develop devices for use in many

(weeks) periods by the judicious choice of

scientific or technological fields including

PEO– and PPO–chain molecular weights

medicine, pharmaceutics, agriculture,

(Mw), respectively. A well–known sol–gel

chemistry and materials science, delivering

synthesis6 was adopted for the PEO with

drugs, agrochemicals and other biologically

Mw of 500 and 1900 g.mol–1 (labelled

active agents.1–5 Controlled release systems

PEO500 and PEO1900 hybrids) and also

present many advantages as compared

for PPO with Mw of 300 and 2000 g.mol –1

with conventional forms of administration

(labelled PPO300 and PPO2000 hybrids)

of different active substances, including

hybrids. SDCF, an antipyretic, analgesic

high delivery efficiency, precise control

and non–steroidal anti–inflammatory

of the dose for prolonged time periods

agent, was chosen as the model drug due

(i.e., days, weeks or months) and reduced

to its limited solubility in acidic medium,

toxicity. The suitability of polymers as a

especially in gastric juice.

biomedical material and their performance

As a result of the nanostructural

in a delivery device depend, to a large

uniformity of the network produced by the

extend, on their bulk structure and also, on

organic–inorganic hybrid approach different

their interface properties with biological

shaped, transparent and rubbery xerogels

systems. In this context, poly(ethylene

were obtained (Figure 1). The nanostructural

oxide) (PEO) and its inclusions in block

homogeneity and the swellability of the

copolymers or in cross–linked networks

ureasil cross–linked network were analyzed

(hydrogels) represent a good standard

by SAXS measurements performed at the

of bio–interfacial compatibility. 3,5 The

D11A–SAXS1 beamline of LNLS during

hydrophilic nature of PEO inhibits protein

the swelling–drug release experiment

adsorption, cell adhesion, and provides

carried out at 37 °C. As expected from

its own full excretion, but its aqueous

the hydrophilic nature of the PEO, the

solubility allows unpredicted bulk erosion

hydration of the PEO1900 hybrid matrix

of drug delivery devices.

during the swelling–drug release experiment

In 2009, we reported 6 the use of a

leads to a shift in the peak position to

biomedically safe formulation to synthesize

low q–values and to an increase of the

rubbery, flexible, transparent and insoluble

peak intensity (Figure 1d). The former

ureasil cross–linked polyether (PEO

is an evidence of the increase of the

and PPO) material presenting tunable

electronic–density contrast between the

swellability and drug–release rate. This

ureasil nodes and the polymeric matrix,

set of properties is attractively convenient

whereas the later reveals the expansion

for the pharmaceutical formulation of

of the average distance between adjacent

ophthalmic (contact lenses), trans–dermal

nodes from 4.2 to 6.5 nm. This feature,

(patches) and implantable (soft tissue)

which was also observed for the PEO500

drug delivery systems. Moreover, we

hybrids, successfully demonstrated the

reported the possibility to fine tune

swellability of the ureasil cross–linked

the sodium diclofenac (SDCF) deliver

PEO network.

Activity Report 2009 | 55

Controlled Swollen and Drug Release from Urea-Cross-Linked Polyether/Siloxane Hybrids

and dried weight (wd), the thickness (hd) or the average distance between nodes (ξd), are displayed as a function of the immersion time in Figure 2. The excellent agreement between the nanoscopic and the macroscopic expansion give

evidence of the uniformity of the hydration process and of the quick formation of fully water–embedded ureasil–PEO matrices. On opposition, as expected from the hydrophobic nature of PPO, all the studied ureasil–PPO matrices showed a very low water uptake (∆w/wd ~ 0.06)

and an undetectable expansion in water at 37 °C. As shown in Figure 3 the drug release from swellable ureasil–PEO matrices is faster than that of unswellable ureasil–PPO, the latter presenting a sustained SDCF release pattern over the entire monitoring period. Since the hydrophilicity of PPO300 and PPO2000 hybrid matrices is very low, the water accessibility does not change significantly during the drug release period, so that the equilibrium conditions are not

Figure 1.

Schematic representation of the silicon based cross–linking nodes (a) uniformly

achieved. Therefore, the drug diffusion

distributed in the hybrid network (b).

through the ureasil– PPO matrices is

Image of the flexible transparent film of PEO1990 hybrids before (right) and

much faster than the drug dissolution rate,

after (left) drug release (c) related to

allowing a linear release profile.

the time dependence of SAXS curves m o n i to re d i n s i t u d u r i n g t h e d r u g release experiments (d).

For the hydrophilic ureasil–PEO matrices, the drug molecules can easily diffuse to the release medium through the

Motivated by the effect of water swelling

free volume of the swollen network.

of the ureasil–PEO hybrids observed on

Under these conditions, the diffusion of

the nanoscopic–scale, we examined the

dissolved drug molecules to the liquid

macroscopic dimensional change and

environment is a time–dependent process

the water uptake of monolithic disks

that can be predicted by assuming a

(Figure 1c) immersed in deionized water

pseudo first–order kinetic. The estimated

at 37 °C. The water uptake (∆w/wd) and

first order rate constant (k1) is about

the expansion factor (∆h/h d or ∆ξ /ξ d)

five–times lower for the PEO500 hybrid

calculated from the swollen (ws, hs or ξs)

(k1 ~ 0.05 h–1) when compared to that of

56 | Activity Report 2009

Science Highlights

Figure 2.

Time dependence of water uptake (∆m/m d), macroscopic (∆h/h d) and nanoscopic (∆ξ/ξ d) expansion ratio for hybrids loaded with 0.01w/w of SDCF: a) PEO1900 hybrid; b) PEO500 hybrid.

Figure 3.

Cumulative percentage of SDCF released from ureasil cross–linked polyether: a) unswellable PPO300 and PPO2000 hybrids; and b) swellable PEO500 and PEO1900 hybrids.

the SDCF released from the PEO1900

sustained and controlled drug–release

matrix (k1 ~ 0.23 h ). It is also noticeable

profiles arising from the osmotic transport

that the swelling–equilibrium expansion

through the less hydrophilic PPO–skin

factor for PEO1900 hybrids is about five

from the swellable PEO–core. Furthermore,

times higher than that of PEO500 hybrids.

we propose that the different properties

This clearly demonstrates that the drug

reported for PEO and PPO based hybrids

release profile is mainly dependent on the

may be conjugated by blending ureasil–PEO

swellability of the ureasil–PEO hybrids

and ureasil–PPO networks or by fabricating

–1

We believe that the behaviors emerging from the different release and swelling patterns of PEO and PPO based hybrid,

heteropolymers such as PEO–ureasil–PPO di–block copolymers in order to design new functional materials.

combined with the simplicity and flexibility of their sol–gel synthesis, can inspire the design of advanced delivery devices such

Acknowledgements

as nanocapsules with an ureasil–PEO core

This work has been financially

and an ureasil–PPO skin. This core–shell

supported by CAPES/COFECUB, CNPQ

type structure should generate new

and FAPESP.

Activity Report 2009 | 57

Controlled Swollen and Drug Release from Urea-Cross-Linked Polyether/Siloxane Hybrids

References 1. Belting, M.; Sandgren, S.; Wittrup, A. Nuclear delivery of macromolecules: barriers and carriers. Advanced Dr ug Deliver y Reviews, v. 57, n. 4, p. 505-527, 2005. 2. Nori, A.; Kopecek, J. Intracellular targeting of polymer-bound drugs for cancer chemotherapy. Advanced Dr ug Deliver y Reviews, v. 57, n. 4, p. 609-636, 2005. 3. Uhrich, K. E. et al. Polymeric systems for controlled drug release. Chemica l Reviews, v. 99, n.Â 11, p. 3181-3198, 1999. 4. Orive, G. et al. Micro and nano drug delivery systems in cancer therapy. Cancer Therapy, v. 3, p. 131-138, 2005. 5. Peppas, N. A. et al. Hydrogels in biology and medicine: from fundamentals to bionanotechnology. Advanced Materia ls, v. 18, n. 11, p. 1345â&#x20AC;&#x201C;1360, 2006. 6. Santilli, C. V. et al. Controlled drug release from ureasil-polyether hybrid materials. Chemistr y of Materia ls, v. 21, n. 3, p. 463-467, 2009.

58 | Activity Report 2009

Correlation Between AO6 Polyhedral Distortion and Negative Thermal Expansion in the A2M3O12 Family

Bojan A. Marinkovic,1 Monica Ari,1 Roberto R. de Avillez,1 Fernando Rizzo,1 Fabio F. Ferreira,2 Kimberly J. Miller,3 Michel B. Johnson, 3 Mary Anne White3

Departamento de Engenharia de Materiais – DEMa,

Pontifícia Universidade Católica do Rio de Janeiro – PUC–Rio, RJ, Brasil Laboratório Nacional de Luz Síncrotron – LNLS, Campinas, SP, Brasil

Department of Chemistry and Institute for Research in Materials,

Dalhousie University, Halifax, Canada

The Pbcn orthorhombic phase of Y2Mo3O12 has been examined through in situ high–resolution X–ray powder diffraction (10 K to 450 K) on the D10B–XPD beamline, heat capacity determination (2 K to 390 K) and differential scanning calorimetry (103 K to 673 K). From a thorough analysis of the structure of Y2Mo3O12, we found that the YO6 octahedra and MoO4 tetrahedra increased their distortion with increasing temperature. The inherent volume distortion parameter (υ) of AO6 has been introduced to quantitatively evaluate polyhedral distortion and it was observed that this parameter is strongly correlated with the linear coefficient of thermal expansion (αl) for different members of the A2M3O12 family.

Facility: XPD Publication: Chemistry of Materials, 21: 2886-2894 (2009) Funding: FAPERJ

Correlation Between AO6 Polyhedral Distortion and Negative Thermal Expansion in the A2M3O12 Family

Most solids and liquids expand on

the existence of an orthorhombic–to–

heating due to the asymmetry of inter–atomic

monoclinic phase transition; because the

potential well. However, a few shrink

low–temperature monoclinic counterparts

during heating. This property is known

of the orthorhombic phases have very

as negative thermal expansion (NTE)

different thermal expansion properties, their

and it is not restricted to exotic classes of

linear coefficients of thermal expansion

materials. As matter of fact, very familiar

being highly positive.

compounds such as hexagonal ice (Ih)

The thermal expansion and phase

and water show NTE in temperatures

transition of the orthorhombic Y2Mo3O12

below 73 K for ice1 and between 273 K

phase (with Pbcn space group) were

and 277 K in the case of water.2

recently studied for the first time, and it was

The field has been growing since the re–discovery of NTE in cubic ZrW2O8 (AM2O8

observed that this phase presents very high NTE between 403 K and 1073 K.6

family) by X–ray powder diffraction (XRPD),3

In the present work, high–resolution X–ray

while several other open–framework

powder diffraction (HRXRPD) data were

classes of known ceramics, such as AO2,

collected, in vacuum (8–10 mTorr), at four

AMO 5, AM 2O 7, A 2O and A 2M 3O 124 have

different temperatures (20, 150, 300 and

emerged as potential sources of crystal

450 K), using a commercial closed–cycle

phases with low or NTE. Generally, it is

He cryostat (Advanced Research Systems),

assumed that the low–energy transverse

with vibration damping and temperature

thermal vibrations of the two–coordinate

control (10 to 450 K), at the X–ray Powder

atoms are responsible for NTE in the

Diffraction (D10B–XPD) beamline7 of the

open–framework orthorhombic structures.

Brazilian Synchrotron Light Laboratory

The possibility of controlling the coefficient

(LNLS). X–rays of λ = 1.23989 Å wavelength

of thermal expansion in pure and composite

were selected by a double–bounced Si(111)

materials has been the principal driving

monochromator with water refrigeration

force in the search for crystal phases

in the first crystal, while the second one

with unusually low, zero, or even negative

is bent for sagittal focusing. The beam

thermal expansion.

was vertically focused in the sample’s

The A2M3O12 family is especially attractive

position on a spot of ~1 mm (vertical)

due to the chemical flexibility within the

× ~2 mm (horizontal). The experiments were

orthorhombic Pbcn (No. 60) space group

performed in the vertical scattering plane,

that results in a large range of variation of

i.e., perpendicular to the linear polarization

linear coefficients of thermal expansion

of the incident photons. Values of the X–ray

(a1) for the orthorhombic A2M3O12 phases,

wavelength used in this study and the

from low positive to large negative values.5

zero–point displacement were determined

This feature of orthorhombic A 2M 3O 12

from several reflections of an external

phases makes it possible to synthesize

SRM640c Si standard. The diffracted

solid solutions with controlled coefficients

beam was analyzed using a Ge(111)

of thermal expansion. Another important

single crystal and detected using a NaI(Tl)

characteristic of the A 2M 3O 12 family is

scintillation counter with a pulse–height

60 | Activity Report 2009

Science Highlights

discriminator in the counting chain. The

The crystal structure of open–framework

incoming beam also was monitored by

orthorhombic Y2Mo3O12 at 300 K, consisting

a scintillation counter to normalize the

of corner–shared YO6 octahedra and MoO4

decay of the primary beam. Data were

tetrahedra is depicted in Figure 1. Analysis of

recorded at different temperatures for 2 s

polyhedral distortion was carried out using

at each 2θ in steps of 0.004° from 10° to

the IVTON program. The distortion of the

70°. Rietveld refinements were performed

polyhedra (YO6, Mo1O4 and Mo2O4) in Y2Mo3O12

using Topas–Academic software. Atomic

was expressed using the volume distortion

positions and isotropic displacement

parameter (υ) proposed by Makovicky and

factors for 20 K, 300 K and 450 K,

Balic–Zunic,8 υ = (Vi–Vr)/Vi, where Vi is the

adjusted through the Rietveld method,

volume of the ideal polyhedron and Vr is

are deposited in the Inorganic Crystal

the volume of the real polyhedron. Rietveld

Structure Database (ICSD), codes 420151,

analyses of HRXRPD data indicated that the

420152 and 420153, respectively.

Y2Mo3O12 phase maintained the orthorhombic

Figure 1.

Y2Mo3O12 network as corner-sharing YO6 octahedra and MoO4 tetrahedra at 300 K.

Activity Report 2009 | 61

Correlation Between AO6 Polyhedral Distortion and Negative Thermal Expansion in the A2M3O12 Family

Pbcn structure from 450 K to at least 20 K.

the cell parameters leads to a nearly linear

The variation of unit–cell parameters of

reduction of the cell volume as a function

Y2Mo3O12 is shown in Figure 2. The b– and

of temperature. The net volume coefficient

c–axes diminish with increasing temperature

of thermal expansion, αV, of Y2Mo3O12 in the

throughout the temperature range. On the

range 20 K to 450 K was highly negative,

other hand, the a–axis increases from 20 K

–27.1 x 10–6 K–1, giving a linear coefficient

to 300 K, but then remains unchanged

of expansion, αl (= α V /3) of –9.02 × 10–6 K–1

between 300 K and 450 K. This behavior of

averaged over this temperature range. Heat capacity was determined over the temperature range 2 K to 390 K, using a commercial relaxation calorimeter (Physical Property Measurement System model 6000 from Quantum Design). The heat capacity results, Figure 3, show no thermal anomalies over the examined temperature range, 2 K to 390 K, ruling out first or second order phase transitions over that temperature range. The change of the sign of thermal expansion along the a–axis in Y2Mo3O12 can be understood as a change in balance of two different contributions to thermal expansion between 300 K and 450 K. Taking into account the recent findings of Liang et al.9 based on Raman spectroscopy, there are high–energy optical phonons

Figure 2.

Lattice parameters of Y 2Mo 3O 12 as a function of temperature.

contributing to NTE in Y2Mo3O12, together with the well known low–energy (soft) modes. Therefore, it can be proposed that joint action of these two modes (high–energy optical and low–energy translational/librational modes) both contribute to NTE in competition with a

positive thermal expansion term, eventually provoking the change of the sign in thermal expansion along the a–axis, from positive to negative. It is worth mentioning that this kind of change in a–axis thermal expansion never occurs for members of Figure 3.

Heat capacity results for Y2Mo3O12 over the temperature

A2M3O12 family with lower NTE, such as

+, measurements with Apiezon H.

Sc2W3O12 and Sc2Mo3O12, this axis showing

range 2 to 390 K, ο , measurements with Apiezon T;

62 | Activity Report 2009

Science Highlights

positive thermal expansion over the whole

data.3 In Y2Mo3O12, the YO6 polyhedra are

temperature range. On the other hand,

intrinsically more distorted than the two

low–energy translational and librational

MoO4 polyhedra. For comparison, υ also

modes predominate over a positive

was calculated for other members of the

thermal expansion contribution along the

A2M3O12 family from literature (Sc2W3O12,

b– and c–axes in Y2Mo3O12 already from

Y2W3O12 and Al2W3O12).

the lowest temperatures.

An interesting correlation exists

The details of the mechanism that

between υ of AO6 polyhedra in A2M3O12

promotes NTE in A2M3O12 were not as well

structures determined at the lowest

understood as for the AM2O8 family, until recently.9 It had been generally assumed for A2M3O12 that transverse low–energy

phonon modes of two–coordinate oxygens are responsible for this phenomenon, while their polyhedra are quasi–rigid, whereas in AM2O8 the polyhedra are fully rigid. Also, it was generally assumed that AO6 and MO4 polyhedra in A2M3O12 are inherently distorted in order to make a framework connected via vertices. However, these assumptions have never been quantitatively evaluated at structural level, although it has been strongly suggested that stretching and bending

modes (high–energy optical phonons) of MoO4 tetrahedra contribute to NTE. We have carried out calculations of polyhedra distortion through the volume distortion parameter (υ) as proposed by Makovicky and Balic–Zunic.8 This parameter quantifies the regularity of the ligand distribution in the polyhedra, taking into account both the internal bond angles of polyhedra and the central atom to ligand bond lengths. Therefore, υ is more indicative of polyhedral distortion than just the variation of internal polyhedra bond angles. The polyhedra in Y2Mo3O12 have small inherent distortion at 20 K, υ of ~ 0.4% for YO6 and ~ 0.1% for both MoO4 tetrahedra. For comparison, ZrO6 in α–ZrW2O8 (low–temperature form) has υ of 19.75 % at 0.3 K, as calculated from literature

Figure 4.

a) Average linear coefficient thermal expansion (αl) as a function of inherent AO 6 volume distortion parameter, υ. b) Volume distortion parameter of AO6 polyhedral as a function of temperature for A2M3O12 family.

Activity Report 2009 | 63

Correlation Between AO6 Polyhedral Distortion and Negative Thermal Expansion in the A2M3O12 Family

of υ with temperature, provides quantitative insight concerning the rigidity of AO 6 (Figure 4b) and MO 4 polyhedra (not shown here). For comparison, υ of ZrO6 in α–ZrW2O8 was calculated for the whole range of its existence based on data

reported elsewhere3 and it was confirmed that its polyhedra are completely rigid, i.e., υ is essentially unchanged at ~19.75% over the whole temperature interval. On the other hand, υ of AO6 and MO4 polyhedra increase with temperature for most of the

Figure 5.

