Effective chemical oxidation on the structure of multiwalled carbon nanotubes.

A two-step chemical oxidation of multiwalled carbon nanotubes (MWCNTs) with different oxidation reagents was particularly studied. The reagents used in first step were the acidic mixture of sulfuric acid and nitric acid, and the reagents used in the second step were a mixture of sulfuric acid and hydrogen peroxide for different time. After each treatment, the functionalization yield of the oxygen-containing groups such as carboxylic group, hydroxyl functional groups and other functional groups on the surface of the carbon nanotubes (CNTs), was quantified by the analysis of XPS measurements. Two-step for a short period of time treated MWCNTs exhibited a larger fraction of carboxyl (COOH) groups compared to one step and two step for longer-time oxidative treatments, and the defect formation on the CNTs was verified mild by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy and transmission electron microscopy (TEM) graphs, which is necessary for derived reaction and better manipulation of the material and use in the application of the carbon nanotubes.