Effect of Bundling on the Tangential Displacement Mode in the Raman Spectra of Semiconducting Single-Walled Carbon Nanotubes during Electrochemical Charging

A detailed in situ Raman spectroelectrochemical analysis of semiconducting single-walled carbon nanotubes (SWCNTs) in bundles is presented. Special attention has been given to the development of the frequency and intensity of the tangential displacement mode (TG) during electrochemical charging. For negative charging, the frequency of the G + component of the TG mode increased, decreased, and remained unchanged for the 2.18, 2.54, and 2.41 eV laser photon energies, respectively. For positive charging, only an increase in the frequency of the G + component has been observed. The maximum frequency upshift (at the applied electrochemical potential of 1.5 V vs Ag-pseudoreference) increased for decreasing photon energies in the series from 2.54 to 2.41 and 2.18 eV. The frequency of the G + component of the TG mode changes significantly at potentials of approximately 0.8−1.0 and −1.2 V for positive and negative doping, respectively. This is in contrast to the change in intensity of the G + component of the TG mode of semiconducting SWCNTs, which exhibits distinct changes when the potential of the first Van Hove singularity is achieved (0.5 V).