Nonbonded parameters in Y 2 Mo 3 O 12 as a function of

members of the A2M3O12 family. Therefore,

temperature. (a) Mean nonbonded Y−Mo distances and

it can be inferred that the polyhedra in

(b) Y−O−Mo bond angles.

Y2Mo3O12 are softer than in ZrW2O8. The reduction of the mean Y–Mo

available temperature (denoted inherent volume distortion parameter), and their linear thermal expansion coefficient, as

non–bonded distances and mean Y–O–Mo angles (Figure 5) with increasing temperature can be identified as the

shown in Figure 4a: NTE increases with

basic structural origin of negative thermal

the increase of inherent volume distortion

expansion of the unit–cell volume in

parameter of AO6. This correlation can be

Y 2Mo 3O 12.

seen as a more quantitative expression

In summary, thermal properties of

of the earlier rationalization that NTE in

orthorhombic Pbcn Y2Mo3O12, such as

A2M3O12 increases with increase of A 3+

thermal expansion, stability and heat

radius, which promotes more distortion in

capacity were investigated over a wide

AO6.10 It seems that this new correlation is

temperature range, as low as 2 K (heat

more robust and can provide more insight

capacity) and as high as 673 K (DSC).

into understanding NTE in the A2M3O12

The orthorhombic–to–monoclinic phase

family. For example, it was demonstrated

transition, commonly observed in A2M3O12

by several authors, and reconfirmed in the

structures, is absent over the temperature

present study, that αl is more negative for

range 2 K to 670 K. In its orthorhombic

Y2Mo3O12 than Y2W3O12. Thus, using the

Pbcn phase, Y 2Mo 3O 12 exhibited large

inherent volume distortion parameter (υ)

negative thermal expansion (average

for YO6, one can understand the difference

αl = –9.02 × 10–6 K–1, averaged over T = 20 K

in NTE between Y2Mo3O12 and Y2W3O12,

to T = 450 K). The unit–cell parameter, a,

since υ is higher for the YO6 polyhedra in

shows anomalous behavior, increasing

Y2Mo3O12 than in Y2W3O12. The difference

in the range between 20 K and 300 K,

in thermal expansion cannot be explained

then decreasing as the temperature is

by the difference in A3+ radii, as proposed

increased further. The latter is not due to

in the earlier rationalization. The variation

a first– or second–order phase transition,

64 | Activity Report 2009

Science Highlights

but can be explained through a change

basic structural features that provoke

of balance of atomic–level mechanisms

negative thermal expansion in Y2Mo3O12

contributing to expansion and reduction of interatomic distances. The inherent volume distortion parameter of AO6 has been introduced to quantitatively evaluate polyhedral distortion. This parameter, is

and other isostructural compounds. B.A.M. is grateful to the Brazilian Synchrotron Light Laboratory (LNLS) for the beam time and financial support

strongly correlated with the linear coefficient

under the project D10B–XPD 7756. M.A.

thermal expansion of different members

thanks FAPERJ for financial support. M.A.W.

of the A2M3O12 family and can successfully

acknowledges support from NSERC of

explain the previously unresolved cases. Although the AO 6 and MO 4 polyhedra increase their distortion with increasing temperature, their distortion is two orders of magnitude lower than in ZrW2O8. Finally,

Canada, along with the Canada Foundation for Innovation, Atlantic Innovation Fund and other partners that fund the Facilities for Materials Characterization managed

we find that the Y–Mo non–bonding

by the Institute for Research in Materials

distances and Y–O–Mo angles are the

at Dalhousie University.

References 1. Rottger, K.; Endriss, A.; Ihringer, J. Lattice constants and thermal expansion of H2O and D2O Ice Ih between 10 and 265 K. Ac ta Cr ysta l log raphica B, v. 50, n. 1, p. 644-648, 1994. 2. White, H. E. Classica l and modern physics: a descriptive introduction. New York: D. Van Nostrand Company, 1940. 712 p. 3. Evans, J. S. O. et al. Negative thermal expansion in ZrW2O8 and HfW2O8. Chemistr y of Materials, v. 8, n. 12, p. 2809–2823, 1996. 4. Sleight, A. W.; Tao J. Z. The role of rigid unit modes in negative thermal expansion. Jou rna l of Solid State Chemistr y, v. 173, p. 442-448, 2003. 5. Ari, M. et al. Thermal expansion of Cr2xFe2−2xMo3O12, Al2xFe2−2xMo3O12 and Al2xCr2−2xMo3O12 solid solutions. Jou rna l of Solid State Chemistr y, v. 181, n. 6, p. 1472-1479, 2008. 6. Marinkovic, B. A. et al. Negative thermal expansion in Y2Mo3O12. Solid State Sciences, v. 7, n. 11, p. 1377-1383, 2005. 7. Ferreira, F. F. et al. X-ray powder diffraction beamline at D10B of the LNLS: application to the Ba2FeReO6 double Perovskite. Jou rna l of Synchrotron Radiation, v. 13, n. 1, p. 46-53, 2006. 8. Makovicky, E.; Balic-Zunic, T. New Measure of distortion for coordination polyhedra. Ac ta Cr ysta l log raphica B, v. 54, n. 1, p. 766-773, 1998. 9. Liang, E. et al. Effect of water species on the phonon modes in orthorhombic Y2 (MoO4)3 revealed by Raman spectroscopy. Jou rna l of Physica l Chemistr y C , v. 112, n. 16, p. 6577-6581, 2008. 10. Forster, P. M.; Yokochi, A.; Sleight, A. W. Enhanced negative thermal expansion in Lu2W3O12. Jou rna l of Solid State Chemistr y, v. 140, n. 1, p. 157-158, 1998.

Activity Report 2009 | 65

Structural Aspects of the Distinct Biochemical Properties of Glutaredoxin 1 and Glutaredoxin 2 from Saccharomyces cerevisiae Karen Fulan Discola,1 Marcos Antonio de Oliveira,2 José Renato Rosa Cussiol,1 Gisele Monteiro,1 José Antonio Bárcena,3 Pablo Porras,3 Carmen Alicia Padilla,3 Beatriz Gomes Guimarães,4 Luis Eduardo Soares Netto 1

Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo – USP, São Paulo, Brazil

Departamento de Biologia, Universidade Estadual Paulista – UNESP, São Vicente, Brazil 3

Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, 14071, Córdoba, Spain 4

Synchrotron SOLEIL, Saint-Aubin, France

Glutaredoxins (Grxs) are small thiol–dependent oxidoreductases with disulfide reductase activity endowed by at least one cysteine at their active sites. Although Grxs are implicated in many cellular processes, including protein folding and protection against reactive oxygen species, few of their targets are known. In the yeast Saccharomyces cerevisiae, eight Grxs isoforms were identified (ScGrx1–8). Two of them (ScGrx1–2) are dithiolic, possessing a conserved Cys–Pro–Tyr–Cys motif. In spite of the fact that ScGrx1 and ScGrx2 share 85% of amino acid sequence similarity, we have shown that ScGrx2 is fifteen times more active as oxidoreductase than ScGrx1. In an attempt to better understand the mechanisms and differences between yeast dithiol Grxs activities, we elucidated the crystallographic structures of ScGrx2 in the oxidized state and of the ScGrx2–C30S mutant with a glutathionyl mixed disulfide at resolutions of 2.05 and 1.91 Å, respectively. Comparisons among these structures and those available for ScGrx1 provided insights into the remarkable functional divergence between these enzymes. We hypothesize that the substitutions of Ser23 and Gln52 in ScGrx1 by Ala23 and Glu52 in ScGrx2 can modify the capability of the active site C–terminal cysteine to attack the mixed disulfide between the N–terminal active site cysteine and the glutathione molecule. Mutagenesis studies supported this hypothesis. The observed structural and functional differences between ScGrx1 and ScGrx2 may reflect variations in substrate specificity and non–redundant biological functions.

Facility: MX1 Publication: Journal of Molecular Biology, 385: 889-901 (2009) Funding: FAPESP, CNPq, MCyT (Spain)

Science Highlights

Introduction Glutaredoxins (Grxs) are small heat stable thiol-dependent oxido-reductases

with conserved cysteine residues at their active sites (CXXC), endowed with disulfide reductase activity.1 One of the

main activities attributed to Grxs is the reduction of mixed disulfides formed between proteins and glutathione. These

reactions proceed by the monothiolic mechanism, which involves only the N-terminal active site cysteine.2 In the monothiolic mechanism, Grxs specifically interact with the glutathione of the mixed disulfide target. This results in the formation of a covalent Grx-glutathione

Figure 1.

In the monothiol mechanism, the N-terminal cysteine of the Grx active site interacts with the GSH moiety of the proteinSG mixed disulfide target, then a covalent Grx-SG mixed intermediate is formed and the target protein is released in its reduced form (a). A second molecule of GSH reduces the Grx-SG mixed intermediate, generating reduced Grx and glutathione disulfide (GSSG, b). The oxidized form

mixed disulfide intermediate and in the

of Grx, with an intramolecular disulfide bridge, can be

release of the reduced protein (Figure 1a).

molecules.

formed in a side reaction (c), and is reduced by two GSH

The Grx-glutathione disulfide intermediate is reduced by a second glutathione molecule (Figure 1b), and this second

(11.9 and 15.9 kDa), each synthesized by

step is the rate determining of the overall

one of two in-frame translation initiation

reaction.2,3

start sites. 4 The cytosolic isoform is

The side reaction of attack of the

synthesized from the second AUG and

C-terminal active site cysteine over the

lacks an N-terminal extension, while the

mixed disulfide formed between the

long isoform, that carries a mitochondrial

N-terminal cysteine and glutathione that

targeting pre-sequence, results from

results in the formation of the intramolecular

translation from the first AUG.4

disulfide (Figure 1c), would detract from the

The current work is focused on the

maximal catalytic rate by involving some

two dithiolic enzymes, yGrx1 and the

of the enzyme and glutathione molecules

short isoform of yGrx2. These proteins

in nonproductive exchange reactions.

are highly similar (64% identity and 85%

This side reaction also takes part in the

similarity), although deletions of their

dithiol mechanism, which involves both

respective genes have rendered yeast

active site cysteines.

mutants with distinct phenotypes.5 GRX1

In the yeast Saccharomyces cerevisiae,

mutants are sensitive to oxidative stress

eight Grx genes have been identified

caused by superoxide anion, whereas GRX2

(yGRX1-8). yGrx1 and yGrx2 are dithiolic

mutants are sensitive to stress induced by

Grxs, which contain the conserved

hydrogen peroxide.5 Furthermore, studies

CPYC motif in their active sites. yGrx2 is

with yeast knockouts have indicated

present in two molecular weight isoforms

that yGrx2 accounts for most of the

Activity Report 2009 | 67

Structural Aspects of the Distinct Biochemical Properties of Glutaredoxin 1 and Glutaredoxin 2 from Saccharomyces cerevisiae

glutathione-dependent oxidoreductase

as the search model. Then, the refined

activity in the cell. Since yGrx1 and

structure of oxidized yGrx2 was used to

yGrx2 expression levels are similar, the

solve the structure of yGrx2 bonded to

exhibited phenotypes in knockout strains

glutathione by molecular replacement.

could reflect the fact that yGrx2 is a more efficient enzyme than yGrx1.

The structures of yGrx2 were analyzed and compared to the structures of yGrx1 available in the Protein Data Bank (PDB codes 2JAC and 2JAD). 7 Our structural

Results and Discussion Since yeast cell-free extracts from ∆GRX2 but not ∆GRX1 lose most of their glutathione-dependent oxidoreductase activity,5 we measured the specific activities of pure recombinant yeast dithiolic Grxs, using the standard assay of reduction of the mixed disulfide formed between HED and glutathione (β-ME-SG). In spite of the high sequence similarity, yGrx2 presents a specific activity as an oxidoreductase fifteen times higher than yGrx1 in the reduction

analyses suggest that in the structure of yGrx2 bonded to glutathione (cyan), the C-terminal active site cysteine Cys30 (replaced by a serine) is turned to the opposite side in relation to the mixed disulfide between the N-terminal cysteine and glutathione and would be in an unfavorable conformation to attack the mixed disulfide (Figure 2). This probably due to interactions established with the Glu52 that appear to be possible due to the

of mixed disulfides with glutathione by

non-interfering side chain of Ala23. If the

the monothiolic mechanism (Table 1).

side reaction that results in the formation

To investigate the reasons for this

of the intramolecular disulfide would be

biochemical difference, we elucidated the

unfavoured, the reduction of the mixed

crystal structure of yGrx2 in the oxidized

intermediate of yGrx2 and glutathione by

form and complexed to glutathione. X-ray

another glutathione molecule would be

diffraction data were collected at the

favored, and consequently the monothiolic

D03B‑MX1 beam line of the Brazilian

mechanism would be also favored.

Synchrotron Light Laboratory. The

In contrast, in the structure of yGrx1

oxidized structure was solved by molecular

bonded to glutathione (light gray), the

replacement using a theoretical model

C-terminal active site cysteine Cys30 (replaced

built with the atomic coordinates of the

by a serine) is turned directly to the mixed

Grx from Sus scrofa (PDB code 1KTE)6

disulfide formed between the N-terminal active site cysteine and glutathione and would be in a favorable conformation

Table 1.

Specific activity and pKa of Cys27 for yGrx1, yGrx2 and their mutants.

Specific activity (µmol/min/mg) Grx1 Grx1-S23A Grx1-C30S Grx2 Grx2-A23S Grx2-C30S

8.2 28.2 39 125 67 38

68 | Activity Report 2009

± ± ± ± ± ±

0.3 0.3 1 7 1 2

pKa Cys27 3.2 3.5 3.7 3.7 3.1 3.7

± ± ± ± ± ±

0.2 0.2 0.2 0.2 0.2 0.2

to attack the mixed disulfide, probably because in yGrx1 the 23 residue is a Ser, which forms a hydrogen bond with the Gln52, avoiding the interaction between Cys30 and Gln52 (Figure 2). Consequently, the side reaction of attack of the C-terminal active site cysteine over the mixed disulfide

Science Highlights

Figure 2.

Side chain conformation of Ser30 in the structures of the C30S mutants of yGrx119 (gray) and yGrx2 (cyan) in their glutathionylated forms. Considering that the conformation of a Ser residue is similar to that adopted by a Cys, the attack of Cys30 on the mixed disulfide is less favorable in yGrx2 than in yGrx1.

would be favored and would detract from

about the influence of residue 23 in the

the maximal catalytic rate.

activity of yeast dithiol Grxs.

Then, the substitution of Ser

Also, the substitution of Cys30 in yGrx1

yGrx1 by Ala23 in yGrx2 could modify

by a serine causes an increase in the

the capability of the active-site C-terminal

specific activity, once the side reaction

cysteine to attack the mixed disulfide

that detracts from the maximal catalytic

between the N-terminal active-site cysteine

rate was eliminated (Table 1). However the

and glutathione, changing the overall

same mutant of yGrx2 presents a decrease

rate reaction.

in the specific activity. Cys 30 probably has

To test our hypothesis we constructed

different roles in the reaction mechanism

mutant Grxs and performed a kinetic

of yGrx1 and yGrx2, and could be related

analysis for native and mutants Grxs. The

to substrate specificity in yGrx2.

substitution of Ser23 by Ala in yGrx1 results

The low pka value of the N-terminal active

in an increase in the specific activity in

site cysteine, around 3.5, is an important

comparison with native yGrx1. And the

feature to the reactivity of Grxs, so we

substitution of Ala by Ser in yGrx2 results

determined the pKa of these cysteines for

in a decrease in the specific activity in

native and mutant proteins. However, for all

comparison with the native protein (Table 1).

isoforms tested, the pKa values obtained

These results support our hypothesis

are low and close to each other, indicating

Activity Report 2009 | 69

Structural Aspects of the Distinct Biochemical Properties of Glutaredoxin 1 and Glutaredoxin 2 from Saccharomyces cerevisiae

that this physico-chemical property is not

structures and the influence of Ser23/Ala23 in

responsible for the different activities of

the yGrx1 and yGrx2 activities, respectively,

these Grxs (Table 1).

we hypothesize that yGrx2 could be

In conclusion, the great enzymatic

more specially adapted to the monothiol

difference observed between yGrx1 and

mechanism than yGrx1. These structural

yGrx2 does not appear to be related to

and functional differences between yGrx1

the pKa of their reactive cysteines, but

and yGrx2 might reflect variations in

to specific structural features of these

substrate specificity, which would have

enzymes. Considering the conformation of

consequences in terms of cellular redox

Ser /Cys in dithiolic yGrxs glutathionylated

pathways.

References 1. Holmgren, A. Thioredoxin and glutaredoxin systems. Journal of Biological Chemistr y, v. 264, n. 24, p. 13963 -13966, 1989. 2. Fernandes, A. P.; Holmgren, A. Glutaredoxins: glutathione-dependent redox enzymes with functions far beyond a simple thioredoxin backup system. A ntiox idants Redox Signa ling , v. 6, n. 1, p. 63-74, 2004. 3. Srinivasan, U.; Mieyal, P. A.; Mieyal, J. J. pH profiles indicative of rate-limiting nucleophilic displacement in thioltransferase catalysis. Biochemistr y, v. 36, n. 11, p. 3199-3206, 1997. 4. Pedrajas, J. R. et al. Two isoforms of Saccharomyces cerevisiae glutaredoxin 2 are expressed in vivo and localize to different subcellular compartments. Biochemica l Jou rna l, v. 364, n. 3, p. 617-623, 2002 5. Luikenhuis, S. et al. The yeast Saccharomyces cerevisiae contains two glutaredoxin genes that are required for protection against reactive oxygen species. Molec u lar Biology of the Cel l, v. 9, n. 5, p. 1081-1091, 1998. 6. Katti, S. K. et al. Crystal structure of thioltransferase at 2.2 Å resolution. Protein Science, v. 4, n. 10, p. 1998-2005, 1995. 7. Håkansson, K. O.; Winther, J. R. Structure of glutaredoxin Grx1p C30S mutant from yeast. Ac ta Cr ysta l log raphica D, v. 63, n. 3, p. 288-294, 2007.

