Synthesis,Structure And Properties Of Gold Nanoclusters Protected By Glutathione Ligand

Due to the quantum size effect of noble metal nanoclusters（NCs）,they exhibit excellent luminescent properties and physical properties,and have great potential in biological applications.However,most of the NCs developed in the early stage were synthesized under organic systems,which made them not biocompatible;in addition,although some reports about the application of NCs in biomedicine.However,most of the applications of NCs in biomedicine do not use atomically precise NCs,which exhibit different molecular properties such as photoluminescence in the same ultra-small size range.And there are problems such as low yield of NCs,complicated separation steps and poor repeatability.Therefore,realizing the synthesis of water-soluble atomically precise NCs is crucial for subsequent biological applications.In this paper,glutathione（GSH）with good biocompatibility was selected as the ligand,and atomically accurate gold nanoclusters were synthesized by kinetic regulation and solid-state grinding methods,and UV-vis,ESI-MS,NMR,FT-IR and other characterization methods explored the structural composition,optical and phase transfer properties of the prepared NCs.The main research contents are as follows:1.A series of reaction parameters involved in the synthesis of Au₁₈SG₁₄ by the kinetic control method were systematically studied.The effects of reaction solvent,Au（I）-SG complex and reaction temperature on the synthesis of Au₁₈SG₁₄ NCs were explored,resulting in the preparation of Au₁₈SG₁₄ in high-yield.The influence of p H value on Au₁₈SG₁₄ was investigated,and the stability and phase transfer optimal conditions of Au₁₈SG₁₄ NCs were explored.A feasible phase transfer method（solvent dilution method）was proposed to solve the problem of unsuccessful phase transfer under alkaline conditions（p H>9）.By diluting the NCs aqueous solution to increase the degree of dissociation of the carboxylic acid groups and thereby enhance the negative charge on the surface of NCs,thereby facilitating its phase transfer.The luminescence quantum yield of Au₁₈SG₁₄-TOA NCs after phase transfer was increased by 3 to 9 times,and the average photoluminescence lifetime was increased by 1.5 to 2.5 times.2.In order to solve the problems of low yield and complicated operation in the separation of glutathione ligand-protected Au NCs by gel electrophoresis.A method for directly preparing Au₃₂SG₁₈ NCs by solid-state milling is reported,which has the advantages of simple operation,strong reproducibility,and large-scale promotion.The composition and surface ligand structure of the clusters were determined by electrospray ionization time-of-flight mass spectrometry（ESI-TOF-MS）and 1D and 2D NMR.The stability of the clusters was studied by the absorption spectrum versus time curve and the separation technique.The results show that Au₃₂SG₁₈ NCs will undergo fission reaction in normal temperature water with time,and stable Au₂₅SG₁₈ NCs will be formed after long-time etching.3.In order to explore the effect of reducing agent on the synthesis of gold nanoclusters.A route was developed using a mild reducing agent Na BH₃CN to prepare glutathione-protected gold nanoclusters.It is found that the reduction performance of Na BH₃CN will be affected by many factors such as aging method,stirring rate,p H value and so on.The law of solvent dilution-induced trapping of Au₃₅SG₁₇ NCs was demonstrated,and finally Au₃₅SG₁₇ NCs was successfully prepared by solid-phase kinetic regulation method,which also improved the reproducibility of Au₃₅SG₁₇ preparation.The composition and paramagnetic properties of Au₃₅SG₁₇ were also explored by MS,NMR,EPR and other characterization methods.