Perovskite Quantum Dot-Based Luminescent Sensors for Cu2+ Detection: Stability Engineering and Performance Across Aqueous, Organic, and Confined Media.

Perovskite quantum dots (PQDs) have emerged as highly promising luminescent materials for sensitive and selective detection of heavy metal ions, particularly Cu2+, owing to their exceptional photophysical properties, defect-tolerant structures, and tunable surface chemistry. However, their practical implementation remains limited by intrinsic instability, environmental sensitivity, and incomplete mechanistic understanding. This review provides a design-driven framework that integrates fundamental principles, advanced engineering strategies, and mechanistic insights essential for developing next-generation PQD-based luminescent sensors. Key aspects discussed include the evolution of synthesis routes, the impact of surface defects and ligand dynamics on optical response, and the roles of encapsulation, compositional tuning, polymeric confinement, and MOF-based architectures in overcoming moisture, oxygen, and thermal degradation pathways. Signal transduction mechanisms such as electron transfer, FRET, ratiometric emission, and aggregation-induced modulation are critically analyzed with emphasis on their relevance to Cu2+ sensing performance. By summarizing analytical metrics, stability barriers, and emerging hybrid platforms, this review highlights strategic directions for achieving high-performance, reproducible, and durable PQD sensors. The insights presented establish a foundation for rational design and application-oriented development of luminescent PQD-based Cu2+ detection technologies.