In this study, oxidation of carbon nanotubes with ozone in the presence of hydrogen peroxide was investigated. The reaction was performed under clean and mild conditions and oxidized products with high concentration of oxygenated groups were yielded. The reaction products were characterized with attenuated total reflectance (ATR), Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffractometry (XRD), back titration, X-ray photoelectron spectroscopy (XPS) and the dispersion behavior of the oxidized multiwalled carbon nanotubes (MWCNTs) was also studied. The results confirmed the presence of high concentrations of oxidative groups on the carbon nanotubes (CNTs) treated by the method of the present work. (c) 2009 Elsevier B.V. All rights reserved.