70 | Activity Report 2009

Structure and Calcium Binding Activity of LipL32, the Major Surface Antigen of Pathogenic Leptospira sp. Pricila Hauk,1,2,3 Cristiane R. Guzzo,3 Henrique Roman–Ramos,1,3 Paulo Lee Ho,1,2,3 Chuck S. Farah3

Centro de Biotecnologia, Instituto Butantan, 05.503-900, São Paulo, SP, Brazil

Programa de Pós-Graduação Interunidades em Biotecnologia,

Instituto de Pesquisas Tecnológicas – IPT, Instituto Butantan, Instituto de Ciências Biomédicas, Universidade de São Paulo – USP, 05.508-900, São Paulo, SP, Brazil 3

Departamento de Bioquímica, Instituto de Química,

Universidade de São Paulo, USP, 05.508-000, São Paulo, SP, Brazil

Leptospirosis, caused by the spirochaete Leptospira, is an important emerging infectious disease. LipL32 is the major exposed outer membrane protein (OMP) found exclusively in pathogenic leptospires. It is highly immunogenic and has been shown to bind to host extracellular matrix (ECM) components, including collagens, fibronectin and laminin. In this work we crystallized recombinant LipL32 protein and determined its structure to 2.25 Å resolution. Initial phases were determined using the multi-wavelength anomalous dispersion technique with data collected from selenomethionine-containing crystals at the MX2 beamline at the LNLS. The LipL32 monomer is made of a jelly-roll fold core from which protrude several peripheral secondary structures. Some structural features suggested that LipL32 could bind Ca2+ ions and indeed, spectroscopic data (circular dichroism, intrinsic tryptophan fluorescence and extrinsic 1-amino‑2‑naphthol‑4‑sulfonic acid fluorescence) confirmed the calcium binding properties of LipL32. Keywords Leptospira, LipL32, MAD-phasing, jelly-roll fold, calcium-binding.

Facility: MX2 Publication: Journal of Molecular Biology, 390: 722-736 (2009) Funding: FAPESP, CNPq, Fundação Butantan

Structure and Calcium Binding Activity of LipL32, the Major Surface Antigen of Pathogenic Leptospira sp.

Introduction

were collected from two crystals at the

Many fundamental aspects of Leptospira

MX2 beamline at the LNLS.1, 2 Initial phases

interrogans biology are poorly understood.

were estimated using a MAD data set

The most abundant antigen found in the

collected from one crystal (crystal 1 in

leptospiral total protein profile is LipL32.

Table 1) at two wavelengths, 0.97814 and

This highly immunogenic outer–membrane

0.978308 Å, corresponding to the peak

lipoprotein is conserved among pathogenic

and inflection points of the fluorescence

Leptospira species but not observed in the

spectrum, respectively. The f´ and f´´

non–pathogenic saprophytic L. biflexa.4, 5 It

anomalous scattering factors in Table 1

is therefore considered a promising target

were estimated from the fluorescence

for vaccine development and diagnosis

spectrum of the SeMet–labelled protein

of leptospirosis. Recently, studies using a Leptospira interrogans lipL32 mutant showed that LipL32 does not play a essential role in either acute or chronic models of animal infection.6 While these data did not identify an indispensible role in pathogenesis, it does not exclude an important function for LipL32 in mediating the host–pathogen interaction. Here, we describe the resolution of the X–ray structure of LipL32, which represents a fundamental step towards understanding its structure–function relationships. The resolved tertiary structure showed a jelly roll fold similar to those presented by some calcium–binding and ECM–binding proteins. Additional biochemical characterizations confirmed the capacity of LipL32 to bind calcium ions.

crystal using the program CHOOCH. The program SHELXD was used to find the selenium sites in the asymmetric unit and these positions were refined and phases calculated up to 2.6 Å resolution using the program SHARP (note that while the dataset for this crystal was complete only up to 2.93 Å, incomplete data was collected up to 2.6 Å). Phases were refined by density modification and the electron–density map was used to construct a preliminary polyalanine model using the program ARP/wARP that contained 303 residues distributed over 27 peptide segments. Interpretation of electron–density maps and construction of missing residues was performed using the program COOT. Subsequently, a second dataset was collected from a new crystal that diffracted to 2.25 Å resolution using

Results and Discussion

1.459 Å radiation.2 The initial model was

1. Resolution of the LipL32 structure

used to calculate phases for the 2.25 Å

Recombinant LipL3221–272 containing

resolution dataset using the Phaser

selenometionine was crystallized in space

program. Structural refinement of the

group P3221. This fragment corresponds

LipL32 model was done using ARP/wARP,

to the full–length mature protein minus

REFMAC, CNS, and COOT. TLS was used

the N–terminal lipid–anchored cysteine

in the final cycles of refinement with each

residue. The X–ray diffraction datasets

chain in the asymmetric unit divided into

(Table 1) used to resolve the structure

15 independent group segments.

72 | Activity Report 2009

Science Highlights

Table 1.

Recombinant SeMet-labelled LipL32 crystal parameters and data-reduction statistics.

Crystal 1 Space group = P3221 Unit-cell parameters (Å) a (Å) b (Å) c (Å) Resolution range (Å)1,2 No observed reflections No unique reflections <I/errorI>1,2 Multiplicity1,2 Completeness (%)1,2 Rmerge (%)1,3 No images Oscillation angle λ (Å) f’ f”

Crystal 2

Peak

Inflection

126.2 126.2 95.9 40.00 – 2.93 (3.03 – 2.93) 184445 36676 10.8 (2.0) 5.0 (4.1) 99.6 (96.6) 11.5 (47.7) 160 1° 0.97814 –8.40 6.65

126.3 126.3 95.9 40.00 – 3.00 (3.11 – 3.00) 175481 34340 9.5 (1.8) 5.1 (4.6) 100.0 (99.7) 12.8 (59.5) 160 1° 0.97831 –11.4 3.80

126.7 126.7 96.0 40.00 – 2.25 (2.33 – 2.25) 444816 42419 22.0 (1.9) 10.5 (5.6) 99.4 (95.8) 7.1 (46.6) 204 1° 1.459

Values in parentheses refer to the highest resolution shell. Values in square brackets in the Peak dataset refer to statistics obtained using reflections in the range 40.00-2.93 Å. 3 Rmerge = Σ(I – <I>)**2/Σ(I)**2 For Crystal 1, each member of a Friedel pair is counted as a separate reflection. Table reproduced from Hauk et al.2 2

Even though Matthews coefficient

Table 2. Refinement statistics for P3221 LipL3221‑272 crystal structure.

Refinement (35.0 – 2.25 Å)

analysis suggested 3 or 4 molecules

No. of molecules/A.U. residues/chain waters Rfactor ‫ד‬ Rfree ‫ד‬ R.m.s.d. bond lengths (Å) bond angles (º) % of residues in Ramachandran regions most favored additional allowed generously allowed disallowed

in the asymmetric unit, the final model contained only two monomers (Mathews coefficient = 4.03) and 69.5% solvent. The refined structure converged to Rwork and R free values of 0.184 and 0.227, respectively. Refinement data statistics are shown in Table 2. The two monomers in the asymmetric unit are related by a non–crystallographic two–fold axis and are very similar in structure, with a RMSD of 0.6 Å for all atoms. The LipL32 structure

2 254 295 0.184 0.227 0.017 1.582

91.5 8.5 0.0 0.0

Rfactor = Σ|FO – FC|/Σ FO 5% of the data were excluded for Rfree calculation. Table reproduced from Hauk et al.1 ‫ד‬

has been deposited in the Protein Data Bank (pdb) under code 3FRL. elements (Figures 1a, b). Some of these 2. LipL32 structure

peripheral structures are β–strands (β4, β7

The monomer structure is built around

and β13) that associate with the edges

a central jelly–fold β–sandwich topology

of the central β–sandwich. Four alpha

of 8 β–strands (strands 3, 5, 6, 8, 9, 10,

helices and two 310 helices are also found

11, 12) from which protrude loops that

in these loops (Figures 1a, b). The two

carry the other secondary structure

310 helices are both found in a stretch Activity Report 2009 | 73

Structure and Calcium Binding Activity of LipL32, the Major Surface Antigen of Pathogenic Leptospira sp.

Figure 1.

LipL3221–272 structure and crystal contacts. (a) Cartoon model of the LipL3221–272 monomer. The N– and C–termini are indicated. β–strands, α–helices and 310 helices are numbered in the order in which they appear in the sequence. Helices are colored red, the eight β–strands that form the core jelly-roll topology are shown in blue, while the other β–strands are show in yellow. (b) Topology diagram for LipL3221–272 in which helices are represented as red rectangles and β–strands as arrows. Figure reproduced from Hauk et al.1

between β10 and β11. 3101 is two turns

similar to that of LipL3221–272. This analysis

in length (residues 193–198) while 3102

found a small group of proteins with

is made up of only one turn (residues

Z–scores above 5.0. All these proteins

201–203). One conspicuous feature of

share a common jelly–roll fold topology

the LipL3221–272 structure is an N–terminal

at their core (shown in blue in Figures 1a)

β–hairpin (β1–β2) that protrudes from the

but all differ in the nature and number of

more compact portion of the molecule.

secondary structure elements inserted

Another interesting feature is the loop

in the loops between these strands. The

between α3 and β9 (residues 154–169),

structure with the highest Dali z–score (8.8)

that contains a large proportion of acidic

was that of the isolated domain III from

amino acids (AKPVQKLDDDDDGDD) of

human calpain 7 (pdb 2qfe; unpublished)

which those underlined are disordered

which is distinguished from the others

with no significant electron density in both monomers). This loop has been subsequently shown to be involved in Ca2+–binding.7

by the presence of a C–terminal β–strand that is topologically analogous to β13 of LipL3221–272. Many of the proteins with topologies most similar to LipL32 have been shown

3. Comparison of LipL3221–272 with

to bind calcium ions. For example, domain

other protein structures

III from calpain, collagen–binding domain

LipL3221–272 has no significant sequence

(CBD) from ColG, and many icosahedral

similarity with proteins of known structure.

RNA virus coat proteins, undergo significant

We therefore used the Dali program8 to

structural rearrangements upon binding

search for protein structures with topologies

calcium.9–12 Analysis of the superposition

74 | Activity Report 2009

Science Highlights

Figure 2.

Ca2+–induced conformational and stability changes in LipL3221–272. (a) Circular dichroism (CD) spectra of LipL3221–272 in the absence or presence of Ca2+ or Mg 2+. CD experiments were performed with 10 µM protein in 10 mM Tris–Cl pH 8.0, 50 mM KCl in the presence or absence of either 1 mM CaCl2 or 1 mM MgCl2. (b) LipL3221–272 tryptophan fluorescence in the absence of divalent metals or in the presence of Ca2+ or Mg2+. A blue–shift in Trp emission is observed in the presence of Ca2+. Intrinsic fluorescence experiments were performed with 2 µM protein in 10 mM Tris–Cl pH 8.0, 50 mM KCl in the presence or absence of either 1mM CaCl2 or 1mM MgCl 2. Excitation wavelength was 285 nm. (c) Thermal stability of LipL32 21–272 in different conditions. Circular dichroism was used to detect temperature–induced changes in LipL32 21–272 secondary structure (see Materials and Methods). Conditions were the same as in part (a). Figure reproduced from Hauk et al.1

of LipL3221–272 with the Ca2+–ColG collagen

the loop between α3 and β9 that contains

binding domain structure revealed that

seven aspartate residues within an eight

some of the secondary structure elements

amino acid stretch (residues 161–168).

that contribute to the ColG Ca2+–binding

A portion of this loop containing the first

site are absent in LipL32 21–272. Another

three aspartates (residues 161–168) are

possible Ca –binding site was identified as

absent in our crystal structure due to lack

Activity Report 2009 | 75

Structure and Calcium Binding Activity of LipL32, the Major Surface Antigen of Pathogenic Leptospira sp.

of electron density. We predicted that this

LipL3221–272. CD and ANS fluorescence were

loop could adopt a more ordered structure

monitored during thermal denaturation of

upon ligand binding. This prediction was

the protein in the presence or absence of

born out by the subsequent determination

Ca2+.1 In the CD experiments, the midpoint

of the Ca2+–LipL32 crystal structure.7

of the conformational transition (Tm) was

4. LipL3221–272 specifically binds calcium ions

observed to increase from 50 °C in the absence of Ca2+ to 56 °C in the presence of Ca2+ while only a very small change in the

The above observations led us to

Tm (+1 °C) was observed upon addition

test whether LipL32 21–272 is capable of

of MgCl2 (Figure 2c). A similar result was

interacting with calcium ions. We therefore

obtained by monitoring ANS fluorescence:

used circular dichroism and fluorescence

in the presence or absence of Mg2+ the Tm

spectroscopy to detect structural changes

was 51 °C while in the presence of Ca2+

in LipL3221–272 induced by the addition of

it increased to 58 °C (data not shown).1

calcium ions.1 Circular dichroism spectra

No changes in thermal stability were

of LipL32 21–272 clearly demonstrate a

observed in the presence of 1 mM ZnCl2

change in secondary structure content

or CuCl2 (data not shown).

upon the addition of Ca2+ but not upon the addition of Mg2+ (Figure 2a). LipL3221–272

Conclusions

possesses three tryptophan residues,

The importance of calcium as a key

Trp85, Trp130 and Trp134 all of which are

regulator in several fundamental aspects

significantly buried within the LipL3221–272

of eukaryote biology is well established.

structure and a significant blue–shift in

An increasing importance for a role for

the LipL32 21–272 tryptophan emission

calcium in prokaryotes is also being

was observed upon the addition of 1 mM

implicated in several processes, including

CaCl2 but not upon addition of 1 mM MgCl2

signal transduction, cell cycle and division

(Figure 2b). Furthermore, the fluorescence

control, competence, pathogenesis,

of 1–amino–2–naphthol–4–sulfonic acid

motility and chemotaxis, host–pathogen

(ANS) was observed to increase upon

interactions, stability and integrity of

the addition of Ca

(data not shown),

the outer lipopolysaccharide layer and

indicating an overall structural change with

bacterial cell wall and specific enzyme

an increase in the surface hydrophobicity

activity13–16 and calcium ions are absolutely

of the LipL32 21–272 molecule. None of

required for Leptospira spp to grow and

these changes were observed when the

survive.17, 18

experiments were repeated using Mg2+, Zn2+ or Cu2+ ions (data not shown).1 5. Calcium binding by LipL3221–272 increases protein stability

We demonstrated for the first time that LipL32 binds Ca2+. The data also suggest that LipL32 does not bind Mg2+, Zn2+ or Cu2+ ions, at least not in a manner similar to that observed for Ca2+, since no significant

We then tested whether the addition of

structural changes or increases in thermal

Ca affected the conformational stability of

stability were observed in these cases.

76 | Activity Report 2009

Science Highlights

Analysis of the LipL32 structure pointed

The crystal structures of this important

to two putative Ca –binding sites. One of

leptospiral protein1, 7, 19 have provided a wealth

these, the loop between α3 and β9 that

of information from which to raise hypothesis

contains seven aspartate residues within

regarding the molecular mechanisms by

an eight amino acid stretch (residues

which LipL32 interacts with Ca2+ and with

161–168) has recently been shown to

ECM proteins. These hypotheses will be

contribute significantly to the Ca –binding

addressed in future experimental studies

site in the Ca2+–LipL32 structure.7

using site–directed LipL32 mutants.

References 1. Hauk, P. et al. Structure and calcium-binding activity of LipL32, the major surface antigen of pathogenic Leptospira sp. Jou rna l of Molec u lar Biology, v. 390, n. 4, p. 722-736, 2009. 2. Hauk, P. et al. Crystallization and preliminary X-ray analysis of LipL32 from Leptospira interrogans serovar Copenhageni. Ac ta Cr ysta l log raphica F, v. 65, n. 3, p. 307-309, 2009. 3. Zuerner, R. L. et al. Characterization of outer membrane and secreted proteins of Leptospira interrogans serovar pomona. Microbia l Pathogenesis, v. 10, n. 4, p. 311-322, 1991. 4. Haake, D. A. et al. The leptospiral major outer membrane protein LipL32 is a lipoprotein expressed during mammalian infection. Infec tion and Immunit y, v. 68, n. 4, p. 2276-2285, 2000. 5. Picardeau, M. et al. Genome sequence of the saprophyte leptospira biflexa provides insights into the evolution of leptospira and the pathogenesis of leptospirosis. PLoS One, v. 3, n. 2, p. e1607, 2008. 6. Murray, G. L. et al. Major surface protein LipL32 is not required for either acute or chronic infection with Leptospira interrogans. Infec tion and Immunit y, v. 77, n. 3, p. 952-958, 2009. 7. Tung, J. Y. et al. Calcium binds to LipL32, a lipoprotein from pathogenic leptospira, and modulates fibronectin binding. Jou rna l of Biolog ica l Chemistr y, v. 285, n. 5, p. 3245-3252, 2010. 8. Holm, L. et al. Searching protein structure databases with DaliLite v.3. Bioinformatics, v. 24, n. 23, p. 2780-2781, 2008. 9. Johnson, J. E. Virus particle dynamics. Advances in Protein Chemistr y, v. 64, p. 197-218. 2003. 10. Speir, J. A. et al. Enhanced local symmetry interactions globally stabilize a mutant virus capsid that maintains infectivity and capsid dynamics. Journa l of Virology, v. 80, n. 7, p. 3582-3591, 2006. 11. Tompa, P. et al. Domain III of calpain is a Ca2+-regulated phospholipid-binding domain. Biochemical and Biophysica l Research Communications, v. 280, n. 5, p. 1333-1339, 2001. 12. Wilson, J. J. et al. A bacterial collagen-binding domain with novel calcium-binding motif controls domain orientation. EMBO Jou rna l, v. 22, n. 8, p. 1743-1752, 2003. 13. Michiels, J. et al. The functions of Ca2+ in bacteria: a role for EF-hand proteins? Trends in Microbiology, v. 10, n. 2, p. 87-93, 2002. 14. Norris, V. et al. Calcium in bacteria: a solution to which problem? Molec u lar Microbiology, v. 5, n. 4, p. 775-778, 1991. 15. Norris, V. et al. Calcium signalling in bacteria. Journal of Bacteriology, v. 178, n. 13, p. 3677‑3682, 1996. 16. Onek, L. A.; Smith, R. J. Calmodulin and calcium mediated regulation in prokaryotes. Jou rna l of Genera l Microbiology, v. 138, n. 6, p. 1039-1049, 1992. 17. Johnson, R. C.; Gary, N. D. Nutrition of Leptospira Pomona III. Calcium, magnesium, and potassium requirements. Jou rna l of Bac teriology, v. 85, n. 5, p. 983-985, 1993. 18. Shenberg, E. Growth of pathogenic leptospira in chemically defined media. Jou rna l of Bac teriology, v. 93, n. 5, p. 1598-1606, 1967. 19. Vivian, J. P. et al. Crystal structure of LipL32, the most abundant surface protein of pathogenic Leptospira spp. Jou rna l of Molec u lar Biology, v. 387, n. 5, p. 1229-1238, 2009.

