Absolute potential of the Fermi level of isolated single-walled carbon nanotubes

Electrochemical potential dependence of Raman intensity of isolated single-walled carbon nanotubes (SWNT) on gold electrode in aqueous solution was investigated employing in situ resonant confocal micro Raman spectroscopy. Absolute potential of the Fermi level of individual tubes was estimated from the potential dependence. Observations suggest that the work function of the tube becomes larger in a manner inversely proportional to the diameter of SWNT. The structural dependence of a metallic tube is larger than that of a semiconducting tube.