Novel Janus MoSiGeN 4 nanosheet: adsorption behaviour and sensing performance for NO and NO 2 gas molecules.

A novel Janus MoSiGeN 4 nanosheet is proposed for detecting poisonous gas molecules. Herein, the adsorption behaviour and sensing performance of both sides of the MoSiGeN 4 monolayer to NO and NO 2 gas molecules were investigated by first-principles calculations. Firstly, it is found that the MoSiGeN 4 monolayer exhibits structural stability and indirect gap semiconductor characteristics. The largest adsorption energy of NO 2 molecules on the MoSiGeN 4 monolayer is -0.24 eV, which is higher than the -0.13 eV for NO molecules. Of course, the physisorption between gas molecules and the MoSiGeN 4 monolayer appears with slight charge transfer. It is confirmed that NO molecules and NO 2 molecules act as electron donors and electron acceptors, respectively. Meanwhile, the generation of small band gaps and impurity levels in the electronic structures after gas adsorption is in favour of the enhancement of electronic conductivity. Furthermore, the longest recovery times of NO and NO 2 molecules are predicted to be 0.15 and 10.67 ns at room temperature, and the lateral diffusion at the surface requires crossing a large energy barrier. These findings provide indisputable evidence for further design and fabrication of highly sensitive gas sensors based on the MoSiGeN 4 monolayer.