Thermolysis of C60 thin films yields Ni-filled tapered nanotubes

Highly graphitic needle-like elongated carbon nanotubes, containing encapsulated Ni, are produced by heating a sandwich consisting of alternating thin films of C-60 and Ni deposited on a silica plate at 950 degrees C. High-resolution transmission electron microscopy (HRTEM) studies reveal that these tapered structures are almost completely filled with Ni and are closed at both ends. The diameters of the needles (2-5 mu m in length) range between 10-20 nm at one end and 30-200 nm at the other. A surprisingly high degree of graphitization is observed in the walls of the nanotubes. These unique structures may prove useful as electrodes with various applications such as precision probes in biological systems or scanning tunnelling microscope tips.