Featured paper: Disclosing structural disorder in nanomaterials.

[Paper: Decreasing Nanocrystal Structural Disorder by Ligand Exchange: An Experimental and Theoretical Analysis. Gabriel R. Schleder, Gustavo M. Azevedo, Içamira C. Nogueira, Querem H. F. Rebelo, Jefferson Bettini, Adalberto Fazzio, Edson R. Leite. J. Phys. Chem. Lett. 2019 10 1471-1476. https://doi.org/10.1021/acs.jpclett.9b00439]

Disclosing structural disorder in nanomaterials

It is known that it is very important to know and control the structure of a material (how its atoms are arranged in three-dimensional space) as it is largely responsible for the properties of the material and therefore for its applications. For example: regions of disorder in crystalline materials (whose atoms, ideally, are ordered in regular patterns) change some expected behaviors for these materials. Unfortunately, knowing the structure of some materials in detail can be a difficult task – particularly when it comes to nanomaterials.

Concentrating various skills and experimental and theoretical resources, a Brazilian team developed a method to establish the degree and location of disorder in the structure of crystalline and non-crystalline nanomaterials, interfaces and surfaces. The method, which is based on the combination of an experimental technique (transmission electron microscopy), a data analysis method (pair distribution function) and computational simulations, is already available to the scientific community at the Brazilian National Nanotechnology Laboratory (LNNano), and should help develop better performing materials.

In addition to developing the technique, the team applied it in the study of structural disorder in nanocrystals, which are basic elements of nanotechnology and are used for example, in solar cells and electronic devices. Although by definition they have ordered structures, these crystals of nanometric dimension can exhibit, in practice, regions with structural disorder.

In order to carry out the study, the scientists produced faceted nanocrystals of about 3.2 nm in diameter, formed by a core of zirconium dioxide (ZrO2), inorganic material, and a shell made up of organic substances known as ligands, whose atoms form chemical bonds with atoms that are on the surface of the inorganic nucleus. Ligands have the important role of stabilizing the nanocrystals, thus preventing them from aggregating.

The team produced a first series of nanoparticles with ligands containing an aromatic ring and analyzed it using the developed method. The samples were then subjected to a process known as ligand exchange in which chemical reactions occur in the material in the presence of a solvent at a temperature above its boiling point. In these reactions, some connections break down and new connections occur. As a result of the ligand exchange, the team was able to produce nanoparticles with shells containing oleic acid, which were also analyzed using the developed method.

This figure refers to a nanocrystal of ZrO2 before and after the ligand exchange. The figure includes high-resolution images of transmission electron microscopy, structural models and PDF patterns obtained by the developed method.
This figure refers to a nanocrystal of ZrO2 before and after the ligand exchange. The figure includes high-resolution images of transmission electron microscopy, structural models and PDF patterns obtained by the developed method.

The scientists concluded that, unlike the ideal nanocrystal of zirconium dioxide, the two types of nanocrystals analyzed had a degree of structural disorder located on the surface of the nucleus.  In addition, in the second group of nanoparticles, the disorder was significantly lower. The researchers interpreted this reduction as a result of the high temperature of the ligand exchange process, which altered the tensions of the network of atoms.

“In our work, we were able to directly assess the degree and location of disorder in the nanocrystals, which until then was not technically feasible,” says Gabriel Schleder, PhD candidate in the Graduate Program in Nanosciences and Advanced Materials of the Brazilian Federal University of the ABC (UFABC).

By better understanding structural disorder and its causes, the researchers were able to point out a way to control it. “Any property that significantly depends on surface-located structural disorder could be in principle controlled by this kind of ligand exchange process,” says Schleder. “Mechanical properties, photoluminescence, electronic transport and catalytic properties are some of them,” he adds.

The research was reported in a recently published article in The Journal of Physical Chemistry Letters (impact factor = 8,709).

Overcoming the challenge through collaborations

The initial idea of the study appeared in a meeting held at the end of 2017 at the National Center for Research in Energy and Materials (CNPEM), located in the city of Campinas, São Paulo. At the meeting, a group of reserachers discussed the implementation in Sirius (the next Brazilian synchrotron light source) of a technique that allows locally analyzing structural issues such as disorder and defects, called pair distribution function (PDF). The technique describes the distances between pairs of atoms by means of a mathematical function. To apply it, the specialist generally uses the results of X-ray diffraction measurements – an experimental technique that provides information about the structure of materials. However, in order to implement the analysis by PDF, the X-ray beam focused on the sample must be of very high energy – higher than that provided by the current Brazilian synchrotron light source.

During the meeting at CNPEM, Professor Gustavo de Medeiros Azevedo, researcher at the National Laboratory of Synchrotron Light (LNLS), and Professor Edson Leite, LNNano’s scientific director, decided to begin applying PDF using electron diffraction results, a specialty of LNNano’s researcher Jefferson Bettini. The electron beams would be generated by the transmission electron microscope (TEM) of LNNano. In fact, this instrument allows the control of the electron beam so that it focuses a small area of the sample, allowing the desired local analysis of the structure. Besides that, when switching from the “diffraction mode” to the “image mode”, the microscope would made possible to choose precisely the area of the sample to be analyzed.

Simulation of an ideal ZrO2 nanocrystal.
Simulation of an ideal ZrO2 nanocrystal.

The development team also involved professors Içamira Costa Nogueira, from the Federal University of Amazonas (UFAM) and Querem Hapuque Felix Rebelo, from the Federal University of the West of Pará (UFOPA), who contributed with the synthesis of nanocrystals that would be studied and with the development of the analysis methodology.

During the development of the technique, another challenge had to be faced. To interpret the PDF results, it would be necessary to have a simulation of an ideal nanocrystal – a nanocrystal model without structural disorganization that could be used as a reference.

New skills were then incorporated into the team, which was then joined by Professor Adalberto Fazzio, director general of LNNano and leader of a UFABC research group dedicated to computational techniques applied to materials, and his doctoral student Gabriel Schleder. Based on the Density Functional Theory (DFT), a computational modeling method in the field of Quantum Physics, the researchers were able to simulate the ideal nanocrystal that served as the analysis model.

