Preparation Of Gold And Silver Nanoclusters And Their Detection Of Hg²⁺ And L-cysteine

The metal fluorescent nanoclusters with excellent biocompatibility,photoluminescence,strong magnetic properties and catalytic properties are a core composed of noble metal atoms such as Au,Ag or Pt,and core/shell type molecular-level fluorescent material assembled as protective groups such as organic monomolecules?thiol compounds?or biomolecules?proteins?.The conventional detection methods of Hg²⁺and L-cysteine?Cys?are complicated and their conditions are demanding.It is of great significance to establish a simple,rapid,high-sensitivity and high-selectivity detection method for environmental protection and human health protection.In this paper,the preparation of glutathione-capped gold nanoclusters?GSH-AuNCs?solution and the characterization of its morphology,structure?TEM,FTIR,TGA and XPS?and optical properties were studied.The results showed that AuNCs had good dispersibility and the size was less than 2nm;GSH formed a stable Au-S bond with gold nucleus;the molar ratio of GSH to Au was 0.48:1,and the content ratio of Au?I?to Au?0?was about 17:3.AuNCs solution had the highest emission peak at?_em=566 nm when the excitation wavelength was 330 nm.Based on the significant fluorescence quenching of AuNCs by Hg²⁺,a fluorescence analysis method for the determination of Hg²⁺was established.The experimental results showed that the equilibrium time of AuNCs solution with Hg²⁺reaction was 10 min,and the fluorescence quenching degree of AuNCs solution showed a good linear relationship with Hg²⁺concentration in the range of 4.0²00 nmol/L?R²=0.998?,with a detection limit of 2.4 nmol/L?S/N=3?.The AuNCs solution had good stability,reproducibility and high selectivity for Hg²⁺detection.The simple AuNCs test strip had a good detection effect on the concentration of Hg²⁺in tap water and the average recoveries were 92.5%¹05.3%,and relative standard deviation?RSD?was below 5%.This method had high sensitivity and good selectivity,and potential practical application value.In this paper,the synthesis of dihydrolipoic acid-coated silver nanoclusters?DHLA-AgNCs?solution under normal temperature conditions was studied and characterized by TEM,FTIR,XPS and HR-MS.The results showed that AgNCs were spherical and had good dispersibility with a nanometer particle size of less than 2 nm;DHLA formed a stable Ag-S bond with silver nucleus;the S element was assigned to sulfur atoms bound to silver surfaces as thiolate species,and the binding energy of Ag3d_5/2 and Ag 3d_3/2 were close to that of Ag?0?;AgNCs only contain Ag₄ and Ag₅ and the molar ratio to DHLA was 1:1;the optimal excitation wavelength of AgNCs was425nm.Based on the fluorescence quenching phenomenon of Cys to AgNCs,a fluorescence analysis method of AgNCs to Cys detection was constructed.The results showed that under optimized experimental conditions,a linear relationship had been obtained between the fluorescence quenching degree at 625 nm and the concentration of Cys in the range of 2.0¹00?mol/L?R²=0.998?,with a detection limit?LOD,S/N=3?of 1.77?mol/L.The AgNCs solution had good stability,reproducibility and specific recognition ability for Cys.The recoveries of Cys in river water and human serum samples were 98.0%¹05.0%and 94.0%¹02.4%,respectively,and the relative standard deviation were below 4.5%.This method was simple,rapid,high-sensitivity and high-selectivity and had a good application prospect in the field of environment and biomedicine.