Cu2+-catalyzed and H2O2-facilitated oxidation strategy for sensing copper(ii) based on cysteine-mediated aggregation of gold nanoparticles

Abstract

As an essential element, copper ions (Cu²⁺) play important roles in human beings for their participation in diverse metabolic processes, as a cofactor or a structural component of enzymes. However, excessive uptake of Cu²⁺ gives rise to the risk of certain diseases. Then it is important to develop simple ways to monitor and detect Cu²⁺. In this study, a facile colorimetric sensor for the sensitive determination of Cu²⁺ was developed based on the Cu²⁺-catalyzed oxidation of cysteine by H₂O₂ to cystine, a process that prohibits the cysteine-triggered aggregation of the Au nanoparticles (AuNPs) stabilized by polyethylene glycol (PEG). With this strategy, the concentration of Cu²⁺ could be detected with the naked eye or with ultraviolet-visible spectroscopy, and the limits of detection for Cu²⁺ were 250 nM and 50 nM, respectively. Additionally, the proposed method shows excellent anti-interference capability against many other metal ions, and in real water samples.