Professor Neerish Revaprasadu, research chair in nanotechnology at the University of Zululand, says electricity production using solar photovoltaics is an area where nanotechnology could make a significant contribution. “The photovoltaic market has been rapidly expanding in areas where the connection to a power grid is difficult, such as in developing nations that do not have a well developed electrical distribution network.”
With his research, Revaprasadu aims to better understand the mechanisms of particle self-assembly and alignment in solar cells, as their efficiency is not very high. “It's partly an architectural problem, as different sizes and shapes allow for the efficient transport of electrons. By understanding size and shape problems better, we can create new solar cell applications.”
For solar cells to become an attractive and commercially viable source of energy, says Revaprasadu, it will require improvements in efficiency, combined with decreased manufacturing costs. “Nanotechnology is currently being used to address this dilemma,” he says, adding that semiconductor nanoparticles are potentially ideal for increasing the efficiency of some solar cells.
The reason nanotechnology is a powerful enabler, according to Revaprasadu, is due to the changes in particles' properties that take place at the nanoscale. “Firstly, their physical size becomes comparable to that of many important properties in a given class of functional materials. Secondly, the large surface-to-volume atom ratio alters their chemical potential, enhancing the surface functionality of particles at this scale.”“If you imagine taking a Rubik's cube, for example, and taking apart all the little blocks, you immediately increase the surface area of the object,” explains Dr Rui Krause, associate professor in the Department of Chemical Technology at the University of Johannesburg. This is useful, he explains, because materials that can act catalytically do so better when the surface area is maximised. Significant changes in electron behaviour also occur at the nanoscale.
Revaprasadu adds: “If you can get these particles to assemble at the nanolevel, you can create completely new materials with unique properties, and so enable wide-ranging new applications.”
It's estimated that about a billion people worldwide, mostly in developing countries, lack access to clean, potable water. The World Health Organisation estimates 80% of water-related deaths could be prevented through the provision of clean water.
According to Krause, nanotechnology could play an important role in improving water purification systems and increasing access to clean water.
In a South African context, he says, nanomaterials are generally used in the industrial cluster and the social cluster. In government's 10-year strategy for nanomaterials, one of the key drivers is social development needs. ”There's huge involvement from across the board, although industry is still a bit hesitant in terms of accepting it as technology they can implement now.”
Krause's research work involves looking at nanomaterials and their potential uses for improving existing water treatment methods.
He explains the challenge with water purification is that there are so many kinds of pollutants; the three major types being bacterial, inorganic, and organic. “It's a very broad group of chemicals – some are small, some are large, some heavy, some light... so how do you apply filters to deal with this wide range of pollutants?”
His research team is examining where the deficiencies in existing water purification systems are, while at the same time developing technology for the future that could potentially replace them. The solution is a polymer-based system, similar to plastic, which uses two to three compounds in combination with cyclodextrins, he explains. “These are little cup-shaped molecules which have a good capacity for hosting pollutants. By taking advantage of their hosting capacity, we can turn cyclodextrins into polymers and use them to trap waste.”
Krause point out that they can enhance the system by adding other materials, such as carbon nanotubes. “These can be applied in making stronger materials – harder ceramics, longer-lasting plastics, thinner structures so less material is needed for the same application,” he explains.
“By adding components to the filter, you create a modular system on the back of the polymer.”
This is significant because there are a host of molecules, such as natural organic matter, which are bigger than the nanometre-sized cavities, says Krause. However, he adds the advantage of a modular approach is that you can take out the cyclodextrins and put in another molecule which will effectively trap larger particles.
While they're still a long way from commercialisation, Krause says the project is quite far along in terms of research and development. “We hope to incorporate these materials into existing technologies, like membrane and cartridge filters, and investigate its uses. It's an adaptable technology that uses little energy and is easy to manufacture.”
According to Krause, taking environmental impacts into consideration has become a strong focus among researchers. “Intrinsically, nanotechnology leans towards this anyway, as it uses less material to do the same job.” He says scientists are becoming much more rigorous in ensuring harmful materials don't end up in the environment and don't cause pollution. “Everywhere you look, aspects of green chemistry are creeping into nanotechnology research.”
He adds that the Department of Science and Technology has seen the potential of green science, and gone all out to introduce green initiatives in research and manufacturing. “In the next six months, there's going to be quite a lot of activity. The 'clean and green' idea makes so much more sense, if you take a long-term, sustainable view.”
Krause says there's greater awareness of the impact processes can have both globally and in SA. “There's more responsibility and stewardship among people, from the research and development side. Business is also starting to take it into account,” he adds. “There's a growing recognition that solutions can be beneficial both for business and the environment.”
Outside of labs and research centres, Revaprasadu says it's important to create a greater understanding of nanotechnology. “The public should be better informed, because the funding comes from taxpayers' money, and they should know what it's going toward.”
He adds there's been a big drive towards putting money into nanotechnology equipment, as well as education initiatives such as bursaries. “It's important to get more students into nanotechnology research at the undergraduate-level,” he argues.
“The biggest challenge is getting industry involved, because traditional industries such as paper can gain a lot from nanotechnology through improvements in efficiency and processes.” He explains this is often due to a poor understanding of nanotechnology, or because companies don't have the expertise to implement it. “There's huge ignorance in the industry, and not much research and development going on.”
According to Revaprasadu, most of the technology is brought into the country, although this is changing. “The private sector must invest in research, because some of the ideas could be very lucrative.” He adds there should be greater impetus in encouraging start-up companies, innovation, and driving entrepreneurship in nanotechnology.
“We've jumped in a bit late, but there's an opportunity to make a mark, particularly in the minerals sector. Cultivating good ideas requires getting more students involved.”
Despite its potential for creating more efficient electricity generation and water purification systems, nanotechnology has raised concerns around its long-term impact on both people and the environment.
Revaprasadu notes that research is ongoing around toxicity. ”We don't know how toxic the long-term effects are, and what happens when these materials degrade. A lot of research is being done on that side.”
Krause notes there are lots of unanswered questions regarding toxicity, and manufacturing concerns. “It's potentially a technology that can make big impact, not only in water treatment, but in various other environmental applications, but it's not a magic wand.”
Revaprasadu says nanotechnology is increasingly being recognised as the platform for 21st-century innovation. “However, while global nanotechnology research increases exponentially, the impact of this new technology on the environment has yet to be fully assessed or understood.
“It seems this new technology, with all its challenges and opportunities, will play an unavoidable role in our future.”
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