Colorimetric detection of Hg2+ by Au nanoparticles formed by H2O2 reduction of HAuCl4 using Au nanoclusters as the catalyst

Gold nanoclusters (AuNCs), due to their enzyme-like activity, can catalyze the decomposition of hydrogen peroxide (H 2 O 2 ), which can be used to reduce HAuCl 4 into gold nanoparticles (AuNPs). Hg 2+ effectively decreases the catalytic ability of AuNCs to decompose H 2 O 2 by the interactions between Au + on surface of AuNCs and Hg 2+ . In a system containing AuNCs, H 2 O 2 , and HAuCl 4 , increasing the Hg 2+ concentration prompts a color change from purple to red of the solution of as-synthesized AuNPs, which results from the increase in residual H 2 O 2 after decomposition by AuNCs. Based on this principle, a novel colorimetric method for ultrasensitive detection of mercury ions was developed in this work. AuNPs synthesized by a one-step method without modification were used to directly detect mercury ions in lake and river water samples. The detection limit of the present method was determined to be 8:9   pM with a linear response range of 0.1   nM–10   μM, which is much lower than the standard value defined by the Environmental Protection Agency (EPA). The method not only possesses advantages of convenience and simplicity, but also is promising for application in real samples.