Fluorescent Chemosensors in the Detection of Ultra-trace Quantity of Toxic Hg2+, Pb2+, Al3+, F-, AsO43- & AsO33- in Water Towards Better Health Management-A Comprehensive Review.

Chemosensors have extensive applications in chemical, biological and environmental sciences. Fluorescent chemosensors are the most powerful techniques for rapid detection of ultra-trace quantity of inorganic ions in water samples with high sensitivity. Water is contaminated with various pollutant ions e.g., Cd2+ Cu2+, Hg2+, Pb2+, Mn2+, Zn2+, Al3+, AsO43-, AsO33- and F- due to increase industrialisation, usage of fertilizers, through food -beverages, water purification instruments and e-wastes. Thus, contaminated water is a potential threat to life as it transmits various bacterial waterborne diseases, so detection of contaminants is essential. This review focuses the recently developed single, dual and multi-analyte fluorescent chemosensors ligands for the detection through selective binding of trace quantity of critically toxic ions e.g., Hg2+, Pb2+ Al3+, F-, AsO33- and AsO43- in water and food samples. Binding of ions through Sensing mechanism: Intramolecular Charge transfer (ICT), Foster Resonance energy transfer (FRET), Aggregation based approaches, Photo induced electron transfer (PET) etc. have also discussed. Ligands i) derivatives of rhodamine dyes and phenanthroline ii) Schiff base with rhodamine B thiohydrazide and quinoline moiety iii) a chromone-quinolinyl hydrazide Schiff base as dual sensors iv) Nitro-furaldehyde based Schiff base as multi-analyte sensors having potential doner atoms to bind the concerned ions and easily synthesizable have been selected for reviews. The detections of toxic ions were accomplished by spectroscopic studies. Such comprehensive review has not yet been reported. This review emphasizes the works of pioneering researchers on chemosensors during the period 1990-2025. This review will also help future researchers to design new Schiff bases chemosensor and its selectivity for the detection of trace quantity of hazardous ions from environment and biological samples thereby monitoring human health.