Synthesis Of Gold Nanoclusters And Its Application In Fluorescence Analysis

Gold nanoclusters（AuNCs）are a new type of inorganic nanomaterials which particle size is generally less than 2 nm.Due to the size effect and the influence of surface ligands,it have many special properties such as photoluminescence and high catalytic activity.The synthesis methods of gold nanoclusters are varied.The main synthesis methods include chemical reduction,electrochemical synthesis,microwave synthesis,photoreduction and so on.Due to the simple synthesis steps and low energy consumption,the chemical reduction method has become the most commonly synthesis method.Due to the small size,high surface activation energy and easy aggregation of gold nanoclusters,a templating agent is required to enhance their stability during the synthesis process.Commonly used templates are polymers,proteins,DNA,thiol small molecules,etc.Among these templates,protein templates are widely used due to its rich spatial structure and good biocompatibility.Polymer templates contain a large number of functional groups and are also favored by scholars.The structure of polymer cavity can block the interaction between AuNCs and the external environment,so that the synthesized AuNCs have good stability.In this paper,BSA-AuNCs with excellent fluorescence properties were synthesized by chemical reduction method using bovine serum albumin（BSA）as template;PEI-AuNCs with excellent fluorescence properties were synthesized by etching method using polyethyleneimine（PEI）as template.The synthesized gold clusters were used for the detection of metal ions and the halide ions（Br^-）.The main work is as follows:1.Synthesis of gold nanoclusters templatedby BSA and their application in the detection of chromium ionsIn this work,BSA-AuNCs with uniform size and good stability were synthesized by chemical reduction method using BSA as template and ascorbic acid as reducing agent.The synthesized water-soluble BSA-AuNCs were characterized by transmission electron microscopy（TEM）,fluorescence spectroscopy and UV-Vis spectroscopy.The characterization results showed that the synthesized BSA-AuNCs were uniformly dispersed with an average particle size about 1.5 nm.Based on the fluorescence quenching effect of chromium ions（Cr（VI））on BSA-AuNCs,a new method for the detection of Cr（VI）was established by using BSA-AuNCs as fluorescent probes.The method has good selectivity,simple operation and can be used forthe detection of Cr（VI）in environmental samples.The BSA-AuNCs test paper was prepared by immobilized on the filter paper by the soaking method to realize the intuitive,rapid and visual detection of Cr（VI）.2.Synthesis of gold nanoclusters with PEI as template and the detection of ferrous ionsIn this work,gold nanoparticles were first synthesized using PEI as a template and ascorbic acid as a reducing agent.Then,the blue fluorescent PEI-AuNCs were obtained by etching the gold nanoparticles with hydrogen peroxide as the etchant.Based on the fluorescence quenching effect of ferrous ions(Fe²⁺)on PEI-AuNCs,a fluorescence analysis method for quantitative detection of Fe²⁺was established.The influence of reaction conditions on the experiment was investigated and the reaction mechanism was preliminarily discussed.Under the optimized experimental conditions,the quenching degree of PEI-AuNCs has a linear relationship with the concentration of Fe²⁺in the range of 1.88×10^-11～9.80×10^-9 mol/L.The detection limit of this method is 1.84×10^-12mol/L.3.Synthesis of gold nanoclusters with PEI as template and the detection of bromide ionsSynthesis of PEI-Au NPs with high fluorescence emission by etching method using PEI as template and ascorbic acid as reducing agent.Based on the fluorescence quenching effect of bromide ion（Br^-）on PEI-AuNCs,a fluorescence analysis method for quantitative detection of Br^-was established.Experimental data show that bromide ions weaken the fluorescence of PEI-AuNCs.Under the optimized experimental conditions,the quenching degree of PEI-AuNCs has a linear relationship with the concentration of Br^-in the range of 1.50×10^-7～7.50×10^-5 mol/L.The detection limit of this method is 2.93×10^-8mol/L.