Abstract
The present study demonstrates a novel preparation method for water-soluble carbon nanotubes (CNTs) using microplasma generated in water suspension of CNTs. The microplasma was achieved by generating pulsed streamer discharges, which were triggered by applying multiple square high voltage pulses to a wire-to-plane electrode system immersed in the CNT suspension. The CNTs treated by the microplasma were solubilized and homogeneously dispersed in water for a month or longer. The functional group of -OH seemed to be bound to the CNT surface and responsible for the solubilization effect. The -OH group might be formed by chemical reactions between O and H radicals, which were detected by optical emission spectroscopy of the microplasma. The proposed method does not need any particular chemical agents or additives for solubilization. Of particular importance is its simplicity and time-efficiency in contrast to the usual time-consuming chemical treatments developed thus far. It was demonstrated that bio-nano interfaces between the water-soluble CNTs and biological cells could be readily fabricated by simultaneous electrokinetic manipulation of them in water using dielectrophoresis (DEP). The DEP trapped CNTs could serve as a NO2 gas sensor, showing that the surface adsorption of gas molecules on the CNTs did not deteriorate by the microplasma treatment.
