Effect of different strategies for modifying graphene on the adsorption and gas sensing of trimethylamine: Insights from DFT study

Graphene materials have shown a great promise for gas sensors, however, the effect of different modification strategies on gas sensing mechanisms has not been studied. In this research, the adsorption and sensitivity properties of trimethylamine (TMA) on pristine (PG), Zn-decorated (Zn-G1), Zn-doped (Zn-G2), ZnN4-embedded (ZnN4-G), Zn-defect combined (ZnC4-G) graphene are carefully discussed by density functional theory (DFT) calculations. Among five substrates, Zn-G2, ZnN4-G, and ZnC4-G exhibit high sensitivity and selectivity toward TMA due to the shorter adsorption distances, large amount of charge transfer and stronger adsorption strengths. Especially for Zn-G2, energy gap and work function are obviously altered after interaction with the TMA molecule. The recovery time of ZnN4-G and ZnC4-G are 269 and 6 s at 398 K, respectively. When the conditional temperature reaches 498 K, the recovery time of Zn-G2 only takes 91 s by applying negative electric field of 8 x 106 a.u. Such short recovery time makes Zn-G2, ZnN4-G, and ZnC4-G as a reversible gas sensor. Moreover, the applied positive electric fields can further enhance the selectivity and sensitivity of Zn-G2, ZnN4-G, and ZnC4-G. In light of these findings may provide theoretical guidance for developing high selectivity and sensitivity graphene-based gas sensor.