Brazilian researchers seek photonic applications for graphene
June 12, 2013
By José Tadeu Arantes
Agência FAPESP – Graphene, which has been called the “wonder material of the 21st century,” has numerous potential applications and is already on research agenda in Brazil.
One example is the Thematic Project “Graphene: photonic and optoelectronics. A UPM-NUS Collaboration,” funded by FAPESP. The project, which was initiated in April 2013 and is slated to run through March 18, is part of the São Paulo Excellence Chairs Program, which seeks to establish collaborations between institutions in São Paulo State and high-level researchers abroad. In this case, a collaboration was established between the Universidade Presbiteriana Mackenzie (UPM) and researcher Antonio Hélio de Castro Neto, the coordinator of the Thematic Project, who is based abroad.
Dividing his time between his duties as the director of the Graphene Research Center at the National University of Singapore and as a physics professor at Boston University in the United States, Brazilian national Castro Neto has been to São Paulo twice this year to begin work on the project. He will continue to visit regularly for the duration of the project.
The research is likely to be applied before the end date of the Thematic Project because representatives of some of the largest companies in Brazil have already met the researchers to establish partnerships. Moreover, several representatives were present at a major event on May 27–28 in Singapore: the Brazil-Singapore Network for Technology Opportunities (RBCOT).
“In brief, our project has three objectives: to carry out the artificial synthesis of graphene; to physically characterize the material produced, from both a structural and an electronic standpoint; and to build optoelectronic devices based on the material, with applications in optical communications and other areas,” commented Castro Neto to Agência FAPESP.
To this end, the project will utilize the Center for Advanced Research in Graphene, Nanomaterials and Nanotechnology (MackGrafe), which is under construction on the Higienópolis campus of the UPM in São Paulo. The Center is funded by FAPESP under the auspices of the Thematic Project. The first of center of its kind in Brazil, it is slated for inauguration in May 2014 and will host sophisticated equipment and a large research area of 6,500 square meters.
In addition to producing scientific knowledge, MackGrafe will be focused on developing products that generate patents, licenses and royalties for its host institution. “The most immediate application that we have in mind is the creation of graphene modulators for use in optoelectronic communication,” stated Eunézio Antonio Thoroh de Souza, the coordinator of MackGrafe and one of the main researchers on the Thematic Project.
To understand this and other possible applications, one must know a little about the structure of graphene. This material is a nearly bidimensional sheet of carbon atoms organized in a hexagonal pattern. This network, whose surface can, in principle, extend indefinitely, is only one atom thick. Graphene’s surprising stability is the result of the strong connection that the carbon atoms establish with each other.
Each atom, which has four electrons in its external electronic layer, connects to three other atoms, and the fourth electron is free on the surface of the network. It is these loosely connected electrons, which are very mobile, that make graphene an excellent conductor of electrical energy. Additionally, the one-atom-thickness makes graphene sheets transparent. The excellent properties of the material for optoelectronic applications are due to the combination of these two characteristics: conductivity and transparency.
“Being transparent, light can pass through graphene and, in the process, excites the free electrons on the surface of the sheet. Almost immediately, luminous electric energy conversion occurs. This conversion is exactly what the modulator of optical frequency does,” explained Castro Neto.
Castro Neto, considered one of the foremost experts in the field worldwide, worked with the Russian-born, Dutch-naturalized physicist Andre Geim, winner of the Nobel Prize in Physics in 2010 for his research on graphene. Together, they have published three scientific articles.
The ingenious method utilized by Geim in 2004 to obtain the material for the first time involved applying adhesive tape to a graphite board and using the tape to remove a sheet of graphene, because graphite is formed precisely from the “stacking” of these hexagonal carbon networks. “But knowledge has evolved a lot since 2004. Currently, we produce graphene artificially, through catalysis,” explained Castro Neto.
Thoroh de Souza gave a more detailed explanation of how this process occurs. “The starting point is heating a hydrocarbonate [a chemical substance made solely from carbon atoms and hydrogen] in a gaseous state. By a mechanism known as ‘chemical vapor deposition,’ the heated carbon and hydrogen atoms are deposited onto a metallic surface [such as copper], which is adopted as a support. When they [the atoms] are deposited, they naturally arrange themselves in a hexagonal pattern.”
Support and subgroups
According to the researchers, prospective graphene applications range from cellular telephones to airplanes. The versatility of the material could radically transform the shape and function of numerous types of equipment used in day-to-day life and could facilitate the creation of many others.
Because of its nearly bidimensional structure, graphene always requires support. One of the major technical challenges associated with graphene production is how to transfer the carbon network on the metallic base to another base comprising polymer.
“One of the methods is depositing the polymer on the metallic board that has adhered to the graphene network. And, afterwards, the metal is corroded, leaving the graphene stuck on the polymer,” explained Thoroh de Souza.
“All this is crucial for technological application because many of the functionalities of graphene depend on the type of support, as well as the purity, the size of the grains and other physical characteristics of the material,” commented Castro Neto.
To design the entire cycle, from synthesis to application, the project team was divided into three subgroups: the chemists, charged with the task of synthesizing and characterizing the graphene; the materials engineers, responsible for transferring the graphene board to other substrates; and the physicists and electrical engineers, in charge of the optoelectronic devices project.
“These subgroups have been formed, but there are still open positions,” said Thoroh de Souza. Information about job opportunities can be viewed on the Mackgrafe site under the “Positions” tab on the horizontal bar menu. One vacancy for a postdoctoral researcher, with a FAPESP fellowship offer, can be found on the site under “Opportunities at FAPESP.”
Agência FAPESP licenses news reports under Creative Commons license CC-BY-NC-ND so that they can be republished free of charge and in a straightforward manner by other digital media or by print media. The name of the author or reporter (when applied) must be cited, as must the source (Agência FAPESP). Using the button HTML below ensures compliance with the rules described in Agência FAPESP’s Digital Content Republication Policy.