Theoretical screening into Urea-based receptor as a promising toxic gas sensor upon SO2, NH3 and H2S

Abstract

The adsorption of toxic gases such as NH3, SO2, H2S, on 1,3 bis (4-nitrophenyl) urea (BNPU) was investigated via the M062X/6-311++ g (d, p) level of theory to evaluate the utility of BNPU-based gas sensors. For each gas molecule, the most stable configuration was determined and the adsorption energies were calculated. The trend of adsorption stability of complexes is observed as, SO2@BNPU≈NH3@BNPU>H2S@BNPU. Further, electronic properties such as orbital analysis, natural bond orbital analysis, and density of states were investigated to understand the mechanism of sensing. The HOMO-LUMO gap was lowered upon adsorption with these gases. The QTAIM analysis was carried out to sketch the nature of the hydrogen bond. An external electric field (EF) of intensity -0.15 V/Å up to +0.15 V/Å was used to further improve the toxic gas-sensing properties of the BNPU. Furthermore, the presence of the EF has a significant effect on the dipole moment and the HOMO-LUMO energy gap.