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

The population of valence-band electronic states of single-walled carbon na notubes (SWCNTs) was tuned electrochemically in acetonitrile electrolyte so lution. In dry and oxygen-free solution, the electrochemistry of SWCNTs is controlled by capacitive charging. Reversible changes of intensity and freq uency of the Raman spectra can be monitored during cyclic voltammetry at lo w scan rates. Electrochemical charging of SWCNTs can be also traced via rev ersible bleaching of the electronic transitions in the vis-NIR region. An a protic medium offers a broader electrochemical window for tuning of electro nic properties of SWCNTs. Electrochemical charging of SWCNTs in an aprotic electrolyte solution allows easy and precise control of the electronic stru cture of SWCNTs. In addition to commercial SWCNTs, a material made from gas -phase catalytic decomposition of CO by the HiPco process was also studied. Selective quenching of vis-NIR and Raman spectra is a useful tool to the a nalysis of tubes of varying diameter and helicity.