Monitoring oxidation of multiwalled carbon nanotubes by Raman spectroscopy

TLDR

The study aimed to generate a high density of carboxyl groups on MWCNTs while minimizing sample loss for use in nanocomposites. MWCNTs were oxidized under varied conditions and characterized in real time by Raman spectroscopy, with defect levels quantified by the D/G intensity ratio and further analyzed by TEM, FTIR, TGA, and electrophoretic mobility. Strongest functionalization was achieved with 6‑hour acid oxidation, but a 15‑minute air flash oxidation at 550 °C also produced efficient, cost‑effective, environmentally friendly carboxylation. © 2007 John Wiley & Sons, Ltd.

Abstract

Abstract Multiwalled carbon nanotubes (MWCNTs) were oxidized in air and acids while varying the treatment time and/or temperature. The goal of this approach was to create the highest density of carboxyl groups with moderate sample loss, which is necessary for nanocomposite applications. In situ Raman experiments allowed real‐time observation of the structural changes in MWCNTs upon oxidation. The ratio of the Raman intensities of the D and G bands was used to estimate the concentration of defects. It was found that while an oxidation for 6 h in H 2 SO 4 /HNO 3 provided the strongest effect, a ‘flash oxidation’ in air (15 min at 550 °C) also leads to an efficient functionalization in a cost‐effective and environmentally friendly way. Transmission electron microscopy, Fourier‐transform infrared (FTIR) spectroscopy, thermogravimetric analysis and electrophoretic mobility analysis were used to study the oxidized nanotubes. Copyright © 2007 John Wiley & Sons, Ltd.