Nanomaterials tools developed to minimise risk to environment

Nanoparticles of materials are increasingly used in electronics, from flexible circuits to solar cells. The properties of materials at the extremely small scale are not obvious to designers and knowing their potential effects on the environment, if released, and energy costs when manufactured, would help engineers make better materials choices.

“As nanomaterials have already become the new hot emerging materials its more and more important to fully understand the environmental and human health effects of our use of these materials,” said Mark Falinski, a graduate student at Yale University’s Center for Green Chemistry and Green Engineering. Falinski is part of a team of Yale researchers that have been developing a strategy and database to give designers the tools that will help them make better informed decisions. The database includes materials’ nanoparticles’ size, shape, toxicity and antimicrobial activity. It is designed to allow researchers to enter their data, bringing an element of crowdsourcing to it and widening its potential usefulness for engineers.

While engineers normally think about the functionality and financial cost of a material, the researchers want to provide methods to gauge carbon dioxide production and what the environmental impact could be. The importance of a material’s particle size and how tiny particles can spread in the environment has been demonstrated by the issue of microplastics that have been found in Arctic sea ice and sources of drinking water.

What can be thought of as benign, such as inert plastic, can have unintended consequences when released as tiny particles. Falinski points to Iron oxide as an example of a material of interest. “Iron oxide is a very safe material [but] what properties of iron oxide make them unsafe and how can I as a nanomaterials designer introduce those features to the [nanoscale] to be as safe as possible.”

An example of how materials behaviour changes is the Brownian motion of these tiny particles in water. Another is their ability to penetrate into places that bulk materials cannot. “Under the right conditions carbonaceous nanomaterials could penetrate a [biological] cell,” Falnski explained. Particles of soot from car fumes have been found to have penetrated into the human brain.

The very small scale can also have inherently good properties, such as anti-microbial effects. The relative large surface area of a nanomaterial particle, such as silver, sees “higher anti-microbial activity,” Falinski said. “This becomes higher anti-microbial activity as it gets smaller.” Silver ions have a natural germicidal property. But, at the same time it costs a lot more energy to create small particles, he added. As part of the carbon footprint calculation, a substance such as silver would have a much higher impact because it is not as abundant as carbon and therefore more expensive to mine.

The next step in the researchers’ work is to look at other materials, not just silver and carbon, and their different characteristics; including a material well known to electronics circles, carbon nanotubes. Falinski and his colleagues will study the, “impact of their environmental behaviour including toxicity and safety,” he said. The Yale team worked with researchers at the University of Illinois-Chicago and the University of Pittsburgh.”