A new simple and reliable Hg2+ detection system based on anti-aggregation of unmodified gold nanoparticles in the presence of O-phenylenediamine

A simple and reliable colorimetric detection system based on anti-aggregation of gold nanoparticles (AuNPs) is proposed for rapid detection of Hg 2+ with high selectivity and sensitivity. O -phenylenediamine (OPD) can cause the aggregation of AuNPs due to formation of the strong covalent NH Au bond, and then induce color change of the AuNPs solution from red to blue. However, in the presence of Hg 2+ , OPD prefers to combine with Hg 2+ rather than AuNPs resulting in inhibition of the color change. Based on the anti-aggregation mechanism, Hg 2+ can be detected by observing the color change of AuNPs solution containing OPD. After optimization, the selectivity of this Hg 2+ detection system by the naked eyes and UV–vis spectra is excellent comparing with other ions. The limit of the detection (LOD) is 0.1   μM by the naked eyes and 5.0   nM by UV–vis spectroscopy, which is lower than the mercury toxic level (10   nM) defined by US Environmental Protection Agency. It's a good linear relationship between A 520 / A 680 and Hg 2+ concentration from 0.01   μM to 2.0   μM, which is used for the quantitative assay of Hg 2+ . The applicability of our detection system is also verified by analysis of Hg 2+ in tap water and lake water.