Separation of metallic and semiconducting single-walled carbon nanotubes via covalent functionatization

Fifteen years after their discovery,[1,2] carbon nanotubes continue to fascinate the scientific community. Single-walled carbon nanotubes (SWNTs) can be seen as sheets of graphite rolled up to form hollow tubes. Depending on the orientation of the tube axis with respect to the hexagonal lattice, the structure of a nanotube can be completely specified through its chiral vector, which is denoted by the chiral indices (n,m). Nanotubes in which n=m are metallic and quasi metallic (with a tiny bandgap) if nm is divisible by 3. All other tubes are semiconducting with bandgaps of the order of 0.5 eV. The electronic properties of SWNTs depend on the geometry of the tube: to date, carbon nanotubes are the only material known to have this unique property