Sensitive and selective colorimetric detection of Cu2+ in aqueous medium via aggregation of thiomalic acid functionalized Ag nanoparticles

Abstract

A simple and effective colorimetric method for determination of Cu²⁺ in real samples was developed. In this method, thiomalic acid functionalized silver nanoparticles (TMA-AgNPs) were prepared and changes in solution color, induced by the aggregation of TMA-AgNPs in the presence of Cu²⁺, were employed for quantitative analysis. The surface plasmon resonance (SPR) band of our synthesized TMA-AgNPs was located at 392 nm and shifted to a longer wavelength after aggregation due to the interactions between carboxylate and Cu²⁺. A band intensity ratio of A₄₅₅/(A₃₉₂ − A₄₅₅) was constructed and used to correlate with the concentration of Cu²⁺. A linear relationship was found with a linear response up to 50 nM of Cu²⁺. Due to the formation of a stable carboxylate Cu²⁺ complex, highly sensitive detection of Cu²⁺ was achieved with the estimated detection limit approaching 1 nM. Moreover, the formation of the stable complex leads to high selectivity in the detection of Cu²⁺, which was verified by examination of 12 other metal ions. In the detection of Cu²⁺ in real samples, results indicated that our proposed method is simple, sensitive and selective for application in such measurements.