在Britton-Robinson(BR)(pH为9.0)缓冲介质中, 微量Hg(Ⅱ)离子能诱使被巯基乙酸钠包被的AuNPs发生聚集, 以此诱发局域表面等离子体共振(localized surface plasmon resonance, LSPR)散射峰的出现, 随着Hg(Ⅱ)浓度的不断增加, 体系在548 nm的LSPR散射信号显著增强, 其散射强度与Hg(Ⅱ)的浓度具有相关性, 且在0.08～0.8 μmol·L-1范围内呈现一定的线性关系, 由此构建了以Hg(Ⅱ)为目标分析物的LSPR散射分析检测方法, 检测限为8 nmol·L-1。 研究了体系的LSPR散射光谱以及吸收光谱, 利用扫描电镜考察了AuNPs与Hg(Ⅱ)反应前后粒径的变化情况, 发现单独的AuNPs呈现良好的分散状态, 当加入Hg(Ⅱ)后, AuNPs呈现聚集状态。 同时探讨了体系反应机理, 结果表明Hg(Ⅱ)的加入与AuNPs表面的羧基发生螯合作用诱导了AuNPs的聚集。 考察了体系对金属离子Hg(Ⅱ)的选择性, 实验中选择了一系列的金属离子与AuNPs作用, 其结果表明Hg(Ⅱ)与AuNPs作用的LSPR散射信号增强效果最为明显, 而其余离子即使在浓度较高时其LSPR散射强度依然较弱, 说明了实验设计方案对Hg(Ⅱ)具有优异的选择性。 此外, 研究了体系酸度, 离子强度以及稳定剂对体系的影响。 实验所建立起来的方法操作简单, 分析速度快速, 检测灵敏度较高。 该方法已经成功用于环境水样中痕量Hg(Ⅱ)的检测。

Heavy-metal ions pose severe risks for human health and the environment. In particular, mercury-based pollutants are of great environmental concern because of the high toxicity of many Hg compounds. It is important to monitor the levels of potentially toxic metal Hg(Ⅱ) in aquatic ecosystems. Gold nanoparticles (AuNPs) as nanomaterials have been generally studied. It is because their unique electrical, chemical, optical, and catalytic properties, AuNPs have caused widespread interest for applications in biological and chemical analysis and detection. In the present work, the authors took advantage of the aggregation-induced localized surface plasmon resonance (LSPR) light scattering signal change of sodium thioglycolate functionalized AuNPs in aqueous solutions to develop a highly efficient optical sensor for Hg(Ⅱ). The as-modified AuNPs demonstrate that high negative charge densities exist on their surfaces at pH 9.0 Britton-Robinson (BR) buffer solution. The AuNPs occur aggregate in solution through chelation in the presence of Hg(Ⅱ). The scanning electron microscope (SEM) images for the AuNPs display typical shapes of these AuNPs as regular and almost individual spherical particles. The color change of the AuNPs solution was induced by the addition of Hg(Ⅱ) and it immediately changed from red to purple due to the aggregation. Under optimum conditions, a good linear relationship was obtained from 0.08 to 0.8 μmol·L-1 with a correlation coefficient of 0.997 6, and the limit of detection (LOD) was 8.0 nmol·L-1. PEG20000 was employed as a system stabilizer. The proposed method has an excellent selectivity for Hg(Ⅱ) in aqueous medium over other metal ions. The optimum test of reaction conditions, including the amount of AuNPs, pH value, reaction stability and ionic strength, were also investigated. This method has been used for determination of Hg(Ⅱ) successfully in environmental water sample. This approach manifested several advantages including short analysis time, high sensitivity, low cost, excellent selectivity and ease of operation.