A sensitive and selective colorimetric method for detection of copper ions based on anti-aggregation of unmodified gold nanoparticles

A highly sensitive and selective colorimetric method for detection of copper ions, based on anti-aggregation of D-penicillamine (D-PC) induced aggregated gold nanoparticles (AuNPs) was developed. Copper ions can hinder the aggregation of AuNPs induced by D-PC, through formation of mixed-valence complex with D-PC that is a selective copper chelator. In the presence of a fixed amount of D-PC, the aggregation of AuNPs decreases with increasing concentrations of Cu2+ along with a color change from blue to red in AuNPs solution and an increase in the absorption ratio (A520/A650). Under the optimum experimental conditions (pH 7, [AuNPs] =3.0 nmol L−1 and [NaCl]=25 mmol L−1), a linear calibration curve for Cu2+ was obtained within the range of 0.05–1.85 µmol L−1 with a limit of detection (3Sb) of 30 nmol L−1. Excellent selectivity toward Cu2+ was observed among various metal ions due to a specific complex formation between Cu2+ and D-PC. The proposed method has been successfully applied for the detection of Cu2+ in various real samples.