rGO-Modified ZnWO4/WO3 Nanocomposite for Detection of NH3

The composite of ZnWO4/12WO3-0.5 wt % rGO was successfully synthesized for the first time by one-step precursor calcination of equimolar W and Zn precursors, followed by loading rGO prepared by hydrazine reduction. The structure, composition, and morphology of the as-synthesized composite were characterized by various spectral analyses. Compared with reported metal-oxide-based NH3 sensors, our sensor can detect low concentrations of NH3, and the method used herein is simple, low-cost, and effective. The composite-based sensor exhibits the highest response of 10.1–20 ppm NH3, which is 3.98 times that of WO3, and has better selectivity and stability at an operating temperature of 140 °C. The improvement is attributed to the synergistic effect of p–n heterojunction formation and rGO decoration; the former creates an additional depletion layer to expand the resistance change in air and gas, while the latter provides more surface active sites to increase gas adsorption and accelerates the electron transfer for enhancing gas-sensing performance. The work has reference value to develop novel metal-oxide-based NH3 sensors.