There is fast growing research on designing and improving the metal recognition methodologies in the ecosystems and biological media. The fluorescent based techniques proved a mile stones for non-invasive metal sensation and quantification in the multichannel environment. Metals as the natural components of Earth's crust are generally present in trace concentrations in the environmental samples where the humic substances have complexation affinity toward them. Iron, zinc and copper are the 1 st , 2 nd and 3 rd adequate elements indispensable to the body in trace playing the crucial roles in many biological processes. However, the unregulated amounts either as excess or deficient may exacerbate deterioration to the vital organs and triggered the progression of complications. Beside these three essential elements, mercury is widely considered to be one of the most hazardous pollutants and highly dangerous elements due to its recognized accumulative and toxic characters in the environment and the ecosystem. In the current scenario, we have tried to summarize the maximum amount of recently developed fluorescent signaling materials for the Cu 2+ , Fe 2+ / Fe 3+ , Zn 2+ and Hg 2+ . The spectral shifting in the molecules on metal chelation, mode of complexation and stoichiometries of resulting adducts have been discussed in detail. Furthermore, the molecules which have been reported as intracellular metal detector via bioimaging are specifically highlighted that might be useful for the design and development of cell viable and membrane permeable molecular probes in the future perspective.

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Due to the deleterious effects of mercury on human health and natural ecosystems, high reactivity, non-degradability, extreme volatility and relative water and tissue solubility, it would consider as one of the most toxic environmental pollutants among the transition metals. In the present investigation, we have tried to summarized the several organic material based fluorescent sensor including rhodamine, boron-dipyrromethene (BODIPYs), thiourea, crown-ether, coumarine, squaraines, pyrene, imidazole, triazole, anthracene, dansyl, naphthalenedimide/ naphthalene/ naphthalimide, naphthyridine, iridium (III) complexes, polymeric materials, cyclodextrin, phthalic anhydride, indole, calix [4]arene, chromenone, 1,8-naphthalimides, lysine, styrylindolium, phenothiazine, thiocarbonyl quinacridone, oxadiazole, triphenylamine-triazines, tetraphenylethene, peptidyl and semicarbazone for the trace mercury detection in the aqueous, aqueous-organic and cellular media. The present review provides a brief look over the previous development in the organic material based fluorescent sensor for mercuric ion detection. Furthermore, the ligand-metal binding stoichiometry, binding/association/dissociation constants and the detection limit by the receptors have been particularly highlighted which might be useful for the future design and development of more sensitive and robust fluorescent chemosensor/chemodosimeter for the mercuric ion detection. Graphical Abstract Dummy.