Spacer-induced dual monomer emission in pyrene-uryl chemosensors for Hg(2+) detection across vegetables, seafood, plants, cosmetics and cells.

Two newly designed thiourea-derived fluorescent chemosensors, APS and PMS, were synthesized from pyrene fluorophore and phenyl isothiocyanate and characterized by H NMR, C NMR, and mass spectrometry. The spacer-induced dual monomer emission in these pyrene-uryl chemosensors enabled selective detection of Hg and pesticides in DMSO-HO (1:1, pH 7.4). Hg sensing occurred via PET suppression with enhanced fluorescence intensity, while Job's plots and binding studies confirmed a 1:1 stoichiometry. The detection limit (LOD) and limit of quantification (LOQ) of Hg were found to be 1.0 μM and 3.6 μM for APS and 0.5 μM and 1.9 μM for PMS respectively. Probe APS selectively bound MNZ through fluorescence quenching, whereas the probe PMS showed specificity for AZA with a distinct, red-shifted emission. Fluorescence lifetime decay and quantum yields were evaluated to support the sensing mechanism. Furthermore, both probes were successfully applied for Hg detection in seafood, cosmetic samples, and bacterial imaging (E. coli), as well as for pesticide detection in fruits, vegetables, and soil.