A simple process is described for directly synthesizing pure graphene and N-doped graphene sheets from ethanol flame and amine plus ethanol flames respectively. The microstructures and nitrogen contents of the graphenes were characterized using scanning and transmission electron spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The results reveal that: (1) The graphene sheets from flame exhibit good transparency and a large size up to 400 mu m(2) with few layers and folded edges; (2) The nitrogen-doped graphene sheets have a dominant 'pyridine-type' structure with C=N bonds (one N atom bonded to two C atoms); (3) Compared with other methods, the graphene sheets from flame have more surface defects due to the environmental conditions and introduction of nitrogen atoms, which makes it a promising material for supercapacitors and catalyst supports. (C) 2012 Elsevier B.V. All rights reserved.