Fluorescent sensors for volatile acids: design strategies and sensing mechanisms

With increasing demands in industrial safety, environmental monitoring, and public health, the highly sensitive and selective detection of acidic species in the gas phase has become particularly critical. Conventional analytical techniques, while accurate, are often hindered by complex instrumentation and time-consuming procedures. In contrast, fluorescence sensing technology offers rapid response, high sensitivity, and real-time visual detection, positioning it as an emerging tool for acid vapor sensing. This review establishes a structure-property-performance framework by bridging fundamental photophysical mechanisms with rational material design. We systematically categorize sensing mechanisms into five classes: aggregation-induced emission (AIE), photoinduced electron transfer (PET), Förster resonance energy transfer (FRET), excited-state intramolecular proton transfer (ESIPT), and intramolecular charge transfer (ICT). Building upon this foundation, we further analyse the research progress of small-molecule probes, polymers, and porous organic materials, as well as quantum dots for acid vapor sensing. By elucidating the correlations between material types, structures, and sensing performance, this review provides actionable design principles for the development of next-generation acid vapor sensors.