Sensitive and selective colorimetric detection of Cu(2+) in aqueous medium via aggregation of thiomalic acid...

A simple and effective colorimetric method for determination of Cu(2+) 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 Cu(2+), 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 Cu(2+). A band intensity ratio of A455/(A392-A455) was constructed and used to correlate with the concentration of Cu(2+). A linear relationship was found with a linear response up to 50 nM of Cu(2+). Due to the formation of a stable carboxylate Cu(2+) complex, highly sensitive detection of Cu(2+) 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 Cu(2+), which was verified by examination of 12 other metal ions. In the detection of Cu(2+) in real samples, results indicated that our proposed method is simple, sensitive and selective for application in such measurements.