Ratiometric fluorescent detection of silver nanoparticles in aqueous samples using peptide-based fluorogenic probes with aggregation-induced emission characteristics.

The quantification of silver nanoparticles and Ag contamination in the aquatic ecosystem has attracted considerable interest. Benzoimidazolyl-cyanovinylene (1) was synthesized as an aggregation-induced emission fluorophore, and a fluorescent peptidyl probe (2 and 3) bearing this fluorophore was developed. The fluorescent peptidyl probes coordinated with Ag selectively among various metal ions, leading to a ratiometric response to Ag in pure aqueous solutions. Furthermore, an "in situ" protocol was developed to quantify AgNPs using 2 with HO as an oxidizing reagent. The fluorescent detection method for Ag and AgNPs showed promising detection properties such as high selectivity, high sensitivity, fast response, visible light excitation, well-operations in pure aqueous solution, and large fluorescent signal change. The detection limits of Ag (0.64 ppb) and AgNPs (1.1 ppb) were significantly low. According to the binding mode study, Ag induced the formation of a 2:1 complex between 2 and Ag and the chirality of the peptide part of the probe was not critical for this process. The formation of aggregates of the probe triggered by Ag from AgNPs induced a significant change in fluorescence. Furthermore, the amounts of spiked AgNPs in groundwater and tap water were quantified using the fluorescent detection method with 2.