Raman studies of new carbon nanotube sample types

Generation of new carbon nanotube sample types, including individualized nanotubes suspended in surfactant solutions and recently synthesized ultralong nanotubes, has enabled new experimental studies that provide useful insight into nanotube structure and photophysical behavior. We present a review of Raman studies performed in our laboratory on these newly available sample types. Results from Raman excitation profile studies of individualized HiPco-produced nanotubes have confirmed fluorescence-based chirality assignments and have revealed chiral-dependences in the Raman scattering cross-sections. These studies have also enabled a direct evaluation of the effects of nanotube bundling on electronic and vibrational structure. Confocal Raman imaging is demonstrated as a useful technique for probing vibrational structure of ultralong nanotubes over large length scales and has resulted in the detection and imaging of a semiconductor-to-metallic nanotube intramolecular junction.