1e:T4a7,The interactions between four different graphenes (including pristine, B- or N-doped and defective graphenes) and small gas molecules (CO, NO, NO(2) and NH(3)) were investigated by using density functional computations to exploit their potential applications as gas sensors. The structural and electronic properties of the graphene-molecule adsorption adducts are strongly dependent on the graphene structure and the molecular adsorption configuration. All four gas molecules show much stronger adsorption on the doped or defective graphenes than that on the pristine graphene. The defective graphene shows the highest adsorption energy with CO, NO and NO(2) molecules, while the B-doped graphene gives the tightest binding with NH(3). Meanwhile, the strong interactions between the adsorbed molecules and the modified graphenes induce dramatic changes to graphene's electronic properties. The transport behavior of a gas sensor using B-doped graphene shows a sensitivity two orders of magnitude higher than that of pristine graphene. This work reveals that the sensitivity of graphene-based chemical gas sensors could be drastically improved by introducing the appropriate dopant or defect.1f:T550,A gas sensor is used to detect SF₆ decomposed gases, which are related to insulation faults, to accurately assess the insulated status of electrical equipment. Graphene films (GrF) modified with Au nanoparticles are used as an adsorbent for the detection of H₂S and SOF₂, which are two characteristic products of SF₆ decomposed gases. Sensing experiments are conducted at room temperature. Results demonstrate that Au-modified GrF yields opposite responses to the tested gases and is thus considered a promising material for developing H₂S- and SOF₂-selective sensors. The first-principles approach is applied to simulate the interaction between the gases and Au-modified GrF systems and to interpret experimental data. The observed opposite resistance responses can be attributed to the charge-transfer differences related to the interfacial interaction between the gases and systems. The density of states and Mulliken population analysis results confirm the apparent charge transfer in Au-modified GrF chemisorption, whereas the van der Waals effect dominates the pristine graphene adsorption systems. Calculation results can also explicate the significant SOF₂ responses on Au-modified GrF. This work is important in graphene modulation and device design for selective detection.

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