Interaction of molecular oxygen with single-wall carbon nanotube bundles and graphite

The adsorption of oxygen on highly oriented pyrolytic graphite (HOPG) and bundles of single-wall carbon nanotubes (SWNTs) at 28 K is studied using thermal desorption spectroscopy and by a measurement. of sticking probabilities. The low-coverage binding energy of oxygen adsorbed on SWNT bundles, 18.5 kJ/mol, is 55% higher than the low-coverage binding energy on HOPG, 12.0 kJ/mol. Molecular mechanics calculations reveal that such an increase can be attributed to the higher effective coordination of binding sites on SWNT bundles. The character of the oxygen-SWNT interaction should therefore be van der Waals type which suggests that the observed oxygen species is physisorbed and does not facilitate bulk doping of SWNT samples. (C) 2003 Elsevier Science B.V. All rights reserved.