Preparation, characterization of WO3–SnO2 nanocomposites and their sensing properties for NO2

WO3–SnO2 nanocomposites of various compositions have been successfully synthesized by a controlled two-step sol-precipitation method using tin chloride and ammonium metatungstate hydrate as precursors. The performances of the material were characterized by various analysis methods. The sensors based on the nanocomposites were used to detect the NO2 at operating temperature range 100–300 °C, the response is defined as the ratio of the sensor resistance in an air–NO2 mixture to that in air (Rg/Ra). The experimental results show that the 20 mol.% WO3–SnO2 nanocomposite based sensor exhibits the highest response of 186 to 200 ppm NO2 at operating temperature of 200 °C. The responses were further enhanced to 251 and 418 by doping 3 wt.% Zn element as dopant and 3 wt.% MgO as surface modifier, respectively, and the optimum operating temperature reduced to 150 °C. The doping effect and sensing mechanism were also discussed by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) analysis.