Quantum chemical studies of mercaptan gas detection with calcium oxide nanocluster

The electronic sensitivity and adsorption behavior for mercaptan natural gas of a Ca₁₂O₁₂ nanocluster were studied via ab initio computations. To be more specific, to fully grasp the influence of mercaptan molecules on the chemical and electronic features of Ca₁₂O₁₂ nanocluster, some parameters, namely, charge transfer of natural bond orbital, molecular electrostatic potential, binding energies, and frontier molecular orbitals, are computed. The interaction between CH₄S molecule and calcium atoms of Ca₁₂O₁₂ nanocluster through the sulfur head is strong. This strong interaction leads to a considerable transfer of charge from CH₄S to the nanocluster. After mercaptan adsorption, the existing energy gap between two levels, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the nanostructure, dropped by 2.21 eV, illustrating that the dissociation process has extensively increased the electrical conductance of nanostructure. This electrical signal can help to detect CH₄S molecules. Moreover, it could be concluded that Ca₁₂O₁₂ nanocluster has a short recovery time. In addition, solvent considerably influences the geometry factors and electronic features of CH₄S/Ca₁₂O₁₂ complexes, and the interactions between species are significantly weaker in the aqueous medium compared with those in the vacuum.