Carbon nanotubes do some bonding

Many materials scientists predict that the tiny, hollow cylinders of carbon atoms known as carbon nanotubes will eventually lead to a new generation of supersmall transistors. But first, researchers will need to join nanotubes together.

A new welding technique may be the answer. Pulickel M. Ajayan of Rensselaer Polytechnic Institute in Troy, N.Y., and his colleagues have managed to join pairs of so-called single-walled carbon nanotubes into structures that resemble Xs, Ys, and Ts.

He and his coworkers made the structures by first identifying overlapping nanotubes in a sample under a transmission electron microscope. When they bombarded the nanotubes with electrons and applied heat, carbon-carbon bonds broke apart and reformed between the overlapping tubes where they touched.

Carbon nanotubes come in two forms: the single-walled variety, which is characterized by a cylinder of carbon with walls just one atom thick, and a multiple-walled variety marked by several tubes nested one inside another.

While other researchers had welded together multiwalled nanotubes, they had never done so with the single-walled variety. The latter has superior electronic properties compared with nested nanotubes and is therefore the tube of choice for future nanoscale electronics, says Ajayan. He and his coworkers report their results in the Aug. 12 Physical Review Letters.

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