Carbon cage structures in single wall carbon nanotubes: a new class of materials

A new class of materials, carbon cage structures contained within single-wall carbon nanotubes (SWNTs) has been discovered. This class of hybrid materials could form the basis of functional devices for application in electronics, biomedicine and microelectromechanical systems. The cage structures internal to the SWNTs are found to be C-60 fullerenes resembling nanoscopic peapods. Peapods are found to coalesce into capsules and interior tubes under prolonged exposure to a 100 keV electron beam. Through in-situ experiments, it is found that peapods form via the motion of C-60 molecules to the nanotubes. The fullerenes enter the SWNTs, presumably through open ends and/or sidewall defects and are found to cluster in chains. In this paper, the structure, some properties and synthesis routes of these hybrid structures will be explained. (C) 2000 Elsevier Science Ltd. All rights reserved.