Application Research Of Gold Nanoclusters And Their Composites In Fluorescence Sensing

Nanomaterials are widely used in many fields,including materials science,medicine,environmental science,and biochemistry.Among them,the noble metal nanocluster（NMNCs）is a new type of nanomaterial,composed of several to tens of metal atoms,and the gold nanocluster（AuNCs）is a typical noble metal nanocluster.Compared with the traditional gold nanoparticles（AuNPs）with larger size and plasmon resonance effect,AuNCs have unique and excellent fluorescence characteristics,which are characterized by emitting strong fluorescence under the excitation of light of a specific wavelength.AuNCs has the characteristics of good biocompatibility and easy surface modification.The practical application of a single AuNCs is relatively limited.In order to expand its application fields and enrich its functions,AuNCs can also be assembled or conjugated with other nanomaterials.The practical application of AuNCs is mostly due to their good photoluminescence properties,and different types of AuNCs can be obtained by using different preparation materials or preparation methods,which usually exhibit different fluorescence characteristics,which is closely related to the small size of AuNCs.In addition,different types of AuNCs can be combined with a variety of nanomaterials to obtain fluorescent nanocomposite probes with excellent properties.In summary,this thesis focuses on the preparation and application of AuNCs@Lys and its nanocomposite AuNCs@Lys-MnO₂,a gold nanocluster with lysine（Lys）as the template,and the optical properties of the material in-depth exploration.Using its fluorescence characteristics,AuNCs@Lys is used to detect the concentration of divalent copper ions in water samples,and AuNCs@Lys-MnO₂ is used to detect the concentration of glutathione（GSH）in human serum.The specific research content is as follows:（1）The concentration of copper ions in water can be detected by the specific fluorescence quenching of copper ions by AuNCs@Lys.The specific principle is as follows.Using lysine as a template,AuNCs@Lys nanoclusters were successfully synthesized with the coating of lysine residue.Copper ions have a strong coordination effect on amino groups,which leads to the aggregation of small-sized gold clusters in the aqueous solution,and the quantum size effect is weakened,which is manifested as fluorescence quenching.The higher the copper ion concentration is,the greater the degree fluorescence quenching is.The linear response range is 0.2 nM-40μM,and the detection limit is 3 nM.（2）By degrading AuNCs@Lys-MnO₂ fluorescence resonance energy transfer（FRET）system to turn on the fluorescence to realize the detection of GSH.The specific principle is:the above-mentioned AuNCs@Lys-MnO₂ and manganese dioxide nanosheets（MnO₂ nanosheets,MnO₂）are conjugated through electrostatic adsorption to obtain AuNCs@Lys-MnO₂ nanocomposite.MnO₂ has strong fluorescence quenching ability.Under certain conditions,the FRET reaction occurs betweenMnO₂ and AuNCs@Lys,and the fluorescence of AuNCs@Lys is quenched by MnO₂.MnO₂ can be rapidly degraded by reducing substances.When different concentrations of GSH are added to the nanocomposite probe solution,the fluorescence signal of AuNCs@Lys recovers to varying degrees.By monitoring the changes in the fluorescence intensity of AuNCs@Lys,the specific detection of the GSH concentration can be achieved.The linear response range is 0.5-1000μM,and the detection limit is 5 nM.