Nature Chem. 5, 572–576 (2013)

Carbon nanotubes are of interest in a variety of applications because of their electronic, optical and mechanical properties. These properties are, however, sensitive to the diameter and sidewall structure (or chirality) of the nanotubes, and current synthesis methods cannot produce materials with well-defined diameters and chiralities. The recent synthesis of carbon nanorings (cycloparaphenylenes), which are the basic structural units of a carbon nanotube, with precise diameters and chiralities has suggested that a bottom-up method for synthesizing carbon nanotubes could be developed.

Kenichiro Itami and colleagues at Nagoya University have now shown that cycloparaphenylene nanorings can be used as templates to grow carbon nanotubes with diameters similar to those of the templates. The nanotubes are created by heating the template molecules to around 500 °C in flowing ethanol gas that acts as a carbon source. Itami and co-workers suggest that the tube growth is probably due to a radical mechanism in which active carbon species from ethanol replace hydrogen atoms in the nanoring molecules. The distribution of nanotube diameters created with the approach is, however, far from monodisperse because radical reactions alter the structure of the tube and introduce 'errors' during growth.