Producing microfibers from materials of the graphene family is a challenge some international research groups have decided to face in recent years. Because they are flexible and can readily conduct electricity, these elongated structures of a few tens of micrometers in diameter have several applications, largely as components of flexible electronic devices. However, the methods for microfibers production have failed as regards the control of their dimensions and shapes, impacting the properties of the material.
Now, a scientific team from Brazil, led by Professor Cecília de Carvalho Castro Silva (Mackenzie), has managed to overcome this challenge through an innovative graphene oxide (GO) processing strategy. The research was reported in an article published in Nanoscale, a journal of the Royal Society of Chemistry, featured on the journal’s back cover. In addition, the paper is part of a special edition of the journal, which brings together the work of young researchers with the potential to influence the direction of nanoscience and nanotechnology, which had the participation of Professor Cecília de Carvalho Castro Silva.
“In this work, we present to the Materials Science and Engineering community a simple strategy to obtain graphene oxide (GO) microfibers with high structural and dimension control, homogeneous shapes and adjustable diameter, through the use of microfluidic,” says Cecília, researcher at MackGraphe, a research center at Mackenzie Presbyterian University focused on graphene and other nanomaterials. The new approach could extend to the production of microfibers based on other two-dimensional or one-dimensional materials.
The work gathered MackGraphe’s expertise in two-dimensional materials for electro-optical devices and the experience of the São Paulo Institute for Technological Research (IPT) in Microfluidics – a multidisciplinary area dedicated to understanding and controlling the behavior of liquid or gaseous fluids on the micrometric scale, using it for this purpose tubes or cameras that confine fluids.
Interaction between fluids
The challenge of the MackGraphe and IPT team was to homogeneously group the graphene oxide sheets, of nanometric thickness, within the desired dimension, forming fibers. Thus, the scientists developed a device composed of needles and micrometric channels that was designed to confine two different liquids so they could interact in a controlled way.
A dispersion of graphene oxide (main liquid) and a compound with coagulating and surfactant properties (support liquid) are injected in the microfluidic device. Both liquids flow together in a channel, in such a way that the support liquid uniformly envelops the main liquid, preventing it from touching the walls of the device. This allows to precisely control the diameter of the fibers leaving the device: the greater the flow of the support liquid, the greater the compression it exerts on the dispersion of GO, and the finer the fibers formed.
To determine how to modulate the diameter of the microfibers according to the flow of the injected liquids, the team used computer simulations. This theoretical work was carried out by researcher Martha Lucía Mora Bejarano, from IPT, using the computational fluid dynamics (CFD) technique.
The method developed by the Brazilian researchers includes a phase to improve the electrical properties of microfibers. In fact, graphene oxide, compared to graphene, is a material that is easier and cheaper to produce, but due to the presence of oxygenated functional groups in its structure, it is an electrical insulator. However, simple treatments can remove a part of these elements, generating the so-called reduced graphene oxide (rGO), whose ability to conduct electricity reaches levels close to those of pure graphene.
In the work reported at Nanoscale, thermal and microwave treatments were carried out on microfibers to improve their electrical properties. The result was very positive, and the researchers were able to use graphene oxide fibers to assemble transistors (basic components of electronics that fulfill the fundamental functions of turning on, off or amplifying the electric current). Fully flexible, these transistors could be used in the most diverse wearable devices, from sensors for health monitoring to devices for energy generation and storage in electronic tissues.
The origin of the study dates back to 2017, when Professor Cecília de Carvalho Castro Silva started to develop graphene oxide microfibers in her newly created research group at MackGraphe, and she faced numerous problems regarding the stability of the mechanical properties of the fibers and the control of its thickness and length.
That same year, Cecília was part of the organizing committee of the VII Microfluidics Workshop, which was held at IPT, in São Paulo. The senior IPT researcher Mario Ricardo Gongora Rubio, who has extensive experience in the development of microfluidic devices, was also on this committee.
“In conversations with Mario, we had this idea of exploring the use of microfluidic devices with 3D hydrodynamics, focusing to obtain GO microfibers with high structural and diameter control,” recalls the scientist. As the strategy had already been shown to be effective in obtaining polymeric microfibers, the research team thought about adapting it to the production of graphene oxide microfibers.
