Selective and sensitive colorimetric sensor of mercury (II) based on gold nanoparticles and 4-mercaptophenylboronic acid

Abstract

A simple and rapid colorimetric sensor for Hg2+ in aqueous solution was developed based on the observation that the detection target, Hg2+, could inhibit the aggregation of gold nanoparticles (AuNPs) induced by 4-mercaptophenylboronic acid (MPBA). Without a potent competitor, MPBA can bind to the AuNPs via Au-S bonds and induces the aggregation of AuNPs by self-dehydration condensation of boronic acid groups, resulting in a visible color change of the AuNPs solution from red to blue. In the presence of Hg2+, the thiol group of MPBA preferentially binds to Hg2+ and thus MPBA loses the ability to induce aggregation of AuNPs, which is mechanism behind the color change of the solution from blue to red. Our results showed that the absorbance ratio (A520/A690) was linear with the Hg2+ concentration in the range of 0.01–5μM (R=0.998). The detection limit of the colorimetric sensor was 8nM (S/N=3). The colorimetric changes of the sensor were extremely specific for Hg2+ and no obvious color change was observed when adding other competitive metal ions in parallel. Further promising results from Hg2+ detection in water samples indicated that our newly developed assay might open a new assay avenue for Hg2+ determination.