▎ 摘　　要

In order to exploit the potential applications of graphene as gas sensors, the adsorptions of a series of small gas molecules (such as CO, O-2, NO2 and H2O) on pristine graphene (PG) and Si-doped graphene (SiG) have been investigated by ab initio calculations. Our results indicate that the electronic properties of PG are sensitive to O-2 and NO2 molecules, but not changed much by the adsorption of CO and H2O molecules. Compared with PG, SiG is much more reactive in the adsorption of CO, O-2, NO2 and H2O. The strong interactions between SiG and the adsorbed molecules induce dramatic changes to the electronic properties of SiG. Therefore, we suggest that SiG could be a good gas sensor for CO, O-2, NO2 and H2O.