Optical spectroscopic studies of photochemically oxidized single-walled carbon nanotubes.

We examined the time-dependent changes in the optical properties of single-walled carbon nanotubes which were consecutively oxidized by irradiation with vacuum ultraviolet light. It is demonstrated that photochemical oxidation is a mild and controllable method for manipulating the surface of nanotubes in order to convert their affinity from hydrophobic to hydrophilic by controlling the density of functional groups on their sidewalls without destroying their tubular morphology.