Superior selectivity for NH3 (NO2) gas molecules in In2SSe (Ga2SSe) Janus materials: a first-principles study

Abstract Anthropogenic gasses are very detrimental, requiring superior sensitive and selective materials to sense and segregate them. Using first-principles density functional theory (DFT) tools we have explored the sensitivity and selectivity of CO 2 , CO, NH 3 , NO 2 , H 2 S, and SO 2 gases in the promising group-III Janus Ga 2 SSe and In 2 SSe nanostructured materials. We have explored all the possible adsorption sites in the Ga 2 SSe and In 2 SSe monolayer for sensing the gases and found that all the gasses are physisorbed in the sites with the lowest adsorption energy of −0.392 eV (−0.167 eV) for NH 3 (NO 2 ) on top of Indium (on the bridge-3 site) site of In 2 SSe (Ga 2 SSe). All adsorbed gasses significantly alter the bandgap of Ga 2 SSe and In 2 SSe from their pristine value and NO 2 -adsorbed M 2 SSe (M = Ga, In) structure exhibits significant bandgap changes: ∼0.16 eV reduction in Ga 2 SSe and ∼0.3 eV reduction in In 2 SSe from the pristine value, signifying substantial increase in conductivity. Additionally, analyzing the total density of states (TDOS), it can be concluded that NH 3 at the Indium site of In 2 SSe and NO 2 at the Bridge-3 site of Ga 2 SSe exhibit the most significant conductivity changes. Considering charge transfer, it is determined that 0.727 e/Å −3 of charge is transferred from In 2 SSe to NH 3 , while 1.05 e/Å −3 of charge is transferred from Ga 2 SSe to NO 2 gas molecules, inferring that both NH 3 and NO 2 act as electron acceptors. Through this analysis, we found that NH 3 is very selective on In 2 SSe while NO 2 is selective on Ga 2 SSe Janus materials among the control gasses. This selectivity toward NH 3 (NO 2 ) gas on In 2 SSe (Ga 2 SSe) Janus material can open the new possibility of these materials for noxious gas sensing as well as NO 2 utilization applications.