▎ 摘　　要

N-doped multi-layered graphene sheets were synthesized in large scale by the method of direct current arc-discharge between pure graphite rods. For the use of NH3 as one of the buffer gas, the multi-layered graphene sheets were doped with N without the addition of other nitrogen source. The product so obtained has been characterized by transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and element analysis. The graphene sheets are mainly of 2-6 layers and their sizes are about 100-200 nm. The multi-layered graphene sheets can be purified by a simple heat treatment process. The content of N atoms on the multi-layered graphene sheets can be tuned by simply changing the proportion of NH3 in the atmosphere. (C) 2009 Elsevier Ltd. All rights reserved.