Probing the electronic state of onion-like carbon

Spherical and polyhedral onion-like carbon (OLC) particles prepared by annealing of nanodiamonds at 1600 and 1900 °C were studied by X-ray emission spectroscopy. $CKα$ spectrum of the spherical particles exhibited an increase of high-energy maximum intensity compared to that of the polyhedral particles. Quantum-chemical calculations of the carbon cages indicated this enhancement might be caused by the localized electronic states on the edges of holes. The occurrence of holes in OLC formed at the lower temperature correlates with the results of magnetoresistance measurement.