“Something very positive we perceived is that the main results arose from the process of interaction, discussion and exchange of information mainly between theory/computational simulation and experiments. Without this, we certainly would not have good final conclusions,” says Schleder.

The authors of the paper. From the left: Gabriel R. Schleder, Gustavo M. Azevedo, Içamira C. Nogueira, Querem H. F. Rebelo, Jefferson Bettini, Adalberto Fazzio and Edson R. Leite.
The authors of the paper. From the left: Gabriel R. Schleder, Gustavo M. Azevedo, Içamira C. Nogueira, Querem H. F. Rebelo, Jefferson Bettini, Adalberto Fazzio and Edson R. Leite.

Featured paper: Moving nanoparticles for asymmetric nanowires.

[Exploring Au Droplet Motion in Nanowire Growth: A Simple Route toward Asymmetric GaP Morphologies. Bruno C. da Silva*, Douglas S. Oliveira, Fernando Iikawa, Odilon D. D. Couto Jr., Jefferson Bettini, Luiz F. Zagonel, and Mônica A. Cotta*. Nano Lett., 2017, 17 (12), pp 7274–7282. DOI: 10.1021/acs.nanolett.7b02770]

Moving nanoparticles for asymmetric nanowires.

Scanning electron microscopy image of asymmetric gallium phosphide (GaP) nanowires.
Scanning electron microscopy image of asymmetric gallium phosphide (GaP) nanowires.

A team of scientists presented a route to grow semiconductor nanowires having an asymmetric morphology, different from the traditional cylindrical one. The possibility of producing, in a controlled manner, nanowires with particular formats and without defects, can be exploited in several applications, including the production of more efficient solar cells.

The research was led by scientists from the Brazilian university UNICAMP and the Brazilian Nanotechnology National Laboratory (LNNANO), who reported their findings in a paper in NanoLetters.

The researchers discovered the process while studying the production of nanowires of gallium phosphide (GaP) for optoelectronic applications. The team chose to produce the nanowires by chemical beam epitaxy (CBE), preceded by a thermal treatment (annealing). In this technique, a substrate of a suitable material – in this case gallium arsenide (GaAs) – is placed inside a chamber. Then, chemical compounds in the form of vapor are introduced into the chamber. Some elements of the vapored material deposit over the substrate, layer upon layer, generating films. To promote the growth of nanowires instead of films, metallic nanoparticles (in this case, gold nanoparticles) are placed on the substrate before being exposed to vapor. During exposure, these catalytic nanoparticles cause the material to deposit preferentially underneath them, causing wire-like structures to grow.

While the researchers were analyzing the nanowires they had obtained in the first few months of the work, they found a significant amount of asymmetric nanostructures. “Besides having a particular morphology, we saw that these nanowires had an hexagonal crystal structure (wurtzite) and a very low density of crystallographic defects, which motivated us to study in detail the causes for the formation of this unusual structure,” says Bruno da Silva, PhD student at UNICAMP and corresponding author of the paper.

Da Silva and his supervisor Prof. Mônica Cotta then began to raise and test hypotheses for the cause behind the formation of the peculiar structures. After several experiments and analyses, they focused on a phenomenon that caught their attention: in the early stages of the process, the gold nanoparticles spontaneously moved over the substrate. Hence, the duo undertook a systematic work on heating substrates with nanoparticle catalysts, growing nanowires under various conditions, and analyzing the resulting samples through scanning and transmission electron microscopes and atomic force microscopy.

Atomic force microscopy image of a gold nanoparticle on GaAs substrate showing the trail left by its movement.
Atomic force microscopy image of a gold nanoparticle on GaAs substrate showing the trail left by its movement.

Da Silva, Prof. Cotta and their collaborators from UNICAMP and LNNano were able to find out why the growth process they used resulted in asymmetric nanowires. The main reason was the movement of the gold nanoparticles, which was thermally activated with the initial annealing. Based on that discovery, the team established a recipe for producing asymmetric semiconductor nanowires in a controlled manner. “Our work was the first to show that the mechanical instability of the nanoparticle catalyst can be used to modify the growth of semiconductor nanowires, in our case, particularly affecting their morphology,” says Bruno da Silva.

The mechanism of the asymmetric nanowires growth presented in the NanoLetters paper can be described as follow. When heated together with the substrate, the nanoparticles begin to crawl and advance through the substrate while consuming the oxide layer that naturally covers the gallium arsenide. Thus, the nanoparticles form asymmetric grooves a few nanometers deep and a few hundred nanometers long. These trails become fertile ground for the growth of the nanowires, since the deposition rate of the vapored material is greater there than in the rest of the substrate, which is covered by the oxide. A pedestal then forms along the grooves and the nanowire grows on top of the pedestal with an asymmetrical format.  “We showed that the movement of the particle generates a zone of preferential deposition, and that the combination of this phenomenon with the axial growth “vapor – liquid – solid” leads to the asymmetry in the nanowire,” summarizes da Silva.

Besides describing the formation mechanism of asymmetric nanowires, the work of the Brazilian team generated detailed knowledge about the movement of heated metallic nanoparticles. “We have shown that in addition to temperature, vacuum conditions and surface quality of the substrate are crucial for nanoparticle stability, and that the motion direction is related to the asymmetry of gold dissolution on semiconductor surfaces III-V,” details the doctorate student.

Concerning possible applications, the asymmetry of these nanowires can be explored, for example, in the construction of antireflective layers that reduce the amount of light lost by reflection in solar cells.  Another possibility would be to exploit the green emission of these wurtzite gallium phosphide nanowire in lighting devices. Or, why not, to develop an alternative process to electronic litography taking advantage of the gold nanoparticles movement and the trails it forms on the substrate.

The work was funded by Unicamp, the Brazilian federal agencies CNPq and CAPES and the São Paulo Research Foundation (FAPESP).


Featured paper: Rubber under Pressure for Solid-State Cooling.

