AbstractA colorimetric approach is presented for the determinaton of cadmium(II) using unmodified gold nanoparticles (AuNPs) as a colorimetric probe. The assay is based on AuNP aggregation that is induced by the complexes formed between Cd(II) and glutathione (GSH) in a concentrated solution of NaCl. Unmodified AuNPs are known to aggregate in high-salt medium, but GSH can prevent aggregation. In the presence of Cd(II), it will bind GSH, and this will cause the AuNPs to aggregate as indicated by yellow and red dots under dark-field microscopy observation and the formation of a blue coloration. By monitoring the intensity change of AuNPs (as a ratio of absorbances at 600 and 520 nm), Cd(II) can be quantified with a linear response in the 17 pM to 16.7 nM concentration range and a detection limit of 4.3 pM. The method was successfully applied to the determination of Cd(II) in spiked lake water by the standard addition mode, and the detection limit is 4.5 pM. Graphical abstractA ultrasensitive colorimetric assay of cadmium ions using unmodified gold nanoparticles as colorimetric probes with dark-field microscopy

中文翻译：

---

使用未修饰的金纳米粒子并基于谷胱甘肽-镉 (II) 复合物的形成，比色和暗场显微测定镉 (II)

摘要提出了使用未修饰的金纳米粒子 (AuNPs) 作为比色探针测定镉 (II) 的比色方法。该测定基于由 Cd(II) 和谷胱甘肽 (GSH) 在 NaCl 浓缩溶液中形成的复合物诱导的 AuNP 聚集。已知未修饰的 AuNP 在高盐介质中会聚集，但 GSH 可以防止聚集。在 Cd(II) 存在的情况下，它会结合 GSH，这将导致 AuNPs 聚集，如暗场显微镜观察下的黄色和红色点所示，并形成蓝色。通过监测 AuNPs 的强度变化（作为 600 和 520 nm 处的吸光度比），Cd(II) 可以在 17 pM 至 16.7 nM 浓度范围内以线性响应进行量化，检测限为 4.3 pM。该方法成功应用于加标湖水中Cd(II)的标准添加测定，检出限为4.5 pM。图形摘要使用未修饰的金纳米粒子作为暗场显微镜的比色探针对镉离子进行超灵敏比色测定