Room-temperature H2S gas sensing by selectively synthesized Cux(x=1,2)O:SnO2 thin film nanocomposites with oblique & vertically assembled SnO2 ceramic nanorods

Abstract

A facile spray method was adopted to fabricate hierarchical Cux(x=1,2)O:SnO2 thin film nanocomposites with an oblique and vertical assembly of SnO2 ceramic nanorods for hazardous H2S gas sensing at room temperature (24.0 +/- 1 degrees C). The CuO- and Cu2O-doped SnO2 films were selectively synthesized by a one-step heat treatment process from an identical precursor on the surface of a spray-deposited SnO2 film. The coordination of CuxO doping layers with thicknesses less than 5 nm scattered on the extended SnO2 nanorods (30-80 nm thick) created numerous domains of p-n heterojunctions on the resulting CuO:SnO2 film surfaces, which led to enhanced adsorption sites when exposed to sub-ppm concentrations of H2S gas. The Cu2O-doped SnO2 thin films exhibited a fast response (21 s) and recovery speed (204 s) to 5 ppm H2S and 10% response upon exposure to 500 ppb H2S. Besides, the nanohybrid sensor showed excellent selectivity towards other gases such as CO2 and H2 including toxic NO2 and, NH3 gases at room temperature (24.0 +/- 1 degrees C). The mechanism for the enhancement of the H2S gas sensing was elucidated with respect to the unique hierarchical surface morphology and generation of active sites.