[Paper: Giant Barocaloric Effects in Natural Rubber: A Relevant Step toward Solid-State Cooling. N. M. Bom, W. Imamura, E. O. Usuda, L. S. Paixão, and A. M. G. Carvalho. ACS Macro Lett. 2018, 7, 31-36. dx.doi.org/10.1021/acsmacrolett.7b00744]

Rubber under Pressure for Solid-State Cooling

A team of researchers from Brazil has found that vulcanized natural rubber prevails over any other material already studied in its capacity to change temperature by being compressed and decompressed – a phenomenon known as “barocaloric effect.”

The discovery opens up interesting possibilities of using vulcanized natural rubber in advanced applications, especially in the area of “solid-state cooling.” This term refers to refrigeration systems (such as refrigerators or air conditioners) that are based on the use of solid state refrigerant materials to absorb the heat of the system to be cooled and transferred to an external environment. Conventional devices use fluids (gaseous and liquid states). The research was reported in an article recently published in ACS Macro Letters, a journal of the American Chemical Society publisher in the field of Polymer Science and the related matters, whose impact factor is 6,185.

“Since natural rubber heats up when pressed (more than 20 degrees above the initial temperature) and cools when the pressure is released (at least 20 degrees below the initial temperature), we believe it can be used as refrigerant material in a refrigerator,” explains Alexandre Magnus Gomes Carvalho, researcher at the Brazilian Synchrotron Light Laboratory (LNLS) and corresponding author of the article.

Schematic representation of the barocaloric cycle, based on confined compression and decompression processes.
Schematic representation of the barocaloric cycle, based on confined compression and decompression processes.

The representation of the barocaloric cycle of a solid material, shown on the side, gives an idea of how vulcanized natural rubber can cool a system, removing heat from it and releasing it to the external environment. In process 1 of the cycle, the rubber (represented by the yellow rectangles) compresses quickly and consequently its temperature increases abruptly (Thot).  In process 2, pressure on the rubber is kept constant, but its temperature is reduced by releasing heat to the external environment for thermal equilibrium. Interestingly, in nature two bodies or systems with different temperatures tend to seek thermal equilibrium – the state in which both temperatures are equal. This equilibrium is achieved by transferring heat from the system or hotter body to the cooler one. In process 3 of the cycle, when the rubber reaches its initial temperature (Ti), the pressure rapidly drops, causing the rubber temperature to decrease abruptly (Tcold). In process 4, the external environment transfers heat to the rubber, again for thermal equilibrium. When the rubber reaches the initial temperature, the cycle resumes from a new compression process.

To investigate the barocaloric effect of rubber, Carvalho and the other authors of the paper used samples of vulcanized natural rubber of about 1 cm in diameter. They carried out a systematic study changing the pressure exerted on the samples and their initial temperature and measuring the temperature and entropy variations (both directly related to the heat variation of a system). The experiments were carried out at the Laboratory of i-Caloric Materials (LMiC), one of the thematic laboratories of LNLS, at CNPEM, whose coordinator is Alexandre Carvalho.

After obtaining the experimental measurements of the barocaloric properties of vulcanized natural rubber, the researchers compared them with the results, found in the scientific literature, of other materials with giant or large barocaloric effect. In this comparison, vulcanized natural rubber surpassed all its “competitors.”

Foreground: pressure cell and sample of vulcanized natural rubber subjected to several cycles of compression and decompression. Background: chart showing temperature measurements as a function of time for different pressure variations.
Foreground: pressure cell and sample of vulcanized natural rubber subjected to several cycles of compression and decompression. Background: chart showing temperature measurements as a function of time for different pressure variations.

The barocaloric effect of vulcanized natural rubber also has advantages with respect to caloric effects generated from the application of a magnetic or electric field, for example – effects that are also studied for solid refrigeration applications. In fact, while relatively low pressures have generated a giant caloric effect on rubber, to produce significant magnetocaloric and electrocaloric effects, very high fields and much more expensive materials than natural rubber are necessary, explains Carvalho.

Besides reporting for the first time in the scientific literature the giant barocaloric effect of vulcanized natural rubber, the paper in ACS Macro Letters contains another important scientific contribution. “The second major contribution is the fact that, for the first time, the effect of the glassy transition of a polymer on the barocaloric effect has been shown,” states Carvalho. The glass transition is a reversible change that occurs in rubber and other materials at a certain temperature. Above the transition temperature, the polymer chains of the rubber acquire more mobility, making the material “rubbery” (more flexible and less hard). Below that temperature, the mobility of the chains decreases and becomes “vitreous” (rigid and relatively brittle). In the ACS Macro Letters article, the authors proposed that the temperature and entropy changes that derive from the compression and decompression of natural rubber are related to the heat generated by the mobility of the polymer chains. Compression of the rubber would lead to a decrease in mobility, which would explain the much lower temperature changes in the vitreous state than in the rubbery state.

As for the application of the discovery, the cooling mechanism based on the barocaloric effect of solid state materials may seem simple, but transferring it to a real device is not easy.  “The barocaloric effect on different materials has been studied for several years, but there is still no barocaloric refrigerator prototype patented or described in a paper, as far as we know,” says Carvalho. “Despite the difficulties, we are considering developing a prototype together with researchers from the Department of Mechanical Engineering at the Brazilian State University of Maringá (UEM),” he announces.

