Single-molecule fluorescent probes for metal ion detection in food: From coordination mechanisms to real-world testing

Metal ion contamination in food poses severe health risks, necessitating rapid, sensitive, and selective detection strategies. Fluorescent probes have emerged as powerful tools for on-site monitoring due to their high sensitivity, structural tunability, and compatibility with complex food matrices. This review critically analyzes recent advances in fluorescent probes for food safety, focusing on photophysical modulation mechanisms such as photoinduced electron transfer (PET), intramolecular charge transfer (ICT), and chelation-enhanced fluorescence (CHEF). Detailed studies highlight probes for toxic (Ag⁺, Pb2⁺, Hg2⁺, Cd2⁺, Cr6⁺, Cu2⁺) and essential (Zn²⁺, Fe²⁺, Al³⁺) ions, incorporating DFT-based structural insights, binding stoichiometry, and practical applications in diverse food samples. Comparative evaluations identify structure relationships, synthetic design strategies, and performance determinants, concluding with a discussion on the most efficient and least effective systems. The review further outlines emerging trends, including smartphone-assisted sensing, NIR-emissive probes, and multi-analyte platforms, providing a roadmap for translating molecular designs into industrial-scale food safety solutions.