The idea was realized in the master’s degree of Jaqueline Falchi da Rocha, which began in 2018 under the guidance of Professor Cecília de Carvalho Castro Silva in the Postgraduate Program in Materials Engineering and Nanotechnologies at Mackenzie. “We had the opportunity to submit a project to IPT’s New Talents Program, which funds scholarships for promising students to develop research in conjunction with the institute,” reports the researcher. The project was approved, and Mario became the co-supervisor of Jaqueline’s work, whose master’s thesis was defended in July 2020.
The research received funding from the Brazilian agencies CNPq, Finep and Fapesp, the Mackenzie Research Fund and IPT.
On April 8 of this year, doctoral student Roger Borges had a unique experience. He shared a (virtual) discussion table on the importance of science with 19 other students from Brazilian universities and with the scientist May-Britt Moser, who received the Nobel Prize in Medicine in 2014. Each student was able to ask the Nobelist a question. In another discussion table, another 20 students were able to interact with Serge Haroche, recipient of the Nobel Prize in Physics in 2012.
The discussions took place within the online event “O Valor da Ciência”, which was organized by the Brazilian Academy of Sciences (ABC) and the Nobel Prize Outreach (communication arm of the Nobel Foundation) with support from Instituto Serrapilheira, aimed at promoting reflections on the importance of science for society and public policies based on scientific knowledge. The event was broadcast on the official Nobel Prize channel on YouTube.
To participate in the event, Roger Borges went through a selection process. In the first stage, 90 public and private universities from all regions of Brazil indicated a total of 170 students to ABC. In the second phase, ABC selected the 40 young people who ultimately participated in the discussion tables.
Roger Borges (28 years old) is a member and secretary of the B-MRS University Chapter at the Brazilian Federal University of ABC (UFABC) since the creation of this unit, in 2019. Roger graduated in Science and Technology in 2016 and in Materials Engineering in 2020 – in both cases from UFABC. In 2018, he started a master’s course in Nanosciences and Advanced Materials at the same university, where he currently pursues doctorate in Nanosciences and Advanced Materials. Since his scientific initiation, he has been researching materials based on glass and glass-ceramics for biomedical applications. Both as an undergraduate student and in his doctorate, he has done research internships abroad, more precisely at the University of Idaho (USA), Alfred University (USA) and Politecnico di Torino (Italy). He is co-author of 17 articles published in peer review international journals and 6 book chapters.
Read our brief interview with Roger Borges.
B-MRS newsletter: Participating in a round table with a Nobel Prize winner and with students from different areas and different institutions/regions in Brazil is a unique experience. Comment what most impressed you about this experience.
Roger Borges: Without a doubt, this was a unique experience. Participating in an event with a Nobelist, broadcasted by The Nobel Prize was a great honor for my academic career. However, what most impressed me was the important role diversity played regarding the students chosen. There was gender, race, and regional diversity, as well as in the academic profile. Consequently, the range of questions was incredible! For example, some students from the Northern region asked questions more related to environmental issues, female students asked questions related to feminist issues, a black student asked about the importance of plurality in science, a journalism student asked about how to fight fake news. It is at this moment that the need for diversity in science becomes even more than explicit, as well as affirmative policies that favor this diversity. Society wins, science wins, everyone wins, and nobody loses! I believe that if the round table had no such diversity, it would not have been as successful as it was. In this regard, I congratulate ABC that was intentionally careful to guarantee the diversity of the round table. Having a Science Academy that has this vision is a source of pride for our Brazil.
B-MRS newsletter: At the discussion table with the scientist and Nobelist May-Britt Moser, you asked how international collaboration can reduce inequalities in science and innovation in developing countries. What are your thoughts today on the value of science, innovation and international collaboration?
