A theoretical simulation of small-molecules sensing on an S-vacancy SnS₂ monolayer

Using first-principle atomistic simulations, we focused on the electronic structures of small gas molecules (CO, H₂O, NH₃, NO, and NO₂) adsorbed on the S-vacancy SnS₂ monolayer. The results show that H₂O and CO molecules were physisorbed on the S-vacancy SnS₂ monolayer, whereas NH₃, NO, and NO₂ molecules were chemisorbed on the S-vacancy SnS₂ monolayer via strong covalent bonds. Moreover, our calculations show that H₂O and NH₃ act as charge donors, whereas CO, NO, and NO₂ gas molecules act as acceptors. Different adsorption behaviors of common gas molecules on the S-vacancy SnS₂ monolayer provide a feasible way to exploit chemical gas sensors and electrical devices. In particular, our results also show that under applied biaxial strains, the adsorption energy and charge transfer of gas molecules on the S-vacancy SnS₂ monolayer dramatically changed, which indicates that external factors on the S-vacancy SnS₂ monolayer are highly preferred.