Reducing structural defects and improving homogeneity of nitric acid treated multi-walled carbon nanotubes

Scanning Raman spectroscopy was employed to statistically examine the effects of nitric acid treatments on the defects and their distribution on the surface of multi-walled carbon nanotubes (MWCNTs). After acid treatments, the amount of structural defects significantly increased and the homogeneity became worse. However, after a 384-h base wash the amount of structural defects remarkably decreased and the homogeneity was significantly improved. By comparison of these values we can conclude that the observed increase of structural defects of MWCNTs caused by acid treatment mainly originates from oxidation debris covering the surface of MWCNTs after acid treatment. These oxidation debris can protect MWCNTs from further destruction in acidic condition leaving MWCNTs with little defects after base wash. Simultaneously, base wash is capable of largely improving the homogeneity of MWCNTs. (C) 2015 Elsevier Ltd. All rights reserved.