Roger Borges: We live in an extremely unequal world, where not all countries enjoy equal opportunities for research and investment. I believe that science is the driving force of innovations that can reduce economic and social inequalities between different countries, while science is also the tool that supports implementing policies aimed at reducing these inequalities. This is the remarkable value of science: allowing us to live in a better world and giving us the means to move in this direction. Within this context, I see that reducing inequalities – be they of a scientific, economic or social nature – is everyone’s duty, that is, for the privileged and the least privileged. Thus, international collaboration is a mechanism that allows access to infrastructure and human resources training to those who do not enjoy the same opportunities; in addition to being a way to collaborate scientifically in order to develop innovations and policies that lead us to a more equitable world.
B-MRS newsletter: You participate in the B-MRS UC Program, you are a member of the Brazilian Association of Black Researchers (ABPN), you have participated in Brazilian student associations abroad. You probably think it is important to participate in peer groups. Comment a little on this question.
Roger Borges: I carry a thought that guides my actions: whoever writes the story decides what to give visibility to and what to drop into oblivion. When you get involved in a group/association that works for causes aimed at social and/or scientific development, you can contribute to this group and help write the story. It is at this point that you help to decide what to give visibility to. Thus, you can contribute to improvements, give your perspective, in short, help write the story in how you believe it would also be satisfying for others and for you. So, getting involved with groups and agendas that are important to us is the approach we find to make our contribution in an active and more effective way. Getting involved in what we believe is extremely important – and it is also very enriching! We learn a lot, get updated, it’s really an exchange that helps us become better people and professionals.
We know that, after a year without the B-MRS annual meeting, our community is particularly eager to meet again around high quality science. That is why our organizing team has been working hard to ensure an interactive and fruitful virtual event this year.
In the joint event XIX B-MRS Meeting + IURMS ICEM, from August 30 to September 3, we will offer you all the possibilities to exchange information, network and chat with colleagues, lecturers and exhibitors, in a multidisciplinar and international environment.
This year, our meeting comprises 7 plenary lectures by leading scientists from around the world and more than twenty thematic symposia with invited, oral and poster sessions covering fields ranging from Biomaterials to Electronic Structure Calculations.
The meeting also features a virtual exhibition of products and services for the materials research community. And, of course, we will enjoy virtually our traditional Memorial Lecture in the opening session and, at the end of the event, the exciting Student Awards Ceremony, where more than 50 prizes and awards will be given.
Abstract submission is open until April 25th May 11th. Submit your abstract, invite your collaborators. Join us for the largest conference in the area of Materials Science in Latin America.
Newsletter of the
Year 8, issue 3. April 12, 2021.
In a study performed in Brazil, scientists were able to radically modify the optical properties of a semiconductor nanomembrane by promoting its spontaneous rolling-up, forming a tube. The discovery is expected to impact the engineering of light-emitting devices for the future of communications. The work was recently reported on ACS Applied Nano Materials. Know more.
Interview with Cid de Araújo, Professor Emeritus at UFPE and one of the pioneers of Nonlinear Optics in Brazil. Professor Araujo told us a little about his scientific trajectory, related to the creation of the Physics Department at UFPE, while also mentioning his favorite scientific works. At the XIX B-MRS Meeting, Professor Araújo will deliver the Joaquim da Costa Ribeiro Memorial Lecture. Know more.
XIX B-MRS Meeting + IUMRS ICEM 2021 (virtual)
– Submission. Abstract submission is open until April 25th. See instructions for authors, here.
– Symposia. Abstracts can be submitted within the 24 thematic symposia that comprise the event, covering the most diverse materials, from design to applications. See the list of symposia, here.
– Awards for undergraduate and graduate students. The Bernhard Gross Awards, from B-MRS, will distinguish the best poster and best oral presentation of each symposium. ACS Publications Prizes will award cash prizes to the best works of the entire event. Find out how to compete for prizes, here.
– Plenary and memorial lecture. 8 internationally renowned scientists confirmed their presence at the event. See here.
– Registration. Early registration discount is available until July 30th. Check the fees, here.
– Support and sponsorship. This virtual edition of the event offers several possibilities for companies and entities interested in connecting with the community and exhibiting their products and services. Interested parties can contact Alexandre Alves at firstname.lastname@example.org.
– Paper with Brazilian participation presents a platform based on gold nanorods that can help in the early diagnosis and treatment of serious diseases such as pancreatic cancer and Alzheimer (Science). Know more.
