Colorimetric detection of Cu2+ using 4-mercaptobenzoic acid modified silver nanoparticles

A highly sensitive and selective method is proposed for colorimetric detection of copper ions using 4-mercaptobenzoic acid (4-MBA) modified silver nanoparticles (AgNPs). The presence of Cu2+ induces the aggregation of 4-MBA modified AgNPs, this resulting in a color change from bright yellow to purple. The concentration of Cu2+ could be quantified by naked eyes or a UV–vis spectrometer. The absorbance ratio (A560 nm/A393 nm) is linear with the concentration of Cu2+ ranging from 1 × 10−7 M to 1 × 10−4 M with a coefficient of 0.998. The detection limit is as low as 2.5 × 10−8 M. The proposed method could be successfully applied to determine Cu2+ in drinking water.