Self-Cascade System Based on Cupric Oxide Nanoparticles as Dual-Functional Enzyme Mimics for Ultrasensitive Detection of Silver Ions

Abstract

Artificial enzyme mimics based on nanomaterials have attracted sustained attention owing to their multiple advantages compared with natural enzymes. However, there are a few enzyme self-cascade systems for the highly sensitive detection of analytical targets. Herein, we have described a self-cascade catalytic system based on single-component cupric oxide nanoparticles (CuO NPs) for an ultrasensitive fluorescent detection toward glutathione (GSH) and Ag+ ions. The limit of detection is lower for nanomolar (nM) and picomolar (pM) levels for GSH and Ag+, respectively. To the best of our knowledge, for the first time, we find that CuO NPs possess the intrinsic GSH-oxidase and peroxidase-like activity as a dual-functional nanozyme, coupling with terephthalic acid (TA) and GSH to construct a self-cascade fluorescent system. The turn-on fluorescence signal of oxidation hydroxyterephthalate (TAOH) is generated in the presence of GSH. Then, the fluorescence of a reaction mixture is quenched after the addition of A...