History of the work

The idea of the work reported in ACS Macro Letters began in mid-2016 at CNPEM, when the researcher Alexandre Carvalho, the postdoc Nicolau Bom and the student Érik Oda Usuda came across a paper on the elasto-caloric effect of natural rubber (the temperature variation induced by stretching the material), published in Applied Physics Letters. The scientific trio then wondered if an equivalent effect would occur if the rubber were compressed rather than stretched. “More specifically, we wanted to know what would happen in a confined compression,” Carvalho details. They performed the first tests with simple equipment: a pressure cell developed by them and a manual hydraulic press to apply different loads. To prepare the sample, the team used an old school eraser turned into a billet to be fitted into the pressure cell. “The results were encouraging, as we observed that the rubber heated and cooled about 10 degrees from ambient temperature under a relatively low pressure range,” says Carvalho. In early 2017, PhD student William Imamura and postdoc Lucas Soares de Oliveira Paixão joined the group and also devoted their efforts to studying the barocaloric effect of vulcanized natural rubber and other polymers. “We improved our experimental apparatus and our methodology, culminating in the results published in ACS Macro Letters, which will be part of Érik Usuda’s master’s dissertation,” relates Carvalho, who coordinates the LMiC as well as the LNLS XRD1 beamline. In this line, which will be transferred to Sirius (the latest generation synchrotron light source under construction at CNPEM), studies of thermomechanical properties of polymers can be carried out simultaneously with synchrotron radiation analyses, announces Carvalho.

The research was carried out with funding from Brazilian agencies Fapesp, CNPq and Capes, and also LNLS and CNPEM funding.

The authors of the paper in the XRD1 beamline. From left, Lucas Soares de Oliveira Paixão (LNLS postdoc), Alexandre Magnus Gomes Carvalho (LNLS researcher), William Imamura (PhD student at Unicamp and LNLS), Érik Oda Usuda (master student at Unifesp and LNLS), and Nicolau Molina Bom (LNLS postdoc).
The authors of the paper in the XRD1 beamline. From left, Lucas Soares de Oliveira Paixão (LNLS postdoc), Alexandre Magnus Gomes Carvalho (LNLS researcher), William Imamura (PhD student at Unicamp and LNLS), Érik Oda Usuda (master student at Unifesp and LNLS), and Nicolau Molina Bom (LNLS postdoc).

Featured article: Probing electrons of actinide compounds.

box englishA team led by researchers from Brazil was able to unveil details of the distribution of electrons in materials based on actinide elements (the 15 chemical radioactive elements, with atomic numbers ranging from 89 to 103).

The group of scientists developed an experimental method that allowed a unique probing of the 5f and 6d orbitals and their hybridization in materials based on uranium (one of the most abundant actinide elements in the earth’s crust). This allowed the team to demonstrate, for example, that 5f-6d hybridization determines the magnetic properties of the studied materials. The work left as a legacy an experimental system for research on various magnetic materials (3d metals, rare earths, actinides and others), available to be used by the international scientific community at the Brazilian Synchrotron Light Laboratory (LNLS).

The study was reported in a paper that was recently published in Nature Communications (Impact Factor 12,124). “In this paper, we demonstrate the use of magnetic circular dichroism (XMCD) on the L-border of uranium to directly probe the 6d and 5f orbitals and also their degree of hybridization, rather than just probing the 5f orbitals as for instance the actinides M absorption edges,” details the corresponding author of the paper, Narcizo Marques de Souza Neto, professor at UNICAMP and researcher at LNLS.

In order to probe the orbitals of the uranium compounds, especially UCu2Si2 and UMn2Si2, the scientists had to overcome the difficulties of manipulating the materials due to their toxicity. They also had to make a series of adjustments in the high-energy XMCD technique to improve its sensitivity (to extend its detection limits).

These developments were initially performed at the LNLS DXAS line, dedicated to X-ray absorption techniques. Currently, the XMCD instrumentation is part of the XDS line of LNLS which is dedicated to X-ray diffraction and spectroscopy, where it is being used and improved. In the future the technique will be available in Sirius (the latest generation of synchrotron light source which is being built in Campinas), more precisely in the EMA line, which will be dedicated to X-ray techniques under extreme conditions of pressure and temperature. According to Souza-Neto, who coordinates both the XDS line and the EMA project, the conditions for studying actinides and similar materials by XMCD will be unparalleled in Sirius.

In addition to advancing the knowledge on actinides, the research demonstrated the potential of the XMCD technique improved by the Brazilian team to continue unveiling the characteristics of these still experimentally understudied elements. A deeper understanding of actinides, says Souza-Neto, is necessary to propose new uses for these elements, and also to be able to use them more efficiently in existing applications, such as, for example, power generation, diagnosis and treatment of diseases and the production of special glasses.

Ricardo dos Reis (left) and Narcizo Souza-Neto (right), main authors of the paper. Between them, a screen with the representation of EMA beamline where XMCD experiments will be available in Sirius fourth-generation synchrotron source.
Ricardo dos Reis (left) and Narcizo Souza-Neto (right), main authors of the paper. Between them, a screen with the representation of EMA beamline where XMCD experiments will be available in Sirius fourth-generation synchrotron source.

The history behind this work

The origin of this work dates back to 2009, when Souza-Neto was studying rare earth electronic structure and magnetism during his postdoctoral fellowship at the Argonne National Laboratory in the United States. “I had the idea of expanding the study of rare earths to actinide compounds (Souza-Neto et al., Phys. Rev. Lett., 102, 057206 (2009)) using XMCD to probe a charge transfer in the 4f and 5d orbitals”, the researcher reports. Looking for materials with similar characteristics, he came across uranium compounds. “We first tried to start this study in Argonne, but the conditions there to carry this out were not as we had hoped,” he adds. He returned to Brazil in 2010 as a researcher of CNPEM, with the desire to continue this initiative. Thus, in 2011, Souza-Neto began to guide the doctoral research of Ricardo Donizeth dos Reis on this subject together with the co-supervisor Flávio César Guimarães Gandra, a professor at Unicamp, with whom he had previously collaborated.

Samples of uranium compounds were prepared and characterized in the Laboratory of Metals and Alloys of Unicamp, coordinated by Professor Gandra, where there was already research experience on actinide and rare earth materials. The X-ray absorption spectroscopy experiments were performed at Argonne’s Advanced Photon Source and at LNLS. “All experiments on the L edges of uranium, which make up the main innovative contribution of this work, were carried out at LNLS,” Souza-Neto details. “At Argonne the experiments were carried out on the M edge of uranium to probe the contribution of the 5f orbitals separately and corroborate our interpretation of the results,” he adds. Furthermore, the Brazilian group had the participation of a researcher from France in the theoretical simulations performed for interpreting the data.

