Optical Transition Energies for Carbon Nanotubes from Resonant Raman Spectroscopy: Environment and Temperature Effects

Abstract

This Letter reports the laser energy dependence of the Stokes and anti-Stokes Raman spectra of carbon nanotubes dispersed in aqueous solution and within solid bundles, in the energy range 1.52-2.71 eV. The electronic transition energies (E(ii)) and the radial breathing mode frequencies (omega(RBM)) are obtained for 46 different (18 metallic and 28 semiconducting) nanotubes, and the (n,m) assignment is discussed based on the observation of geometrical patterns for E(ii) versus omega(RBM) graphs. Only the low energy component of the E(M)(11) value is observed from each metallic nanotube. For a given nanotube, the resonant window is broadened and down-shifted for single wall carbon nanotube (SWNT) bundles compared to SWNTs in solution, while by increasing the temperature, the E(S)(22) energies are redshifted for S1 [(2n+m) mod 3=1] nanotubes and blueshifted for S2 [(2n+m) mod 3=2] nanotubes.

Asymmetric excitation profiles in the resonance Raman response of armchair carbon nanotubes

“…The RBM frequencies found for the (8,8), (7,7), and (6,6), are 219, 248, and 287 cm −1 , respectively and match those found in previous work 7,19,20,26,27 . The (5,5) RBM frequency is found here to be 338 cm −1 .…”

“…The (5,5) RBM frequency is found here to be 338 cm −1 . The observed frequencies are fit well by the typical empirical relation relating the frequency (ω RBM ) to the tube diameter, d t , such that ω RBM = A/d t + B, with A and B given as 216±4 cm −1 nm and 21±4 cm −1 , respectively 26,27 .…”

Chirality-controlled synthesis of single-wall carbon nanotubes using vapour-phase epitaxy

“…To determine whether the original chiralities were preserved during the cloning process, we used micro-Raman to characterize the pristine and cloned SWCNTs. For the (7,6) case, we used 1.96 eV laser excitation, which is close to the second optical transition E 22 ¼ 1.92 eV of the (7, 6) nanotubes 28 . To further enhance the signal-to-noise ratio, surface-enhanced Raman spectroscopy was used after e-beam evaporation of 5 nm silver on the substrate (Supplementary Fig.…”

Carbon nanotubes for ultrafast fibre lasers

“…It shows the (n,m) SWNT configuration for the tubes, which energies E ii are in resonance with the laser line. Raman measurements at a different wavelength can provide detailed information on diameter distribution in the sample [193].…”