Surface defect site density on single walled carbon nanotubes by titration

Closed end single walled carbon nanotubes (c-SWNT) purified by acidic oxida tion have been studied in order to determine the fraction of oxidized carbo n sites present. This has been done by measuring the evolution of CO2(g) an d CO(g) on heating to 1273 K. Following a 1273 K treatment, the defect site s were titrated repeatedly with O-3. The results indicate that similar to 5 % of the carbon atoms in the c-SWNT samples pretreated to 1273 K are locate d at defective sites, capable of facile oxidation by O-3. This high defect site density indicates that a significant number of these sites exist on th e graphene walls of the nanotubes. (C) 2000 Elsevier Science B.V. All right s reserved.