Ratiometric Optical Sensing of Hydrogen Sulfide at Room Temperature Using CsPbBr _<b>3</b> and InP/ZnSeS Quantum Dots for Environmental and Industrial Monitoring

This study presents a facile fabrication method for an optical sensing film designed for the detection of H2S at the ppb level, based on a ratiometric approach using CsPbBr3 and E610-InP/ZnSeS quantum dots. The sensing film exhibited excellent linearity, with correlation coefficients (R2) of 0.9684 in the 100–500 ppb range and 0.9844 in the 1–10 ppm range, while maintaining high reproducibility with relative standard deviations (RSD) below 5.2%. Minimal interference was observed from O2 (100%), CO2 (100%), NO (100 ppm), NH3 (300 ppm), and water vapor. Furthermore, the film demonstrated robust photostability under continuous LED illumination for 90 min. At a concentration of 10 ppm, the response time (↓t90) and recovery time (↑t90) were 95 and 490 s, respectively. Mechanistic investigations using XRD, Raman spectroscopy, temperature-dependent analysis, partial irreversibility assessment, and Stern–Volmer evaluation confirmed that photoluminescence quenching in CsPbBr3 arises from both static and dynamic mechanisms, involving PbS formation and excited-state energy transfer, respectively. The integration of stable E610-InP/ZnSeS reference quantum dots enabled real-time signal normalization, ensuring reproducible and reliable H2S detection under varying environmental conditions. These results highlight the potential of the proposed ratiometric sensing film for H2S monitoring across a broad concentration range, suitable for environmental and industrial monitoring applications.