The research was carried out with financial resources from the São Paulo Research Foundation; from the Brazilian federal agency Capes; from the Ministry of Science, Technology and Innovation of Brazil, and from the Office of Science of the United States Department of Energy.

Scientific paper:

“Unraveling 5f-6dhybridization in uraniumcompounds via spin-resolved L-edge spectroscopy”. R. D. dos Reis, L. S. I. Veiga, C. A. Escanhoela Jr., J. C. Lang, Y. Joly, F. G. Gandra, D. Haskel & N. M. Souza-Neto. Nature Communications 8:1203 (2017). DOI: 10.1038/s41467-017-01524-1. Link: https://www.nature.com/articles/s41467-017-01524-1

Special feature: Sirius, the latest generation Brazilian Synchrotron.

Before the end of this decade, the Brazilian Synchrotron Light Laboratory (LNLS), located in Campinas (SP), will be receiving researchers from Brazil and from the rest of the world to use the Sirius, the fourth generation Brazilian synchrotron that will replace or supplement the UVX – the current second generation Brazilian synchrotron, which has been operating since 1997 and is the only synchrotron in Latin America.

Highly appreciated by the scientific community of Materials Science, and by many other areas, synchrotrons are the best sources of beams of X-rays and ultraviolet light, two very useful types of radiation in the study of matter. The process of producing radiation is achieved by the acceleration of electrons moving near the speed of light and subjected to deviations in its path. When diverted, the electrons lose some of their energy in the form of synchrotron light, which is filtered by monochromators that will release radiation by selectively passing the desired wavelength. Therefore, the X-ray beams or ultraviolet light are carried to the experimental stations or light lines, around the accelerator, which have various scientific instruments. The users of the synchrotron make use of the radiation to analyze its interaction with matter through the scientific instruments to obtain information about the structure and properties of the materials at micro and nanoscale.

Sirius, as its name suggests the brightest star in the night sky, will be able to generate extremely bright light beams (up to a billion times higher than the brightness of UVX) – a very important feature that will allow to perform more and better experiments.

This high-brightness radiation, together with advanced scientific instruments and powerful computers to quickly process large amounts of data, will allow performing a wide range of experiments that will generate scientific and technological results in sectors such as Agriculture, Biology, Geology, Energy and Health, and of course in the Materials Science area.

Synchrotron light sources in construction and operating around the world. Map provided by LNLS-CNPEM.

About 300 people are currently working on the project and construction of Sirius, a large-scale and complex project that involves many challenges. One is the development of the synchrotron light source. As a matter of fact, Sirius is one of the first fourth generation light sources in the world (there is only one more currently under construction in Sweden, but neither one operating). There are many challenges, such as developing a system for the monitoring, diagnosis and correction so that the sensitive electron beam trajectory remains stable. Even the construction of the building itself must meet very specific conditions, in order to ensure an almost complete absence of vibration, however small.

This large-scale Brazilian undertaking, whose value is estimated at 1.3 billion reais, is being conducted by LNLS, which developed the UVX and has taken care of its operation, maintenance and upgrades for 19 years. The general management and direction of the team is under the responsibility of the current director of LNLS, Antonio José Roque da Silva. Full Professor of the University of São Paulo (USP), Roque da Silva has an undergraduate and master’s degree in Physics from Unicamp, and a doctorate (PhD), also in Physics, from the University of California, Berkeley. He is the author of over 120 scientific papers published in indexed journals, many of them related to materials science studies. According to Google Scholar, his publications have over 4,400 citations.

The SBPMat Newsletter interviewed Roque da Silva on the technical characteristics of Sirius, the possibilities it offers to the materials science community, the progress of the project and the future of UVX, among other issues.

SBPMat: Newsletter – Sirius will be a high brightness synchrotron light source. What is the importance of brightness for research in Materials Science and Technology?

Antonio José Roque da Silva: – For a given frequency of radiation, its brightness is directly proportional to the flux (number of photons per unit time) and inversely proportional to the product of the beam size times the beam divergence angle). The latter quantity is the beam emittance. Therefore, the lower the emittance, the higher the brightness.

The high-brightness affects the analysis of the materials in different ways:

a.  The higher the brightness of the light produced by the synchrotron, the higher the number of samples that can be analyzed within a time period; This allows performing experiments with temporal resolution, which allows to monitor the progress of reactions or processes, e.g., as a function of time.

b.  Higher brightness means a better signal-to-noise ratio of different analysis techniques.

c.  Low emittance, hence higher brightness, allows probing smaller spatial scales by analytical techniques. This opens study opportunities using nanometer-sized beams, important in areas such as nanotechnology, and other areas.

d. Higher brightness allows the emergence of new techniques or to explore them more effectively. This occurs, for example, with the Coherent Diffraction Imaging technique. Higher brightness will greatly benefit imaging techniques, tomography and microscopy.

The first 13 beamlines that will be installed in Sirius. Data provided by the LNLS-CNPEM.

SBPMat Newsletter: – What are the limitations of UVX synchrotron that will be overcome by Sirius? For example, will there be characterization techniques of materials in the experimental stations of Sirius that cannot be installed in UVX?

Antonio José Roque da Silva: – The major difference between the two machines is the energy range in which they operate. The electrons in the storage ring of Sirius will be accelerated up to the energy of 3 GeV, more than double the energy of UVX. This results in producing higher energy X-rays and enables more in depth studies of materials such as steel, concrete and rock due to the penetration of X-rays up to a few centimeters, against some micrometers of the UVX.

Also because of the energy difference, the number of chemicals that may be studied by soft X-ray spectroscopic absorption is also different. In the UVX less than half of the chemicals can be studied, while almost all elements of the Periodic Table can be studied in the Sirius.

