Tuning stable and unstable aggregates of gallic acid capped gold nanoparticles using Mg2+ as coordinating agent

Abstract

High reducibility of gallic acid allows synthesis of small sized monodisperse gold nanoparticles (GNPs) at ambient temperature (25°C). Mg²⁺ rapidly interacts with the gallic acid ligands and suppresses the dispersion of GNPs therefore, causing a decrease in UV-vis absorbance intensity, and color change from red to blue. Thus, the colorimetric response of GNPs with Mg²⁺ was investigated by observing temporal quenching of UV-vis absorbance and precise tuning of fractal growth of GNP aggregates. Moreover, Mg²⁺ at concentrations as low as 200ppb can be detected using gallic acid ligand-mediated coordination chemistry which results quenching in UV-vis absorbance proportional to the exposure time. This gallic acid-based colorimetric sensor shown a great potential for the selective detection of pathologically important electrolyte Mg²⁺ without any interference from other cations Ca²⁺ and K⁺.

Keywords: Aggregates; Electrolyte; Gallic acid; Gold nanoparticles; Mg(2+); Quenching.