Detection of chloride ions in hydrochloric acidic wastewater using DBSA-stabilised CsPbBr₃ perovskite quantum dots

Abstract

Perovskite quantum dots (PQDs) show great promise for chloride ion (Cl⁻) detection in acidic laboratory wastewater owing to their excellent optical properties. However, their practical applications have been severely hampered by intrinsic instability. In this study, a method for the rapid detection of Cl⁻ was developed using PQDs modified with dodecylbenzenesulfonic acid (DBSA), which effectively enhanced stability. Optimised synthesis yielded PQDs with more uniform size and enhanced stability. After 15 days in ambient air, the DBSA-modified PQDs retained 70% of their initial PL intensity, in contrast to 30% for unmodified ones. Furthermore, the average carrier lifetime increased from 6.62 ns to 11.54 ns, indicating suppressed non-radiative recombination. A highly sensitive fluorescence-based sensor for Cl⁻ was constructed using these optimised PQDs. It showed a broad linear detection range between 0.274 and 2.741 M (R² = 0.98454), effectively covering the typical concentration range (1-10%) found in laboratory hydrochloric acid waste, and exhibited high specificity for Cl⁻ in complex aqueous matrices. This is attributed to the fact that the sensor operates via a specific halide exchange mechanism, where Cl⁻ in the solution replaces Br⁻ in the PQDs, causing the PL emission to gradually shift to the blue. This reliable sensing performance, combined with the visual detection capability, provides a valuable approach for monitoring acidic wastewater, thereby contributing to environmental protection efforts.