Fluorescence detections of hydrogen peroxide and glucose with polyethyleneimine-capped silver nanoclusters.

Detection of hydrogen peroxide is of significant importance for biological assays, and fluorescence methods are intensively reported for this purpose. Due to the highly oxidative property of this species, usually fluorescence quenching is obtained during the interactions and decreased signals are rendered. In this report, this oxidative property was adopted for an increased fluorescence signaling. Photoluminescent silver nanoclusters (AgNCs) were synthesized with polyethyleneimine as the stabilizer. This fluorescence from these nanoclusters could be quenched by reduced glutathione (GSH) through an interaction from its thiol group. As an oxidant, hydrogen peroxide converted GSH into an oxidized form (GSSG) with an elimination of the free thiols, and inhibited the quenching. This interaction presented an increased response toward hydrogen peroxide in the range of 0.1-20 μM with a detection limit of 35 nM. The scheme was further coupled with glucose oxidase for a glucose analysis down to 0.11 μM. This method was selective and was successfully applied for glucose measurement in human serum samples.