– Scientists reveal that, in halogen perovskites, movements of the crystal lattice are essential to better understand the properties that make these materials very attractive for applications in the area of energy (Nature Materials). Know more.
– Scientists develop polymeric hydrogel contact lenses with gold nanoparticles that can help people with color blindness distinguish red from green. Produced without paints, these new lenses would be safer and more effective than those available on the market (ACS Nano). Know more.
– Researchers from Brazil produce highly conductive graphene oxide films using a low-cost, low-environmental impact method, and apply the material to sensors for rapid disease diagnosis (Applied Surface Science). Know more.
– A team led by scientists from IFSC-USP (Brazil) and a university in Nigeria develops low-cost nanocomposites, capable of decontaminating waters using solar energy. Know more.
– New computational tool for scientometry allows comparing the impact of scientific production by different authors and evaluate its congruence with the “hot” themes in their area. The software was co-developed by Prof Edgar Zanotto, B-MRS founding member. Know more.
– News article in Nature discusses results of a poll with readers of the journal: 74% want to continue with virtual or hybrid scientific conferences, even when the pandemic is over. Some of the advantages regard the online format that has made participation more accessible. Know more.
– VIRTUAL. 47th International Conference on Metallurgical Coatings & Thin Films (ICMCTF). April26 – 30, 2021. Site.
– VIRTUAL. 4th International Conference on Applied Surface Science. June29 – 30 de junho, 2021. Site.
– VIRTUAL.XIX B-MRS Meeting + IUMRS ICEM (International Conference on Electronic Materials). August 30 – September 3, 2021. Site.
– 7th International Polysaccharide Conference (EPNOE 2021). Nantes (France). October 11 – 15, 2021. Site.
– 4th Workshop on Coated Tools & Multifunctional Thin Films. Campinas, SP (Brazil). March 29 – April 1, 2022.Site.
– XVIII International Small Angle Scattering Conference. Campinas, SP (Brazil). September 11 – 16, 2022.Site.
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Cid Bartolomeu de Araújo was born in Recife, the capital of the Brazilian state of Pernambuco, in 1945. When he was in high school, he was very fond of Physics. However, he was not able to choose this undergraduate course because it was not yet offered in Pernambuco in the 1960s.
He graduated with an Electrical Engineering degree from the Federal University of Pernambuco (UFPE) in 1968. After the B.S. degree, he received a master’s degree in Physics from the Pontifical Catholic University of Rio de Janeiro (PUC-Rio). After that, he became an adjunct professor at UFPE, where he actively participated in the creation and development of the Physics Department. At the same time, he started his doctorate, again at PUC-Rio, and in 1975 he obtained a PhD diploma in physics.
Throughout 1976 and 1977, he held a postdoctoral position at Harvard University (USA), in the research group of Nicolaas Bloembergen, who, at that time, had one of the best laboratories in the world in Nonlinear Optics (area of knowledge dedicated to the study of phenomena that occur when high intensity light interacts with matter). In 1981 Bloembergen was awarded the Nobel Prize in Physics.
Back in Brazil in 1978, Professor Araújo created the Laboratory of Nonlinear Optics, which placed UFPE on the world map in this research area. Since then, Cid de Araújo has contributed to the advancement of scientific progress and development of human resources. He produced around 350 articles published in international scientific journals and supervised almost 100 masters and doctoral students and postdocs. His scientific production has more than 9,300 citations, according to Google Scholar. In 2020, Professor Araújo, whose h-index is 48, was listed among the 100,000 most influential scientists in the world in the ranking published in the journal Plos Biology.
Currently Professor Emeritus at UFPE, Cid de Araújo was Full Professor at the university from 1989 until 2013. He was a Visiting Professor at the Université d´Angers (France) and a Visiting Researcher at the State University of Campinas, École Polytechnique (France), Université Paris-Nord (France) and IBM Thomas J. Watson Research Center (USA).
