Smartphone-enabled colorimetric determination of silver ions exploiting the peroxidase-mimetic behavior of bowl-shaped Pd3Pt nanocrystals

Abstract

Excessive silver ions (Ag+) pose significant risks to both human health and the environment, necessitating the rapid and sensitive detection of Ag+ in aqueous systems to ensure public health and environmental safety. In this study, we present a novel and expeditious colorimetric methodology for Ag+ detection, employing bowl-shaped Pd3Pt nanocrystals as an effective probe. The distinctive bowl-like structure of Pd3Pt provides an abundance of catalytic active sites, endowing them with peroxidase-like activity. Upon exposure to hydrogen peroxide, these Pd3Pt nanobowls facilitate the oxidation of the colorless substrate 3,3′,5,5′-tetramethylbenzidine (TMB), resulting in the formation of the blue product oxTMB, which exhibits a pronounced characteristic absorption peak at 652 nm. By virtue of the metal affinity and electrostatic attraction between Ag+ ions and Pd3Pt nanobowls, Ag+ species effectively adsorb onto the nanobowls surface, preferentially occupying the catalytic active sites and impeding the production of the blue oxTMB product. Based on this mechanism, we have established a novel colorimetric approach for the quantitative determination of Ag+, enabling facile Ag+ detection using either a UV–vis absorption spectrometer or a smartphone as the detection instrument. The developed method demonstrates an impressive detectable range spanning 1–100 nmol/L, accompanied by a detection limit of 0.72 nmol/L. Notably, this technique boasts several desirable attributes, including rapid detection, simplified operational procedures, heightened sensitivity, and commendable selectivity. Moreover, we have successfully applied this method to assess Ag+ levels in water samples procured from diverse sources, further attesting to its practical utility and versatility.