Characterization of carbon nanotube filters and other carbonaceous materials by Raman spectroscopy - II: study on dispersion and disorder parameters

Recently, we have reported on the characterization of various carbonaceous materials including multiwalled carbon nanotube (MWCNT) filters, which have specific molecular filtering capabilities and good mechanical strength and can be produced in bulk as highly aligned arrays of bundles of CNTs. We have extended our studies using Fourier transform-Raman spectroscopy with 1064 nm excitation wavelength and a rotating sample holder in the region 1000-2800 cm(-1), in addition to 532 and 785 nm, which were used for Raman excitation in our previous study. Raman spectra were analyzed for band positions and line shape with special emphasis on the D-, G-and G'-bands. For the single-walled species, Carbotrap and graphite spectra were also recorded with 488 nm excitation. A dispersion study has been made from the Raman data available with the different excitation wavelengths. Slight band shifts and band broadening could be observed under the two sample conditions, one with the stationary sample and the other with sample rotation. The spectral changes are related to the excessive heating caused in a stationary sample by laser irradiation. Based on our findings in this study combined with our earlier study, we can state that only a careful line shape analysis and study of intensity pattern of the D-and G-Raman bands underwell-defined measurement conditions lends itself as a good measure of degree of alignment in the MWCNT bundles. Copyright (C) 2010 John Wiley & Sons, Ltd.