Nanotubes get smaller
Jan 28, 2000
Chinese researchers have created the world's narrowest carbon nanotube. The tube had a diameter of just 0.5 nm and the researchers think that it might have been capped by half a carbon-36 molecule (Nature 403 384). They hope to refine their electric-arc technique to make tubes with diameters of 0.4 nm, which is the theoretical limit.
The 0.5 nm nanotube was made by boring a hole into a graphite rod. The hole was then filled with cobalt metal powder - which acts as a catalyst - and a mixture of nanotubes and other carbon-based material. A high-voltage electric arc was then applied to the graphite rod generating an carbon plasma from which the nanotubes were produced. The team believe that the nanotubes grow from curved carbon fragments in the rod. The diameter of the nanotube was measured with a high-resolution electron microscope. The 0.5 nm diameter nanotube was the innermost shell in a multiwall nanotube. It is not yet clear if such small tubes can occur as single-wall nanotubes.
The smallest nanotube previously reported had a diameter of 0.7 nm, which is the same as the diameter of a carbon-60 molecule. Since carbon-36 and carbon-60 molecules have any different properties, the researchers speculate that the new nanotubes may have "many unusual properties."