Structure analysis of purified multiwalled carbon nanotubes Original Research Article

High quality multiwalled carbon nanotubes (MWNTs) prepared by hydrogen DC arc discharge were purified by infrared irradiation in air at about 500°C. The morphology and nanostructure of the purified MWNTs were investigated by using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and micro-Raman spectroscopy. Each MWNT was highly graphitized and most of the MWNTs had approximate 1.0 nm inner diameter. The radial breathing modes corresponding to the innermost nanotubes were observed in the micro-Raman spectra of the purified MWNTs. The dependence on the incident laser power of Raman-allowed mode, E2g, and new Raman peak at about 1840 cm−1 was also studied.