Colorimetric Determination of Mercury(II) by Secondary Gold Nanoparticles Formation on Primary Gold Nanoparticles as an Efficient Nanozyme

Schematic illustration of the enzymatic-like activity of gold nanoparticles for colorimetric sensing of mercury(II). Gold nanoparticles (Au-NPs) shows promise enzyme-like activity for hydrogen peroxide decomposition and produced free electrons for metal ion reduction. Thus, we focused on the design and construction of primary Au-NPs (p-Au-NPs) for decomposition hydrogen peroxide and subsequently reduction of Au 3+ to form secondary Au-NPs (s-Au-NPs). Since mercury(II) as soft metal ion can make amalgam with the Au-NPs this can be applied as a boosting idea for indirect detection of mercury(II). Therefore, s-Au-NPs preparation in presence of different concentrations of mercury(II) on surface of p-Au-NPs that cause a color change by final oxidation of 3,4-diaminotoluene while s-Au-NPs/p-Au-NPs cannot oxidize 3,4-diaminotoluene marker and no color change is achieved become as a goal. This occurrence causes a colorimetric procedure, from mauve to dark wine, which facilitates determination of mercury(II) ions in a reasonable range from 2.15 to 25.12 µM with a UV–Vis spectrometer. Sensor characterized by analysis such as UV–Vis, DLS, SEM, EDS, XRD and FT-IR. At last, accuracy of the model investigated with recovery process and observed that method could be advantageously applied as a simple method for the determination of mercury (II) in real samples have been developed to monitor the water quality by tracing different amount of analyte ions in samples. The different water sample such as lake water, tap water, and any water with the necessity of checking the quality of it to help the environment for places with the lack of high-tech technology.