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.
