Conversion of single-crystalline C60 nanodisks and nanorods into graphitic nanostructures via hydrogen thermal annealing.

We have developed a process to convert C60 nanostructures into graphitic nanostructures. Disk-shaped and wire-shaped C60 nanostructures synthesized by the liquid–liquid interfacial precipitation method, the vapor–solid process, and solvent evaporation were successfully converted into graphitic structures by thermal annealing in hydrogen at 900 °C. Scanning electron and tunneling electron microscopic studies confirmed that the converted nanostructures were composed of multi-graphitic structures such as multi-walled carbon nanotubes, carbon nanofibers, and carbon onions. Fourier transform Raman spectroscopy and conductance measurements were carried out to further confirm the successful formation of graphitic layers. In the Raman spectra, the nanostructures converted from C60 disks showed signature D, G, and G' bands of graphitic structures, while the Ag mode (1469 cm−1) of the original C60 molecule disappeared. C60 nanowire devices fabricated for the conductance measurements of the converted structures showed dramatically decreased resistance (R≈100 kΩ) compared to the pristine C60 wire (R>100 MΩ). Further manipulation of the reaction environment, including the gas and the annealing temperature, may reveal a new way to attain diverse graphitic nanostructures economically.