J. Am. Chem. Soc. doi:10.1021/ja804164y (2008)

Carbon nanotubes produced by the commonly used high-pressure carbon monoxide method are normally one-third metallic or semi-metallic and two-thirds semiconductor, and of various diameters. Now James Tour and his colleagues at Rice University in Houston, Texas, have developed what should be an easy way to separate these types in a reaction that may enable their use in a variety of micro-electronic components.

Their reaction uses ultraviolet light with a wavelength of 254 nanometres to add hydroxyl groups first to the semiconducting nanotubes in a mixture and then to metallic tubes of small diameters. This should mean that the larger metallic tubes could be easily separated from the mix.