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One-Atom-Thick Carbon Sheets Made Simply

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Solar Cells

Jan. 29, 2008 -- Australian researchers have discovered a cheap and simple way to make sheets of carbon just one atom thick.

Their finding has implications for a range of developments from solar cells to bionic ears.

The sheets, known as graphene, normally stack together to make the kind of graphite used in pencils.

But when separated, graphene sheets have extraordinary electronic, thermal and mechanical characteristics, says Gordon Wallace from the University of Wollongong in New South Whales, Australia.

"People have known that if you can separate sheets of graphene from graphite you can get some pretty interesting properties," he explained.

Most researchers thought creating these sheets in a cost-effective way was an insurmountable challenge, due to their strong tendency to clump together. But in the journal Nature Nanotechnology this week, Wallace's team shows stopping the sheets from aggregating is actually a fairly simple matter.

The Australian team did not use chemical stabilizers to keep the sheet apart. Instead, they used water with some ammonia added to increase its pH value, making it more alkaline.

"It's actually a really simple discovery but with fairly significant implications," Wallace said.

"It's a matter of understanding that simple chemistries can be applied to graphite sheets."

Increasing the pH of the water raises the electrostatic charge on the graphene sheets, he explained, making sure they repel one another instead of clumping together.

This low cost approach raises the possibility that scientists could produce large amounts of stable graphene that could be used in a range of settings.

"The very unusual electronic properties of graphene sheets means they could be used in solar cells or new battery technology," he said. "Because of the biological affinity of carbon, they might also be useful as electrodes for a range of medical bionic devices such as cochlear implants."

The research also has practical implications for the development of coatings to reduce static build-up on materials and for transparent electronics, the researchers say.

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