When the light beam emitted by a laser pointer hits a glass window a few millimeters thick, some of the light is refracted, which means that the speed of the light wave changed when it entered the glass. This change can be easily quantified: the refractive index for air and glass is approximately 1.00029 and 1.5. The refraction phenomenon is well known; it is usually taught in High School Physics and fits in the theory of Linear Optics.

The light emitted by the laser pointer has low power, a few thousandths of a watt. However, when the laser power is very high (tens or thousands of watts), other phenomena occur in the interaction between the light and the material, which are called “non-linear.” One makes the glass act like a convex or concave lens. The magnitude of this effect depends not only on the characteristics of the light beam, but also on the material, and can be quantified by the non-linear refractive index.

A multidisciplinary team that included researchers from the Brazilian Federal University of Pernambuco (UFPE), the Brazilian Mackenzie Presbyterian University and the United States Air Force Research Laboratory (AFRL) was able to determine, for the first time, the non-linear refractive coefficient of ZrTe2 (zirconium telluride) – a two-dimensional material, still little studied, from the family of transition metal dichalcogenides (TMDs). The study was recently reported in an article published in Applied Physics Letters.

TMDs have unique electrical and optical properties that depend on their thickness, which can reach the subnanometer scale. In fact, extremely thin, transparent and flexible layers can be produced with these metals, which, of course, have aroused much interest for several applications. Important detail: for several of these applications, such as those related to medical imaging, the most important properties are those of the Non-Linear Optics universe.

In this context, Professor Anderson Stevens Leonidas Gomes (UFPE) has been working on, for about three years, a research line focused on the study of the nonlinear properties of TMDs, carried out in collaboration with researchers from AFRL. “They prepare the material and we perform the nonlinear optical characterization,” says the scientist. “The role of Melissa Maldonado, who completed a doctorate and is now a postdoctoral fellow under my supervision, was and is critical, since she has mastered the characterization techniques and was the main researcher responsible for the work in this line of research,” he adds.

Several materials from the family of two-dimensional TMDs have been studied by the group. In the work published in Applied Physics Letters, AFRL researchers prepared zirconium telluride nanoflakes of about 1 nm thick and 50 to 100 nm long, using a method based on laminating the surface of thicker nanoparticles. The samples traveled from the state of Ohio to São Paulo and arrived at Mackenzie, where part of the characterization was carried out. Finally, the samples were sent to UFPE, where their nonlinear optical properties were probed using a laser emitting extremely short and strong pulses, which interacted with the zirconium telluride nanoflakes. After performing a series of mathematical calculations, Professor Gomes and his group were able to determine the material’s nonlinear refractive coefficient. Through computer simulations, the authors were also able to understand the origin of the phenomenon and, therefore, create possibilities to control it.

“The main scientific contribution of this study is to measure, unequivocally and appropriately, one of the optical coefficients that indicate the magnitude of the material’s optical non-linearity,” says Professor Anderson Gomes, who is the corresponding author of the article. “This coefficient is important to define which photonic applications can be explored in this material,” he adds.

The study received financial support from the Brazilian federal agencies CNPq and Capes, the INCT-Nanocarbono, the Foundation for the Support of Science and Technology of the State of Pernambuco (FACEPE) and the US agency AFOSR. The authors used computational resources from the Advanced High Performance Computing Center (NACAD) at COPPE/UFRJ (Brazil).

Paper: Femtosecond nonlinear refraction of 2D semi-metallic redox exfoliated ZrTe2 at 800nm. Melissa Maldonado, Manoel L. da Silva Neto, Pilar G. Vianna, Henrique B. Ribeiro, Cid B. de Araujo, Christiano J. S. de Matos, Leandro Seixas, Ali M. Jawaid, Robert Busch, Allyson J. Ritter,  Richard A. Vaia, and Anderson S. L. Gomes. Appl. Phys. Lett. 118, 011101 (2021); doi: 10.1063/5.0031649

Contact: Prof Anderson Gomes (UFPE) – anderson.lgomes@ufpe.br

Dear Colleagues

We are happy to announce that we’ve just released the list of symposia that will be held at the XIX B-MRS and IUMRS-ICEM 2021. A total of 24 symposia were selected, covering areas ranging from Biomaterials to Electronic Structure Calculations.

