| Affiliation: | (1) Chemistry Division, Analytical Chemistry Sciences, Los Alamos National Laboratory, 87545 Los Alamos, NM, USA;(2) Department of Chemistry, University of Illinois – Urbana/Champaign, 61801 Urbana, IL, USA;(3) Department of Chemical and Biomolecular Engineering, University of Illinois – Urbana/Champaign, 61801 Urbana, IL, USA |
| Abstract: | Raman excitation profiles were generated between 695 and 985 nm for individual carbon nanotubes dispersed in aqueous solution. We confirmed that previously published spectral assignments for semi-conducting and metallic carbon nanotubes are able to predict the location and resonant maxima of radial breathing mode features in the Raman spectrum. Three large diameter features were observed within the excitation space over the scan range and accurately predicted as metallic species. There was significant agreement between predicted and observed Raman modes. However, one discrepancy is noted with the (6,4) nanotubes. This species is not observed when excited at or near its absorption transition. We find that the Raman cross-sections in general, assuming a diameter-based distribution of nanotubes, are disproportionately smaller for mod(n-m,3)=1 semi-conducting nanotubes than their counterparts by at least an order of magnitude. These results have important implications for the use of Raman spectroscopy to effectively characterize the chirality distribution of carbon nanotube samples. PACS 61.46.+w; 73.22.-f; 78.30.-j |
