Analyte-triggered citrate-stabilized Au nanoparticle aggregation with accelerated peroxidase-mimicking activity for catalysis-based colorimetric sensing of arsenite

Arsenite is a well-known toxic species widely distributed in many matrices, and exploring reliable and facile methods for its detection is always desired for environmental analysis and food safety control. Here we propose a catalytic colorimetric assay of arsenite based on the analyte inducing the aggregation of citrate-stabilized Au nanoparticles (AuNPs) with promoted peroxidase-mimicking activity. Originally, highly dispersed AuNPs with a mean size of ∼20 nm show negligible enzyme-like activity. However, when a small amount of arsenite is added, it triggers the rapid aggregation of AuNPs via the interactions between the analyte and the stabilizer citrate on AuNP surface, and it is further observed that the formed AuNP agglomerate can exhibit significantly accelerated peroxidase-mimetic activity to catalyze the 3,3′,5,5′-tetramethylbenzidine chromogenic reaction with the participation of H2O2. Based on this phenomenon, a facile colorimetric strategy with catalytic signal amplification was established for the efficient sensing of arsenite. With the catalysis-based strategy, arsenite in a wide range (0.0111.67 mg/L) was linearly determined with a detection limit lower than the standard approved by the US EPA and the EEA. Stable and reliable measurement of the analyte in various water matrices was also verified, promising our assay’s great potential in practical applications.