Jun 15, 2014
Brazil’s research investment yields returns at the nanoscale
Brazil’s contribution to the global science scene is changing. Previously a nation known primarily for its theoretical output, a massive boost in funding since the turn of the century has enabled researchers to invest in state-of-the-art equipment for increasingly ambitious experimental work. Nanotechweb.org speaks to researchers from some of the leading nanotechnology labs in Brazil to find out more about how they are pushing the frontiers in nanomaterial synthesis and characterization, crucial processes for bringing nanotechnology into real-world devices and furthering research in all aspects of the field.
"Until over a decade ago there was one set of electron-beam lithography equipment in the whole country," says Monica Cotta, a physicist at the State University of Campinas (UNICAMP), about 100 km north-west of São Paulo. "We would travel one and a half hours by plane with the processed sample to use this equipment – these samples shouldn’t even have left the clean room!"
Cotta's access to research equipment has changed radically since those days, allowing her group to successfully undertake pioneering work in semiconductor nanowires. "Our research has shown a new way to produce III-V nanowires with control over the crystal structure," she explains. Cotta's approach builds on models established in the 1940s and 1960s, but her group was the first to recognize that the principles could be applied to nanowire synthesis. "We modelled the process so we understand it too," she adds.
Nanowires made from III-V materials such as InP and GaAs are in high demand for applications ranging from higher-efficiency solar cells and LEDs to optoelectronics. The properties of the nanowires depend hugely on the crystal structure of the material, and Cotta adds that they are currently investigating whether the nanowires could be used for thermoelectric devices too.
Great equipment requires great experience
The improved lab facilities at UNICAMP have been crucial for the group's progress in experimental research, and Cotta will soon be able to take advantage of the Sirius third-generation synchrotron currently being built in Campinas (see "Sirius shines brightly for Brazil" in the Physics World, Special report on Brazil). If all goes according to plan, the new synchrotron will provide the first such radiation source to allow complex biological structures to be resolved at the nanoscale.
Yet while the new equipment is undoubtedly good news, Cotta suggests there is still a lack of experienced users. "To invest in this accessible equipment and teach people how to use it takes time. Now we have a lot of equipment but not enough people who know what to do with it - you can miss things you weren’t looking for."
Developing functionalised nanomaterials at UNICAMP
Elsewhere at UNICAMP different aspects of one-dimensional nanomaterials have been studied. Oswaldo Luis Alves and colleagues in the Institute of Chemistry have been investigating nanowires and metal nanoparticles, as well as their functionalization for different applications. A Nanotechnology report described work in collaboration with researchers in the physics and biology institutes to synthesize silver vanadate nanowires decorated with silver nanoparticles. The report describes the antibacterial properties of the nanowires as well as how different experimental conditions – such as the molar ratio of the reactants and pH – affect the synthesized product.
Alves and colleagues point out in the report that the antimicrobial properties of silver have been well known for 3000 years. They add, "A true 're-emergence' of the research field related to the development of silver-based materials has happened in recent years, and this has been in part due to the promising antibacterial performance obtained using silver nanoparticles and silver-based nanomaterials against different microorganisms."
While the high surface area of nanoparticles makes them particularly useful as antibacterial agents, it has been a challenge to administer them in a form that prevents them from aggregating. Decorating the nanowires with silver nanoparticles provides an ideal structure for maintaining well dispersed nanoparticles, while the nanowires also contribute to the antibacterial action through the silver ions in the silver vanadate.
Alves and his team have since been engaged in studies of two-dimensional materials such as graphene. Silver nanoparticles have also been exploited here to better understand 'oxidation debris' – oxidised graphitic material found on graphene oxide. The effect of oxidation debris on the nucleation and stabilization of silver nanoparticles helped to shed light on some of the kinetic processes associated with these forms of carbon compound.