Activity Report 2009 | 77

A Multi–technique Study of Structure and Dynamics of Polyfluorenes Cast Films and the Influence on Their Photoluminescent Properties Gregório Couto Faria,1 Tomás Sigfrido Plivelic,2,5 Rafael DiFalco Cossiello,3 André Alves de Sousa,1 Teresa Dib Zambom Atvars,3 Iris Concepcion Linares de Torriani,2,4 Eduardo Ribeiro de Azevedo1

Instituto de Física de São Carlos, Universidade de São Paulo – USP, CP 369, 13.560–970, São Carlos, SP, Brazil 2 Laboratório Nacional de Luz Síncrotron – LNLS, CP 6192, 13.083–970, Campinas, SP, Brazil 3 Instituto de Química, Universidade Estadual de Campinas – UNICAMP, CP 6154, 13.084–971, Campinas, SP, Brazil 4 Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas – UNICAMP, CP 6165, 13.084–971, Campinas, SP, Brazil 1

MAX–lab, Lund University, PO Box 118, SE–22100, Lund, Sweden

In the last few years the use of conjugated polymers as active layers in the so called “organic electronics” has progressed rapidly from being an interesting academic material to become a reality on electronic industries, being applied even for thin flexible displays. However, understanding how the structural and dynamic properties of the polymer chain may affect the light emission still remains a challenge. Here we report a multi–technique study of the microstructure and dynamics in solid state of polyfluorene based polymers, poly(9,9–dioctylfluorenyl–2,7–diyl) (PFO) a semi–crystalline polymer and poly[(9,9–dioctyl–2,7–divinylene–fluorenylene)–alt–co– {2–methoxy–5–(2‑ethyl‑hexyloxy)–1,4–phenylene vinylene} (PFO–alt–co– MEHPV), a copolymer with mesomorphic phase properties. The Wide–Angle X–ray Scattering (WAXS) measurements revealed the structures, the structural transformations and the local packing variations that occurred as a function of temperature as a result of polymer chain relaxations, also identified by Dynamical Mechanical Thermal Analysis (DMTA) and Solid–State Nuclear Magnetic Resonance (NMR). For PFO–altco–MEHPV, the variation in the packing and the chains motion could explain the changes produced in the fluorescence of the polymer. In contrast, for PFO, besides the molecular relaxation and local packing variations in the more disordered regions, strong modifications in its luminescent behavior is observed as a results of the phase transformations induced by temperature.

Facility: SAXS2 Publication: Journal of Physical Chemistry B, 113: 11403–11413 (2009) Funding: FAPESP, CNPq, MCT, CAPES

Science Highlights

Introduction Organic electronics is currently an important subject concerning new developing technologies. The use of organic molecules in optoelectronic and photovoltaic devices provides many advantages, such as easy material processing, simple device manufacture, and the possibility of producing flexible devices. The use of conjugated polymers in organic electronics is already a reality (Figure 1), but there are still many points that must be overcome for achieving stable devices. One challenge is to understand how the structural and dynamic properties of the polymers could affect the desired properties. For example, the

Figure 1.

Some examples of optical devices based on luminescent p o l y m e rs : A n exa m p l e o f p h o t o l u m i n e s c e n c e o f polyfluorene derivative; Two rigid white emitting display (one made in the Bernhard Gross polymer group at IFSC); A flexible blue monochromatic large area display and a flexible colored prototype display designed by Sony.

efficiency of the electroluminescence (EL) and photoluminescence (PL) is changed depending on the structure

poly(9,9–dioctylf luorenyl–2,7–diyl)

and the dynamics of the polymer

(PFO) and the alternated copolymer

chains. Among the conjugated polymers,

poly[(9,9–dioctilfluorenil–2,7–diyl)–co–{1,4

polyfluorene–based polymers form a large category of thermal and chemical stable polymers emitting from the blue

vinilenofenilene)] (see chemical structure in Figure 2a), using WAXS, Solid–State NMR, DMTA and PL.

to the red,1,2 depending on the chemical structure, substituent and side–chain. 3

Experimental

These chemical modifications control

The samples were purchased from

the supramolecular structure and their

American Dye Source (ADS) Company

optical properties. 4 Thus, in addition to the

under the trademarks ADS 329BE (PFO)

relaxation processes involving segments

and ADS108GE (PFO–altco–MEHPV).

of the polymer chains, the emission of

Self–standing 15 µ m thick polymer films,

polyfluorenes is also related to the solid

obtained from 20 mg/mL of toluene

state phase transitions because some of

solution, were used in all measurements

them crystallize in more than one phase

here reported. WAXS experiments were

and others form molecular aggregates

performed at the D02A–SAXS beam line of

with mesomorphic phases.

In this

the LNLS, using 1.488 Å wavelength and

report we summarize the investigation

a sample detector distance of 189.62 mm.

of the microstructure and dynamics

Multilayer samples of up to 500 µ m

of two representative polyf luorene

thickness were prepared stacking pieces

based polymers, the homopolymer

cut from a single film and set–up in two

Activity Report 2009 | 79

A Multi-technique Study of Structure and Dynamics of Polyfluorenes Cast Films and the Influence on Their Photoluminescent Properties

configurations: with the incident X–ray beam perpendicular (⊥) and near–parallel

The 2D–WAXS images for both

(//) to the film plane. WAXS patterns were

studied materials shown in Figure 2a

obtained at several temperatures using a two–dimensional (2D) CCD detector and a sample support adapted to a hot stage cell designed for X–ray scattering measurements. Steady–state fluorescence

are composed of scattering rings with roughly uniform intensity when the X–ray beam is perpendicular to the film surface, but we observe short arcs and rings of non–uniform intensity when the X–ray incidence is nearly parallel. This shows

spectra were recorded using a PC1 TM

that the scattering from certain periodic

Photon Counting Spectrofluorimeter from

structures in the sample have a preferential

ISS Inc with excitation was performed

orientation, with a tendency to be arranged

using the 337 nm emission of a He–Cd

parallel to the film surface and randomly

laser. Dynamical Mechanical Thermal

distributed in the plane. However, while

Analysis were performed in a Netzsch 242 C instrument using the tension mode at frequencies ranging from 0.01 to 100 Hz and heating rate of 1 K/min from 150 K to 400 K. Solid–State NMR experiments

the 2D images of PFO show both sharp and broad rings, consistent with the presence of crystalline microstructures diluted in a more disordered matrix, for PFO–alt–co–MEHPV only broad rings are observed, showing that there is

were performed using a 9.4 T VARIAN

no crystalline phase in this polymer.

spectrometer in a 7 mm MAS–VT probe

Figure 2b (left) shows a series of PFO

head.

diffractograms as a function of temperature

Figure 2.

Results and Discussions

a) Chemical structures and 2D WAXS imagens of PFO and PFO-alt-co-MEHPV. b) Temperature dependence of the diffratograms taken from meridional and equatorial cuts from the 2D imagens obtained for PFO (left) and PFO‑alt‑co-MEHPV (right).

80 | Activity Report 2009

Science Highlights

corresponding to equatorial cuts taken

(di = 2p/qi) of d1 = 15.9 Å, d2 = 7.9 Å, d3 = 4.5 Å

from the 2D images in the normal and near

suggesting an aggregation structure where

parallel incidence. At low temperatures,

the backbone rings are stacked parallel

the equatorial and meridional intensity

to each other with interplanar distances

profiles have some sharp reflections. The

of 4.5 Å and laterally spaced by the side

peaks associated to the distances 12.6 Å,

chains with average distances of 15.9 Å.

6.6 Å and 4.2 Å are fairly equally spaced

In this supramolecular structure, other

in q–space, suggesting that they arise from

important characteristic distance d2 = 7.9 Å

different order reflections of a lamellar

corresponds to the separation between

phase, referred as β phase. The profiles

monomeric units (which is about the size

are identical bellow 373 K, showing that

of a fluorene unit). A sketch of the packing

the β phase is stable in this temperature

structure is shown in Figure 3a. Note

range. Above 373 K the characteristic diffraction peaks corresponding to the

β phase have their intensity reduced, indicating the dissipation of this phase. At 413 K a series of sharp peaks start showing up, accounting for the onset of the sample crystallization, which results in a diffractogram with well defined peaks at 433 K, when the crystalline phase seems to be fully formed. The peaks at q = 3.5 nm–1 (d = 17.9 Å), q = 4.5 nm–1 (d = 13.9 Å), q = 5.2 nm–1 (d = 12.0 Å), q = 7.3 nm–1 (d = 8.6 Å) correspond to the (110), (200), (210) and (310) reflections correspond to the PFO α phase, which has a helical structure as reported in

also that, the PFO diffractograms have a background contribution (“amorphous halo”) that resembles the pattern observed for PFO–altco–MEHPV, also suggesting a similar structural packing in the amorphous phase of PFO. Figure 2b (right) show the PFO–altco–MEHPV diffraction profiles corresponding to equatorial and meridional sectors of the 2D Images obtained for near parallel incidence as a function of temperature. These X–ray profiles basically show the changes in two characteristic distances d1 and d3, which are plotted as a function of temperature in Figure 3a. No temperature dependence is observed for

reference. 6 At 453 K the crystalline α

the distance d2 (not shown), but clear trends

phase is melted giving rise to a typical

are observed for d1 and d3. Note that, while

nematic liquid crystalline phase pattern.

d1 generally increases as the temperature

In contrast to the PFO case, the 2D–WAXS

is raised, there is a jump in the slope of the

images of PFO–altco–MEHPV, Figure 2a

d1 vs. T curve at about 383 K. The slope of

(right), are composed of broad scattering

the d3 vs. T curve also changes at about

peaks, indicating the presence of only

383 K, bending downwards in contrast

local ordering in the PFO–altco–MEHPV.

with the behavior of d1. These results show

The three defined broad maxima in the

that, although the aggregated structures

diffractograms shown in Figure 2b (right)

are present at all temperatures explored in

(see vertical dashed lines), taken from both

these measurements, the intermolecular

meridian and equatorial sectors of the 2D

distances inside these structures depend

images, correspond to characteristic lengths

on temperature, which can be attributed to

Activity Report 2009 | 81

A Multi-technique Study of Structure and Dynamics of Polyfluorenes Cast Films and the Influence on Their Photoluminescent Properties

Figure 3.

a) Temperature dependence of the d1 and d3 characteristic length corresponding to the illustrated supramolecular aggregation of PFO–alt–co–MEHPV. b) PL spectra at different temperatures for the two studied samples.

82 | Activity Report 2009

Science Highlights

molecular motions associated to thermal relaxations process. The relaxation processes were identified by Dynamical Mechanical Thermal Analysis (DMTA), revealing three processes in both samples which were elucidated by solid–state NMR:7 γ (motion of the CH3 groups in the end of the side–chain) and β process (molecular motions in the side–groups) at ~ 120 and ~ 130K, respectively, and two relaxations named as α A, ~ 330 K (local rotations in the backbone) and αB, ~ 380 K (glass transition).

Figure 4.

Sketch of the of PFO and PFO–alt–co–MEHPV chemical structure and the motions responsible for the distinct molecular relaxations. Tem temperatures indicated the maximum of the relaxation for 1Hz excitation in DMTA.

Figure 4 show a schematic drawing of the observed relaxation process. The

structural phase transitions (β to α and

assignments of the molecular relaxations

α to liquid crystalline phase).

presented in Figure 4 allow us to understand

In general, the fluorescence emissions

behavior of the characteristic WAXS length

of conjugated polymers in the solid state

parameters d1,d2, and d3 observed in the

are strongly affected by modifications in

PFO–altco–MEHPV. Below ~380 K a clear

their local structure and packing, showing

variation of d1 value is observed, while d3

why it is so important to understand how

remains almost constant. This behavior can

molecular motions and structural features

be directly associated with the onset of the

affect their photoluminescence. This can

side chain motion, which may produce a

be achieved by correlating the temperature

substantial increase in the lateral spacing

dependence of the photoluminescence

of the rings (d1 parameter), but should

processes with the microstructure and

not produce a significant change in the

dynamic processes as revealed by X–ray,

interplanar ring distance (d3 parameter). For

NMR and DMTA. Figure 3b shows the

temperatures higher than 380 K, the side

steady–state photoluminescence spectra

chain motion is already fully established,

of PFO and PFO–altco–MEHPV films as a

but the backbone motion start to be more

function of temperature. The temperature

effective producing a more pronounced

dependence of the emission of PFO is very

increase in the interplanar ring distance

complex, because it is a semicrystalline

as function of temperature. This is again in

material. The spectra are shaper at lower

full agreement with the results observed in

temperatures, with a higher intensity peak

Figure 2. The detection of similar relaxation

at 425 nm, two overlapped peaks at around

processes in PFO, show that despite being

470–480 nm and a green emission around

difficult to observe in the WAXS patterns,

510 nm. Polyfluorene emission around

both β and α processes are also present.

420 nm and 500 nm can be assigned

However, in this case the most prominent

to the isolated fluorenyl moieties and

features observed by WAXS are the two

aggregated species, respectively. 8 This

Activity Report 2009 | 83

A Multi-technique Study of Structure and Dynamics of Polyfluorenes Cast Films and the Influence on Their Photoluminescent Properties

behavior is indicating that more than one

Conclusions

species are emitting, which is consisting

In summary, results show that the

with the WAXS results that points to the

light emission of complex materials like

presence of an amorphous phase where

luminescent polymers, are strongly affected

the phenyl rings are face to face, leading to aggregated–like emission, and a crystalline phase were the rings are apart and not facing each other,6 leading to a more isolated fluorenyl emission . Moreover, these spectra are blue–shifted under the sample heating and the vibronic structure

by the morphology, local structure as well as the molecular dynamics of the chains. Due the complexity of this kind of systems, a multi–technique approach is needed in order to understand structural and dynamic features and make the bridge between properties and functioning. In this context, X–ray techniques play an essential role,

due to the onset of the relaxation processes.

since they can provide a rather complete

For PFO–altco–MEHPV (Figure 3b) the

picture of the structural behavior of

spectral profile at lower temperatures is

the system. Specifically, the combined

red–shift compared with the PFO. This

results of this multi–technique study

emission centered at 510 nm originates

allowed the identification of four polymer

probably from the short segments of the

relaxation processes in two representative

MEH–PV groups. In addition, as suggested

polyfluorene based polymers, PFO and

by the WAXS results, the presence of

PFO–altco–MEHPV. We were able to describe

conformational disorder of the main chains confers to every group in the electronic excited state experiences different environments, which then are unable to relax within the excited state lifetime producing the broad spectra observed at lower temperatures.9 The temperature

the type of macromolecular relaxation, molecular motion and supramolecular structure ascribed to every one of them.

γ–relaxation is observed around 130 K, β–relaxation local occurs at 200–220 K, glass transition at 330 and 380 K and the melting temperature of the ordered phase is observed for PFO at 430 K. All

dependence of the fluorescence intensity

processes change the photoluminescence

decays monotonically from 20 K to 290 K,

processes in terms of the emission profile,

consistently with the presence of thermal

peak positions and relative intensity of

induced molecular motions.

the emission bands.

84 | Activity Report 2009

Science Highlights

References 1. Chang, L. H.; Lee, Y. D.; Chen, C. T. Synthesis and characterization of 3,4-Diphenylmaleimide Copolymers that exhibit orange to red photoluminescence and electroluminescence. Macromolec u les, v. 39, n. 9, p. 3262-3269, 2006. 2. Zhang, H. A. et al. Novel green-emitting polymer containing fluorene and 1-(2-benzothiazolyl)-3,5diphenylpyrazoline. Jou rna l of Materia ls Science, v. 42, n. 12, p. 4476-4479, 2007. 3. Akcelrud, L. Electroluminescent polymers. Progress in Polymer Science, v. 28, n. 6, p. 875‑962, 2003. 4. Grey, J. K. et al. Effect of temperature and chain length on the bimodal emission properties of single polyfluorene copolymer molecules. Jou rna l of Physica l Chemistr y B, v. 110, n. 38, p. 18898-18903, 2006. 5.

Grell, M. et al. Interplay of physical structure and photophysics for a liquid crystalline polyfluorene. Macromolec u les, v. 32, n. 18, p. 5810-5817, 1999.

6. Chen, S. et al. Crystalline forms and emission behavior of poly (9,9-di-n-octyl-2,7-fluorene). Macromolec u les, v. 38, n. 2, p. 379-385, 2005. 7.

de Azevedo, E. R.; Bonagamba, T. J.; Reichert, D. Molecular dynamics in solid polymers. Progress in Nuclear Magnetic Resonance Spec troscopy, v. 47, n. 3-4, p. 137-164, 2005.

8. Oliveira, H. P. M. et al. Photophysical properties and quantum chemical studies of poly(2,7-9,9’dihexylfluorene-dyil). Jou rna l of the Brazi lian Chemica l Societ y, v. 20, n. 1, p. 160-166, 2009. 9.

Lakowicz, J. R. Principles of f luorescence spec troscopy. New York: Kluwer Academic/ Plenum Publishers, 1999. 698 p.

Activity Report 2009 | 85

Accelerator Development and Operation

New Source

Beamlines

101

Nanoscience and Nanotechnology

106

Industrial Research Activities

110

Main Events

114

Facts and Figures

118

Accelerator Development and Operation

Although the storage ring underwent a major vacuum intervention in late 2008, its routine operation for users started smoothly in 2009. The preparations for the installation of the new superconducting wiggler required a new mode of operation for the storage ring that proved to be much more demanding with respect to the magnetic lattice standardization procedures and affected the average injection times to a certain extent. However, in 2009 the machine occasionally faced some problems that could be traced to the aging of some of its subsystems, which were exacerbated by failures in the power supply grid of the campus. Nevertheless, in the overall balance, 2009 was a good year in terms of reliability of the light source. During the endâ&#x20AC;&#x2018;ofâ&#x20AC;&#x2018;year machine shutdown, the replacement of the old beam position monitors was completed and the superconducting wiggler was installed in the storage ring.

Facility Report

Introduction

introduced by the insertion devices. It

Since it started its routine operation as

has been the standard operational mode

an open facility for synchrotron light users

of the machine since the beginning of

12 years ago, the LNLS synchrotron light

2009, replacing what had been roughly

source has undergone several upgrades that

the standard mode since the first days

have substantially increased its performance

of operation for users. Throughout the

and effectiveness as an important research

whole year, machine study periods were

instrument available to the Brazilian scientific

used mainly to characterize and refine

community. Throughout this period, a wide

this new operational mode.

range of improvements and upgrades were

Several activities of the engineering

implemented in the light source and its

and accelerator groups have already

beamlines. Insertion devices were added

been organized considering the studies

to the magnetic lattice to broaden the light

and developments for a new synchrotron

spectrum available, thereby expanding the

light source. There are plans to develop

experimental capabilities of the machine.

prototypes of various subsystems for

Improvements were made in the injector

installation in the current light source,

system to reduce the injection time, thereby

which will certainly benefit its performance

reducing the effects of thermal drifts in

and reliability, since the tolerances for the

both the machine and the experimental

systems of the new source are much tighter

stations. A large scale upgrade of the

than those of the current machine.

machine shielding was implemented to

In the first half of 2009, eleven beamlines

enable users to work in the experimental

were available for the user community.

hall during injections. In recent years, substantial efforts have been dedicated to improving the machineâ&#x20AC;&#x2122;s performance and reliability, with specific focus on orbit stability issues. The main achievement with respect to the performance of the light source was an increase in the average beam lifetime, which led to a small increase of the average beam current in the user shifts. This is mainly a result of the machineâ&#x20AC;&#x2122;s new operational mode with low vertical beam size in the long straight sections of the

After being upgraded, the XPD and SAXS1 beamlines were put into operation in the second half of the year. The SXS beamline is being upgraded and should become operational in 2010. The project of the PGM beamline was reappraised and the activities related to the design and construction of its components were rescheduled. After extensive review and a commitment to overcome the main difficulties of the project, the expectation is that the line will be assembled and ready for commissioning in August 2010.

storage ring. It was implemented as part of the preparations for the installation of

Accelerator Operations

the superconducting wiggler in the storage

In 2009, the operation of the synchrotron

ring. The main advantage of this mode of

light source for users followed the same

operation is that it reduces the sensitivity

pattern of previous years, with beam time

of the magnetic lattice to perturbations

for users 24 hours a day from Monday

Activity Report 2009 | 89

Accelerator Development and Operation

through Saturday morning. Machine operation for users was scheduled from January to October and was followed by an 8-week shutdown for upgrades and new installations in the Storage Ring. In low energy machines long shutdowns are necessary if any vacuum intervention is to be performed since beam lifetime recovery time is usually quite long. The last two weeks of user beam time were Figure 1.

