Electrochemical tuning of electronic structure of carbon nanotubes and fullerene peapods Original Research Article

Single-wall carbon nanotubes, fullerene peapods (C60@SWCNT, C70@SWCNT) and double-wall carbon nanotubes can be charged electrochemically in various media, such as acetonitrile electrolyte solutions or 1-butyl-3-methylimidazolium tetrafluoroborate/hexafluorophosphate melts (ionic liquid). Electrochemistry of nanotubes and peapods is dominated by their capacitive double-layer charging. In-situ Vis-NIR spectra of nanotubes and peapods demonstrate reversible bleaching of the allowed optical transitions between van Hove singularities. The bleaching of optical transitions, induced by charge-transfer, is mirrored by quenching of resonance Raman spectra in the region of tube-related modes. The Raman modes of intratubular C60 in peapods exhibit considerable intensity increase upon anodic doping, but these modes are not enhanced at cathodic charging. The “anodic Raman enhancement” is specific for C60@SWCNT only. In the case of C70@SWCNT, symmetric quenching of the C70 Raman modes is detected at both cathodic and anodic potentials. Electrochemical charging in DWCNT points at specific response of the inner and outer tubes, the latter being more sensitive to doping.