Ultrasensitive Fluorimetric Detection of Hg Using a Thiourea-Based Chemosensor.

In this work we have successfully designed and synthesized a fluorescence "turn-on" chemosensor, TS-1. The structure of TS-1 was thoroughly investigated using H NMR, FT-IR, and fluorescence spectroscopy was used for confirming its suitability for sensing applications. TS-1 exhibited a significant fluorescence enhancement upon binding with Hg in a MeOH/HO (5:95, v/v) solvent system, demonstrating high selectivity when tested against various competing metal ions, including Pb, Ca, Na, Zn, Al, Cu, Ni, Mg, Cd, Mn, Co, Cr, Ag, and K. The sensing mechanism of TS-1 was explored in detail using fluorescence spectroscopy and Job's plot analysis. The results indicated the formation of a strong complex between TS-1 and Hg ions, leading to the disruption of a photoinduced electron transfer (PET) process resulting in fluorescence enhancement. TS-1 demonstrated exceptional sensitivity, with a detection limit as low as 0.0029 µg mL, making it highly suitable for detecting trace levels of Hg in aqueous media. The robust performance of TS-1 highlights its potential as an effective chemosensor for the detection of Hg. To validate the practical applicability of TS-1, recovery experiments were conducted using environmental and agricultural samples spiked with Hg ions. The method achieved impressive recovery ranging from 93.00 ± 0.14% to 104.00 ± 0.54%, confirming its accuracy and reliability across diverse sample matrices.