Total beam time delivered to users since 1997.

scheduled for single bunch operation, dedicated to time-resolved experiments in the UV and soft X-ray beamlines. A total of 4059 hours of beam time were delivered to users out of the 4107 hours scheduled (Figure 1), representing a reliability of 96.4% for the light source in 2009 (Figure 2). Reliability accounts for the fraction of the scheduled beam time that was effectively implemented on time. Machine reliability in 2009 declined slightly when compared to 2008. The total delivered beam charge (Figure 3) was similar to that of the previous two years. Beam lifetime and average beam current in usersâ&#x20AC;&#x2122; shifts increased in

Figure 2.

Machine reliability in usersâ&#x20AC;&#x2122; shifts since 1997.

comparison to 2008 (cf Figures 4 and 5). The increase in beam lifetime resulted from the introduction of a new operational mode for the machine. Reliability, injection efficiency and beam orbit stability have improved continuously over the years. Regular meetings to discuss and analyze the fault logs in the operation logbook have led to investments in critical subsystems to overcome bottlenecks and weaknesses. The mean time between failures in 2009 was 61.5 hours, replicating the performance of 2007, both below the outcome of 2008. The mean time to recovery was 1.3 hour, about 30% longer

Figure 3.

Total beam charge delivered to users since 1997.

90 | Activity Report 2009

than in the previous year. Failures in the

Facility Report

electric power supply triggered several problems in critical subsystems of the light source, such as the digital control and radiofrequency systems. Some of these problems were exacerbated by the aging of the subsystems, despite sustained efforts of renovation and modernization by the technical groups. As a result, a large scale renovation of the digital control system is slated to begin in 2010. Difficulties with machine recovery after a typical maintenance day occurred on two occasions. To minimize

Figure 4.

Average beam lifetime in usersâ&#x20AC;&#x2122; shifts since 1997.

Figure 5.

Average beam current in usersâ&#x20AC;&#x2122; shifts since 1997.

the risk of compromising the operation for users, maintenance stoppages in 2010 are scheduled to be performed on Fridays, followed by a period of machine studies. This will allow for more comprehensive maintenance procedures as well as short range upgrades. The new operational mode had a negative impact on a few performance parameters that had been improving over the last few years. The new mode requires a longer standardization procedure for the magnets, resulting in longer recovery times of the machine after failures or interventions that require powering off the main magnet power supplies. It also led to an average increase in the mean injection time when compared to the very fast injections in the second half of 2008. Even so, overall, the average injection time is still shorter than it was in early 2008.

Beam Stability The ongoing goal of improved stability for the electron beam orbit led to the replacement of two thirds of the machine beam position monitors, concluding the procedure initiated in 2008. The intervention was performed at the end of the year

Figure 6.

Distribution of the injection times in 2009 compared to half year of 2008. Most of the injections where performed in less than 15 minutes.

Activity Report 2009 | 91

Accelerator Development and Operation

and resulted in venting a corresponding

beam lines. The improvements in beam

fraction of the vacuum chamber. In recent

orbit control implemented in recent years

years, a series of improvements have

have significantly reduced the short-term

been implemented in the beam position

changes of the orbit of the electrons. The

measurement system by the beam

new activities of the task force will involve

stability task force established in 2004.

attempts to reduce the long-term drifts of

The main goal was to investigate and

the electron orbit.

identify the causes of beam motions and

Other important activities were performed

instrumental problems in the BPM system

concomitantly to the BPMs. Improvements

and coordinate efforts to solve them. A

are being made in the diagnostic lines of

new model of beam position monitor was

the electron beam to provide better tools

developed which is less sensitive to thermal

for the detection of beam-related problems.

drifts and less susceptible to mechanical

Moreover, efforts to reduce the injection

deformation than the old stripline model.

time continued. New single pass BPMs

Water-cooled masks were installed at several

have been tested. After they are installed,

points in the vacuum chamber to prevent

it will be possible to measure the position

synchrotron light from hitting the walls of

of the electron beam in the transport lines,

the chamber, thereby reducing thermal

which isan important tool for improving the

drifts and their effects on the orbit of the

repeatability of the injection process.

electron beam. Over the years, several

Due to the installation of the active shunts

engineering groups have been involved in

in 2008 it was possible to apply beam-

the development, specification and testing

based alignment procedures to measure

of the new components. The results of the first set of BPMs replaced in 2008 indicate the greatly improved behavior of the new BPMs during usersâ&#x20AC;&#x2122; shifts. All the remaining old BPMs were replaced in the long machine shutdown started at the end of October. By the end of 2009, the vacuum conditions and therefore the lifetime of the electron beam were still far from the levels achieved during the year, although they are expected to be back to normal after the first months of

the position of the new beam position monitors referenced to the magnetic centre of the storage ring quadrupole magnets. These measurements were important for the characterization of new beam position monitors and for the definition of the new orbit of reference for the beamlines. Machine studies related to improvements in the electron beam diagnostic system and to the implementation of a fast feedback system to control multibunch instabilities were performed during the year.

operation in 2010. The orbit stability task force is now focused on achieving better temperature

Superconducting Wiggler for Material Sciences

control of the storage ring tunnel and of

The superconducting wiggler dedicated

the experimental hall. The goal is to reduce

to research in material sciences was

the effect of environmental temperature

installed in the storage ring in December

changes on the electron beam orbit and

2009. The factory acceptance tests were

92 | Activity Report 2009

Facility Report

successfully carried out at the Budker

higher efficiency, solid state amplifiers

Institute in Novosibirsk (Russia) in April,

have the great advantage of modularity.

under the supervision of a team from

Reliability and lower electricity costs are

LNLS. The wiggler arrived at the LNLS in

the main features of the new technology.

July and assembly and site acceptance

The current klystron-based RF system in the

tests were conducted in August by a team

LNLS storage ring is much less efficient and

from the manufacturer. Installation in the

has fixed power consumption, regardless

storage ring was carried out as planned

of the instantaneous power requirements

and the tests with the electron beam have

of the accelerator. In contrast, the power

been successful. Although still under the

consumption of the solid state devices will

impact of the BPM vacuum intervention,

follow the RF power demand. Moreover, its

it was possible to accumulate more than

intrinsic modularity makes the solid state

200 mA in the storage ring for tests with

amplifier more reliable since it continues

the SC wiggler. Accumulation and ramping

to operate even if a few modules fail.

tests were successfully performed, but

LNLS started working with high power

it is clear that several hours of machine

RF solid state amplifiers in 1999, in the

studies will still be required to have these

wake of developments that were going on

processes ready for routine operation.

at LURE, in France. At the time, LURE was

In particular, it will be necessary to

designing the new top level synchrotron

commission the injection process with

light source SOLEIL, bravely planning to

the wiggler partially energized.

have its RF system totally based on solid

In addition, a major problem appeared after installation of the wiggler in the storage ring, involving higher than expected consumption of liquid helium. This has required constant monitoring and analysis of the device to discover the source of the problem. This does not jeopardize the operation of the wiggler, but makes it much more expensive. Therefore, to facilitate the diagnosis of the problem and enable whatever intervention may be required to solve it, the wiggler was removed from the storage ring in early 2010.

state amplifiers. In close collaboration with LUREâ&#x20AC;&#x2122;s RF group, LNLS built a 900Â W solid state amplifier operating at 476Â MHz to drive the booster RF cavity. The SOLEIL RF system operates at 352 MHz, which means that the booster amplifier had to be developed entirely in-house. The booster amplifier was upgraded to 2 kW in 2007 and has been operating successfully since 2001. The high operating cost of the klystron system, represented by its electric power consumption and/or the need to keep a set of expensive spare klystron tubes on

RF Solid State Amplifier

hand, motivated LNLS to move towards

Solid state amplifiers are an effective

solid state technology. In 2007, the federal

alternative to commercial UHF electron tubes

funding agency FINEP approved a project to

like klystrons and IOTs, whose purchase

design and build two solid state amplifiers

price and operating costs are becoming

with capacity to deliver the 100 kW of power

increasingly expensive. In addition to their

at 476 MHz necessary to drive the current

Activity Report 2009 | 93

Accelerator Development and Operation

storage ring RF system. In 2008, in close collaboration with the SOLEIL RF group, the amplifiers were designed and the main components were prototyped, specified and ordered. The heart of the system is the MOSFET-based amplifier module, with integrated circulator and individual power supply. Each module is able to deliver over 330 W of power at 476 MHz. Two amplifiers have been assembled, each one built from a combination of 162 such modules and with 48 kW of maximum nominal output power. More than four hundred amplifier modules were specified and ordered. The components Figure 7.

SC wiggler installed in the straight section 09 of the LNLS storage ring.

arrived at LNLS in 2009. Modules, cables, combiners, dividers, power supplies, in short, all the components of the amplifier were extensively characterized at the RF laboratory prior to assembly. The control, monitoring and interlock systems of the amplifiers were tested carefully. By the end of 2009 the first amplifier was fully assembled and ready for commissioning (Figure 8). The amplifiers must pass a series of tests and are expected to be installed in the storage ring in late 2010.

Upgrade of the Control System An upgrade of the low level control system is planned for implementation in 2010. Since the booster synchrotron was installed in 2001, different versions of the communication cards have been introduced using either a proprietary serial or Ethernet protocol. The adoption of Ethernet communication began in 2005 with the 2 T wiggler, and has been Figure 8.

The tower of the first solid state amplifier, completely a s s e m b l e d a n d re a d y fo r c o m m i s s i o n i n g a t t h e test area.

94 | Activity Report 2009

expanding considerably since then. The whole orbit measurement system as well

Facility Report

as all the insertion devices are currently connected to the main control computer by Ethernet communication. However, there is no longer a supplier for the main components of these cards and a new solution had to be devised. The new version of the low level control system is based on single board computers, which will replace both communication (serial and Ethernet) and CPU cards. The solution is close to what is being planned for the new light source and is based on the Ethernet communication protocol. Since it is planned to be a fast solution for

Figure 9.

The single board computer card that will replace both the communication and CPU cards of the control system network.

problems that were intensified in 2009, mainly involving the communication and CPU cards, the focus of the current upgrade is to gradually replace these cards while keeping the same local controller crates with minimum changes in the topology of the control network. A prototype of the new system was bench tested and is currently inserted in the control network of the synchrotron light source. A great deal of communication software is being developed to make the new card completely transparent for the high level control software. The SBC runs high level software under Slax, a compact Linux operating system, in order to communicate with both the main

Figure 10. 3D view of the monocromator assembly of the PGM beamline which is under construction.

control programs and the equipment. Long debugging sessions and tests are still needed, but parts of the old control system will probably begin to be replaced by the new version by late 2010.

from technical support for the beamlines to the development of subsystems for the accelerators. The construction of the PGM beamline is one of the many multitask activities in which several

Other Activities

groups of the Division are engaged. An

The activities of the technical groups

overall evaluation of the PGM beamline

of the Engineering and Accelerator

project in 2009 resulted in a review and

Division have a wide scope, ranging

rescheduling of all its activities. All the

Activity Report 2009 | 95

Accelerator Development and Operation

carried out in-house. Preparations have begun for the installation of a Gleeble thermal-mechanical simulation system in the XRD1 beamline, which will allow in situ dynamic characterization of materials by X-ray diffraction techniques. Special supports have been manufactured for the SAXS1 Pilatus detector and for the DXAS 7 T superconducting magnet. A special support is being developed for the precise positioning and alignment of optical components at the beamlines. This hexapod is a mechanical system Figure 11.

View of the hexapod assembly under development at LNLS.

for positioning and moving objects in space with six degrees of freedom. The

critical components of the beamline were reviewed carefully, the main bottlenecks were identified and a special effort was made to eliminate every difficulty that could hinder the conclusion of the project within the slated time frame. In late 2009, the second mirror vacuum chamber was successfully tested, and the monocromator chamber and its main components, as

hexapod has been fully simulated and is now in the prototyping stage. The Accelerator Physics and Magnet groups are deeply involved in the design of the new light source. Blocks of permanent magnet were specified and ordered for the first full size prototype of the main dipoles of the new machine. The status of the project of the new light source is

well as the first mirror vacuum chamber,

described in the section dedicated to the

were under construction. The beamline is

SIRIUS project. Other technical groups of

expected to be ready for commissioning

the Engineering and Accelerators Division

in August 2010.

are also involved in the project, albeit to

In addition to the PGM, a set of beamline

a lesser extent. New developments in

development projects is under way. The

vacuum technology, power supplies and

new superconducting wiggler beamline

beam diagnostic instrumentation which are

was specified and ordered from third-

currently underway at the LNLS are meant

party vendors but its integration will be

for application in the new project.

96 | Activity Report 2009

New Source

Aerial view of the LNLS campus with an artistâ&#x20AC;&#x2122;s view of the new light source building.

The accelerator parameters for the new Brazilian synchrotron light source were revised and redefined in 2009. Project variables such as the accelerator energy, its proposed magnetic lattice and consequently the expected source emission at each section were tailored in order to improve the quality of the obtained radiation. The proposed source will then be competitive with its best foreign counterparts, allowing the community to perform experiments in worldâ&#x20AC;&#x2018;class equipments with much broader research scope than the actual LNLS source.

New Source

In 2009 our tasks concentrated on the definition of major parameters for the new

performance parameters of the source and the magnitude of the project.

storage ring and its basic lattice design.

The basic lattice design will serve

This is the first phase of the project and

as basis for the detailed planning of

reflects a compromise between the desired

the various subsystems, including civil engineering and layout of the accelerators on the LNLS site. Several designs for the storage ring were studied during the year, with energies ranging from 2.5 to 3.0 GeV, ring circumferences of 330 to 460 m, beam emittance of 2.6 to 1.7 nm. rad, and number of dipoles from 48 to 60, and so on.

Figure 1.

Layout of the modified TBA cell with the high field slice in the center of the middle.

A preliminary set of basic parameters for the new storage ring was devised in early 2009, following previous internal considerations and discussions with the Brazilian scientific community during the “1st Workshop LNLS-2 New Source: Scientific Case”, held on February 10–11 at the LNLS campus. This design was based on a 2.5 GeV electron storage ring with a relatively low field of 0.45 T for the dipole magnets. The 332 m circumference was composed of 16 TBA cells, resulting

Figure 2.

Optical functions of the modified TBA lattice dipole.

in a natural emittance of 2.6 nm.rad. The low bending fields envisage the use of permanent magnets for the dipoles. This

Table 1. Main parameters of the new LNLS source.

Energy Beam current Circumference Natural emittance without damping wigglers Natural emittance with wigglers Critical photon energy from dipoles Energy loss per turn from dipoles Radiation power from dipoles Betatron tune (horizontal/vertical) Natural chromaticity (horizontal/vertical) Natural energy spread Momentum compaction factor Harmonic number RF frequency Long straight sections number × length

98 | Activity Report 2009

3.0 500 460.5

GeV mA m

option is very attractive since the investment

1.7

nm.rad

be reduced through the elimination (or

0.9

nm.rad

significant reduction) of power supplies

12.0

keV

and cooling systems. A Preliminary

417.7 208.8 24.2 / 13.2 –53.4 / –48.0 0.079 6.9 × 10–4 768 500 10 × 9.4 m 10 × 5.0 m

keV kW

Conceptual Design Report describing

and operation costs of the project can

this design was prepared in April. In the course of further explorations of

the proposed design, new ideas emerged on the scene, and the project evolved to a

MHz

3.0 GeV electron storage ring with 20 TBA cells, or 20 long straight sections. The permanent magnet dipoles now combine

Facility Report

Figure 3.

Dynamic aperture for on-energy particles and frequency map analysis after preliminary sextupole optimization.

a low bending field of 0.5 T for the main beam deflection and a high field of 2.0 T over a very short longitudinal extent (1 degree, a slice magnet) to produce high energy photons. This configuration allows photons of critical energy of 12 KeV to be produced from dipole beamlines while keeping the total radiated power at low level. The high power is produced only at the beamline exit. These new ideas were incorporated into the design in the second half of 2009 and were presented and discussed with the scientific community in the â&#x20AC;&#x153;2nd Workshop LNLS-2 New Source: Scientific Caseâ&#x20AC;?, held on August 27â&#x20AC;&#x201C;28.

Figure 4.

Comparison of the performance of the existing IDs in the present LNLS UVX storage ring and expected performance in the new ring.

Following the workshop, several lattice configurations were simulated and designed in greater detail, aided by the advice of

lengths of 5 and 9 m. The lattice has

Prof. Helmut Wiedemann during the first

a distributed dispersion function and

three weeks of September.

provides a beam with 1.7 nm.rad emittance.

The present lattice configuration is a

Table I lists the main parameters of the

modified TBA lattice with a 1 degree high

lattice, while Figure 2 shows the optical

bending field slice in the center of the

functions. The dynamic aperture with

middle dipole, as illustrated in Figure 1.

preliminary sextupole optimization and the

The circumference of 460.5 m contains

corresponding frequency map analysis

20 long straight sections with alternating

are depicted in Figure 3.

Activity Report 2009 | 99

New Source

Figure 4 compares the performance of the IDs currently installed in the LNLS UVX storage ring with their expected performance in the new ring. Although permanent magnets are routinely used in many synchrotron sources in wiggler and undulator insertion devices, their large scale use in lattice magnets is much less common. Several engineering issues remain to be analyzed and R&D in this field is crucial to the success of this choice of dipole design. First prototypes for the low and high field permanent magnet dipoles have been designed and the parts are being fabricated. Figure 5 shows a schematic drawing of the low field dipole prototype. A preliminary proposal for the injector includes a full energy booster synchrotron concentric with the storage ring, allowing Figure 5.

Prototype of the low (left) and high (right) field def lection permanent magnet dipole.

Figure 6.

it to be placed in the same tunnel, as illustrated in Figure 6.

Schematic drawing of the concentric booster in the same tunnel as the storage ring.

