Structure and electronic states of single-wall carbon nanohorns prepared under nitrogen atmosphere

Nitrogen-doped single wall carbon nanohorns (N-SWCNHs) were prepared by CO2 laser ablation of a graphite target under nitrogen atmosphere. X-ray photoelectron spectra showed that the doped nitrogen quantities were about 1.7 and 1.1 at.% under nitrogen and nitrogen/Ar mixed atmospheres, respectively. The nitrogen atoms were implicated as the pyridine-like and threefold coordinated sp2 bonding in graphene lattice of SWCNHs, and they were p-type dopants. The number of defect sites of N-SWCNHs was larger than that of SWCNHs prepared under Ar atmospheres, which was revealed by Raman and electron spin resonance measurements.