Perovskite quantum dot-based gas sensors for environmental monitoring: mechanisms, materials, and perspectives on next-generation pollution control.

Perovskite quantum dots (PQDs) have recently emerged as transformative nanomaterials for gas sensing, offering exceptional optoelectronic properties, high surface-to-volume ratios, and compositional tunability. This is the first comprehensive review that systematically analyzes gas sensing technologies based on PQDs, with a particular emphasis on their relevance to environmental monitoring and pollution control. We summarize the latest advances in sensing mechanisms-including fluorescence quenching and enhancement, ratiometric detection, and chemiresistive/conductometric responses-and evaluate how synthesis strategies, surface ligand engineering, and hybrid architectures govern sensor performance. Key applications are critically assessed in the detection of toxic gases (NO2, NH3, H2S, SO2), volatile organic compounds, oxygen, and humidity, all of which are central to air quality assessment and environmental safety. Special focus is given to stability challenges under ambient and humid conditions, the environmental toxicity of lead-based PQDs, and mitigation strategies such as encapsulation, ligand engineering, and the development of lead-free alternatives. By integrating nanoscale material design with real-world environmental needs, this review not only consolidates current knowledge but also provides forward-looking perspectives for developing robust, selective, and sustainable PQD-based sensors for next-generation environmental monitoring systems.