Nature 512, 61–64 (2014)

The properties of single-walled carbon nanotubes depend on their precise structure and, as a result, many of the intended applications of these materials require samples of only one specific type. Methods for growing carbon nanotubes, however, typically lead to a mixture of species. Konstantin Amsharov, Roman Fasel and colleagues at the Swiss Federal Laboratories for Materials Science and Technology, the Max Planck Institute for Solid State Research and the University of Bern have now shown that specific nanotubes can be grown from the bottom up using 'seed' molecules on a platinum surface.

The structure of a carbon nanotube is denoted by two integers (n,m), which are known as chirality indices and refer to the direction in which a hexagonal sheet of carbon atoms would be rolled up to create a given nanotube. Fasel and colleagues created (6,6) carbon nanotubes starting from a polycyclic aromatic hydrocarbon molecule C96H54 that was prepared using a multistep organic synthesis. The precursor molecules were adsorbed on the platinum surface and converted into ultrashort singly capped nanotube seeds through a surface-catalysed cyclodehydrogenation reaction. From these seeds, the nanotubes were then grown by incorporating carbon atoms into the bottom of the structures via the surface-catalysed decomposition of a carbon feedstock gas. The resulting nanotubes were defect free and had lengths of up to a few hundred nanometres.