In this study, we proposed a novel anti-aggregation of gold nanoparticles (AuNPs) strategy for colorimetric sensing of iodide ions (I-) regulated by the redox reaction between the target ions and the ion cross-linking agent. Cu2+ as interlinking ion can induce aggregation of arginine capped AuNPs (Arg-AuNPs) due to the formation of Arg-Cu2+-Arg analogous structure resulting from the chelation between Cu2+ and arginine, with a clear color change of solution from red to blue. In the presence of I-, however, Cu2+ would be readily reduced owing to the formation of CuI, AuNPs underwent a transformation from an aggregation to a dispersion state depending on the concentration of I-, leading color changes from blue to red. The corresponding color variation in the process of anti-aggregation of AuNPs can be monitored through UV-vis spectrophotometer or by the naked-eye, making quantitative analysis of I- feasible in a convenient colorimetric or visual way. The assay only took 5 min, showing high sensitivity with a lowest detectable concentration of 10 nM and excellent selectivity for I- over other anions tested, which was successfully applied for the detection of I- in drinking water and table salt samples.

中文翻译：

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Cu(Ⅱ)触发氧化还原调节的金纳米粒子抗聚集用于碘化物的超灵敏视觉传感

在这项研究中，我们提出了一种新的金纳米粒子 (AuNPs) 抗聚集策略，用于通过目标离子和离子交联剂之间的氧化还原反应调节碘离子 (I-) 的比色传感。由于 Cu2+ 和精氨酸之间的螯合导致形成 Arg-Cu2+-Arg 类似结构，Cu2+ 作为互连离子可以诱导精氨酸封端的 AuNPs（Arg-AuNPs）的聚集，溶液颜色从红色变为蓝色。然而，在 I- 存在下，Cu2+ 会由于 CuI 的形成而容易被还原，AuNPs 经历了从聚集状态到分散状态的转变，这取决于 I- 的浓度，导致颜色从蓝色变为红色。AuNPs反聚集过程中相应的颜色变化可以通过紫外-可见分光光度计或肉眼监测，从而以方便的比色或目视方式对I-进行定量分析。该测定只需要 5 分钟，显示出高灵敏度，最低可检测浓度为 10 nM，对 I- 比其他测试的阴离子具有出色的选择性，已成功应用于检测饮用水和食盐样品中的 I-。