Colorimetric Detection of Trace Copper Ions Based on Catalytic Leaching of Silver-Coated Gold Nanoparticles

Abstract

A colorimetric, label-free, and nonaggregation-based silver coated gold nanoparticles (Ag/Au NPs) probe has been developed for detection of trace Cu²⁺ in aqueous solution, based on the fact that Cu²⁺ can accelerate the leaching rate of Ag/Au NPs by thiosulfate (S₂O₃^2–). The leaching of Ag/Au NPs would lead to dramatic decrease in the surface plasmon resonance (SPR) absorption as the size of Ag/Au NPs decreased. This colorimetric strategy based on size-dependence of nanoparticles during their leaching process provided a highly sensitive (1.0 nM) and selective detection toward Cu²⁺, with a wide linear detection range (5–800 nM) over nearly 3 orders of magnitude. The cost-effective probe allows rapid and sensitive detection of trace Cu²⁺ ions in water samples, indicating its potential applicability for the determination of copper in real samples.