A novel dual-function peptide-based fluorescent probe with large Stokes shift for the simultaneous detection and quantification of Ag(I) and Hg(II) ions.

Achieving highly selective detections of Ag and Hg is of great importance because their excessive emission can cause many diseases. Herein, a novel large Stokes shift fluorescent probe DKT based on dansyl fluorophore modified peptide biomolecules (NH-Thr-Lys-Thr-NH) was successfully synthesized, which can simultaneously detect Ag (turn on) and Hg (turn off) based on different fluorescent response patterns in 100% aqueous solution. DKT also enables quantitative detection of Ag and Hg with LODs of 37.1 nM and 26.7 nM, respectively. Besides, ESI-HRMS spectra, Job's plot, and fluorometric titration confirmed that the binding stoichiometry was determined to be 2: 1 between DKT and Ag/Hg. Moreover, DKT has good fluorescence stability and rapidly detected Ag and Hg over a wide pH range. Furthermore, DKT was applied to quantitative detect Ag and Hg in three actual water samples, three tea samples and watermelon juice, which exhibited that DKT has good potential for accuracy in environmental monitoring and water quality control. Additionally, the results of fluorescence bioimaging showed that DKT had significant distinguishing ability to detect Ag and Hg in living cells and zebrafish larvae. More importantly, smartphone App platform based on DKT not only provided a reliable new method for the field quantitative monitoring of Ag and Hg, but also expanded its application prospect in the field of heavy metal ions pollution detection.