A new simple and reliable Hg~(2+) detection system based on anti-aggregation of unmodified gold nanoparticles in the presence of O-phenylenediamine

摘要

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.