Trypsin encapsulated gold-silver bimetallic nanoclusters for recognition of quinalphos via fluorescence quenching and of Zn2+ and Cd2+ ions via fluorescence enhancement

Abstract

In this work, gold‑silver bimetallic nanoclusters (Au[sbnd]Ag NCs) were produced via a simple synthetic approach by using trypsin as a ligand. The synthesized bimetallic nanoclusters have high intensity and shown red fluorescence. The trypsin-encapsulated Au[sbnd]Ag bimetallic NCs exhibit emission peak at 418 nm and 665 nm at excitation of 350 nm. The trypsin-decorated Au[sbnd]Ag NCs were successfully applied as probes for fluorescence “turn-off” for quinalphos and “turn-on” for Cd2+ and Zn2+ ions. Under optimal conditions, multiple analytes i.e., quinalphos, Cd2+ and Zn2+ ions were detected and exhibited linear range from 1.0 to 100 μM, achieved detection limits at nanomolar concentration. Attractively, the present study provides a new analytical strategy for multiple pollutants assay of quinalphos via fluorescence “turn-off” and of Cd2+ and Zn2+ ions via fluorescence “turn-on” mechanisms. The practicability of the method is validated by quantifying quinalphos, Cu2+ and Zn2+ ions from food and environmental samples. © 2020