Besides these exciting symposia, that will count with invited speakers and oral and poster presentations, we will also have seven Plenary speakers:

-Alex Zunger (University of Colorado Boulder, USA)
-Edson Leite (LNNano, Brazil)
-Hideo Hosono (Tokyo Institute of Technology, Japan)
-John Rogers (Northwestern University, USA)
-Luisa Torsi (Università degli Studi di Bari “A. Moro”, Italy)
-Tao Deng (Shanghai Jiaotong University, China)
-Thuc-Quyen Nguyen (University of California Santa Barbara, USA).

The Memorial Lecture will be delivered by Cid Bartolomeu de Araújo (UFPE, Brazil).

Owing to the uncertainties brought to us by the COVID pandemic, this year our conferences will be held online, from August 30th until September 3rd. The B-MRS is the largest conference in the area of Materials Science in Latin America, and we believe that the online meeting will bring the possibility to even larger participation.

It will be our great pleasure to welcome you all to the virtual XIX B-MRS and 2021 ICEM meetings next August/September ONLINE.

Stay well and take care,

Gustavo Dalpian
Conference Chair

They are lightweight, thin and flexible. They can be manufactured on an industrial scale using simple, low-cost processes. Organic solar cells have several advantages and appeals, but still represent challenges to researchers, especially in the field of materials. These devices that transform sunlight into electricity owe their name to the use of organic materials (polymers or carbon-based molecules) in the active layer, responsible for absorbing light. But the other layers of the “sandwich” that constitute an organic solar cell are also very important, especially the electrodes, which are in charge of collecting the electrical charges produced by exposure to light.

In Brazil, three groups of researchers combined their skills and developed collaborative research that brought an important contribution for developing electrode materials for organic solar cells. The recently published work was coordinated by the researcher Maria Luiza M. Rocco, professor at the Institute of Chemistry at the Federal University of Rio de Janeiro (UFRJ).

Organic solar cells need electrodes that, in addition to being good conductors of electrical charges, are transparent to allow light to pass through the active layer, like windows. Unfortunately, there are few materials that combine good conductivity and transparency. One of them is indium tin oxide (ITO). Thin films of ITO deposited on glass substrate are, until now, the most used electrode in organic solar cells, in addition to being widely used in electronic screens and other devices on the market. “In the mid-term, this standard electrode will need to be replaced, and scientists are diligently trying to effectively replace it,” says Professor Maria Luiza. In fact, the ITO film production process is expensive, and indium is a scarce material in the earth’s crust. In addition, these electrodes are not fully flexible.

Thus far, the leading alternative to ITO is PEDOT:PSS, a polymer blend that allows the manufacture of conductive and transparent films. By combining this material with graphene oxide (GO), it is possible to obtain a composite material which conductivity not only is higher than that of pure polymer but also can be further increased by treating the material. In addition, GO:PEDOT:PSS films can adapt to the roll-to-roll system, that is the favorite for production of organic solar cells on an industrial scale. In this system, the different layers are printed or deposited on a flexible substrate (for example, plastic). The substrate is rolled up at the beginning of the production line, unrolled to receive the layers and rolled again at the end, with the material almost ready to be used as a solar panel.

Detailed analysis

In the work coordinated by Professor Maria Luiza, the researchers carried out a systematic study of different films, using spectroscopic techniques. They analized samples of pure PEDOT:PSS and of graphene oxide with different proportions of PEDOT:PSS (1, 5 and 10%). In addition, samples from each of these groups were treated by cooling them to -196 ° C (liquid nitrogen temperature) until reaching thermal equilibrium and then returned to room temperature.

The objective was to understand the relationship between the structure and properties of each of the films, and to evaluate which of the combinations would allow greater electron mobility and, therefore, a better performance of the material as an electrode for organic solar cells.

Initially, graphene oxide was synthesized by the Materials Chemistry Group at the Federal University of Paraná (UFPR), led by Professor Aldo J. G. Zarbin. Then, members of the Laboratory of Nanostructured Devices, also from UFPR, developed the mixtures, prepared the films and studied the optical, electrical and heat treatment properties, under the coordination of Professor Lucimara S. Roman. Finally, the group of Professor Maria Luiza M. Rocco, from UFRJ, carried out spectroscopic studies at the Multi-User Photoelectron Spectroscopy Laboratory at UFRJ and at CNPEM’s National Synchrotron Light Laboratory (LNLS). The project had also participation of a representative from CSEM Brazil.

“The possibility of using synchrotron light was fundamental for understanding the electronic, morphological and transport properties of these new materials to be used as electrodes in optoelectronic devices,” states Professor Maria Luiza. Spectroscopic studies included differentiated analysis of the surface and bulk of the films, showing different characteristics in each region of the samples.

