Synergistic Effects of PdOx–CuOx Loadings on Methyl Mercaptan Sensing of Porous WO3 Microspheres Prepared by Ultrasonic Spray Pyrolysis

In this work, PdO x –CuO x co-loaded porous WO 3 microspheres were synthesized with varying loading levels by ultrasonic spray pyrolysis (USP) using polymethyl methacrylate (PMMA) microspheres as a vehicle template. The as-prepared sensing materials and their fabricated sensor properties were characterized by X-ray analysis, nitrogen adsorption, and electron microscopy. The gas-sensing properties were studied toward methyl mercaptan (CH 3 SH), hydrogen sulfide (H 2 S), dimethyl sulfide (CH 3 SCH 3 ), nitric oxide (NO), nitrogen dioxide (NO 2 ), methane (CH 4 ), ethanol (C 2 H 5 OH), and acetone (C 3 H 6 O) at 0.5 ppm under atmospheric conditions with different operating temperatures ranging from 100 to 400 °C. The results showed that the CH 3 SH response of USP-made WO 3 microspheres was collaboratively enhanced by the creation of pores in the microsphere and co-loading of CuO x and PdO x at low operating temperatures (≤200 °C). More importantly, the CH 3 SH selectivity against H 2 S was significantly improved and high selectivity against CH 3 SCH 3, NO, NO 2, CH 4, C 2 H 5 OH, and CH 3 COCH 3 were upheld by the incorporation of PdO x to CuO x -loaded WO 3 sensors. Therefore, the co-loading of PdO x –CuO x on porous WO 3 structures could be promising strategies to achieve highly selective and sensitive CH 3 SH sensors, which would be practically useful for specific applications including biomedical and periodontal diagnoses.