Interface-engineered perovskite nanocrystal composites for Hg 2+ sensing: surface functionalization, interphase design, and structure–mechanism relationships

Perovskite nanocrystals (PNCs) have emerged as highly responsive fluorescent materials for Hg2+detection owing to their defect-tolerant lattices, strong excitonic absorption, and surface-dominated photophysics. However, PNC sensing performance is fundamentally governed by the structure and chemistry of their interfaces, where stability, ion accessibility, and interfacial charge-transfer pathways are simultaneously defined. This review examines recent advances in interface and interphase engineering strategies that transform fragile PNCs into stable and selective Hg2+sensing platforms. The transition from hybrid MAPbX3 to all-inorganic CsPbX3 systems is discussed in relation to lattice rigidity and interfacial reactivity. Surface functionalization approaches, including bifunctional, zwitterionic, and thiol-based ligands, are analyzed for their roles in regulating trap states, adsorption behavior, and ion-exchange kinetics at the nanocrystal interface. Composite architectures based on metal – organic frameworks, polymer matrices, and silica shells are further evaluated as interphase designs that control analyte diffusion while enhancing environmental robustness. Dominant sensing mechanisms, including surface-driven ion exchange and photoinduced electron transfer, are systematically correlated with interfacial structure and composite morphology. To the best of our knowledge, this work provides one of the first comprehensive reviews integrating materials design, interfacial mechanisms, and stability engineering specifically for PNC-based Hg2+ sensing.