UV-switchable dual-mode sensing in a lead-free CsCu₂I₃ perovskite sensor for selective detection of mixed amines

Traditional gas sensors often face challenges in distinguishing between mixed gases owing to their inherent cross-sensitivity, often necessitating complex multi-sensor arrays that increase cost and system intricacy. In this study, we introduce a novel UV-switchable dual-mode gas sensor based on mechanochemically synthesized CsCu₂I₃ microcrystals for selective amine detection at room temperature. The sensor exhibits an instantaneous p-type response to ethylamine (EtNH₂) under ambient conditions and enhanced sensitivity toward diethylamine (Et₂NH) under UV illumination. Leveraging this unique behavior, a single sensor enables quantitative analysis of mixed EtNH₂/Et₂NH gases via a matrix-based analytical approach, achieving <5 % deviation in concentration analysis. Structural and photophysical characterizations confirm the material's stability, with EtNH₂ inducing strong, reversible photoluminescence quenching and a reduced bandgap via charge transfer. The sensing mechanism follows an adsorption-desorption equilibrium model, where UV illumination accelerates catalytic oxidation, modulating selectivity. This work advances lead-free perovskite sensors by introducing a low-power, single-device strategy for multi-analyte detection, with promising applications in environmental monitoring and chemical diagnostics.