Theoretical research of toxic gases adsorbed by Mo-doped two-dimensional VS<sub>2</sub> structure

Abstract

As is well known, the leakage of four toxic gases, NO<sub>2</sub>, NH<sub>3</sub>, mustard gas and sarin greatly threaten the environment and human health. Among of them, mustard gas and sarin are two serious chemical and biological weapons agents, and exposure to a small amount can cause skin burns and immediate death. NO<sub>2</sub> and NH<sub>3</sub> are two common toxic pollutants produced by automobile exhaust, coal combustion and petrochemical industry. The presence of trace amounts of NO<sub>2</sub> and NH<sub>3</sub> gas in human tissues can cause serious respiratory diseases and damage human brain and other systems. Thus, it is very important to realize the rapid detection of NO<sub>2</sub>, NH<sub>3</sub>, mustard gas and sarin in academia and industry. In this study, we use density functional theory to investigate the ability of a transition metal Mo doped two-dimensional VS<sub>2</sub> structure to detect the four representative toxic gases. The results reveal that Mo atom doping has a significant effect on the stability and gas-sensitivity of the VS<sub>2</sub> structure. The Mo atom can be successfully doped on the S-vacancy in the two-dimensional VS<sub>2</sub> structure. Compared with the undoped structure VS<sub>2</sub>, the doped structure Mo-VS<sub>2</sub> has strong interaction with NO<sub>2</sub>, NH<sub>3</sub>, sarin, and mustard gas, realizing effective adsorption of them. The presence of Mo atom in the VS<sub>2</sub> lattice changes the electronic structure of VS<sub>2</sub>, also modifies its band gap and density of states. The interaction between the Mo-VS<sub>2</sub> structure and the target analytes depends strongly on the nature of the gas molecule. The binding energy values for NO<sub>2</sub>, NH<sub>3</sub>, mustard gas, and sarin on the Mo-VS<sub>2</sub> are significantly higher than those on the pristine VS<sub>2</sub>, indicating stronger interaction between the Mo-VS<sub>2</sub> structure and these gases. Our calculations show that the Mo atom in VS<sub>2</sub> changes its electrical resistance after being exposed to the gases, which can be used to distinguish different gases. Moreover, differences in charge redistribution within the Mo-VS<sub>2</sub> structure upon being exposed to different gases can be used to explain their differential gas-sensitivity. Our results can provide sufficient theoretical basis for experimental researchers to design and optimize the performances of sensors in practical applications.