Araújo is a Full Member of the Brazil and Pernambuco Academies of Sciences, and a Fellow of the Optical Society of America (OSA) and TWAS (The World Academy of Sciences). He is a member of the Brazilian National Order of Scientific Merit – Grand Cross and Commander. In 2003, he received the Galileo Galilei award, bestowed annually by the International Commission for Optics (ICO) in recognition of outstanding contributions in the field of Optics, achieved in comparatively unfavorable circumstances. Professor Araújo is the only Brazilian out of 27 scientists who have received the medal so far.
In 2020, B-MRS granted Cid de Araújo the Memorial Lecture “Joaquim da Costa Ribeiro” – a tribute granted annually since 2011 to notable scientists from Brazilian institutions. Thus, Professor Araújo will deliver a lecture at the opening of the XIX B-MRS Meeting + IUMRS ICEM, which will be held virtually from August 30 to September 3 this year. At the event, he will talk about plasmonic nanocomposites (fundamentals, synthesis, linear and non-linear optical properties and applications), a research topic that has engaged the scientist and his group in recent times.
Read our interview with Cid de Araújo.
B-MRS newsletter: Tell us what led you to become a scientist and, in particular, to participate in the field of optical properties of materials.
Cid de Araújo: I don’t have an objective answer to this question… It certainly wasn’t family influence. My mother was a “housewife” and my father was a businessman. He wanted me to become a businessman just like him. He almost convinced me, but the school’s influence was greater. I liked Physics and Mathematics when I was in high school. I also liked History and used to read biographies of famous scientists (physicists, astronomers, mathematicians…). When I took the entrance exam, I chose the Electrical Engineering course because among the possible alternatives in Recife, in 1964, it was the one that seemed to have a larger scientific component than the other engineering courses. During the first two years of the course, I understood that I really liked Physics. From the fifth semester onwards, I decided that I should be in a Physics course; I did not like the subjects of the professional Engineering course. But there was no Physics course in Recife. Fortunately, other colleagues were also attracted to Physics and together with some Physics professors from the School of Engineering, we began to informally study the subjects that constitute the core of the bachelor’s degree in Physics. At the same time, I continued the EE course that I concluded in December 1968.
My fondness for Solid State Physics (currently called Condensed Matter Physics) grew during the undergraduate Electrical Engineering course as a result of reading scientific articles about electrical and magnetic properties of materials.
After completing the course, thanks to previous contacts with two professors from PUC-Rio (Alceu Pinho and Erasmo Ferreira), I traveled to Rio de Janeiro, in January 1969, to enroll in the postgraduate program in physics. In the master’s degree course, I performed experiments that combined microwaves and light to study properties of ferromagnetic crystals. A resulting article was published in Solid State Communications (in 1972) and the co-authors were Sergio Costa Ribeiro and Sergio Machado Rezende. As the article was written when I was already hired in Recife, the article included my UFPE address, and this was the first article in Physics of the Solid State with an UFPE address in the literature. Later, in the doctoral project, I developed works where I explored analogies between nonlinear processes of ferromagnetic magnons and the theory of lasers and optical parametric amplifiers. In the post doctorate program, I started working in Nonlinear Optics with applications in Material Physics (some liquids and semiconductors). The decision for postdoctoral fellow at Harvard University, with Nicolaas Bloembergen, was motivated by the fact that he was one of the pioneers of nonlinear magnetic resonance, and in addition, he was one of the pioneers of Nonlinear Optics.
B-MRS newsletter: From the point of view of scientific discoveries, reflected in the publication of articles or patent applications, from your viewpoint, what are your main contributions and why do you consider them the most relevant? In other words, which are your favorite and why do you like them so much?
Cid de Araújo: I am an experimental physicist, but my doctoral thesis resulted in the publication of five theoretical articles. Infrastructure problems in Recife contributed to this theoretical work. We were building laboratories from empty rooms. I was very happy with these articles because they were published in good scientific journals and so I was able to complete the doctoral thesis, which was presented at PUC-Rio in 1975. These are not the most important publications in my curriculum, but they represent a relevant contribution in the history of the Department of Physics-UFPE.