The low brightness and high emittance of UVX greatly limits the most modern synchrotron techniques available to the scientific community of the country. Nanotomography, coherent diffraction imaging, fluorescence nanomicroscopy, nanocrystals analysis, materials research under extreme conditions (high pressures and high temperatures), inelastic scattering, temporal monitoring of various processes, together with nanometer spatial resolution and chemical resolution (for example, important for catalytic processes), among many other techniques, cannot be performed in UVX or are carried out with great limitations, however they can all be carried out, with high standard, in the Sirius.

SBPMat Newsletter: – What will happen to the UVX?  Will it be dismantled?

Antonio José Roque da Silva: –  It should be emphasized that everything that the UVX does today can be done much better in Sirius. In addition to the large number of new experiments that cannot be performed in the UVX, as mentioned earlier. The LNLS has decided that during the commissioning period of the Sirius beamlines, the UVX will be kept operational to ensure that the community is not affected by any discontinuity. However, it is not known if after Sirius becomes fully operational the current machine will be preserved or disabled. We know that the scientific instrument available today in some experimental stations of UVX will be transferred to Sirius. Additionally, the cost and feasibility of maintaining the simultaneous operation of two synchrotron light sources must be assessed, as well as the staff (engineers, technicians, researchers and etc.) needed to operate both sources. It is also necessary to assess the users’ level of demand for the experimental stations of UVX once Sirius is fully operating.

SBPMat Newsletter: – Will the expertise of professionals (scientists, engineers, technicians) and Brazilian companies developed during the construction of UVX be used in Sirius? If yes, in what way?

Antonio José Roque da Silva: – The Sirius project would not be possible without the expertise and skills of the professionals formed by LNLS over the years, particularly during the construction of UVX. This high-capacity and specialized professional body (scientists, engineers, technicians) formed over the past 30 years, is crucial to the success of Sirius. The amalgamation of experienced professionals that originated with the construction of UVX, including the young people, is a key strategy of the LNLS – for Sirius and for the future of the laboratory. From a technical point of view, the knowledge accumulated by our engineers and technicians during the construction and operation of UVX is what allowed to design a state of the art synchrotron such as Sirius. This experience will also be crucial to the operation of the new synchrotron. And the same goes for the scientists. The involvement with the construction and operation of the beamlines and the experimental stations of UVX is an important factor for the projects of the sophisticated beamlines of Sirius. The ongoing involvement of these researchers in training the new users, which is regularly performed by LNLS, is also fundamental, and which dates back to the beginning of the construction of UVX. We highlight that all of this knowledge acquired over the years also depends on a strong interaction with the international community of synchrotrons. The LNLS is strongly inserted in this community.

From a perspective of companies, the number of companies involved in the construction of the UVX was small. The UVX was not only designed by the LNLS but also mostly built within the LNLS. However, some companies which were important partners of UVX, as for instance Termomecânica, are also participating in the construction of Sirius. But LNLS successfully structured specific programs to involve Brazilian companies in the development and construction of various components for Sirius. These programs are in partnership with research funding agencies like FAPESP and FINEP. The development of partnerships with Brazilian companies will also be important for the future. Finally, the knowledge created by the Brazilian companies that cooperated (and that will continue to cooperate) with the project is extremely important and exceeds the limits of the project itself. This is why we consider Sirius to be a “structuring” project, whose developments will be reflected in new technologies, new products and processes that will bring benefits to the Brazilian high-technology supply chain.

SBPMat Newsletter: – Because it is a very complex, high standard and pioneer engineering project, (there is no other operating 4th generation synchrotron in the world), the construction of Sirius has unprecedented challenges, right? As project director, how do you address these challenges?

Antonio José Roque da Silva: – We rely largely on the experience, knowledge and audacity of the team of scientists, engineers and technicians of the LNLS. The courage of this team to face such challenges is among the greatest legacies dating back to the construction of the UVX. The compelling story of the construction of UVX has already been addressed in other SBPMat newsletters [Newsletter Note: see here the first and second part of this story). The culture of “yes, we can do it”, which comes from the beginning of LNLS, it crucial to overcome the challenges. One strategy is to increase the professional personnel, fundamental given the size of Sirius, mixing young people with the more experienced professionals, ensuring to preserve the existing in-house culture and knowledge. In addition to this experience, competence and courage, the continuous interaction with other laboratories is a key factor. We invested heavily in this area, sending LNLS professionals abroad and bringing experts from abroad to visit the laboratory. In this respect, also important is the assessment of our solutions by leading international experts. This is done through evaluation committees that regularly come to LNLS, and through the presentation of our results in conferences and specialized workshops. Also important is the investment made in cutting-edge infrastructure in both manufacturing and metrology. Finally, an important part is in regard to management and coordination of the activities and staff, thereby ensuring the efficient implementation of the necessary processes.

SBPMat Newsletter: – Tell us about the participation of national and international external companies and institutions in CNPEM regarding the development of Sirius.

Antonio José Roque da Silva: – One of the goals of the Sirius project is to stimulate the development of the Brazilian industry, by promoting demands related to technological developments, services, raw materials, processes and equipment. The goal is to apply between 65% and 70% of the project’s funds in the country. We should bear in mind that the project is 100% Brazilian.

Among the already established partnerships, we mention as an example the partnership created with the company Termomecânica of São Paulo, which developed the process to manufacture the raw material for the vacuum chambers of the storage ring and also the hollow copper wires for the electromagnets that allow cooling the water circulating through the pipes (this development dates back to UVX). Another example is the company WEG Indústrias (SC), a traditional electric motors manufacturer, which will manufacture over 1350 electromagnets for Sirius, designed by the technical staff of LNL. This is an exceptional partnership related to the sophisticated development of production processes and which has been extremely successful.

There are also examples of partnerships with smaller companies, such as FCA Brasil (Campinas, SP), for the manufacture of booster vacuum chambers, and with the Company EXA-M Instrumentação do Nordeste (BA), for the development and manufacturing of the devices for heating the vacuum chamber of the storage ring, and with Engecer of São Carlos for the manufacture of special ceramic vacuum chambers.

