Selective and sensitive colorimetric detection of copper ions based on anti-aggregation of the glutathione-induced aggregated gold nanoparticles and its application for determining sulfide anions

A facile, rapid, selective and sensitive colorimetric method for the detection of copper ions (Cu2+) based on anti-aggregation of the glutathione-induced aggregated gold nanoparticles (AuNPs) was developed. Cu2+ can prevent the aggregation of AuNPs induced by glutathione (GSH) through catalyzing oxygen oxidation of GSH to oxidized glutathione (GSSG). In the presence of a specified amount of GSH, the aggregations of AuNPs decrease with increasing concentrations of Cu2+, which can be monitored by an ultraviolet-visible spectrophotometer or the naked eye. High sensitivity could be achieved for the detection of Cu2+ down to 20 nM. The method shows excellent selectivity toward Cu2+ over other metal ions, which can not prevent the GSH-induced aggregation of AuNPs even at a 20-fold molar excess. We further used the proposed method to selectively and sensitively detect sulfide anions in aqueous solution. The detection limit of sulfide anions (S2-) could reach 100 nM, which is one order of magnitude lower than that of GSH modified AuNPs-based colorimetric S2- assay.