Upon returning from the postdoctoral studies in January 1978, until today, I always worked with several collaborators (students and fellow professors). So, in 1978, while setting up the Nonlinear Optics Laboratory, I began to interact strongly in another laboratory with a professor at DF-UFPE, Erivaldo Montarroyos, who was completing his doctorate using the Raman Scattering technique to study antiferromagnetic materials. The sequence of works that resulted from this project was important for developing the area at UFPE. I also interacted with other students who later entered this research line; the experimental works were carried out exclusively in Recife from 1978 to 1985. At that time in Recife, Experimental Physics was an adventure. In the same period, together with my colleague José Rios Leite, in 1980, we published in Chemical Physics Letters a theoretical article with the prediction of a new effect of Non-Linear Optics: the simultaneous absorption of two photons by a pair of interacting atoms. At that time, it was not possible to carry out the experimental work in the existing laboratories. The effect was observed for the first time in 2002 by a Swiss-German group that, utilizing modern techniques for preparing nanomaterials and nano-optic techniques, observed the phenomenon using an organic solid (para-terphenyl) doped with terrylene molecules (an organic dye). The article appeared on the cover of the journal Science [vol. 298; issue 5592 (2002)]. It was encouraging to know that the effect we had foreseen was observed 22 years after our proposal and that our theoretical article received the due credits. Later, in 2012, this same effect was observed in sodium vapor and published in Physical Review Letters [108, 253004 (2012)] by the group of Vanderlei Bagnato, in São Carlos. In other words: it is a basic phenomenon that can be observed not only in condensed matter but also in atomic vapor and other systems not yet studied. There are some proposals in the literature to study the effect under different situations.
A set of works that I really like is related to the observation, understanding and applications of optical phenomena in plasmonic composites (glasses and colloids with metallic nanoparticles). These are more recent works where we explored the contribution of superficial plasmons in silver (or gold) nanoparticles and their application in studies related to luminescence, using random lasers, with the propagation of space solitons and other phenomena of optics instability influenced by plasmons. We have published several articles in this area and a review of some published works can be seen in Advances in Optics and Photonics 9 (2017) 720-774. This research continues in the present time and we continue to place much effort in this area with recent publications.
B-MRS newsletter: From the point of view of developing researchers, creating laboratories and other aspects of a researcher’s career, what are your most impacting achievements and/or the ones that gave you the greatest satisfaction?
Cid de Araújo: From an institutional perspective, I believe I carried out very important work together with the colleagues when we put together the first research group in Physics in Recife, in 1971. Also in 1971, we implemented the bachelor’s degree in Physics. This group included Ivon Fittipaldi, Mauricio Coutinho, Marco Moura and Sergio Rezende. My colleague José Rios Leite, who participated in the initial project, joined the DF only after completing his doctorate at MIT in 1977. We were conducting research, teaching and administrative work, in order to establish a new research center in Physics. Fortunately, we were successful, and we gradually incorporated new professors who helped consolidate the project. Between 1973 and 2013 I took on several administrative positions: Head of the DF-UFPE, Physics Undergraduate Coordination, Physics Postgraduate Coordination, Postgraduate Coordination in Materials Science, and Direction of the Exact and Nature Sciences Center, which in addition to the DF brought together the Departments of Fundamental Chemistry, Mathematics, Statistics and Informatics.
From the research perspective, I had the opportunity to set up one of the first Non-Linear Optics laboratories in the country. This laboratory has been in operation since 1978, and has remained active since the beginning, contributing to the education of undergraduate and graduate students. To date, there have been about 40 undergraduate students, 44 master’s students, 27 doctoral students, and 20 post-doctoral students. These former students currently work in several Brazilian states, some at DF-UFPE, and some abroad (Canada, USA, Colombia, Peru, Uruguay, China and India) as research leaders.
In the 43 years of the Laboratory, we have been able to introduce in the Country several experimental research techniques in Nonlinear and Photonic Optics, new scientific topics and we have contributed to significant advance in this area.
Currently, the Physics Department of UFPE is completing 50 years of research and teaching activities in PG. The performance of DF radiated to several States, especially the Northeast and Northern regions of the country. I am extremely pleased for the opportunity to participate in this story.
