Using state-of-the-art time-dependent density functional theory and the complex polarization propagator theory, the UV-vis absorption and resonance Raman spectra of pristine and H- and F-decorated single-walled carbon nanotubes were computed. It was found that H- and F-functionalization brightened a low-energy exciton that coupled the single-walled carbon nanotubes local-defect chemistry to its extended p network. The energy of the strongly light-absorbing φ-φ* excitation (S11S) and the Raman shift of the radial breathing mode were not very sensitive to the presence of the defects and, to a lesser degree, their type. In contrast, the resonance Raman intensities of the radial breathing mode resonance profile were reduced by two orders of magnitude upon functionalization, due to changes in the dynamic polarizabilities. The resonance profile showed sensitivity to the defect chemistry where the H-functionalized carbon nanotubes had a factor of ∼4 larger intensities than F-functionalized carbon nanotubes in the near-resonance region. Despite the differences in the nature of the local defects, the findings were in good agreement with experiments on individual single-walled carbon nanotubes containing well-controlled topological defects. The study showed that photoluminescence was not sensitive to low concentrations of defects, but resonance Raman spectroscopy provided a powerful ultra-sensitive tool for identifying and categorizing carbon nanotube defects.

Probing Single-Walled Carbon Nanotube Defect Chemistry using Resonance Raman Spectroscopy. W.A.Saidi, P.Norman: Carbon, 2014, 67, 17-26