Closed-end single-walled carbon nanotubes purified by acidic oxidation were studied in order to determine the fraction of oxidized carbon sites present. This was done by measuring the evolution of CO2(g) and CO(g) on heating to 1273K. Following a 1273K treatment, the defect sites were titrated repeatedly with O3. The results indicated that ~5% of the carbon atoms in the closed-end single-walled carbon nanotube samples pre-treated to 1273K were located at defective sites, capable of easy oxidation by O3. This high defect site density indicated that a significant number of these sites existed on the graphene walls of the nanotubes.

Surface Defect Site Density on Single Walled Carbon Nanotubes by Titration. D.B.Mawhinney, V.Naumenko, A.Kuznetsova, J.T.Yates, J.Liu, R.E.Smalley: Chemical Physics Letters, 2000, 324[1-3], 213-6