Until now, I have been contributing to the physics community by participating in the research commissions of funding agencies (from Brazil and abroad), coordinating research projects and scientific events at the national and international level. I hope to continue doing research for several more years.
B-MRS newsletter: Now we invite you to leave a message for our readers who are starting their scientific careers.
Cid de Araújo: I believe that a career choice should be based on the attraction the professional activity exerts on the individual, and this is particularly true with regard to scientific activity. However, this is not enough. In addition to the attraction for the profession, solid education is required in the specific content of the field and in the fundamentals. The ability to work as a team, the ability to impart knowledge, general culture and the ability to interact with people are very important requirements. Scientific work requires considerable effort and a lot of dedication, but intellectual challenges serve as a permanent stimulus.
[Text by Christoph Deneke, Leonarde do Nascimento Rodrigues and Angelo Malachias, co-authors of the research, with editorial changes by B-MRS Newsletter.]
Changing material properties like the optical ones or the ability to conduct current by straining the material has a long tradition in semiconductor technology. Therefore, researchers have used this mechanism to control fundamental properties of different materials and discover new possibilities for technological application. In this regard, thin, nanometer thick membranes of semiconductor materials are especially well suited as they become extremely compliant and flexible due to being thin. Until now, such engineering was done by applying an external strain to ultra-thin membranes successfully changing fundamental properties like the band structure (the energy level distribution of the electrons inside the material).
A team of researchers from Brazilian universities demonstrated now that they can fundamentally change the optical properties of a semiconductor namomembrane, if they integrated it into a curved system, or in a tubular structure (rolled-up microtube). For this, the authors used a well established technology of releasing a strained layer system, which then self-assembles into a three-dimensional structure, in this case a rolled-up tube.
The way the nanostructures are made is illustrated in the image above. Initially, the team growth first a single crystal compromised of different materials. In following steps, they defined a U-shaped pattern on the surface of the structure by carrying out photolitography – the same kind of technology used to make computer chips. For the last step, that is responsible to form the final geometry in the form of a tube, they selectively removed a sacrificial layer previously introduced below the layers of interest. The schematics on the left of Fig. 1(a-d) represent the different steps of the tube fabrication. The optical microscopy image on the right together with the electron microscopy images (Fig. 1 f-g) depict the obtained structures.
“I am working since 2001 with these kind of systems. We already know that the properties of embedded quantum light sources change by the rolling-up. But until now, we used materials that were less affected by the geometrical change” tells Prof. Ch. Deneke from Unicamp. His long-time collaborator Prof. A. Malachias adds, “By using InGaAs instead of GaAs, we were able to achieve a complete change of the electronic structure of the material and the quantum light source integrated into the tube wall. The control of the band structure shown in the work is of great technological interest in the field of optical devices.” To investigate these changes, the team carried out optical measurements at Unicamp together with Prof. O. Couto Jr. and Prof. F. Iikawa. When using optical spectroscopy techniques to measure the polarization of light (the vibration plane of the light), the authors discovered that the optical response pointed to fundamental changes of the light source.
The image below shows the spectrum obtained by a reference structure (in its planar form) and in its new rolled-up form.
“With the vanishing of any polarization of the rolled-up layers, which included an InGaAs layer, we understood that the electronic structure and the optical properties had undergone fundamental changes. And we achieved this without relying on the application of an external force to control the expansion and compression of the material. The self-formation of these tubular structures is an elegant way to induce a hybrid state of compression and expansion, which in turn induces new effects”, explains Prof. L. N. Rodrigues, who worked in his postdoc together with Prof. Ch. Deneke on the system. Theoretical calculations show that the effect can be expected for all kind of curved systems made into tubes based on the used material system.
InGaAs and GaAs quantum light sources are already used. Basically, all lasers used in fiber communication are based on this material class, building the backbone of the internet communication unbeknownst to most people. Taking this into account, the light sources manufactured with the mentioned material, whose properties can be altered and controlled, are of great interest for the next generation of technology development, which includes, for example, quantum information or quantum computing. The fact that these tube-shaped semiconductor structures can be transformed into a light-emitting device (laser), together with the ability to alter and control physical properties without the need for any external voltage source, provide modern engineering that points in the direction of potential applications regarding light emitters and other fields of science. Furthermore, the results are also transferable to other semiconductor materials. Most important, this could be a model to modify Si (the most important material of the IT technology) in a similar way.
