New Life for Nanotubes

March 2005

New life for nanotubes

To become a technological material, nanotubes may have to be grown to any length and with controlled molecular structures. A new technique shows the way.

The dream of super-strong fibres made from carbon nanotubes is predicated on the notion of being able to grow these nanoscale carbon cylinders to any length. The idea of using such nanotubes as conductive wiring and semiconducting devices in nanoscopic electrical circuits, meanwhile, hinges on the ability to make nanotubes to order in either a metallic or a semiconducting form. Neither of these things is yet possible, but new results from a team of US researchers show that both may be feasible soon.

Nanotube pioneer Richard Smalley at Rice University in Houston, Texas, and his co-workers, have discovered a method for restarting the growth of open-ended carbon nanotubes in a way that preserves the atomic-scale structure of the original tubes

researchers say, the nanotubes will continue to grow as long as they are 'fed' with a source of carbon, such as ethanol or ethylene gas. If that's so, it should be possible to make nanotubes, with diameters of just a few or a few tens of nanometres, that have macroscopic lengths — metres, or even (who knows) kilometres

The researchers believe that this technique should open the way to the formation of fibres of single-walled nanotubes all with identical and pre-selected values of n,m — and thus with identical mechanical and electronic properties. They also say that it provides 'the opportunity to grow nanotubes to unlimited lengths