Systematic investigation of the effect of oxidation on the structure of Single-Walled Carbon Nanotubes (SWNTs)

Purification of single-walled carbon nanotubes (SWNTs) is still remaining a challenging task. The aim of this work is to show novel and fast concepts for the purification of CNTs by combination of different techniques and analyses the effect of that methods on the carbon nanotubes. The carbonaceous particles were presumably etched away by the selective oxidation with faster etching rate than nanotubes. This gives rise to very high yield of about 35%. The oxidation procedure was characterized by using Raman spectroscopy, infrared spectroscopy and scanning electron microscopy (SEM). It was found from Raman scattering measurements that the ratio of the intensity of Gline peak to that of D-line peak increased drastically by this purification process. The D–G ratio of dynamically air oxidized SWNTs (0.06) is much smaller than that of as-received (0.09) or air–HCl purified (0.1) SWNTs, indicating higher purity (and lower level of structural defects) of the dynamically air oxidized sample. The results reveal that the different functional groups can be introduced when the SWNTs are treated with different oxidants. Refluxing in dilute nitric acid introduce the carboxylic acid groups only at those initial defects that already exist. It is confirm by Fourier Transform Infrared spectroscopy (FTIR).