Highly efficient microwave-assisted purification of multiwalled carbon nanotubes

We have developed a new technique for the microwave-assisted purification of multiwalled carbon nanotubes (MWNTs) in a closed vessel at 180 degreesC for 30 min in the presence of 20% hydrogen peroxide. A comparison of the purification efficiencies of hydrogen peroxide and nitric acid was conducted using the gravimetric method and indicated that the former exhibits better at removing defects than the latter. A temperature of 180 degreesC was suitable for the purification of nanotubes without decomposition, as evidenced by Raman spectroscopy and thermogravimetric analysis. Purification temperatures below 180 degreesC were not effective in removing defects, while temperatures above 180 degreesC decomposed the nanotubes. SEM images provide further evidence for the effectiveness of purification at 180 degreesC. This technique is more efficient, with regard to energy and time, than conventional purification methods. (C) 2004 Elsevier B.V. All rights reserved.