Other research by Alves and his colleagues includes the development of functionalised nanomaterials for drug release, ecomaterials, glasses for nonlinear optics and photonics, and nanocomposites. The group are starting a collaborative program called NanoBioss/SisNano to evaluate the toxicological issues and enviromental safety aspects of nanomaterials.
Energy nanotechnology at LIEC
Scientists at the Federal University of São Carlos (UFScar), also in the state of São Paulo, have also enjoyed a welcome boost in research funding. "Research without investment is not possible," says Edson Leite, a professor of chemistry at the Laboratory for Electrochemistry and Ceramics (LIEC). "Since we have a good lab we have good students – this is really important as without good students nothing happens."
Leite's research focuses on the application of nanomaterials in energy storage applications, such as developing photoanodes for water splitting, which allows solar energy to be stored. Leite and his colleagues developed an approach for depositing nanocrystalline hematite for photoanodes that produce photocurrents as high as 2.7 mA cm-2 under a standard solar light simulator. Key to the success of their approach is the use of magnetic fields during deposition of colloidal magehemite, which induces a magnetorheological fluid behaviour. Incorporating a tin precursor further improved the performance.
Another aspect of their research is finding new ways to produce two-dimensional (2D) MoS2. "This is a really interesting material – kind of like graphene – and it can be used in lots of applications," says Leite. "It's a magic material!" He adds that most people produce 2D MoS2 by vapour plasma deposition. "This is fine but if you can use a chemical approach it's cheaper and you can scale it up more easily for industry."
However, it's not easy to synthesize of MoS2 in a 2D configuration - rather than 3D or as nanotubes - using chemical methods alone. "We tried using a graphene substrate to keep the shape," says Leite. “Graphene absorbs microwaves so we synthesized in microwaves and put a layer of MoS2 over graphene." The researchers have now demonstrated electrocatalysis with this material, they have also shown the potential of the material as supercapacitors for energy storage.
Research at Leite’s lab draws on a number of disciplines. Leite himself began as an engineer and the other researchers in the lab are experts in electrochemistry as well as other disciplines.
"I worked 3-4 years as an engineer in an industrial company but in industry in Brazil there is not much opportunity for basic research. So I moved to the UFScar in 1994 and spent a year at LeHigh University in the US as a visiting professor between 1998 and 1999," he explains. His return to Brazil coincided with new project funding for LIEC from São Paolo Research Foundation (FAPESP), amounting to $1 million per year for a period of ten years. "It was a really unbelievable opportunity to build up fantastic lab facilities," he adds.
The lab has had continued success with research funding, but increasingly there is an emphasis on securing more investment from industry. Researchers at LIEC now interact closely with the Braziian petroleum company Petrobras, which now contributes a similar level of research funds as FAPESP. This has allowed the scientists at LIEC to develop a number of useful nanoparticle technologies, including coatings for pipes that transport gas, metallic coatings for areas that are not easy to protect, and gas sensors.
The connection with industry provides the lab with more than just money. "Sometimes we need advice from someone in industry as to what is needed, what properties and materials and so on," explains Leite. "Otherwise it's just basic research - we need good vision of how we can apply it."
Students and startups
"What we need now is good students," continues Leite. "We are not a famous university so it is harder to attract good students from around the world." Second on the wish list is more state-of-the-art equipment, but Leite stresses that "the first priority is the students."
Leite also hopes to motivate early-career researchers to create their own start-up companies to build on their research. "We have a good relationship with Petrobras but we need industry to develop materials to take it further," he says. "It’s not easy."
LIEC aims to create an environment where students are encouraged to create their own start-up firms. According to Leite, projects with other companies help to emphasize the benefits of creating spin-off ventures from scientific research.
Increases in funding seems to have empowered a number of labs across Brazil, encouraging more world-class experimental research that is driving progress withing nanomaterials science. While challenges remain, there is a strong feeling that the country's evolving research requires continued investment - not just in the equipment, but also in the technological and research expertise to best exploit it.
About the author
Anna Demming is online editor for nanotechweb.org.