To increase the participation of national companies in the Sirius project, other systematic initiatives were undertaken. In 2014, negotiations with FINEP and FAPESP culminated in the launching of the first public call to select São Paulo-based companies for the development of 20 technological demands of the Sirius project, with resources of R$ 40 million. These funds were made available under the PIPE/PAPPE grant program, so that each proposal could request up to R$ 1.5 million for its development. Eight companies were selected to develop 13 research projects to carry out the challenges proposed in the bidding process.

In 2015 a second public call for proposals was launched for the development of 13 new technological challenges, with resources amounting to R$ 20 million under the same program. February was the deadline for the submission of bids by the companies, which are currently under analysis by FAPESP. For the second half of 2016 we expect that at least thirteen other companies are approved to develop the challenges of the second FAPESP/Finep call to support the Sirius project.

From an international point of view, as already mentioned, the continuous interaction with several laboratories has been vital to the project. An interesting detail is that today, as we are at the frontier and with several innovative solutions, needless to say there are international groups interested in interacting with the LNLS. That is, Sirius is obviously an important international vector.

SBPMat Newsletter: – What are the funding sources of the project.

Antonio José Roque da Silva: – The project is mainly funded by the Federal Government, through the Ministry of Science, Technology and Innovation, MCTI. It should also be mentioned that the Sirius project was recently included in the Growth Acceleration Program, better known as PAC, and is listed as one of the first MCTI projects to be part of the program.

Other important resources were provided by the State Government of São Paulo. For example, the land area of 150,000 square meters where Sirius will be installed was acquired by the State Government and granted to CNPEM.

Moreover, FAPESP has been an important partner in the interaction programs with companies and in supporting events and in the acquisition of scientific instruments that will be installed in the experimental stations (beamlines) of Sirius.

SBPMat Newsletter: – At what stage is the project now? What is the forecasted inauguration date of the light source and the first experimental stations?

Antonio José Roque da Silva: – The construction work of the Sirius building is about 20% complete. Part of the superstructure of the main building and part of the metal structure of the cover of the main building has already been built. An important milestone is making the tunnel available to begin assembling the accelerators at the end of 2017.

Several components of the accelerator are in the production phase. All quadrupoles and correctors of the booster have already been manufactured (by WEG) and delivered. Last week the pilot-batch of sextupoles was delivered, and the manufacture of the sextupoles will begin in two weeks. The prototypes of the booster dipoles will be delivered by the end of March, and its production should begin in early May. The Linac linear accelerator is ready and undergoing tests at the Shanghai Institute of Physics. Additionally, other components have concluded the development stage and are awaiting approval to start production, such as the vacuum chambers of the booster and part of the vacuum chamber of the storage ring. The RF booster cavities have been ordered, and the RF cavities of the storage ring will be ordered. Several other subsystems are in the final prototyping or in the initial production phase.

With regard to the experimental stations (beamlines), their projects are entering the technical detailing and construction phase and/or components acquisition. The projects of the Ipê, Carnaúba, Ema and Cateretê lines are now entering a detailed components phase of the experimental stations, technical designs and construction/custom component orders, such as inverters and mirrors which have a delivery time of up to two and a half years. Basically all the important beamline prototypes will be completed by the end of 2016. Overall, the chronogram of Sirius is on schedule, and the first beam and initial commissioning phase is expected in 2018, that way in 2019 the machine can receive the first researchers.

SBPMat Newsletter: – Would you like to add any comments or information?

Antonio José Roque da Silva: – It should be highlighted that Sirius is a result of the evolution of both the internal capacity of the laboratory as well as the maturing of the scientific community in Brazil. The concept of an Open National Laboratory, which is the goal of LNLS to provide an extremely sophisticated and unique equipment to the ST&I community is at the heart of the culture in the laboratory. Its high performance operation requires constant investment to train this highly specialized human resources (scientists, engineers, technicians), for the maintenance of cutting-edge equipment and infrastructure (accelerators, beamlines, experimental stations, support groups, metrology, manufacturing techniques, etc.), for user training, for developing new technologies, excellence in communication and management. The synchrotron project in Brazil, from UVX to Sirius, is something that all Brazilians can and should be proud of, bearing in mind it began from “square one” and in thirty years has placed Brazil in the state of the art, with a significant effect on the formation of human resources, high-level science, innovation, high-technology development and internationalization.

Simulation of the Sirius building (round, on the left) at CNPEM campus. Provided by LNLS – CNPEM.

Opportunities for researchers at the Brazilian Synchrotron Light Laboratory (LNLS).

Location: Brazilian Synchrotron Light Laboratory (LNLS) – Campinas City, São Paulo state – Brazil.

Post details (i.e. permanent): Permanent staff member position.

Salary: to be negotiated depending on applicant’s experience.

Application requirements: 1. Solid experience on synchrotron science using micro and nano-probe x-ray scanning techniques. 2. Ph.D. degree or equivalent in Physics, Biology, Chemistry or a related discipline, with emphasis on the use of micro and nano-probe x-ray scanning techniques. 3. Experience with beamline design and commissioning. 4. Language: Advanced level of English. Portuguese as a plus.

Brief job description: The selected applicants will have to carry out their own research projects with x-ray diffraction and spectroscopy, as well as being involved in the project, construction and future operation of the nanoprobe beamline on Sirius (CARNAÚBA) on the operation of the x-ray diffraction beamlines at the current 2nd generation Light Source. For more information on the current LNLS beamlines, please visit www.lnls.br.

Interested, please send CV, Motivation and Recommendation Letter to elisa.turczyn@lnls.br. In the subject line, put “47834”, otherwise the CV will not be considered.


Location: Brazilian Synchrotron Light Laboratory at CNPEM in Campinas/ São Paulo, Brazil.

