New research at Rice University could ultimately show scientists the way to make batches of nanotubes of a single type.
A paper in the online journal Physical Review Letters unveils an elegant formula by Rice University physicist Boris Yakobson and his colleagues that defines the energy of a piece of graphene cut at any angle.
Yakobson, a professor in mechanical engineering and materials science and of chemistry, said this alone is significant because the way graphene handles energy depends upon the angle -- or chirality -- of its edge, and solving that process for odd angles has been extremely challenging. But, he wrote, the research has "profound implications in the context of nanotube growth, offering rational ways to control their chiral symmetry, a tantalizing yet so far elusive goal."
Graphene is the single-atom-thick form of carbon that has become of tremendous interest for its potential to revolutionize electronics, optics, sensing and mechanical devices. Getting a handle on how this chicken-wire-shaped sheet of carbon atoms transports electricity has been the focus of intense study.
A sheet of graphene with zigzag or armchair edges squares up nicely. Zigzags are metallic, armchairs are semiconductors, and their atoms march in rank, evenly spaced, along the edges. A full 30 degrees of rotation separates one from the other.
But if the hexagons that make up a sheet are offset less than 30 degrees, atoms along a straight edge are unevenly spaced. "That makes analysis of the energy very complicated, because it's a large irregular structure. It's like noise," Yakobson said. "We've found a way to calculate the energies in these arbitrary angles," he said.
Yakobson and his co-authors, Yuanyue Liu, a graduate student in his lab, and Alex Dobrinsky, a former graduate student and now a postdoctoral researcher at Brown University, soon wondered how these findings applied to carbon nanotubes.
|Contact: David Ruth|