| Silver nanoclusters(Ag NCs)are a new type of nanomaterials with stable optical properties,easy synthesis,good biocompatibility and low cytotoxicity.At present,many methods have been used in the synthesis of Ag NCs,such as radiation method,phase transfer method,photoinduced reduction method,chemical reduction method,ultrasonic method,electrochemical method,and so on.Inorder to impove the stability of the Ag NCs many stabilizer templates were used in the synthesis process,including small molecules containing sulfur,polymers,protein macromolecules,DNA etc.Among them,polymers were widely used for its high molecular weight,and contain rich functional groups,branch chains and cavity structure,it can block the interaction between Ag NCs and the external environment then made the Ag NCs have excellent stability.In this paper,polyethylenimine(PEI)protected Ag NCs with excellent fluorescence properties were synthesized by chemical reduction,and were used for the detection of drugs,heavy metal ions and pH sensing.The main work is as follows:1.Synthesis of silver nanoclusters and its application in detection of famotidineUsing PEI as template and formaldehyde as reducing agent,Ag NCs with small size and good stability were prepared by chemical reduction method.The synthesized water-soluble Ag NCs were characterized by transmission electron microscopy(TEM),fluorescence spectra and UV-Vis spectra.The results showed that the size of the synthesized silver nanoclusters is about 2.5 nm,and were dispersed without aggregation.Then a new method for the detection of famotidine(FMT)was established by using the Ag NCS as fluorescent probe.The method has the advantages of high sensitivity,good selectivity,low cost and simple operation,and can be used for the content determination of FMT in tablets.It has potential application value in similar sample analysis.2.Synthesis of silver nanoclusters and its application in pH sensingAg NCs was synthesized using PEI as template and ascorbic acid(AA)as reducing agent.It was found that the Ag NCs was very sensitive to the pH of the environment and the fluorescence intensity was decreased with the increase of the pH of the system.Based on this,a new method for pH sensing based on Ag NCs was established.The fluorescence response characteristics of the Ag NCs in different types and pH buffer were investigated.The results showed that it has a good pH response in buffer solutions.In the buffer solution of BR at pH 2.40?9.40 have a linear equation and correlation coefficient of F=-532.81pH+6048.1 and R2=0.991 respectively.The effects of reaction time and temperature on the sensing ablilty were also investigated,the results showed that the fluorescence intensity of Ag NCs decreased with time extension at room temperature,and it should be measured immediately after adding to the solution.There was no significant difference between the fluorescence analysis results and the pH meter measurement value when the Ag NCs sensors were used in the determination of pH of beverages,which indicates that the pH sensor can be used to detect the pH of the actual sample.3.Application of the silver nanoclusters in chromium ion detectionUsing PEI as template and AA as reducing agent,water-soluble silver nanoclusters were synthesized by chemical reduction method at room temperature.Based on the fluorescence quenching effect of chromium ion Cr(?)to the Ag NCs a fluorescence analysis method for determination of Cr(?)was build.The action conditions were investigated and the action mechanism was preliminarily discussed.Under the optimized experimental conditions,the fluorescence quenching effiency of Cr(?)to the Ag NCs was piecewise lineared in range of 8.30×10-8?4.17×10-5 mol·L-1,and with a detection limit of 0.22×10-9 mol·L-1.4.Application of the silver nanoclusters in cobalt ion detectionUsing PEI as template and AA as reducing agent,green fluorescent Ag NCs was synthesized by one-step chemical reduction method,and was applied in the detection of cobalt ions(Co2+).The experiments showed that the fluorescence of Ag NCs was quenched by Co2+in pH=6.4 KH2PO4-Na OH buffer.The reason may be that the electron transfer from PEI protected Ag NCs to Co2+and forme the Co-N bond,and cause the fluorescence quenching of Ag NCs.Under the optimized experimental conditions,the quenching degree of Ag NCs was lineaed in the range of 8.30×10-7?4.17×10-4 mol·L-1,and the detection limit was 0.41×10-8 mol·L-1. |
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