100 | Activity Report 2009

Beamlines

Consonant with its mission as a national laboratory, LNLS invests ongoing efforts in building and upgrading its beamlines. These improvements are essential to meet the demands of the user community and to extract the best scientific results from these facilities. LNLS today has fourteen beamlines in full-time operation for users and two beamlines under construction â&#x20AC;&#x201C; a PGM based on an APPLE II undulator and the SW1 based on a superconducting wiggler. Two other beamlines are dedicated to beam diagnostics and are reserved for internal use. The beamlines are organized into five groups, Macromolecular Crystallography, X-ray Absorption and Fluorescence, X-ray Diffraction, X-ray Scattering and Ultraviolet and Soft-X-ray Spectroscopies.

Beamlines

The year 2009 was somewhat disruptive

little time for instrumental development.

for the beamlines due to changes in

Despite this dramatic situation, a few

management, budgetary uncertainties and

isolated and heroic efforts were still made

the departure of several researchers. The

to continue the development of scientific

average number of Ph.D.s on the staff of

instrumentation for the beamlines, which

each beamline, which used to be about

are described below.

2, has been declining over the last couple of years and by 2009 reached about 0.5

Macromolecular

Ph.D. per beamline. This is undoubtedly

Crystallography and

the lowest Ph.D. occupation of all operating

Spectroscopy

synchrotrons and poses a serious threat

This group has two protein crystallography

to the future of the facility. This diminished

beamlines, one with tunable energy

staff struggles now to keep the beamlines

(W01B:MX2) using a 2 T wiggler as

operational for their users, having very

source and with MAD experimental capability, and another with fixed energy (D03B:MX1) operating at 9 KeV. The stability studies continued in 2009 for MX2 installing temperature sensors, inclinometers and improving the data logging system in order to investigate temperature-driven ground motion and support distortions affecting the optical elements. Remarkable energy stability levels were set by implementing thermal isolation and temperature control for the optical hutch, significantly improving the conditions for MAD experiments. Figure 1 presents the main result. Improvements in the fluorescence scanning routines were also implemented, resulting in faster and more stable operation of the beamline.

X-ray Absorption and Fluorescence LNLS currently has three absorption spectroscopy and one fluorescence beamline in operation. Two of the Figures 1-2. Energy stability measurement for the MX2 beamline. Top

absorption beamlines, D04B:XAFS1 and

graph: Energy drift without optical hutch temperature

D08B:XAF2, perform conventional energy

control. Bottom graph: Energy drift with temperature controlled.

102 | Activity Report 2009

scanning and allow for the performance

Facility Report

of most conventional transmission and

their scientific instrumentation and time

fluorescence experiments. The third one,

allocation.

D06A:DXAS, is an energy dispersive

The control system of the D10A:XRD2

beamline dedicated to time-resolved and

beamline, which was hybrid in the past,

extreme condition experiments. The X-ray

is now fully operational with SPEC

fluorescence beamline D09B:XRF serves

software, which is standard in most

a broad multidisciplinary user community

diffraction beamlines worldwide. The

involved mainly in environmental sciences,

detection system of this beamline has

chemistry and biophysics applications.

also been upgraded by the addition

The WDS detection system used on

of a Pilatus 100 k area detector, also

this beamline was upgraded with the

integrated in SPEC. In 2009, the Pilatus

acquisition of 3 new crystals (Li(220), PET (002) and Ge(220)). The detection system of the D08B:XAF2

detector was initially commissioned for grazing-incidence small angle X-ray scattering (GISAXS) experiments, and

beamline was expanded with the acquisition of a new multi-element silicon drift detector, which is currently being commissioned. A new XYZ sample stage that can hold loads of up to 100 kg of equipment has been developed for this beamline, and will allow more complex setups for in situ experiments. Still with respect to sample conditioning, this beamline underwent a major upgrade with the acquisition of a top-loading cryostat that can reach temperatures as low as 10k with a rapid sample exchange system (10 min). The D06A:DXAS beamline also received a new sample stage with 4 axes (XYZ and theta), which allows for more stable and precise sample alignment.

X-ray Diffraction This group has three X-ray diffraction beamlines: D10A:XRD2, D10B:XPD and D12A:XRD1 working in collaborative mode, with the usersâ&#x20AC;&#x2122; proposals distributed among them according the best possible use of the beamlinesâ&#x20AC;&#x2122; characteristics,

Figures 3-4. Top: Universal stage XYZ (XAFS2) supporting the new cryostat. Bottom: Superconducting magnet.

Activity Report 2009 | 103

Beamlines

procedure, the beamline had to be shut down for almost two months. A temporary solution was then implemented to put the beamline back into operation, although the installation of the new monochromator was postponed to 2010. A new arm for the Huber diffractometer was installed on the D12A:XRD1, which has improved the stability of the analyzing crystals, slits and detector.

X-ray Scattering Since 2009, LNLS has two small angle scattering beamlines operating for external users, D01B:SAXS and D02A:SAXS2. The main efforts in 2009 were concentrated on completing the reassembly and recommissioning of the SAXS1 beamline. This beamline was reopened for the user community in the second half of 2009 with several improvements, especially in the SAXS/ WAXS detection system, which now Figures 5-6. Top: Sagittal monochromator on XPD. Bottom: Detail of the diffraction arm on XD1.

has a Pilatus 300 k for small-angle and a Pilatus 100 k for wide-angle X-ray scattering (from Dectris, Switzerland).

is slated to become fully operative for

These are state-of-the-art detectors with

diffraction and GISAXS measurements

fast response, wide dynamic range and

in 2010, representing a considerable

no readout noise, which will improve

increment in performance for both types

SAXS/WAXS experiments, especially

of experiments. In addition to these

time resolved experiments. A new set

improvements, a new air-conditioning

of slits with scatterless blades has been

system installed on the experimental hutch

acquired from XENOCS (France) for use

has improved the thermal stability of the

as guard slits. This will reduce parasitic

experimental stations. Most of the work on

scattering considerably at small angles.

the D10B:XPD beamline was concentrated

The optics of the beamline is still the

on the installation and commissioning of

side bounce crystal from the original

a new sagittal monochromator with an

project, but a new multilayer mirror has

ESRF type bending system. However,

been designed and will be installed in

due to technical problems during this

2010.

104 | Activity Report 2009

Facility Report

Ultraviolet and Soft X-ray Spectroscopies This group is responsible for three beamlines, two in the UV range (D05A:TGM and D08A:SGM) and one in the soft X-ray range (D04A:SXS). It is also responsible for the construction of the first undulator beamline at LNLS, the U11A:PGM beamline, which will provide a highly brilliant photon flux in the energy range of 100 to 1000 eV. Complete refurbishing of the D04A:SXS beamline was concluded in 2009. This beamline, which fills the spectral gap from 1 to 6 KeV, between the UV and the X-ray beamlines, with techniques such as photoemission and time-of-flight spectroscopies, will be reopened in early 2010 for external users. Among the UV beamlines, the D05A:TGM also received a 3 m extension to allow for the use of samples that require a wider beam spot of up to 8 mm. Some of the optical elements of the D08A:SGM beamline were refurbished, and the mirror for toroidal refocusing, which was contaminated with Carbon, was sent back to Zeiss in Germany for polishing and cleaning.

Figures 7-8. SAXS/WAXS detection system on SAXS1.

Activity Report 2009 | 105

Nanoscience and Nanotechnology

HRTEM phase reconstructed image from a Buried CoSi2:Si(001) hexagonal nanoplatelet.

The small world can also produce big science. Nanotechnology and biotechnology has a potential to change the way we do science and also how we live our lives. But to do this it is necessary to "see and feel" in nanoscale. Therefore, sophisticated microscopy techniques such as electron microscopy and scanning probe microscopy are essential in any high technology effort. In this aspect, the LNLS's microscopy laboratory is a unique place that open its facilities to users nationwide and abroad. It offers an excellent opportunity to access world class tools, along with technical assistance in developing their research. And this kind of interaction has being very successful, as shown by the numbers. The research done by the microscopy laboratory research staff has not only helped to understand the nanoscale phenomena. But it also did develop new instrumentations and methodologies to improve the capabilities of the laboratory. Special attention is devoted to the inâ&#x20AC;&#x2018;situ TEM and SEM experimentation with materials. This has helped to keep up to the edge with other similar institutions around the world.

Facility Report

The electron microscopy facility is located in the Cesar Lattes Nanoscience

physicists, and researchers in nanoscience and nanotechnology at LNLS.

and Nanotechnology Center (C 2Nano),

An overview of the main activities and

where a major part of the nanoscience

new developments in this area during 2009

and nanotechnology activities of the

is presented below.

Brazilian Synchrotron Light Laboratory are performed. This electron microscopy open facility complements the research efforts involving synchrotron radiation, physical and chemical synthesis of 2D and 3D nanostructures, advanced microscopy (AFM, and STM), theoretical modeling, manipulation, microfabrication, and scaling from microscale to nanoscale. These combined efforts help to shed light on the unique behavior and properties of nanoscale materials, the development of new materials, precise control over the production of these materials, and most important, the search for useful applications

Electron Microscopy The electron microscopy laboratory did open the doors eleven years ago to all users over Brazil, the Americas and Europe. Since then, it has delivered more than 54,400 hours of electron microscopy for the development of 1367 research proposals executed by 1291 users, which resulted in 390 indexed journal publications, 227 of them published in the last 4 years. In 2009 alone, approximately 5,945 hours of TEM and SEM were delivered to external users involved in 160 research projects, resulting in 58 indexed journal articles. The

for this new generation of materials and

electron microscopy laboratory continues

devices. The LNLS installations operate

to train electron microscopists as a core

as open and multiuser facilities with strong

feature of the nanoscience program at

emphasis on the training of specialized

LNLS. Several programs are in place for

human resources. In addition, the internal

theoretical and practical training, including

technical and research team focus on the

specialized graduate level courses offered

development of new methodologies and

at nearby universities (UNICAMP and USP).

dedicated instrumentation, which are linked

These are also available free at the LNLS

to world–class research both in–house and

website. In addition, a 3–week summer

by outside users.

course is offered every other year to give

Among the open facilities employed in the

the opportunity to obtain a comprehensive

nanoscience and nanotechnology program

theoretical education and practical training

are the X–ray scattering/diffraction/absorption

in electron microscopy to users living far

beamlines, the electron microscopy laboratory,

away from the LNLS.

the scanning probe microscopy laboratory,

The transfer of all the electron microscopes

and the thin films and microfabrication

to the new C2Nano building was completed

laboratory. In addition, a set of installations

in 2009. Therefore, except for a few specific

dedicated to in–house research into the

TEM sample preparation systems (cryo-

chemical synthesis of nanostructures and

ultramicrotome and evaporators), all the

catalysis are part of the strenuous efforts

LME equipment planned for transfer to this

of a small group of technicians, engineers,

new building has already been moved. The

Activity Report 2009 | 107

Nanoscience and Nanotechnology

remote operation room to operate some

and chemical aspects of micro– and

of the TEMs was set up and is now fully

nanostructured materials.

operational.

A 30 KeV SEM–LV (3.0 nm resolution)

The laboratory currently has five

coupled to an EDS spectrometer, EBSD,

microscopes, as well as the sample preparation

and stages for in situ experimentation

and data analysis tools, described below:

dedicated to the study of morphological,

A 200 KeV TEM–STEM–FEG (1.9 Å point

crystallographic and chemical properties

resolution) coupled to STEM BF–DF and

of microstructured materials, including

HAADF detectors, a TV–rate CCD camera,

advanced in situ experiments involving

a large–collection angle energy–dispersive

heating and deformation.

X–ray spectrometer (EDS), and an electron

A complete TEM sample preparation

energy loss spectrometer (EELS) capable of

facility equipped to work with a wide range

energy–filtered imaging using a 4 megapixel

of bulk and nanostructured materials,

CCD camera. This instrument is dedicated

including ceramics, metals, semiconductors,

to the study of crystallographic, chemical,

and polymers.

and electronic properties of functional

The new SEM sample preparation

nanostructured materials. After extensive

laboratory was equipped using funds

testing, the need to replace the Schottky

provided by Petrobras and FAPESP, through

emission gun of this microscope was identified

industrial research and individual research

in February 2009. The new emission gun

projects overseen by an LME researcher.

was installed and the microscope is currently

The LME’s web page was completely

under testing for certification(2010).

revised and updated to include detailed

A 200 KeV TEM–STEM–MSC (2.5 Å

information about the equipment and the

point resolution) coupled to a TV–rate CCD

possible science and analysis that can be

camera, 1 megapixel CCD camera, and a

performed using it. In addition, more than

EDS spectrometer dedicated to the study

50 technical operation and maintenance

of crystallographic and chemical properties

manuals were prepared and are now available

of nanostructured functional and structural

to LNLS staff and the user community.

materials. In the future, it will also be used in the development of in situ experiments.

Several improvements and developments were introduced in 2009, including:

A 300 KeV TEM–HR (1.7 Å point resolution,

1. Development of the second prototype

1.2 Å information limit) coupled to a TV–rate

of the heating stage for the LV–SEM;

CCD camera, 1 megapixel CCD camera, and

2. Opening of the new SEM sample

a EDS spectrometer, dedicated to the study of crystallographic and chemical aspects of nanostructured materials, particularly metals.

preparation laboratory; 3. Upgrade of the SEM–LV control hardware to extend its service life. As can be seen, LME–LNLS continues

A 30 KeV SEM–FEG (1.5 nm resolution)

to consolidate its position as a word–class

coupled to a EDS spectrometer and plasma–

electron microscopy facility, concentrating

based anti–contaminator dedicated to the

major efforts on human resources education

study of morphological, crystallographic

and training while simultaneously keeping

108 | Activity Report 2009

Facility Report

up its internationally competitive scientific

main chamber. The load–lock (LL) chamber

production. However, to remain on this

is now equipped to provide Ar plasma

successful path requires the continual

treatment of all samples and tips brought

modernization of its facilities and the

into the main chamber.

expansion of its technical and scientific

Additionally, with a base pressure of 10–7

staff. Therefore, three researcher have

Torr or higher, the LL chamber also has a

been hired and the search for new talents

Ar bombardment system, a gas manifold

continues. In addition, several projects/

for O2 and N2 plasmas, and a lamp heating

proposals have been prepared and submitted

system. The main chamber currently has Ge,

to funding agencies and to private and

Hf and Ag e–beam evaporation sources, all

government organizations to raise much

developed at LNLS. The current experiments

needed funds to modernize the scanning

range from reactive deposition of Hf on Si

electron microscopes and the sample

to surface science of metals. The scanning

preparation facilities through the acquisition

probe facility also offers two AFM systems

of state–of–the–art ion milling systems.

(Veeco DI Ns3a, and a NTMDT Solver Pro) for a variety of experiments, including MFM,

Scanning Probe Microscopy

EFM, etc.

Scientific collaboration between the scanning probe microscopy laboratory and the X–ray diffraction and electron microscopy groups at LNLS was consolidated in 2009 and new collaborations were initiated with the LNBio and CTBE. Thanks to the success of the Brazilian scanning probe microscopy network, it was renewed and its scientific leadership was taken over by Prof. Ado Jório from UFMG. Relevant instrumentation upgrades and developments were carried out, and activities relating to the nanoindentation and liquid measurements and the remote SPM and STM operation were set in motion. In addition, a new facility for the laboratory has been planned in the C2Nano building, which includes separate rooms for the two AFM and the STM microscopes, protected by 3.5 ton inertial blocks to improve the systems’ mechanical stability. The UHV–STM is open for users. Currently, the base pressure is in its mid 10–11 Torr, thanks to a 400 l/s ion pump and a non–evaporable getter pump in the

Figure 1.

A 3 0 0 ke V T E M - H R : d e d i c a t e d to t h e s t u d y o f cristrallographic and chemical aspects of nanoestrutures material.

Activity Report 2009 | 109

Industrial Research Activities

Premium screens: used for controlling sand during petroleum extraction.

In 2009, LNLSâ&#x20AC;&#x2122;s industrial program focused on the continuity or conclusion of ongoing projects and partnerships, while the directions of the program have been under review to align its goals to the new operational structure of LNLS. In this scenario, the main highlight was the first technology transfer agreement for exploration of Premium screens signed between LNLS and Adest Ltd as the result of a joint project concluded in late 2009. Among new initiatives, the highlight was a pilot project signed with Petrobras to evaluate the existing technologies and establish the requirements for remote operation of LNLS facilities as Labwebs. The most relevant results are described here.

Facility Report

The first technology transfer agreement

use of synchrotron radiation attractive

between LNLS and Adest Ltd was signed

today not only for material scientists

on October 21, 2009. This agreement is

and engineers but also for the industrial

the result of a joint project initiated in 2007

community. In fact, the combination of a

for the development of the capability to

synchrotron light source and an electron

manufacture Premium screens, which

microscopy laboratory makes the LNLS

are used for controlling sand during

a special place for this type of research.

petroleum extraction (Figure 1). The project

Joint projects were initiated in 2008 with

was funded by FINEP (CTPetro), Adest

Petrobras through the TMEC Network,

Ltd, FAPESP and LNLS. If the product is

targeting advanced structural materials,

approved in the final tests and becomes

joining and characterization. In 2009, two

available commercially, LNLS will receive

Gleeble thermomechanical simulators were

royalties for the next 5 years, which will

designed and purchased and are expected

be reinvested in R&D.

to arrive in 2010. One of these simulators is a customized machine to be installed on

Labâ&#x20AC;&#x201C;web: A Pilot Project for Remote Operation of Beamlines at LNLS This pilot project funded by Petrobras

the diffraction beamline XRD1 at LNLS for in situ studies, which is expected to raise research in materials engineering at LNLS to a new level (Figure 2). This physical simulator comprises a 44 kN hydraulic

through its Nanotechnology Network aims

uniaxial testing machine for tension and

to evaluate existing technologies and

compression. Heating and cooling rates

establish the requirements for implementing

of up to 1,000Â°C/s can be reached easily,

remote operations of LNLS facilities. Two

with mechanical loads superimposed

beamlines, SAXS1 and XRD1, are involved

if required. It is also capable of cyclic

in this phase. Software and hardware

deformation and/or cyclic temperature.

requirements, as well as connection

Microstructural changes representative

speed and user interface, have been tested. The LNLS team will also look for partnerships with other synchrotrons. The main outcome expected in the next few months is the elaboration of a complete project to implement the remote operation of beamlines starting in 2010.

Advanced Structural Materials Simulation, Joining and Characterization The development of experimental techniques suitable for the characterization of engineering materials renders the

Figure 1.

Premium screen prototype fabricated at LNLS.

Activity Report 2009 | 111

Industrial Research Activities

of those experienced during solid–state phase transformation, oxidation, materials processing (e.g., welding, heat treatment and metal forming), and thermomechanical loads (e.g., uniaxial tensile and compressive deformation, fatigue and creep) will be able to be addressed in the near future. A second project involves friction stir welding (FSW) technology, which is a solid–state joining process with numerous advantages such as good dimensional stability and repeatability. Figure 2.

