New insights on chemical oxidation of single-wall carbon nanotubes: A theoretical study

In order to understand the morphology of oxidized positions in single-wall carbon nanotubes (SWNTs), several chemical models, resulting from the interaction of an armchair (5,5) carbon nanotube (a(5,5)) with molecular oxygen and water, have been proposed. Structural and thermodynamic properties were calculated using the density functional theory at the B3LYP/6-31G(d) level, and the results are discussed with an aim to assess the viability of the processes and structures proposed. In addition, the changes in the Raman active modes relative to the D and G absorption regions were analyzed and the characteristic frequencies assigned. In general, our results show a blue shift of about 10 cm in the D band with the progress of the oxidation reaction and an opposite trend for the G band, which is red-shifted by about 5 cm. Although the extension of oxidation was short as reported in the present paper, taking only 1 mol of O2 and water, the main functional groups were generated: C= O, C-O-C, and C-OH. Thus, the analysis described here can be valuable for experimentalists, helping in the molecular characterization of oxidized species. © 2009 American Chemical Society.