A Review on Fluorescent Molecular Probes for Hg 2+ Ion Detection: Mechanisms, Strategies, and Future Directions

Abstract Fluorescent molecular probes have gained significant attention due to their exceptional attributes, such as enhanced specificity, sensitivity, and reversibility. This review explores how organic probe molecules' fluorescence properties change when metal ions like Hg 2+ bind to the probe receptors. The alteration in fluorescence properties results from distinct photophysical mechanisms such as photoinduced electron transfer, proton transfer, energy transfer, charge transfer, excimer formation, aggregation‐induced emission, and C═N isomerization etc. Besides, Hg 2+ ions induce chemical reactions resulting in changes in structural conformation and fluorescence properties. As a result, this effect specifically affects the fluorescence signal of probe molecules, which is beneficial for advancing the fluorescence sensor technology developed to detect Hg 2+ contamination. Focusing on environmental pollution and biological sample analysis, this study highlights applying fluorescent techniques using organic chromophores to detect heavy metal ions, particularly Hg 2+ ions. Thus, fluorescent organic dyes with modifiable functional groups ensure precise detection and analysis, offering a robust platform for environmental monitoring and public health safety. We examine their detection capacities, sensing mechanisms, detection limits, strategies, and methodologies utilized. This review article provides significant insights into the efficacy and progress in the domain of fluorescent sensors for detecting Hg 2+ ions.