Quinoline-Thiourea Conjugate: A Dual-Modal Fluorescent Chemosensor for Selective Detection of Mercury and Cyanide Ions in Seafood, Soil, and Biological Systems.

A quinoline-thiourea conjugate probe, AQS, was developed to selectively detect Hg and CN ions in a DMSO:HO (1:1) buffer solution using fluorescence spectroscopy. Probe AQS, upon binding with Hg, the photon-induced electron transfer (PET) process is inhibited, assisted by the restriction of the C-N bond rotation resulting in significantly enhanced fluorescence intensity. Conversely, CN binding to the two NH groups triggers electron transfer from hydrogen to CN, modulating the PET process and enabling the quenching of fluorescence of the probe AQS. The binding stoichiometry of probe AQS with Hg and CN was determined to be 1:1 and 1:2, respectively, using Job's plot method. Density functional theory (DFT) calculations yielded energy gaps of 3.792 eV for probe AQS, and 0.758 and 0.711 eV for AQS-Hg and AQS-CN complexes, respectively. The sensor AQS demonstrated practical applicability in detecting Hg in real-world samples, including water, soil, and seafood, using PVA-coated gloves. The probe AQS successfully sensed mercury ions in E. coli bacterial cells, as visualized through laser confocal scanning microscopy, showcasing its potential for biological applications.