Zinc oxide nanoclusters and their potential application as CH and CO gas sensors: Insight from DFT and TD-DFT.

We have investigated the adsorption of CH and CO gases on zinc oxide nanoclusters (ZnO NCs) using density functional theory (DFT). It was found that the CH tends to be physically adsorbed on the surface of all the ZnO NCs with adsorption energy in the range -11 to -14 kcal/mol. Even though, the CO is favorably chemisorbed on the Zn O and Zn O NCs, with adsorption energy about -38 kcal/mol at B3LYP/6-311G(d,p) level of theory. When the CH and CO gases are adsorbed on the ZnO NCs, their electrical conductivities are decreased, and thus the studied ZnO NCs do not generate an electrical signal in the presence of CH and CO gases. Interestingly, both pure and gas adsorbed Zn O NC exhibited more favorable electronic and reactive properties than other NCs. Comparison of the structural, electronic, and optical data predicted by DFT/B3LYP and TD-DFT/CAM-B3LYP calculations with those experimentally obtained show good agreement.