Spectroscopic characterization of the electrochemical functionalization of single-walled carbon nanotubes in aqueous and organic media

An electrochemical method of functionalizing of single-walled carbon nanotubes (SWCNTs) in aqueous and organic electrolytes by the electrolysis of bromide solutions at anodic potentials is proposed. Cyclic voltammeter studies point to a substantial increase in the SWCNTs electrode capacitance after its electrochemical treatment, which is associated with an increase in the electrode working surface accessible to solution. This effect is attributed to the formation of functional groups on the SWCNTs surface. This conclusion is confirmed by analyzing the electrochemically processed SWCNTs by the methods Raman, UV-Vis-Nir and X-ray photoelectron spectroscopies. The electrolysis of potassium bromide solutions in both aqueous and nonaqueous media is shown to produce functional groups containing oxygen and, to a smaller extent, bromine. The dependence of the degree of SWCNT functionalization (the number of chemically bound foreign atoms per the number of carbon atoms) on the electrolyte nature is observed experimentally. The degree of functionalization reached in dimethyl sulfoxide is comparable with that of the original SWCNTs, whereas in aqueous solutions, the high density of functional groups (one O atom per 3-4 C atoms) is observed. (C) 2011 Elsevier Ltd. All rights reserved.