Construction And Antibacterial Properties Of Cu-Ag Metal Nanoclusters

As a bridge between discrete metal atoms and metal nanoparticles,metal nanoclusters provide a theoretical model for scientists to understand the structural evolution from atoms to molecules in nature.It has unique quantum effect and discrete electron energy level,which shows different properties from metal nanoparticles.Metal nanoclusters can penetrate the cell wall of microorganisms into the cell interior,and react with sulfhydryl groups on proteins to cause intracellular metabolic disorder,damage the material delivery system and respiratory system,and produce antibacterial effect.Metal nanoclusters have ultra-small molecular like structures,which can be easily removed by the kidney,greatly reducing the toxic and side effects on normal cells.The surface structure of metal nanoclusters determines whether they can approach the target in the cell membrane.The difference of antibacterial performance of metal nanoclusters was investigated by regulating the difference of surface ligand.The main research contents are as follows:1、The structure and antibacterial properties of Ag-Cu alloy nanoclusters were studied by regulating ligand substituents.In this paper,we synthesized three kinds of Ag-Cu alloy nanoclusters with different substituents by means of acetylene and phosphine ligand protection:[Ag3Cu5(C29H23NP2)3(CF3PhC≡C)6](PF6)2(defined as CF3-Ag3Cus),[Cu5Ag3(C29H23NP2)3(FPhC≡C)6](PF6)2(defined as F-Ag3Cu5),[Cu5Ag3(C29H23NP2)3(PhC≡C)6](PF6)2(defined as H-Ag3Cu5),all three of them are Ag3Cu5.The structures of Ag-Cu alloy nanoclusters were confirmed by X-ray single crystal diffraction and high resolution mass spectrometry.Due to different peripheral substitutions,the three crystals exhibit different fluorescence emission behaviors(CF3Ag3Cu5 is yellow light,F-Ag3Cu5 is orange light,and H-Ag3Cu5 is yellow-green light).In addition,CF3-Ag3Cu5、F-Ag3Cu5 and H-Ag3Cu5 showed aggregation induced luminescence in non-benign solvents.The antibacterial activity of three Ag-Cu alloy clusters against E.coli and S.aureus was investigated by liquid phase antibacterial method,respectively.The results showed that CF3-Ag3Cu5 showed high antibacterial activity against E.coli and S.aureus at 20 μM.Furthermore,the surface of E.coli and S.aureus treated with CF3-Ag3Cu5 showed obvious folds by scanning electron microscope,and the bacteria were well inhibited.The high antibacterial activity of CF3-Ag3Cu5 nanoclusters was verified by the determination of silver ion release.In this work,by regulating the surface ligands of Ag-Cu alloy nanoclusters,the alloy nanoclusters modified with trifluoromethyl surface ligands interact more strongly with bacteria,and promote bacterial death by releasing more silver ions,and clarify the structure-activity relationship between surface structure and antibacterial performance.It provides experimental and theoretical basis for changing the physicochemical properties of metal nanoclusters by regulating surface ligands.2、The strategy of using antibacterial drug molecules to construct silver nanoclusters to achieve high antibacterial effect,zidovudine is a drug molecule with high antibacterial effect.Silver nanoclusters Ag14(C10H12N5O4)6(C4H9S)8(Defined as Ag14)with Zidoff as ligand were prepared by one-pot method.The molecular structure of Ag14 was determined by X-ray single crystal diffraction.The antibacterial activity of Ag14 against E.coli and S.aureus was investigated by liquid phase and AGAR plate methods.The results showed that Ag14 exhibited concentration-dependent antibacterial activity against E.coli at 20 ppm.The surface of E.coli and S.aureus treated with Ag14 showed obvious folds under scanning electron microscope,and the bacteria were well inhibited.The silver ion release of Ag14 nanoclusters increased with time.It was found that Ag14 nanoclusters dissolved and released Ag+into the target bacteria,which induced the generation of reactive oxygen species in the bacteria,thus causing bacterial lysis.In this work,an atomically accurate silver nanocluster antibacterial agent was developed to achieve biological antibacterial behavior under relatively safe conditions.