Influence of different buffer gases on synthesis of few-layered graphene by arc discharge method

Few-layered graphene sheets were synthesized by direct current arc discharge using different buffer gases. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) and four-probe method. Moreover, the hydrophobility and the field emission properties of the sprayed-coating graphene films prepared by a direct solution process were studied. As a result, the generation of graphene sheets shows strong dependence on the composition of buffer gases and containing H-2 buffer gases are necessary to prepare few-layered graphene sheets. The graphene sheets produced in H-2-He buffer gases have better crystallinity and higher specific surface area compared with those produced in others containing H-2 buffer gases. The as-obtained graphene sheets are mainly no more than 5 layers and their lateral dimensions are about 40-200 nm. The graphene sheets show excellent thermal stability and there is only less than 3 wt.% weight loss up to 800 degrees C in N-2 atmosphere. The graphene sheets can be easily dispersed into ethanol and the as-obtained suspension can be stable for more than two months. The sprayed graphene films show good hydrophobility and a typical cold cathode field emission behavior. (C) 2012 Elsevier B.V. All rights reserved.