The study showed that cooled graphene oxide samples with PEDOT:PSS (5%) would better perform as solar cell electrodes. “The introduction of an insulating material (GO) in a conductor (PEDOT:PSS) increased the conductivity of the latter by two orders of magnitude,” reveals professor Maria Luiza. Cheaper than PEDOT, the graphene oxide used in the electrodes would lower the cost of the devices. The treatment carried out also helped to improve the conductivity of the material, by organizing the molecules so that it facilitates the displacement of electrons.

The study is part of Soheila Holakoei’s PhD research in Chemistry, defended at UFRJ in 2019, under the guidance of Professor Maria Luiza. The study received funding from LNLS-CNPEM and from Brazilian agencies Faperj (Rio de Janeiro), CNPq, CAPES and Finep.

Paper: Conformational and Electron Dynamics Changes Induced by Cooling Treatment on GO:PEDOT:PSS Transparent Electrodes. Soheila Holakoei, Amanda Garcez Veiga, Cássia Curan Turci, Matheus Felipe Fagundes das Neves, Luana Wouk, João Paulo V. Damasceno, Aldo J. G. Zarbin, Lucimara S. Roman, and Maria Luiza M. Rocco. The Journal of Physical Chemistry C. 2020 124(49), 26640-26647. DOI: 10.1021/acs.jpcc.0c07827

Contact: Prof. Maria Luiza M. Rocco – luiza@iq.ufrj.br.

Professor Gustavo M. Dalpian (UFABC) was appointed editor of the new scientific journal “Discover Materials” (Springer). Prof. Dalpian, a B-MRS member, is the chair of the XIX B-MRS Meeting + IUMRS ICEM 2021, to be held online this year.

The open-access “Discover Materials” journal was launched in 2020 by the editorial group Springer Nature, and covers all topics related to material research, from fundamentals to applications. Dalpian is part of the journal’s associate editors, along with three other scientists from Asia and Europe.

Sorry, this entry is only available in Brazilian Portuguese.

The year 2020 will undoubtedly be marked with sadness in our lives by the pandemic of Covid-19, which violently altered our daily lives, imposed tragic losses for many of us and gave more space to scientific negacionism, reinforcing the feeling of “nonsense” that we experience in today’s society.

However, at the same time, it was in 2020 that Science was once again a safe haven, pointing out alternatives and strategies to combat this terrible disease, while, in record time, decoding the virus genome and manufacturing vaccines with high efficacy. Brazilian researchers played an active part in building this knowledge chain, while resiliently fighting against threats to the country’s Science, Technology and Innovation (ST&I) structure. The materials research community could not abstain at such a critical moment and therefore quickly adapted research on biosensors, drug-carrying nanoparticles, materials with virucidal properties, etc. to combat SARS-CoV-2.

In 2020 B-MRS also had to reinvent itself. With the postponement of its annual meeting due to the health crisis, the virtual platform was our form of communication. And the community responded! With a strong presence in webinars, online events, and participating in awareness actions to maintain the country’s ST&I infrastructure as well as our most precious resource for the future, young PhDs and undergraduate and graduate students. The drive and motivation that students at our University Chapters show in their activities, brings us the certainty that there is a light at the end of the tunnel for Brazil.

And may 2021 come! We will be ready, equipped with the powerful resources of Science, to build a better year, with more health and decent living conditions for Brazilian citizens.

An excellent end of the year to everyone – as far as possible and observing all necessary care :).

B-MRS Board

Prof. Osvaldo Novais de Oliveira Junior (IFSC-USP), B-MRS member, was elected First Vice President of the International Union of Materials Research Societies (IUMRS).

The Brazilian scientist was chosen for the position unanimously, in an election held this December, involving materials research societies from around the world that participate in IUMRS.

He will hold the position of First Vice President for two years, from 2021 to 2022. At the end of his term, Oliveira Junior, who was the President of B-MRS from 2016 to 2020, will automatically assume the presidency of IUMRS.

Prof. Ana Flávia Nogueira (UNICAMP), B-MRS member, took on the position of general director of the Center for Innovation in New Energies (CINE) this December.

Founded in 2018 by the São Paulo Research Foundation (FAPESP) and the company Shell, CINE brings together research groups from UNICAMP, IPEN and USP and their collaborators to develop research on the frontier of knowledge and transfer technology to the industry in the area of new energies.