Colorimetric sensing of silver ion based on anti aggregation of gold nanoparticles

A colorimetric assay with excellent selectivity is reported for detecting silver ion in aqueous solutions. The system works based on the competitive interaction of gold nanoparticles (AuNPs) and Ag+ with tris(hydroxymethyl) aminomethane (tris). The sensing strategy is quite simple, fast, convenient and the detection is by the naked eye. The aggregation of AuNPs with tris was inhibited in the presence of Ag+ ions resulting in a significant hypsochromic spectral shift of the surface plasmon resonance (SPR) of AuNPs and a color change from blue to red. The interaction between tris and Ag+ ion was investigated with cyclic voltammetry. The effect of Ag+ concentration on the aggregation of AuNPs by tris was monitored by UV-vis spectroscopy with the dynamic range of 1-9 mu M and detection limit of 0.41 mu M. The recovery analysis of river water and wastewater samples proved that this colorimetric sensor is successfully operational in environmental monitoring. (C) 2016 Elsevier B.V. All rights reserved.