Thermomechanical simulator customized for synchrotron radiation.

This process should be considered and developed as a key technology in the energy generation industry, especially for advanced construction and repair applications. An extension of this project was signed in 2009. Among the results, different heat inputs were obtained using a fixed travel (welding) speed in combination with several spindle speeds to weld API 5L X80 high strength low alloy steel. The joints presented excellent mechanical properties under several heat input conditions, with elevated CTOD toughness in the heat affected zone (HAZ), making FSW a technically viable technology for

Figure 3.

Heat affected zone of FSW joint, composed of bainitic ferrite and martensite-austenite constituents, a morphology that ensures the joint’s excellent mechanical properties. Scanning electron microscopy (secondary electron signal).

high strength structural steel welding, without compromising the material’s fracture toughness (Figures 3 and 4).

Modified LePera etching.

Research and Development (R&D) 1. Catalysts for Glycerol Hydrogenolysis: Production of Glycols from Biomass Derivatives The conversion of biomass and other renewable sources to higher–valued Figure 4.

Vickers hardness map showing different weld zones in a FSW joint.

112 | Activity Report 2009

chemicals is one of the strategic goals of the 21st century. Glycerol, a major by–product

Facility Report

of biodiesel production, is one of the main examples of low cost, large volume market products that can be used as a starting material for chemical transformation. As part of the partnership between LNLS and OXITENO S/A, a project co–funded by FAPESP was started in late 2008. This project involves the development of selective catalysts for the hydrogenolysis of glycerol to glycols, such as ethylene glycol (EG) and 1,2–propylene glycol (1,2–PG), and studies aimed at shedding light on the physicochemical characteristics that determine their performance. The

Figure 5.

Catalytic unit at LSQ-LNLS.

installation of the infrastructure required for catalytic tests has been concluded,

Ni–Raney catalyst. The next steps involve a

followed by the setup installed at OXITENO

detailed analysis of the gas phase products,

to allow for the routine exchange of

optimization of reaction conditions (closer

information and experience. Figure 5

to industrial requirements), exploration

depicts the catalytic unit installed at

of model reactions, improvement of

LSQ–LNLS. Catalytic tests have already

Ni–W2C catalyst synthesis, and detailed

started, using Ru/C, Ni/C, Ni–W 2C and

characterization.

Activity Report 2009 | 113

Main Events

New directors: Michal Gartenkraut, Managing Director of the ABTLuS (the 3rd, from left to right); Antonio José Roque da Silva, director of the LNLS (the o 6st), and Kleber Franchini, director of the LNBio (the last one, from left to right); in the picture with the former director José Antonio Brum (1st); the rector of Unicamp, Fernando Costa (2nd ); the Brazilian Minister of Science and Technology, Sergio Machado Rezende (in the center of picture); and the chairman of the board of ABTLuS, Rogério Cezar de Cerqueira Leite.

In 2009, following a decision by the ABTLuS Board, the Center for Structural Molecular Biology (CeBiMe) became an autonomous research center. A new administrative structure was set up, with the three autonomous centers – LNLS, CeBiMe and CTBE (Center for Bioethanol Technologies) – operating under the auspices of the ABTLuS association. This new structure has lead to public events aimed at introducing the new centers to the community, as well as increasing their mutual synergy.

Facility Report

LNBio

source, then called LNLS-2. The workshop

Established in 1999 at ABTLuS/LNLS,

focused on accelerator development

the Center for Structural Molecular Biology

and preliminary scientific cases and

(CeBiME) became independent of LNLS in

was held on February 10-11, 2009. The

2009. In December, CeBiME was renamed

discussions were attended by about

the National Laboratory for Biosciences

80 registered participants and many

(LNBio), with facilities open to academic

others who stayed on after the RAU.

researchers and individual users.

The main purpose of this event was to start the project officially, involving

Users Meeting and 1st LNLSâ&#x20AC;&#x201C;2 Workshop

the Brazilian scientific community in the long-term project of building a new synchrotron light source in Brazil. The

The Brazilian Synchrotron Light

event was marked by the first public

Laboratory (LNLS) held its 19th Annual

discussion of the accelerator parameters,

Users Meeting (RAU) with 396 participants,

with more detailed specifications of the

including researchers, students and guests.

new machine. The workshop shed light

About 10% of the attendees came from

on a consistent scientific case, foreseeing

other countries. The meeting was held

the future research areas that will be

from February 9-10 on the LNLS campus

consonant with the present and future

in Campinas.

LNLS user community. A summary of

T h e 19 th u s e rs m e et i n g wa s

the workshopâ&#x20AC;&#x2122;s scientific activities was

complemented by the 1 Workshop for

published in the Synchrotron Radiation

discussions on the new synchrotron

News (SRN).

Figure 1. 19th Annual Users Meeting (RAU).

Activity Report 2009 | 115

Main Events

Figure 2. IV Workshop of Structural Molecular Biology at the LNLS.

2 nd LNLS–2 Workshop The 2 LNLS-2 Workshop was attended nd

by 82 registered participants. Among the

should be on writing a scientific program rather than guidelines for instrumentation requirements.

guest speakers were Sakura Pascarelli (ESRF-France), Thomas Earnest (LBNLUSA), Charles Fadley (LBNL-USA), Paul Morin (Soleil-France), Franz Pfeiffer (PSI-Switzerland), Sergey Borisenko (IFW Dresden-Germany), David L. Ederer (Tulane University-USA) and Stefan W. Kycia (University of Guelph-Canada). The Brazilian and Latin American community was represented by talks given by Rogério

IV Workshop of Structural Molecular Biology The 6th LNLS Workshop on Structural Molecular Biology took place on May 28-29. The aim of this workshop was to bring together the protein crystallography community and related groups, disseminate knowledge, enable contacts and collaborations to be

Paniago (Dept. of Physics-UFMG), Sérgio

established, and promote the formation of

Morelhão (Dept. of Physics–USP), José

new crystallography groups in the State

Marcos Sasaki (Dept. of Physics-UFC) and

of São Paulo, in Brazil and in other South

by other attendees who presented their

American countries. The meeting also

proposed experiments to be performed

marked the beginning of discussions on

on the new source LNLS-2 in a poster

the crystallization of membrane proteins.

session. The 30 posters covered several

This topic is considered strategic, since

scientific areas of interest and helped

the South American community lacks

bring together common scientific interests.

groups devoted to the development

There was a strong recommendation from

of new crystallization techniques. The

all the senior scientists present – at that

presence of three experts in protein

point of the discussion – that the emphasis

crystallization enabled the attendees to

116 | Activity Report 2009

Facility Report

update the methodologies used in their

new directors of the Brazilian Synchrotron

laboratories.

Light Laboratory (LNLS) and the National Biosciences Laboratory (LNBio) (formerly

New Directors for the Associated Centers On May 13, engineer Michal Gartenkraut was announced Managing Director of the

the CeBiME), respectively. The ceremony was held on the ABTLuS campus in Campinas and was attended by the Brazilian Minister of Science and

Brazilian Association for Synchrotron Light

Technology, Sergio Machado Rezende.

Technology (ABTLuS), inaugurating a new

Physicist Jos茅 Ant么nio Brum, who had

administrative structure for the Association

been heading the laboratory as director

according to its new statute.

of LNLS and acting as managing director

At the same ceremony, physicist Ant么nio

of ABTLuS since 2001, returned to his

Jos茅 Roque da Silva and physician Kleber

teaching and research activities at the

Gomes Franchini were introduced as the

University of Campinas (UNICAMP).

Activity Report 2009 | 117

Facts and Figures

The Brazilian Synchrotron Light Laboratory is a national multiâ&#x20AC;&#x2018; user facility whose mission is to provide solutions for scientific and technological challenges. In the last few years, the fields of research covered by the laboratory have expanded considerably, as has the number of outside users, requiring ongoing efforts by its team to maintain and improve the figures shown in this report.

Facility Report

The Brazilian Association for Synchrotron

In 2009, 1656 users submitted

Light Technology (ABTLuS) is a non-profit

455 research proposals and used the

organization that operates the LNLS through

13 synchrotron beamlines. From this

a management agreement signed with

ensemble of proposals, 368 were submitted

the Ministry of Science and Technology

by Brazilian researchers and 87 by foreign

(MCT) and the National Council for Scientific

users, mainly from Argentina (64). Another

and Technological Development (CNPq),

160 research proposals were developed

in line with Executive Order 2405 of

at the facilities of the Cesar Lattes Center

November 26, 1997.

for Nanoscience and Nanotechnology

In 2009, ABTLuS encompassed the Synchrotron facility (LNLS), the Brazilian Biosciences National Laboratory (LNBio) and the Brazilian Bioethanol Science and Technology Laboratory (CTBE). These three centers work in synergy with all the laboratories operated by ABTLuS to advance areas of knowledge that are strategic to Brazil. In 2009, the project of the second Brazilian synchrotron light source advanced considerably. The conditions for conceptual design were discussed and refined, focusing on scientific areas of interest, optimization of projects with impact on radiation brightness and on the quality of radiation sources, and on detailed definitions of the project’s scope and cost. The current source operated from

(C2Nano). In 2009, 274 scientific papers were published in indexed journals, 20 of them with an impact factor greater than 5, the best performance in the last 10 years. The year 2009 ended with ten contracts/agreements with industry, under the coordination of LNLS researchers. The projects were related to the development of catalysis, the characterization of advanced materials for use in petrochemistr y and the development of clean processes for the metallization of optoelectronic devices. The 18 th Summer Program, held in 2009, involved 15 students selected among 296 candidates, who spent 2 months working on scientific and

January to October 2009, 24 hours a

technological programs at the LNLS.

day, Monday through Saturday morning,

The institutional program of scientific

with programmed one-day shutdowns for

initiation for graduate students (PIBIC),

maintenance and machine studies every

developed in partnership with the

two weeks. During 10 months of operation,

National Council for Scientific and

users and researchers used 4060 hours

Technological Development (CNPq),

of beam to conduct experiments on the 13

received 83 subscriptions from which

available beamlines. The source reliability

15 students were selected to work on

index reached 96%, a percentage similar

scientific projects for one year at the

to that of previous years.

LNLS, LNBio and CTBE.

Activity Report 2009 | 119

Facts and Figures

120 | Activity Report 2009

Facility Report

Activity Report 2009 | 121

Facts and Figures

Executed proposals (Synchrotron) 466 423 358

438

434

455

379

231

2002

2003

2004

2006

2005 Year

122 | Activity Report 2009

2007

2008

2009

Facility Report

Executed proposals (electron microscopy) 161 150

160 143

138

125 112 96

2002

2003

2004

2005

2006

2007

2008

2009

Year

Activity Report 2009 | 123

Facts and Figures

124 | Activity Report 2009

XAFS1

TGM

DXAS

SGM

XAFS2

SCW

XRD2

XPD

X-ray Absorption Fine Structure

Toroidal Grating Monochromator

Dispersive X-ray Absorption Spectroscopy

White beam (previously X-ray Lithography)

Spherical Grating Monochromator

X-ray Absorption Fine Structure

Superconducting Wiggler BeamLine

X-ray Fluorescence

X-ray Diffraction

X-ray Powder Diffraction

D04B

D05A

D06A

D06B

D08A

D08B

W09B

D09B

D10A

D10B

Detectors

Image Plate (2D)

Photodiode

Hemispherical Electron Analyzer

CCD or Area Detector

Total Electron Yield

Solid State Detector (with energy resolution)

Activity Report 2009 | 125 Differential Scanning Calorimeter (DSC)

Low Temperature Furnance (up to 300K)

High Temperature Furnance (up to 1000K)

Sample Environment

Reference

Magnetic field (up to 1T)

N 2 Cryojet

Cryostat

Low Pressure Cell (up to 1.2Gpa)

High Pressure Cell (up to 10Gpa)

Single crystal diffraction, Multiple Beam Diffraction

Focusing Double crystal 5-15 keV

Eletrochemichal Cell

Microfocus (Capillary)

Operational

Construction

Surface and Interfaces. Atomic and Molecular Physics, X-ray Magnetic Dichroism

Planar Grating 100-1200 eV

Operational

Design

Operational

Thermal Bath

Power Diffraction Studies in Materials Science

Magnetic Scattering, Grazing Incidence, Nanostructures

Materials Science

Materials Science, thin films and diluted systems

Operational

Status

Surface and Interfaces. Atomic and Molecular Physics

Focusing Double crystal 5-15 keV Focusing Double crystal 5-15 keV

Sample Enviroment

Operational

Detectors

Protein Radiolysis. Desorption measurements

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

Environment and Geochemistry, Biophysics and Agriculture

Cintilator

XRD1

PGM

Applications Structural Molecular Biology using MAD technique

White beam or double crystal 5-25 keV

Focusing Double crystal 4-17 keV

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

Linear Detector (1D)

X-ray Diffraction

SXS

Soft X-ray Spectroscopy

D04A

D12A

MX1

Macromolecular Crystallography

D03B

High Resolution VUV Spectroscopy

SAXS2

Small-Angle X-ray Scattering

D02A

U11A

Spherical Grating 100-1200 eV

SAXS1

Small-Angle X-ray Scattering

D01B

XRF

Filtered white beam 5-20 keV

MX2

W01B

Focusing Double crystal 5-15 keV

Monochromator

Acronym

Name

Macromolecular Crystallography

Dipole

Facility Report

Scientific Reports in www.lnls.br 1)Biology Effects of Addition of a Palmitic Sucrose Ester on Low-trans-Fat Blends Crystallization in Bulk and in Oil-in-Water Emulsions Huck Iriart Cristian, Candal, R. J., and M. L. Herrera Standardization of NMR experiments and Statistical Analysis for Metabolomic studies of Acute Lymphoblastic Leukemia Melo, C. P. S., Brandalise, S. R., Yunes, J. A., and Zeri, A. C. Development and In Vitro Evaluation of Surfactant Systems for Controlled Release of Zidovudine Carvalho, F. C., Sarmento, V. H. V., Chiavacci, L. A., Barbi, M. S., and Gremião, M. P. D. Elemental concentration analysis in Benign Prostatic Hyperplasia tissue cultures by SR-TXRF Leitão, R. G., Palumbo, A. J., Correia, R. C., Souza, P. A. V. R, Canellas, C. G. L., Anjos, M. J., Nasciutti, L. E., and Lopes, R. T. Potential Effects of Some Functional Food in Ovine Breeding: Analysis of Nutrition-Relevant Trace Elements in Sheep Serum by TXRF Mota, C. L., Barroso, R. C., Cardoso, S.C., Lorella, Stefanon, B., Sgorlon, S., Scaini, C., Braz, D., and Moreira, S. A XAS study on Ti doped low silica calcium aluminosilicate glasses Sampaio, J. A., Filadelpho, M. C., dos Santos, D. R., Medina, A. N., Rohling, J. H., and Baesso, M. L. In situ time-resolved XANES study of Ni/CeO2-Al2O3 catalyst promoted with Pd Profeti, L. P. R., Assaf, E. M., and Ticianelli, E. A.

3D Images by XRFCT at LNLS- Brazil Pereira, G. R., Rocha, H. S., Calza, C., Anjos, M. J., LIMA, I., Pérez, C. A., and Lopes, R. T. Evidence of differences in bioaccumulation of hexavalent chromium between fronds and roots of Lemna minor Boeykens, S., Carignano, Laura A., Caracciolo, N. and Vázquez, C.

2) Chemistry Assessment of the electronic structure changes of PEMFC electrocatalysts after accelerated degradation procedure Fernandes, A. C., Lopes, P. P. and Ticianelli, E. A. XAS investigations of the effect of temperature and chemical environment in the electronic properties of Pt/C electrocatalyst Lopes, P. P., Freitas, K. S., Flávio, R. N. and Ticianelli, E. A. Mapping of calcium, iron and zinc in protein spots in Nile tilapia (oreochromis niloticus) liver tissue by SRXRF Lima, M. P., Neves, R. C. F., Pérez, C. A., Arruda, M. A. Z., Moraes, P. M., Barbosa, H. B., Santos, F. A. and Padilha, P. M. Application of NMR to study the mechanisms of antitumor action of goniothalamin Macedo Jr., F. C., Ruiz, A., de Fatima, A., Scarminio, I. S., Carvalho, J. E., Mantovani, M. S., and Semprebon, S. C. Scanning of citrus leaves to evaluate stages of citrus greening disease using micro synchrotron radiation X-ray fluorescence in association with chemometric tools Pereira, F. M. V. and Milori, D. M. B. P.

SAXS characterization of liquid crystals formed by nonylphenol ethoxylated surfactant with different sizes of ethoxylated chains.

XAS study on the gold particle size of Au catalysts

Campos, D. D. P., Lopes, J. H., Silveira, J. R., Carvalho, T. R., and Bertran, C. A.

Ethanol oxidation on Pt nanoparticles supported on carbon-TiO2 composites

126 | Activity Report 2009

Alvarez, M. and Campo, B. C.

Perez, J., Pires, F. I. and Villullas, H. M.

SAXS Study of SBA and Organofunctionalized and CMK Structures

Influence of hexafluoro-2-propanol or acetic acid solvents in the formation of peptide nanostructures

Almeida, R. K. S. and Airoldi. C.

Liberato, M. S., Takahashi, P. M., and Alves, W. A.

Structural characterization of systems formed by polymers and surfactants Percebom, A. M., Alves, F. R., Catini, D. R. and Loh, W. Carbon-supported PtSn and PtSnNi catalysts for ethanol oxidation Bonesi, A. R., Thomas, J., Gentil, R., Godoi, D. R. M., Castro Luna A. M. and Villullas, H. M. Correlating electronic properties of Pt-Fe/C catalysts with activity for oxygen reduction Malheiro, A. R., Gentil, R., Pires, F. I., Perez, J. and Villullas, H. M. Room and Low Temperature Structures for T[Ni(CN)4].2pyz with T = Fe, Co, Ni and pyz = pyrazine Lemus-Santana, A., Rodriguez‑Hernandez, J., Avila, M. and Reguera E. Analysis of time-resolved energy dispersive x-ray absorption spectroscopy data for the study electrocatalyst modification with temperature Colmati, F. Surface modification study of polysulfone films by UV-assisted treatments in the presence of reactive gases using FTIR-ATR, XPS and NEXAFS. Kessler, F., Kuhn, S., and Weibel, D. E. or Weibel, D. Electronic effects on ethanol oxidation on Pt-Sn/C catalysts Godoi, D. R. M., Perez, J., and Villullas, H. M. Ionic fragmentation of selenium oxychloride under VUV irradiation Geronés, Mariana, Rodriguez Pirani, Lucas, Erben, Mauricio F., Cavasso Filho, R. L., Romano, Rosana M., and Della Védova, Carlos O.

