Spectroelectrochemistry of carbon nanostructures.

This review is focused on charge-transfer reactions at carbon nanotubes and fullerenes. The spectroelectrochemistry of fullerenes deals with the spin states of fullerenes, the role of mono-anions and the reactivity of higher charged states in C60. The optical (Vis-NIR) spectroelectrochemistry of single-walled carbon nanotubes (SWNTs) follows changes in the allowed optical transitions among the Van Hove singularities. The Raman spectroelectrochemistry of SWNT benefits from strong resonance enhancement of the Raman scattering. Here, both semiconducting and metallic SWNTs are analyzed using the radial breathing mode (RBM) and G-modes as well as the second order (D, G') and intermediate frequency modes. Raman spectroelectrochemistry of SWNT allows the addressing of index-identified tubes and even single isolated nanotubes. Optical and Raman spectroelectrochemistry of fullerene peapods, C60@SWNT and C70@SWNT indicates effective shielding of the intratubular fullerene (peas). The most striking effect in the spectroelectrochemistry of peapods is the so-called "anodic Raman enhancement" of intratubular C60. Double-walled carbon nanotubes (DWNTs) give a specific spectroscopic response in Vis-NIR spectroelectrochemistry for the inner and the outer tube. They are better distinguishable by Raman spectroelectrochemistry which allows a precise tracing of the specific doping response of outer/inner tubes.