Responsibilities: The extreme condition research group of LNLS has an immediate open Scientist position for an outstanding experimentalist in high-pressure/temperature and materials research. The successful candidate should be heavily involved in the design and implementation of the EMA beamline at the Sirius Synchrotron (under construction). This beamline is intended for spectroscopy (XAS/XMCD/XES) and scattering (XRD/XRMS/XRS) experiments under extreme pressures by taking advantage of submicron beamsize (down to 0.5×0.5 µm2) with high photon flux (up to 10^14 ph/s). In addition, the scientist must develop his/her own research activities and supervise students and post-docs. He/she also must be involved in high pressure/temperature experiments at our current 2nd generation synchrotron in order to prepare the instrumentation and the Latin American community to take advantage of state-of-the-art instrumentation when Sirius is ready.

Requirements: Ph.D. degree in physics, chemistry, materials science, earth science, biophysics, engineering, or a related field. Post-doc experience in the field is desirable but not obligatory. The successful candidate should meet some of the following qualifications (although quick learning scientist with expertise in other areas could also be considered): High pressure and temperature experiments in diamond anvil cells; X-ray diffraction and/or spectroscopy under high pressure/temperature; Visible/IR laser optics instrumentation; Experiments involving high magnetic fields; Commissioning/operation/use of a synchrotron hard x-ray beamline. Fluent English.

Interested, please send CV, Motivation and Recommendation Letter to elisa.turczyn@lnls.br. In the subject line, put “62220”.


The manufacturing of LNLS accelerators and the national materials, by Prof. Cylon Gonçalves da Silva.

Picture of the storage ring of the synchrotron light source, in LNLS (Campinas, SP) in December, 1996, time of the start of its working, 7 months before the inauguration of the laboratory. (Credit M.B.JR)

When we started the construction of LNLS, in 1986, and much before that, in its “pre-history”, there already was the intention of involving the Brazilian national industry in the construction of the equipment. Looking back from 2015, it is difficult to imagine what the Brazilian industry was in 1985. It is even more difficult to conceive that, in some sectors, among them the metal-mechanical sector, it was more sophisticated than it is today. The opening of the Brazilian economy, required, but conducted in a confused and trapping manner by Collor Government, terminated with a good part of the most sophisticated industry that was in Brazil at that time. Out of all the materials required to construct the accelerators, two got highlight for their weight (literally): steel and copper. To the magnets and vacuum chambers, we needed steel, and to the coils of the electromagnets we needed OFHC copper with low content of oxygen.

I remember the visit made to our hangar, by an specialist in ultra-high vacuum of Balzers that states to us, in an arrogant manner, that “it is impossible to manufacture ultra-high vacuum chambers” with Brazilian steel. “You will have to import”. It is not required to say that it was a wonderful incentive so that we would look for a Brazilian supplier to our needs. Ricardo and I shared a healthy disregard to such type of specialist. I think we both thought, without speaking up, each time we´ve heard statements of such type, more or less the same thing: “Ah, yes! No way? You will see!” To the manufacturing of the magnets and vacuum chambers, there were two questions not answered. There would be in Brazil steel with the required characteristics? And the laser-cutting method that we intended to use would not affect in a negative manner the magnetic properties of the material on its edges? No one has used such technique to manufacture precision electromagnets until LNLS considered it as an option, given the very special conditions we were facing. When we started, no one had the answers to such questions. The experience showed that there was the required steel in Brazil, for the magnets (SAE1006, acquired in the national market and re-laminated by Mangels), as well as for the chambers (AISI 316L), and that the laser cutting was a feasible and very flexible technique to the production of batches relatively small of electromagnets*. This, naturally, did not occur from night to day. In another occasion, we could told the long history of the development of the processes for steel, for example, the vacuum chambers cleaning and welding, and, for the magnets, the improvement of the magnetic properties.

Another history, funnier, is the one of copper for the coils of the electromagnets. CERN has recommended the Finnish company Outokumpu to us, which was their supplier. It is clear that, with such recommendation, we were calm regarding the quality of the Finnish product. But, I was not satisfied with having to import copper. A research revealed the existence of Termomecânica in São Paulo, property of Salvador Arena. Referencing to my “specialists”, all of them were unanimous in two points: it was a best-quality company and a company owned by an exceptional businessman, one of the most dedicated to the technological development of his products, only a little moody. I thought he fitted in the profile of a potential supplier to LNLS, and there I went to explain the LNLS project and its needs to him. I was welcomed, I have heard for hours an explanation on the beautiful educational program that was the project of his heart, I could expose our project in a brief manner, but Arena was precise about it – “I do not enter in such business. I do not want anything with the government. I will not go right. Forget it, you will not reach it. Termomecânica will not supply to you.” (I put the text between quotes, safeguarding that they could not have been Arena’s exact words, but the sense is the same.)

I confess I got disappointed, but the talk was not in vain. It served to me to understand how he thought, and to outline a strategy to convince him. We imported, with the help of CERN, a ton of OFHC copper from Outokumpu (a fraction of what we needed) in the specifications required to the coils of the dipole of the ring. The copper supplied by Outokumpu was OFHC/OFE – 99.99% minimum Cu with up to 0.0010% max of oxygen.  As soon as the material arrived, I called to Salvador Arena to tell him: “You did not want to supply, I imported from Outokumpu, your competitor”. What was heard on the other side of the line cannot be reproduced in the profusion of the insulting words where Arena was prodigal. Underneath, I was referred to as frivolous and unreliable, and he assured me in the most emphatic terms that he has never said that Termodinâmica would not provide us with the copper of low content of oxygen we needed. And he virtually ordered me to go back there immediately with the specifications that they would develop the material to us. And it was what they did. Thanks to Outokumpu’s import strategy, the copper supplied by Termomecânica is until today complying with its role with distinction, not only in the dipoles, but in all electromagnets of LNLS (OHFC/OF certificate – 99.95% minimum Cu + Ag with up to 0.0010% max of oxygen, but with OFE quality). Also here, there is a long story of development made by the LNLS team, from the materials up to the finished product. But, let’s leave it to another opportunity.

 Prof. Cylon Gonçalves da Silva

* I thank Guilherme Franco, Osmar Bagnato, and Ricardo Rodrigues, of LNLS team, for having refreshed my memory on the types of steel deployed, as well as the technical details of OFHC copper.