Preparation of water-soluble carbon nanotubes using a pulsed streamer discharge inwater

Abstract

A novel technique for the preparation of water-soluble carbon nanotubes was demonstratedusing a pulsed streamer discharge generated in water. The technique involved chemicalreactions between radicals generated by the pulsed streamer discharge and carbonnanotubes. The pulsed streamer-treated carbon nanotubes were homogeneouslydispersed and well solubilized in water for a month or longer. The mechanism ofsolubilization of carbon nanotubes by the pulsed streamer discharge is discussedbased on FTIR spectroscopy and optical emission spectra measurements. FTIRspectroscopy revealed that –OH groups, which are known to impart a hydrophilic natureto carbon material, were introduced on the carbon nanotube surface. Opticalemission spectra from the pulsed streamer plasma showed that highly oxidativeO* and H* radicals were generated in water. These results suggest that the functionalizationof the carbon nanotube surface by –OH group can be attributed to theO* and H* radicals. An advantage of the proposed method is that there is no need for any chemicalagents or additives for solubilization. Chemical agents for solubilization are generated fromthe water itself by the electrochemical reactions induced by the pulsed streamer discharge.