Interaction of O₂ and C₆₀ with single-wall carbon nanotube bundles from thermal desorption spectroscopy

We have studied the kinetics of oxygen desorption from single-wall carbon nanotube (SWNT) bundles and highly oriented pyrolytic graphite (HOPG) using thermal desorption spectroscopy (TDS). The binding energies for adsorption on SWNT bundles and HOPG at low coverages are 18.5 kJ/mol and 12.0 kJ/mol, respectively. Molecular mechanics calculations using van der Waals pair-potentials show that the higher binding energy found for adsorption on SAINT bundles can be attributed to van der Waals interactions and is due to higher coordinated sites available for adsorption on the tube bundles. We find no evidence for a stronger bound, chemisorbed oxygen species or for dissociative adsorption. We also present preliminary results on the kinetics of desorption of C-60 from nanotube bundles and from HOPG