Large-Scale Fabrication of Fully Printed, Photoactivated Au Decorated Tin Oxide Based Room-Temperature NO 2 Sensors With Ultrahigh Response on Paper Substrates

Conventional metal oxide gas sensors require high-temperature operation (200-300°C), which limits integration with sustainable and biodegradable substrates and contributes to electronic waste. Herein, we demonstrate fully screen printed, room-temperature NO₂ sensors using UV-photoactivated Au decorated SnO/SnO₂ nanoparticles on paper. Tin oxide nanoparticles have been synthesized via precipitation and annealing, followed by controlled Au decoration (0.5 wt.%) through ascorbic acid reduction. Subsequently, screen printing enables scalable device fabrication with interdigitated Ag electrodes and Au-SnO/SnO₂ sensing layers on photo paper. Under 365 nm UV illumination (2.1 mW/cm²), the sensors have exhibited an excellent response of 871 for 3.2 ppm NO₂ at room temperature. The devices demonstrate remarkable sensitivity across 1.4-3.2 ppm level. Response and recovery times have been 253 s and 1120 s, respectively. Excellent selectivity toward NO₂ has been demonstrated against five interfering gases, with stable performance over repeated cycles. Successful integration into a portable USB-powered module has been demonstrated to showcase practical deployment capability. This approach offers a sustainable, scalable route for room-temperature gas sensing suitable for environmental and occupational health monitoring.