Preparation of highly oxidized nitrogen-doped carbon nanotubes.

A method for the preparation of highly oxidized nitrogen-doped carbon nanotubes (N-CNTs) from KMnO(4) + H(2)SO(4) solution is described. The atomic ratio of C/O in oxidized N-CNTs is as low as 1.2. The x-ray photoelectron spectroscopy results show that about 75% of the carbon atoms are oxidized and bound to oxygen-containing functional groups. The oxidation reaction mainly occurs at the outer sidewalls, which destroys the graphene stack to an sp(3)-rich structure and helps to preserve the tubular structure of the inner N-CNTs. The oxidized N-CNTs show an energy gap of ~2.1 eV.