Study On Synthesis Of Polyvinylpyrrolidone Coated Silver Nanoclusters And Thire Application

In recent decades,the discovery and development of metal nanoclusters（MNCs）have brought broad application prospects for metal nanomaterials.Precious metal nanoclusters such as gold and copper,silver nanoclusters have the advantages of good biocompatibility,large Stoke’s shift,higher luminescence property,low toxicity,and also being widely used in optical sensing,catalysis,biomarkers and drug delivery aspects.As a new kind of luminescent material,silver nanoclusters have excellent stability,water solubility and biocompatibility,which make them obtain good detection and analysis results.In traditional templates,silver nanoclusters are very difficult to synthesize due to their easily agglomeration.Therefore,the establishment of a simple and environmentally friendly synthesis method will be of great significance to the practical application of silver nanoclusters.Thus,in this article of the study we used polyvinylpyrrolidone（PVP）as a template to prepare silver nanoclusters（Ag NCs@PVP）with high luminescence properties by using hydrothermal synthesis method.Ultraviolet-visible absorption spectroscopy（UV-vis）,fluorescence spectroscopy（FS）,high-resolution transmission electron microscopy（HRTEM）,X-ray photoelectron spectroscopy（XPS）and other characterization methods were used to analyze and study the structural properties of the synthesized silver nanoclusters.In addition,based on the fluorescence quenching mechanism,a sensor system for Cr⁶⁺ion,metronidazole,and nitrofurantoin were established.The main research contents are as follows:（1）Using hydrothermal synthesis method,under the reduction of aqueous formaldehyde solution,a strong luminescent silver nano-cluster protected by polyvinylpyrrolidone K15（PVP）was synthesized for the first time.The influences on the synthesis of silver nanoclusters which are the mass ratio of Ag NO₃ and PVP,reaction temperature,reaction time and p H have been investigated.It’s luminescence properties,structure and morphology also have been characterized.At the same time,it has been explored that Ag NCs@PVP can be used to detect heavy metal hexavalent chromium ions(Cr⁶⁺).The results show that the concentration of Cr⁶⁺presented has a good linear relationship with the change of the fluorescence emission spectrum intensity of Ag NCs@PVP.Its linear range is 2-340μM,the detection limit is 0.2?M.This method is suitable for the detection of Cr⁶⁺in actual water samples.It was also found that the addition of ascorbic acid（AA）can recover the fluorescence of nano-silver clusters.The quenching and enhancement mechanism of Ag NCs@PVP fluorescence of Cr⁶⁺and AA has been studied in detail respectively.Therefore,fluorescent probes have practical significance and application prospects.The fluorescence of Ag NCs@PVP provides an efficient and reliable strategy for Cr⁶⁺ion detection.（2）Metronidazole can cause the fluorescence response phenomenon of Ag NCs@PVP.A simple and fast new method for the determination of metronidazole in vitro has been established;the linear range is 0.29-585?M,the detection limit is 0.22?M,and the method has good selectivity.When this fluorescent probe was applied to the determination of MTZ in human urine,the recovery rate was between 99.48%and 103.7%,and the relative standard deviation values were all less than 2.25%.Therefore,it is necessary to detect MTZ accurately.This method can be used efficiently and sensitively for the detection of actual samples.（3）Finally,a method for detecting nitrofurantoin using Ag NCs@PVP as an optical probe was constructed,and the influence of nitrofurantoin on the spectrum of Ag NCs@PVP was discussed.The results show that nitrofurantoin can cause obvious quenching of the fluorescence of Ag NCs@PVP,and based on the interaction between nitrofurantoin（NFT）and Ag NCs@PVP can cause fluorescence quenching,a fluorescence emission spectrometry method for detecting NFT was established.The linear range is 4-252?M,and the detection limit is 0.21?M.The method has good selectivity.When this fluorescent probe was applied to the determination of NFT in human urine,the recovery rate was between 97.95%and 100.4%,and the relative standard deviation values were all less than 1.4%.In addition,the detection method established by the optical probe has good selectivity and high sensitivity,which is expected to provide a theoretical basis for the application of the probe in other related fields.