Dissociative Photoionization of FC(O) SCH2CH3 following valence and sulfur 2p excitation Rodriguez Pirani, Lucas, Erben, Mauricio F., Geronés, Mariana, Romano, Rosana M., Cavasso Filho, R. L. and Della Védova, Carlos O. Characterization of carbon supported Pt-Ru nanoparticles prepared by a polyol method Godoi, D. R. M. and Villullas, H. M. Effect of water and salts in the phase separation of isolated natural membranes Oliveira, R. G., Del Boca, M., Gaggiotti M. C. and Borioli, G. A. Study of the conformation of hydrophobically associating polyacrylamide and its polyelectrolyte derivatives through small angle X-ray scattering Maia, A. M. S., Vidal, R. R. L., Garcia, R. B., Borsali, R. and Villetti, M. A. Preparation of Superhydrophobic surfaces using nano/micro texturization combined with surface chemical functionalization Michels, A. F., Feil, A. F., Amaral L., Teixeira, S. R., Horowitz, F. and Weibel, D. E. or Weibel, D. Chemical environment determination using resonant Raman scattering spectroscopy Leani, J. J., Sánchez, H. J., Valentinuzzi, M. C. and Pérez, C. A. Metallocene Supported on SilicaMagnesia Xerogels for Ethylene Polimerization: Effect of Fractal Structure on the Catalyst Activity Brambilla, R., Silveira, N. P. and Dos Santos, J. H. Z.

Morphology Control of Peptide Nanostructure in Solid-Phase Growth

X-ray photodesorption from methanol ice

Amaral, H. R., Kogikoski Jr., S., Takahashi, P. M. and Alves, W. A.

Andrade, D. P. P., Boechat-Roberty, H. M. and Rocco, M. L. M.

Activity Report 2009 | 127

Growth of TiO2 Nanotube Arrays with Simultaneous Au Nanoparticles Impregnation: Photocatalysts for Hydrogen Production

Evidence of differences in bioaccumulation of hexavalent chromium between fronds and roots of Lemna minor

Feil, A. F., Migowski, P., Pezzi, R., Machado, G., Amaral L., Teixeira, S. R., Weibel, D. E. or Weibel, D., and Dupont J.

Boeykens, S., Carignano, L., Caracciolo, N. and Vázquez, C.

Photoresists Comparative Analysis using soft X-ray Synchrotron Radiation and Time-of-Flight Mass Spectrometry Pinho, R. R., Lima, C. R. A. and Rocco, M. L. M.

3) Environment and Geoscience EXAFS study of Cu and Zn in soils contaminated by pig slurry Santanna, M. A., Girotto, E., Schenato, R. B.,

Rheinheimer, D. S., Alves, M. C. M. and de Andrade, A. M. H. Selective structural modification of photoactive organic thin films using a combination of monochromatic synchrotron radiation (SR) and oxygen atmosphere exposure Weibel, D. E. or Weibel, D. and Rodembusch, F. S. XAFS studies of the arsenate adsorption onto substituted goethites Tufo, A. E., Hein, L., Rueda, E. H., and Sileo, E. E.

4) Materials Science XAFS study of Zn0:7Co0:3O powders prepared by ball milling Mudarra Navarro, A. M. Spontaneous Adsorption Of ThiolCapped Gold Nanoparticles On Carbon Ramallo-López, J. M., Giovanetti, L. J., Requejo, F. G., Grumelli, D., Salvarezza R. C., Benitez, G., Vela, M. E. and Vericat, C. Nature of the High Hydrogen Storage Capacity for Copper in Prussian Blue Analogues Reguera, E., Rodriguez-Hernandez, J., Jimenez, J. A. and Yee-Madeira, H. Structure of gels produced from sodium caseinate Huck Iriart Cristian, Alvarez Cerimedo Maria S., Candal, R. J. and M. L. Herrera Influence of polyelectrolite layers over phosphatidylcholine liposomes Silveira, N. P., Lionzo, M. I. Z. and Micheletto, Y. M. S.

Evidences of the mechanism for As(III) immobilization on gibbsite by combining EXAFS and theoretical calculation

TiO2 Nanotubes with CdTe Quantum Dots Adsorbed by Electrophoresis Method Acuña, L. M., Muñoz, F. F., Lamas, D. G., Fantini, M. C. A. and Fuentes, R. O.

Duarte, G., Ciminelli, V. S. T., Dantas, M. S. S., Vasconcelos, I. F., Asare, K. O., Duarte, H. A. and Oliveira, A. F.

Determination of the thickness and crystalline structure of TiO2 coatings made by anodic oxidation of Ti-6Al-4V

Effect of As exposure on element concentration in Argentinian toad (Chaunus arenarum) during development by SR-TXRF

Vera, M. L., Alterach, M.A., Rosenberger, M. R., Lamas, D. G., Schvezov, C. E. and Ares, A.E.

Mardirosian M. N., Pérez, R.D., Pérez, C. A., Venturino, A. and Bongiovanni, G. A. Zinc Mapping in Prostate Tissue Using Synchrotron X-ray Microfluorescence Leitão, R. G., Correia, R. C., Palumbo, A. J., Souza, P. A. V. R., Canellas, C. G. L., Pereira, G. R., Anjos, M. J., Nasciutti, L. E. and Lopes, R. T.

128 | Activity Report 2009

Study of a i-PP/EPDM/organoclay nanocomposite deformed Thompson, A., Crespo, S. J., Samios, D., Bianchi, O., Teixeira, S. R. and Machado, G. Preparation of silver nanoparticles confined in SBA-15 channels Da Costa, L. P., Maroneze, C. M., Sigoli, F. A., Gushikem, Y. and Mazali, I. O.

Microstructure Characterization of β-Si3N4-based Cutting Tool Material Pereira, A. A. and Boehs, L. Nanoparticulas metálicas e ponto quânticos obtidos por síntese assistida de macrociclos do tipo cucurbiturila Dos Santos, E. M. S. and Demets G. J. F.

Controlling the growth of zirconia needles precursor from a liquid crystal template Freitas, F. G., Sarmento, V. H. V., Santilli, C. V. and Pulcinelli, S. H. Development of Diffusion Bonding Joints Between Oxygen Free Copper and AISI 316l Stainless Steel for Accelerator Components

Materials for Hydrogen Storage: Cation Mobility in Zeolite-Like Zinc Hexacyanometallates

Bagnato, O. R., Francisco, F. R., Freitas, D. V., Alonso, T. C. and Manoel, F. E.

Avila, M., Rodriguez-Hernandez, J. and E. Reguera

Microstructural characterization of Ruddlesden-Popper nickelates for use in catalysis

Nanoparticulas metálicas e ponto quânticos obtidos por síntese assistida de macrociclos do tipo cucurbiturila Dos Santos, E. M. S. and Demets, G. J. F. Study of atomization of a suspension of carbon nanotubes in solvents

Pimentel, P. M., Oliveira, R. M. P. B., Oliveira, F. S., Melo, D. M. A. and Melo, M. A. F. Study of Copper Hardened Composites with Nanoparticles of Alumina

Balachova, O. V.

Barros, R. M., Francisco, F. R., Bagnato, O. R. and Santana, E. C. A.

Wear characteristics of β-Si3N4-based cutting tool

Friction stir welding of UNS S32205 duplex stainless steel

Pereira, A. A. and Boehs, L. Size-controllable synthesis and characterization by HR-TEM of functional nanoparticles of TiO2, MoO3, and WO Santos, E. B. and Mazali, I. O. Determination of the thickness and crystalline structure of TiO2 coatings made by sol-gel dip-coating on Ti6Al-4 Alterach, M. A., Vera, M. L., Rosenberger, M. R., Lamas, D. G., Schvezov, C. E. and Ares, A. E. Small-angle X-ray Scattering Studies In Sterically Stabilized Ph-Responsive Polystyrene Colloidal Particles Peruzzo, P. J., Anbinder, P. S., Plivelic, T. S. and Amalvy, J. I. Characterization of high molar mass silicone rubbers reinforced with clay masterbatches by small-angle/wideangle X-ray scattering (SAXS/WAXS) Andrade, M. L. Q. A. and Yoshida, I. V. P. An EXAFS study on Nd doped low silica calcium aluminosilicate glasses Sampaio, J. A., Peixoto, S. M. B., dos Santos, D. R., Filadelpho, M. C., Medina, A. N. and Baesso, M. L.

Santos, T. F. A., Queiroz, R. R. M., Marinho, R. R., Piza, M. and Ramirez, A. J. Nature of the Low Stability of Prussian Blue Analogues - Based Molecular Magnets on Aging or Heating Reguera, E., Rodriguez-Hernandez, J., Avila, M. and Hernández, O. Low Temperature Structural Transition in T[Ni(CN)4].pyz with T = Co, Ni and pyz = Pyrazine Reguera, E., Rodriguez-Hernandez, J., Lemus-Santana, A. and Avila, M. Copper in Spherical Mesoporous Silicates: Cu K XAS study Andrini, L., Chanquía, C. M., Eimer, G. A. and Requejo, F. G. Materials for Hydrogen Storage: Behaviour of Transition Metals Nitroprussides on the Crystal. Water Removal and Under Cryogenic Conditions Reguera, E., Rodriguez-Hernandez, J., and Avila, M. Controlling the growth of zirconia needles precursor from a liquid crystal template Freitas, F. G., Sarmento, V. H. V., Santilli, C. V. and Pulcinelli, S. H.

Activity Report 2009 | 129

Porous Solids for Hydrogen Storage: Ti(3+) Hexacyanometallates (II) Avila, M., Hernández, O., Roque, J. and Reguera, E. Influence of different additives in the internal structure of monoolein: water dispersions Carollo, A. R. H., Fantini, M. C. A. and Bentley, M. V. L. B. Syntesis of DNA nucleobase from simulation of extraterrestrial environment Pilling, S., Andrade, D. P. P., Neto, A. C., Rittner, R. and Naves de Brito, A. Effect of the montmorillonite intercalant on the nanoscopic structure of epoxy-based nanocomposite Soares, B. G., Silva, A. A. and Dahmouche, K. Nature of the High Hydrogen Storage Capacity for Copper in Prussian Blue Analogues SAXS Study of the Structure and kinetics of aggregation of VTES-derived organic/silica hybrids Vollet, D. R., Donatti, D. A., Ibañez Ruiz, A., Awano, C. M., Vicelli, M. R. and Chiappim Junior, W. Characterization of fluorotic enamel using synchrotron X ray diffraction Gonçalves, M. V. C., Barroso, R. C., Porto, I. M., Gerlach, R. F., Costa, F. N., Braz, D. and Droppa Jr., R. Microstructural Characterization of C-Mn Steel welded by Friction HydroPillar Processing Welding (FHPPW) Benati, D. M., Afonso, C. R. M. and Ramirez, A. J. Fundamental mechanism study of ductility-dip cracking in Ni-Cr-Fe superalloys Unfried S. J. and Ramirez, A. J. Characterization of EVOH/PMMAPh blends by small-angle angle X-ray scattering (SAXS) de Lima, J. A. and Felisberti, M. I. Fischer-Tropsch synthesis: optimization of the activation treatment with H2 in a Fe/SBA-15 catalyst Figueroa, S. J. A., Stewart, S. J., Cano, L., Bengoa, J. F., Cagnoli, M. V. and Marchetti, S. G.

130 | Activity Report 2009

The built-up layer characterization Pereira, A. A. and Boehs, L. Morphological characterization of poly(lactic acid)/polyaniline ultrathin electrospun fibers by AFM microscopy Picciani, P. H. S., Medeiros, E. S., Mattoso, L. H. C. and Soares, B. G. Thermal evolution of FePt - iron oxide heterodimer nanocrystals studied by XANES Stewart, S. J., Figueroa, S. J. A. and de la Presa, P. Ionic fragmentation of the CHCl3 molecule following photoexcitation in the vicinity of the Cl 1s edge Lago, A. F., dos Santos, L. C. R., Cavasso Filho, R. L., de Souza, G. G. B. and Santos, A. C. F. An Investigation on the Fractal Structures of Coal-Silica Composites Prepared From Rice Husk Lattuada, R. M., Brambilla, R., Silveira, N. P., Peralba, M. C. R., and Dos Santos, J. H. Z. Characterization of toughened ternary nanocomposites of Poliamide 6, polyepichlorohydrin elastomer and montmorillonite clay by small angle angle X Ray scattering (SAXS) Pinotti, C. A., Gonçalves, M. C., and Felisberti, M. I. Relationships Between Nanostructure and Properties of New Hybrid Proton Conducting Zirconium Oxide-Speek Membranes for Direct Ethanol Fuel Cell Kawaguti, C. A., Dahmouche, K. and Gomes, A. S. XAS and structural characterization of the Ca2MnReO6 double perovskite Orlando, M. T. D., Corrêa, H. P. S. and Souza, D. O.

5) Microscopy and Microfabrication The effects of Cu, P and Ga on the microstructure of sintered Pr-Fe-B type magnets Mendes, T.

Fabrication and Characterization of Piezoresistors for Pressure Sensors Applications Fraga, M. A., Massi, M., Maciel, H. S. and Furlan, H. In situ high Temperature Deformation Experiments at the SEM Torres, E. A., Montoro, F. E. and Ramirez, A. J. A Novel Approach for High Resolution Elastic Behavior Assessment of Alloyed Strained Nanostructure Montoro, L. A., Medeiros-Ribeiro, G. and Ramirez, A. J. The use of new plasma reactors in the silicon etching step of microfabrication process Pessoa, R. S., Fraga, M. A., Tezani, L. L., Wakavaiachi, S. M., Maciel, H. S. and Petraconi, G.

6) Physics

High pressure local probe in RNiO3 (R = Nd, Pr) Massa, N. E., Garcia, F. and Alonso, J. A. The High Energy Resolution System of the XRF Beamline Pérez, C. A. and Sánchez, H. J. X-ray powder diffraction study of finegrained ZrO2-Sc2O3 dense ceramics Abdala, P. M., Lamas, D. G., Fantini, M. C. A. and Craievich, A. F. XAFS study of the local structure of Fe atoms in ZnO powders doped with Fe Mudarra Navarro, A. M., Damonte, L. C., Meyer M. and Rodríguez Torres, C. E. Detection of bornite on chalcopyrite electrodes by chronoamperometry and ex situ synchrotron radiation grazing incidence X-ray diffraction Majuste, D., Ciminelli, V. S. T., Magalhaes-Paniago, R., Caldeira, C. L., Leite, A. O. N. and Asare, K. O. Ozone valence band revised

Images by XRFCT at LNLS- Brazil Pereira, G. R., Rocha, H. S., Calza, C., Anjos, M. J., Lima, I., Pérez, C. A. and Lopes, R. T. Crystallization assays of MpNEP2 Dias, S. M., Dias, S. M. G. and Zaparoli, G.

Lopes, E. G. P., Mundim, M. S. P., Marinho, R. R. T., Naves de Brito, A. and Mocellin, A. Electronics, local structure and morphology of Pt3Co and Pt3Co/Au dumbbell nanoparticles investigated by XAFS and SAXS techniques.

Confocal three-dimensional energydispersive micro x-ray diffraction with polycapillary optic

Giovanetti, L. J., Ramallo-López, J. M., Shevchenko, E. V., Craievich, A. F. and Requejo, F. G.

Pérez, R. D., Sánchez, H. J., Sosa, C., Pérez, C. A. and Sbarato, V.

GI-XRF and GI-XANES study of Co doped SnO2 films

Influence of Pd on the structural properties of Ce-based mixed oxides nanotubes

Rodríguez Torres, C. E., Mudarra Navarro, A. M. and Golmar, F.

Muñoz, F. F., Acuña, L. M., Cabezas, M. D., Lamas, D. G., Leyva, A. G., Baker, R. T. and Fuentes, R. O. XAS studies on Pd/Ce-based mixed oxides nanotubes Acuña, L. M., Muñoz, F. F., Lamas, D. G., Fantini, M. C. A. and Fuentes, R. O. (1s,2p1=2) and (1s,2p3=2) resonant Raman scattering processes in Ti Stutz, G., Bianco, L. and Tirao, G. (1s,3p) processes of resonant x–ray Raman scattering in Co Stutz, G. and Tirao, G.

Magnetic coupling between Gd and Pr ions in Gd0:5Pr0:5Al2 compound Carvalho, A. M. G., Garcia, F., de Sousa, V. S. R., von Ranke, P. J., Rocco, D. L., Loula, G. D., E. J., Carvalho Coelho, A. A., da Silva, L. M., and Gandra F. G. Vertical Shifting of the Magnetization in FeMn/NiFe Systems Tafur, M., Nascimento, V. P., Alayo, W. and Baggio-Saitovitch, E. Control of Structural Properties of InP Semiconductor Nanowires Chiaramonte, Th. Tizei, L. H. G., Ugarte, D. and Cotta, M. A.

Activity Report 2009 | 131

7) Structural Molecular Biology Structural characterization of ovorubin-typsin interaction Dreon, M. S., Ituarte, S., Ceolin M. and Heras, H. Crystallization and preliminary structure analysis of mitochondrial Thioredoxin Reductase 2 from Nakamatsu, E. H., Monteiro, G., Discola, K. F., Murakami, M. T. and Netto, L. E. S. Diffraction data from crystals of the Xanthomonas axonopodis pv. Citri alkanesulfonate-binding protein after soaking with different alkanesulfonates Balan, A.

Evaluation of Multielements in Human Serum of Patients with Sickle Cell Anemia using SRTXRF Canellas, C. G. L., Leitão, R. G., Santos, R. S., Carvalho, S. M. F., Anjos, M. J. and Lopes, R.T. X-ray crystallographic analysis of glucuronosyltransferase GumK from Xanthomonas campestris in soaking experiments with donor substrate Barreras, M., Salinas, S. R. and Ielpi L. Structural analysis of the sweet orange Hsp90 by SAXS Mendonça, Y. M., Aparicio, R. and Ramos, C. H. I. Small Angle X-ray Scattering Analysis of Recombinant Murine Prion Protein Complexed with an RNA Molecule Gomes, M. P. B., Vieira, T. C. R. G., Silva, J. L. and Cordeiro, Y.

Study of reprogramming of murine stem cells at atomic level

First results of the New Electron Analyzer Scienta R4000: a study of the gas phase amino acid DL-Valine

Cardoso, S. C., Stelling, M. P., Paulsen, B., Barroso, R. C. and Rehen, S.

Miranda, Á., Mocellin, A., Mundim, M. S. P. and Naves de Brito, A.

132 | Activity Report 2009

LNLS ACTIVITY REPORT 2009 Editor Management Proofreader

Angelo Malachias Claudia Izique Beatrice Allain

Telephone Fax e-mail

Giuseppe Máximo Scolfaro Street, 10.000 Campinas, São Paulo, Brazil P.O. Box 6192 Postal Code 13083-970 Campinas, São Paulo, Brazil +55 19 3512-1010 +55 19 3512-1004 secre@lnls.br

home page

www.lnls.br

Correspondence

This publication is available at the eletronic format in www.lnls.br/publicacoes Printed in December, 2010

Desktop publishing