The formation of oxygen functional groups and morphological changes of aligned multi-walled carbon nanotube upon exposure to atomic oxygen at various temperatures was reported. Raman spectroscopy revealed that carbon nanotube surfaces had become semiconducting with the strong hole-type doping of graphene layers in an O2 atmosphere. The oxygen functional groups could convert the metallic carbon nanotube to semiconducting; improving the adhesive properties, or functionalizing the surface. The type and abundance of the groups formed and the gasification rate were strongly influenced by the density and size of vacancy defects in the graphene layers of the carbon nanotubes.

Imaging and Spectroscopy of Multiwalled Carbon Nanotubes During Oxidation: Defects and Oxygen Bonding. A.Barinov, L.Gregoratti, P.Dudin, S.L.Rosa, M.Kiskinova: Advanced Materials, 2009, 21[19], 1916-20