WO3/CuWO4 nanocomposite thin films for humidity resilient acetone gas sensing

• Sequential sputtering of CuO nanoparticles and WO₃ films creates tailored WO₃/CuWO₄ nano heterostructures. • Thermal stabilization induces formation of ternary CuWO4 phase at the interfaces. • Optimized WO 3 /CuWO 4 composite showed superior acetone sensing response (S = 23) at 300 °C. • Humidity interference reduced by 95 % compared to pristine WO 3 , maintaining stability even at 90 % RH. • Synergy of heterojunctions & Lewis acidic sites enhanced charge transfer and selectivity. • Detection limit is as low as 0.6 ppm with fast response (38 s dry / 58 s humid), suitable for breath-based diagnostics. We demonstrate a high-performing and selective acetone gas sensor based on WO 3 /CuWO 4 nanocomposites produced by sequentially sputter-deposited WO 3 thin films and CuO nanoparticles, engineered to reduce the humidity interference. By optimizing deposition order and layer thicknesses, we harnessed synergistic p - n / n - n heterojunctions and the formation of a catalytic CuWO₄ ternary phase. The best performing configuration (20 nm of tungsten oxide film on top of nanoparticles) exhibits a high response ( S = 23) to 10 ppm acetone at 300 °C, fast response in dry/humid conditions (38 s/58 s), and low detection limit (0.6 ppm). More importantly, the sensor exhibited > 95 % retention of its response in 90 % relative humidity compared to a loss of >50 % for pristine WO 3 . The reduced humidity interference is assigned to heterojunction formation at the WO 3 /CuWO 4 interface, Lewis acid sites that allow for acetone selective adsorption, and bulk-dominated conduction. This noble-metal-free acetone sensor overcomes a known shortcoming of metal oxide-based sensors, enabling accurate acetone detection in humid environments for breath-based disease diagnosis ( e.g. , diabetes) and industrial safety monitoring.