Abstract
Perovskite nanocrystals (PeNCs) exhibit excellent optoelectronic properties including high quantum yield and tunable bandgap, making them promising for fluorescent sensing. However, their water sensitivity limits aqueous-phase applications. This review provides a critical analysis of strategies for preparing water-dispersible PeNCs, with a focused comparison between inorganic silica coating and organic polymer encapsulation in terms of their stability enhancement mechanisms, optical preservation, and ion permeability. We further explore applications in fluorescence-based ion sensing. Halide ions (Cl(-), I(-)) are detected via anion-exchange chemistry, while metal cations (e.g., Pb(2+), Cs(+), Fe(3+), Hg(2+), Cu(2+)) are sensed through the fluorescence quenching effect or ion-triggered crystallization. The structure-property-performance relationships governing sensing selectivity and sensitivity are analyzed, highlighting the essential balance between environmental stability and controlled ion accessibility. Beyond summarizing recent advances, this review outlines current challenges and future prospects toward multiplexed detection, point-of-care devices, and bioimaging, providing a roadmap for the rational design and practical deployment of PeNCs in next-generation aqueous sensing platforms.