Highly sensitive and selective voltammetric detection of mercury(II) using an ITO electrode modified with 5-methyl-2-thiouracil, graphene oxide and gold nanoparticles

We have developed an electrochemical sensor for highly selective and sensitive determination of Hg(II). It is based on the specific binding of 5-methyl-2-thiouracil (MTU) and Hg(II) to the surface of an indium tin oxide (ITO) electrode modified with a composite made from graphene oxide (GO) and gold nanoparticles (AuNPs). This leads to a largely enhanced differential pulse voltammetric response for Hg(II). Following optimization of the method, a good linear relationship (R = 0.9920) is found between peak current and the concentration of Hg(II) in the 5.0-110.0 nM range. The limit of detection (LOD) is 0.78 nM at a signal-to-noise ratio of 3. A study on the interference by several metal ions revealed no interferences. The feasibility of this method was demonstrated by the analyses of real water samples. The LODs are 6.9, 1.0 and 1.9 nM for tap water, bottled water and lake water samples, respectively, and recoveries for the water samples spiked with 8.0, 50.0 and 100.0 nM were 83.9-96.8 %, with relative standard deviations ranging from 3.3 % to 5.2 %.