Electrochemical tuning of high energy phonon branches of double wall carbon nanotubes

Double wall carbon nanotubes (DWCNT) were studied by Raman spectroscopy and by in situ Raman spectroelectrochemistry. Two components of the G′-mode were assigned to the signals from inner and outer tubes. The dependence of the G′-mode intensity and frequency on the excitation laser energy was different for the inner and outer tubes. The changes in G′-mode caused by the applied electrochemical potential were discussed in detail. The red shifted component of the G′-mode exhibits delayed response to the electrochemical charging. Moreover, bleaching of the red shifted component was less symmetrical than that of the blue shifted component, if the applied electrode potential swept in anodic and cathodic directions. Hence, the Raman G′-mode has favorable properties for detailed characterization of DWCNT, both in the pristine state and upon electrochemical charging.