Conversion of single-crystallineC60 nanodisks and nanorods into graphitic nanostructures via hydrogen thermal annealing

Abstract

We have developed a process to convertC60 nanostructures into graphitic nanostructures. Disk-shaped and wire-shapedC60 nanostructures synthesized by the liquid–liquid interfacial precipitationmethod, the vapor–solid process, and solvent evaporation were successfullyconverted into graphitic structures by thermal annealing in hydrogen at900 °C. Scanning electron and tunneling electron microscopic studies confirmed that the convertednanostructures were composed of multi-graphitic structures such as multi-walled carbonnanotubes, carbon nanofibers, and carbon onions. Fourier transform Raman spectroscopyand conductance measurements were carried out to further confirm the successful formationof graphitic layers. In the Raman spectra, the nanostructures converted fromC60 disks showed signature D,G, and G′ bands of graphiticstructures, while the Ag mode (1469 cm−1) of theoriginal C60 moleculedisappeared. C60 nanowire devices fabricated for the conductance measurements ofthe converted structures showed dramatically decreased resistance(R≈100 kΩ) comparedto the pristine C60 wire (R>100 MΩ). Further manipulation of the reaction environment, including the gas and the annealingtemperature, may reveal a new way to attain diverse graphitic nanostructures economically.