A thiourea-based fluorescent turn-on chemosensor for detecting Hg2+, Ag+ and Au3+ in aqueous medium

Abstract

A thiourea based fluorescence chemosensor (L) was synthesized and applied for the selective detection of Hg2+, Ag+ and Au3+ions in DMSO-H2O (10:90, v/v). The receptor L showed a weak fluorescence emission in DMSO-H2O due to the photo-induced electron transfer (PET) process. The fluorescence intensity of L was enhanced upon addition of Hg2+, Ag+ and Au3+ ions because of the complexation-induced inhibition of PET process. The 1:1 binding stoichiometry between L and the metal ions (Hg2+, Ag+ and Au3+) was found from the Benesi-Hildebrand plot. The density functional theory (DFT) calculations were performed to explain the binding modes. The estimated binding constants and detection limits of L are found to be 5.87 × 106 M−1 and 5.01 × 10-7 M for Hg2+, 8.78 × 106 M−1 and 2.14 × 10-8 M for Ag+, and 7.93 × 106 M−1 and 34 × 10-7 M for Au3+, respectively. The sensor L was applied to detect Hg2+, Ag+ and Au3+ ions in living Drosophila cell lines. Also, sensor L was employed to detect Hg2+ in soil samples.