Adsorption property of volatile molecules on ZnO nanowires: computational and experimental approach

Abstract

ZnO nanowires (NWs) were deposited on a glass substrate by the successive ionic layer adsorption and reaction method (SILAR). Sensing response of ZnO NWs towards reducing vapours was tested at ambient temperature $({\sim }32{^{\circ }}\hbox {C})$ by the chemiresistor method. The vapour response was found to be 80.2, 1.6, 1.1 and 1.1 for $\hbox {NH}_{3}, \hbox {H}_{2}\hbox {O}, (\hbox {CH}_{3})_{2}\hbox {CO}$ and $\hbox {C}_{2}\hbox {H}_{5}\hbox {OH}$, respectively. Also, density functional theory (DFT) calculations were performed to understand the charge transfer and electronic property change during adsorption of molecules over ZnO NW. The band of the Zn 3d state was altered after adsorption and no significant changes were observed in the O 2p state. Higher binding energy (14.6 eV) with significant charge transfer ($0.04{\vert }e{\vert }$) was observed in the ammonia-adsorbed ZnO NW. On comparing response obtained through experimental and computational studies, almost a similar trend of response was observed except for the $\hbox {H}_{2}\hbox {O}$–$\hbox {ZnO}$ system. This was due to lack of dispersion interaction and steric effect influence in the DFT calculation with the chosen computational methods.