Material incorporation inside single-walled carbon nanotubes using plasma-ion irradiation method

An original approach using plasma technology has been performed in order to develop novel functional nanocarbons such as fullerenes (C₆₀) and carbon nanotubes. Fully ionized plasmas, which consist of alkali positive ions, fullerene negative ions, and a small fraction of residual electrons have been produced. When positive or negative bias voltages are applied to single-walled carbon nanotubes (SWNTs) in the plasmas, accelerated negative fullerene or positive alkali-metal ions are irradiated to the SWNTs, respectively. In contrast to pristine samples, a remarkable structural change of the nanotubes is observed after the plasma-ion irradiation. Especially, Cs encapsulation inside the SWNTs is directly observed by field-emission transmission electron microscopy (TEM) and scanning TEM. On the other hand, the fullerene encapsulated SWNTs are successfully formed by fullerene-ion irradiation. In addition to this material incorporation, structural modification such as tube opening is also observed and supposed to occur by momentum transfer from ions to nanotubes. Finally, our method using plasma technology is expected to provide a nanotechnology alternative to conventional chemical process, creating a new possibility for the novel functional nanomaterial synthesis.