Carbon nanotubes get smaller

Physicists at Hong Kong University of Science and Technology have synthesised the world’s narrowest single-walled carbon nanotubes.

The ultra small carbon cylinders they have fabricated are only 4angstroms or 0.4nm (nanometers) in diameter–that is, 75,000 times narrower than a single human hair. Nanotube theory holds these to be the narrowest stable single-walled carbon nanotubes possible.

Before Assistant Professoressors Zikang Tang and Ning Wang’s breakthrough, the narrowest single-walled nanotube fabricated measured 7 angstroms in diameter.

‘Our 4 angstrom single-walled carbon nanotubes are grown in the channels of zeolite crystals instead of by evaporating graphite in an arc-discharge,’ explained Professoressor Tang.

‘We suspected we had succeeded in growing 4 angstrom nanotubes in zeolite as long ago as 1998. However, our first proof was directly observing them by high-resolution transmission electron microscopy in March this year,’ added Professor Wang.

The zeolite crystal method produces arrays of single-walled carbon nanotubes that are highly aligned and uniform in size.

This will, according to the scientists, be a boon for experimental investigation of their electrical and mechanical properties.

‘We are already observing new properties in the 4 angstrom nanotubes not found in larger nanotubes. They are perfect one-dimensional quantum wires,’ reports Professor Wang.

‘In the longer term, nanotubes this small could revolutionise microcomputers and other ultra-thin electronic devices. Another exciting avenue of research is their suitability as a storage medium for pollution-free hydrogen fuel.’