Formation of small-diameter carbon nanotubes from PTCDA arranged inside the single-wall carbon nanotubes

A systematic study was carried out on the doping of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) to the single-wall carbon nanotubes (SWNTs). After the doping reaction, the interior space of SWNTs was fully filled with the dopant. The heat treatment at high temperature in vacuum of this PTCDA-filled SWNTs induced new Raman signals ranging between 300 and 400 cm−1, which was assigned to the radial breathing mode of vibration associated with the inner tubes. Furthermore, transmission electron microscopy clearly showed the existence of one-dimensionally arranged PTCDA molecules in the tube and the secondary inner tubes formed after the high-temperature treatment.