Raman spectroelectrochemistry on SWNTs at higher doping levels: Evidence for a transition to intercalative doping

We studied the transition from the electrochemical double-layer charging regime to intercalative doping of SWNT buckypaper in KCl aqueous solution. For this purpose we used doping levels by applying constant potentials above 1 V approaching and slightly exceeding the oxidation potential for Cl - ions. At each potential in situ Raman measurements of the radial breathing mode (RBM), the high-energy tangential mode (HEM) and the disorder-induced (D) mode were performed. From a comparative analysis of the Raman spectra we conclude that above 1 V a significant penetration of chlorine species into the interstitial channels of the SWNT bundles and possibly functionalization take place.