Analyte-Mediated Peroxidase-Mimicking Activity Enhancement of Cysteine-Capped Silver Nanoparticles for Colorimetric Detection of Copper Ions

Abstract: A novel and efficient colorimetric assay was developed for the detection of copper ions (Cu²⁺) in real environmental water based on analyte-mediated peroxidase-mimicking activity enhancement of cysteine-capped silver nanoparticles (RSH-AgNPs). These RSH-AgNPs show a synergetic effect in the form of peroxidase-mimicking activity enhancement by analyte mediation, and free RSH-AgNPs alone have weak catalytic properties. While coexisting with Cu²⁺, RSH-AgNPs possess excellent enzymatic activity due to the dissociation of cysteine on the interface of silver nanoparticles caused by Cu²⁺ and exposing the catalytic sites of AgNPs, which can catalyze the decomposition of hydrogen peroxide and trigger the oxidation of 3,3',5,5'-tetramethylbenzidine, leading to a change in color from colorless to blue. Using this strategy, Cu²⁺ could be determined within a wide linear range of concentrations (0.1 to 83 μM) with the detection limit of 0.08 μM using colorimetric detection. This method has excellent anti-interference capability and is effective and reliable for the determination of Cu²⁺ in real water samples.