UV Raman spectroscopy of single-walled carbon nanotubes

Deep UV Raman spectroscopy is emerging as a useful tool for the characterization of carbon materials that has many advantages over visible Raman spectroscopy. However, because of resonance enhancement and other effects, UV Raman spectra are often different from visible Raman spectra. UV Raman spectra have not been reported for even some of the most widely known carbon materials. We report Raman spectra of single-walled carbon nanotubes (SWNTs) collected with deep ultraviolet (4.8 eV) laser excitation. There are significant differences between the deep UV and the visible Raman spectrum of SWNTs for the graphitic "G" modes and "disorder-induced" "D" modes, which are common to a wide range of forms of carbon. Furthermore, only semiconducting tubes are observed in the UV Raman spectrum, which is not consistent with an expected resonance enhancement of the scattering from metallic tubes at 4.8 eV.