Current Progress on the Chemical Modification of Carbon Nanotubes

The unique morphology and structure of carbon nanotubes (CNT) keep attracting a great number of researchers to explore the novel properties of these materials. Among various surface functionalization techniques, oxidation of CNTs is probably the most widely studied. Early treatment techniques involved gas-phase oxidation in air and oxidative plasmas. Carboxylated CNTs were extensively used as precursors for further covalent modification of CNTs, through esterification and/or amidation reactions. Moreover, a few other direct esterification/amidation procedures of oxidized CNTs were reported. In one of them, acid purified SWCNTs were treated with molten urea, which functions both as solvent and as reactant. Modification of CNTs with ionic liquids is expected to improve their compatibility and stability, enhancing the potential of CNTs in applications such as sensors and actuators, by improving the electrical contact with media.