Herein, we report the construction of a colorimetric probe used to detecting Cr3+ ions in aqueous solution based on functionalized gold nanoparticles. We investigated 4-mercaptobenzoic acid, 4-nitrobenzenethiol, and a mixture of 4-mercaptobenzoic acid and 4-nitrobenzenethiol as ligands for Cr3+ ions to functionalize the gold nanoparticles, respectively. The results showed that the three probes were all aggregated in the presence of Cr3+ ions, which induces a color change from ruby to violet. Moreover, gold nanoparticles modified with 4-mercaptobenzoic acid exhibit a higher response toward Cr3+ than the two other probes, which can be detected by the naked eye and UV-vis absorption spectroscopy. The detection time was rapid (within 25 min). A linear relationship was obtained from 20 to 25 μM between the ratio of the absorbance observed at 635 nm and 520 nm (A635 nm/A520 nm) with the limit of detection was 5 × 10−6 M. This method exhibited excellent selectivity for Cr3+ ions over other tested heavy metal ions, anions, and organic molecules in the absence of another shielding reagent of metal ion. The system was successfully utilized to detect Cr3+ ions in simulated samples.

中文翻译：

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基于 4-巯基苯甲酸功能化金纳米粒子的 Cr3+ 比色检测

在此，我们报告了基于功能化金纳米粒子的用于检测水溶液中 Cr3+ 离子的比色探针的构建。我们研究了 4-巯基苯甲酸、4-硝基苯硫醇以及 4-巯基苯甲酸和 4-硝基苯硫醇的混合物作为 Cr3+ 离子的配体，分别对金纳米颗粒进行功能化。结果表明，在 Cr3+ 离子的存在下，三个探针都聚集在一起，导致颜色从红宝石变为紫色。此外，用 4-巯基苯甲酸修饰的金纳米粒子对 Cr3+ 表现出比其他两种探针更高的响应，这可以通过肉眼和紫外可见吸收光谱检测到。检测时间很快（25 分钟内）。在 635 nm 和 520 nm 处观察到的吸光度比 (A635 nm/A520 nm) 之间的线性关系为 20 至 25 μM，检测限为 5 × 10−6 M。该方法对 Cr3+ 表现出出色的选择性在没有另一种金属离子屏蔽剂的情况下，离子优于其他测试的重金属离子、阴离子和有机分子。该系统已成功用于检测模拟样品中的 Cr3+ 离子。