Plasma treatment of multi-walled carbon nanotubes using an atmospheric pressure hydroxyl radical (OH) source was monitored by micro-Raman spectroscopy. The dispersion behavior of the intensity ratio, band position and linewidth of the D, G, D′ and G′ bands was used to probe the defect formation and oxidation process in multi-walled carbon nanotubes. A simple kinetic model was used to interpret the observed dispersion trends in plasma-treated multi-walled carbon nanotubes. X-ray photo-electron spectroscopic analysis, scanning electron microscopy and Raman dispersion characterization of multi-walled carbon nanotube surfaces suggested that the dominant effect of OH plasma on multi-walled carbon nanotubes was reduced π-conjugated states, due to creating structural defects and to the attachment of oxygen-containing functional groups.

Probing Plasma-Induced Defect Formation and Oxidation in Carbon Nanotubes by Raman Dispersion Spectroscopy. S.Lee, J.W.Peng, C.H.Liu: Carbon, 2009, 47[15], 3488-97