▎ 摘　　要

The effect of gas molecule (H2CO, NO, NO2, O-2 and SO2) adsorption on the electronic and magnetic properties of Mn-doped graphene (MnG) is investigated by first-principles calculations in the framework of density functional theory (DFT). Our study reveals that after H2CO, NO, NO2 and SO2 adsorption, MnG transforms from half-metal to semiconductor, and this transformation indicates that MnG's conductivity is changed significantly. Meanwhile, O-2 adsorption has no influence on MnG's original electronic property. Therefore, the substrate of MnG is highly sensitive to H2CO, NO, NO2 and SO2. The reconfiguration of electron distribution caused by gas adsorption dramatically alters the spin polarization distribution of the combined system, that is, NO2 and H2CO adsorption leads to local spin polarization, whereas O-2, NO and SO2 adsorption result in complete spin polarization. In addition, the external electric field (E-field) is varied from -0.50 V/angstrom to +0.50 V/angstrom then applied to the adsorption system. A strong interaction is observed between gas and MnG with a positive E-field as reflected in the enhancement of adsorption energy. The interaction is obviously weakened by introducing the E-field in the negative direction. Hence, the adsorption strength and sensitivity of gas on MnG can be effectively tuned by the E-field. The results can serve as useful references for the design of graphene-based gas sensor.