91av

This is a classic article from 91av’s archive, republished as part of our 50th anniversary celebrations

A JAPANESE scientist has discovered cylindrical carbon molecules, which he has dubbed “buckytubes” because of their similarity to fullerenes, or “buckyballs”. The cylinders are made of sheets of carbon atoms, arranged in hexagons, as in graphite. But instead of forming closed cages, as they do in fullerenes, the carbon atoms form open-ended cylinders.

Sumio Iijima, an electron microscopist at the fundamental research laboratory of NEC, the Japanese electronics giant, in Tsukuba, discovered the tubes when attempting to examine buckyballs in his transmission electron microscope. “I found a structure I’d not seen before,” he says. The buckyballs turned out to disintegrate in the intense beam of electrons which forms the image in an electron microscope.

The needles, or tubes, are up to a micrometre long and very fine. Typically, their outside diameter is between 4 and 30 nanometres. Iijima is excited by the helical arrangement of the hexagons. “The preliminary result is that they are very good conductors,” he says. But the pitch of the helix (its repeat length) varies, and “if you choose a different pitch, the electronic properties seem to be different, and it can become an insulator,” he adds. Iijima says he is trying to find the best recipe for making the tubes. He wants to make them longer than the current maximum of a micrometre, and to control their size and the pitch of the helix.

This article was originally published in 91av on 16 November 1991

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