▎ 摘　　要

The toxic gases, such as CO and NO, are highly dangerous to human health and even cause the death of person and animals in a tiny amount. Therefore, it is very necessary to develop the toxic gas sensors that can instantly monitor these gases. In this work, we have used the first-principles calculations to investigate adsorption of gases on defective graphene nanosheets to seek a suitable material for CO sensing. Result indicates that the vancancy graphene can not selectivly sense CO from air, because O-2 in air would disturb the sensing signals of graphene for CO, while the nitrogen-doped graphene is an excellent candidate for selectivly sensing CO from air, because only CO can be chemisorbed on the pyridinic-like N-doped graphene accompanying with a large charge transfer, which can serve as a useful electronic signal for CO sensing. Even in the environment with NO, the N-doped graphene can also detect CO selectively. Therefore, the N-doped graphene is an excellent material for selectively sensing CO, which provides useful information for the design and fabrication of the CO sensors.