Tuning of electronic structure of single-walled carbon nanotubes:: In-situ Raman and vis-NIR spectroelectrochemical study

The population of valence-band electronic states of SWCNT was tuned electrochemically in acetonitrile electrolyte solution. In dry and oxygen-free solution, capacitive charging controls the electrochemistry of SWCNT, but trace water activates faradaic pseudocapacitance. Reversible changes of intensity and frequency of the Raman spectra can be monitored during slow cyclic voltammetry. Electrochemical charging of SWCNT can be also traced via reversible bleaching of the electronic transitions in Vis-NIR region. Aprotic medium offers broader electrochemical window for tuning of electronic properties of SWCNT. Several types of SWCNT, including a material made from catalytic decomposition of CO by the HiPco process, were studied. The selective quenching of Vis-NIR and Raman spectra can be interpreted in terms the zone-folding model. This is a useful tool to the analysis of tubes of varying diameter and helicity.