Comparative study of first- and second-order Raman spectra of MWCNT at visible and infrared laser excitation

Comparative studies of first- and second-order Raman spectra of multi-walled carbon nanotubes (MWCNT) and three other graphitic materials – carbon fiber, powdered graphite and highly ordered pyrolytic graphite – are reported. Three laser excitation wavelengths were used: 514.5, 785 and 1064 nm. In first-order Raman spectra, the positions of the bands D, G and D′ (1100–1700 cm−1) presented very similar behavior, however the intensity (I) ratio ID/IG ratio showed differed behaviors for each material which may be correlated to differences in their structural ordering. In the second-order spectra, the G′ band varied strongly according to structure with the infrared laser excitation.