The work was largely supported by Brazilian agencies FAPESP and CNPq. The samples were grown and processed at LNNano / CNPEM, Campinas. X-ray diffraction measurements were carried out at the National Synchrotron Light Laboratory LNLS / CNPEM, Campinas. The optical spectroscopy measurements were performed at the GPO of the Physics Institute “Gleb Wataghin“ of Unicamp, Campinas.
Paper:Rolled-Up Quantum Wells Comprised of Nanolayered InGaAs/GaAs Heterostructures as Optical Materials for Quantum Information Technology. Leonarde N. Rodrigues, Diego Scolfaro, Lucas da Conceição, Angelo Malachias, Odilon D. D. Couto Jr., Fernando Iikawa, Christoph Deneke. ACS Applied Nano Materials 2021, DOI: 10.1021/acsanm.1c00354. Disponível na modalidade de acesso aberto em https://pubs.acs.org/doi/10.1021/acsanm.1c00354.
Abstract submission is open until April 25th for oral and poster presentation at the XIX B-MRS Meeting + IURMS ICEM 2021, which will be held in virtual format from August 30 to September 3 this year. Registrations to participate in the event are also open with early registration fees until July 30th.
The event brings together the 19th edition of the annual meeting of the Brazilian Materials Research Society (SBPMat/B-MRS) and the 17th edition of the international biennial conference on electronic materials organized by the International Union of Materials Research Societies (IUMRS).
Interdisciplinary and international, the event is dedicated to the presentation and discussion, in English, of scientific and technological advances achieved in the field of materials. In the last editions, the B-MRS Meeting has brought together about 1,500 participants from different parts of Brazil and dozens of other countries.
Abstracts can be submitted within the 24 thematic symposia, covering a wide range of research topics, from materials design to applications, including synthesis, manufacture, modification and characterization of materials. The symposia encompass many types of materials: conductive polymers, hydrogels, hybrid materials and nanocomposites, nanomaterials, metal oxides, electroceramics, biomaterials, superconductors and quantum materials, among others. Concerning the applications, the symposia include advances in materials for energy harvesting, storage and conversion, for oil and gas indystry, for decontamination, health, electronics and photonics, among others. Advances in the field of toxicology and regulation of nanomaterials and nanoregulation will also be discussed. Finally, the event will feature a symposium organized by the B-MRS University Chapters on research, entrepreneurship and the future.
The symposia of the XIX B-MRS Meeting are coordinated by researchers from different parts of Brazil, as well as Argentina, Canada, Denmark, France, Germany, India, Israel, Japan, Norway, Portugal, Sweden, United Kingdom, USA and Uruguay . The general coordinator of the event is Professor Gustavo Martini Dalpian, from the Brazilian Federal University of ABC (UFABC).
Each symposium comprises oral and poster sessions, as well as invited lectures by internationally renowned researchers. The event also features seven plenary lectures by internationally renowned scientists: Prof Alex Zunger (University of Colorado Boulder, USA), Prof Edson Leite (LNNano, Brazil), Prof Hideo Hosono (Tokyo Institute of Technology, Japan), Prof John Rogers (Northwestern University, USA ), Prof Luisa Torsi (Università degli Studi di Bari “A. Moro”, Italy), Prof Tao Deng (Shanghai Jiaotong University, China), Prof Thuc-Quyen Nguyen (University of California Santa Barbara, USA). The traditional Memorial Lecture Joaquim da Costa Ribeiro will be given by Prof Cid Bartolomeu de Araújo (UFPE).
The best works of each symposium presented by undergraduate or graduate students will be distinguished at the end of the event with awards from B-MRS (the Bernhard Gross Award). In addition, ACS Publications will award cash prizes, of R$ 2,000 each, to the five best posters and five best oral presentations of the entire event. To apply for the awards, authors must submit an extended abstract in addition to the conventional one, after being notified of the acceptance of the work at the event.