AbstractA colorimetric and visual method is described for the determination of mercury(II) ion. A gel consisting of agar-stabilized silver-coated gold nanoparticles (Au@Ag NPs) was prepared. The reaction with dithiothreitol (DTT) via thiol-Ag chemistry results in an orange to purple color change of the gel. However, in the presence of Hg(II), the reaction of DTT with the silver shells is suppressed due to the strong thiophilicity of Hg(II). The color of the gel changes from purple to red to orange in the presence of increasing concentrations of Hg(II). The Au@Ag NPs therefore are a viable optical probe for Hg(II) which can be detected in concentration as low as 78 nM via dual-wavelength ratiometric absorbance (A390/A520), and at 1 μM levels with bare eyes. The use of agar as a support is mandatory to prevent the aggregation of the NPs and also improves selectivity. The method was applied to the analysis of spiked samples, and recoveries ranged between 96.3 and 104%. The assay is easy, inexpensive, and in our perception represents an attractive tool for on-site visual detection of Hg(II). Graphical abstractSchematic of the assay. With increasing concentrations of Hg(II), the oxidative etching of silver shells caused by dithiothreitol (DTT) is gradually inhibited, and the color of agar-stabilized Au@Ag NP gel varies from purple to red, and finally to orange. This can be used for visual detection of Hg(II).

中文翻译：

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基于抑制二硫苏糖醇与琼脂稳定的银包金纳米粒子相互作用的汞 (II) 比色和视觉检测

摘要 介绍了一种测定汞(II)离子的比色法和目视法。制备了由琼脂稳定的银包金纳米粒子 (Au@Ag NPs) 组成的凝胶。通过硫醇-Ag 化学与二硫苏糖醇 (DTT) 反应导致凝胶颜色从橙色变为紫色。然而，在 Hg(II) 存在下，由于 Hg(II) 的强亲硫性，DTT 与银壳的反应受到抑制。在 Hg(II) 浓度增加的情况下，凝胶的颜色从紫色变为红色，再到橙色。因此，Au@Ag NPs 是一种可行的 Hg(II) 光学探针，可以通过双波长比率吸光度 (A390/A520) 以低至 78 nM 的浓度和 1 μM 水平用裸眼检测到。必须使用琼脂作为支持物，以防止 NP 聚集并提高选择性。该方法用于分析加标样品，回收率介于 96.3% 和 104% 之间。该测定简单、廉价，在我们看来，它代表了一种用于现场目视检测 Hg(II) 的有吸引力的工具。分析的图形摘要示意图。随着Hg(II)浓度的增加，二硫苏糖醇(DTT)引起的银壳氧化蚀刻逐渐受到抑制，琼脂稳定的Au@Ag NP凝胶的颜色由紫色变为红色，最后变为橙色。这可用于目视检测 Hg(II)。在我们看来，它代表了一种用于现场目视检测 Hg(II) 的有吸引力的工具。分析的图形摘要示意图。随着Hg(II)浓度的增加，二硫苏糖醇(DTT)引起的银壳氧化蚀刻逐渐受到抑制，琼脂稳定的Au@Ag NP凝胶的颜色由紫色变为红色，最后变为橙色。这可用于目视检测 Hg(II)。在我们看来，它代表了一种用于现场目视检测 Hg(II) 的有吸引力的工具。分析的图形摘要示意图。随着Hg(II)浓度的增加，二硫苏糖醇(DTT)引起的银壳氧化蚀刻逐渐受到抑制，琼脂稳定的Au@Ag NP凝胶的颜色由紫色变为红色，最后变为橙色。这可用于目视检测 Hg(II)。