Polyethylenimine-stabilized silver nanoclusters act as an oxidoreductase mimic for colorimetric determination of chromium(VI)

A new and efficient assay is proposed for the photometric determination of Cr 6+ by employing polyethylenimine-stabilized Ag nanoclusters (PEI-AgNCs) as an oxidoreductase mimic. Cr 6+ with certain oxidicability is able to specifically react with 3,3′,5,5′-tetramethylbenzidine (TMB), giving a color change from colorless to blue indicating the presence of Cr 6+ . However, the redox kinetics is so slow that the sensitivity obtained for Cr 6+ determination is very poor. It is interestingly found that PEI-AgNCs can act as an oxidoreductase-like nanozyme to significantly promote the sluggish reaction, making it possible to rapidly detect toxic Cr 6+ with remarkably enhanced performance. With the use of PEI-AgNCs, fast and convenient determination of Cr 6+ was realized, with a limit of detection as low as 1.1 μM. Additionally, the proposed assay exhibited excellent selectivity; other ions, including Cr 3+ , hardly affected the determination of Cr 6+ . Graphical abstract Polyethylenimine-stabilized silver nanoclusters (PEI-AgNCs) act as an oxidoreductase mimic to catalyze the redox reaction of Cr 6+ and 3,3′,5,5′-tetramethylbenzidine (TMB), enabling the high-performance colorimetric determination of toxic Cr 6+ .