Modulating Synthesis,Structures And Properties Of Gold-silver Clusters

Metal nanoclusters are considered as a bridge between small molecules and bulk metal.Compared with metal nanoparticles,metal nanoclusters have potential applications in catalysis,molecular sensing,electronics and biology.Through continuous exploration and improvement of synthetic methods,scientists have synthesized many metal nanoclusters,and determined their crystal structures by single crystal X-ray diffraction.This thesis mainly focuses on synthesis of Au-Ag mixed metal clusters by using different organic and inorganic ligands.This thesis aims at controllable synthesis of high-nuclearity metal clusters.More details are as follows:,?:The regulation of nitrate ions to the synthesis of the gold/silver mixed metal nanoclusters.Based on the direct reduction method developed in our lab for preparation of gold nanoclusters,highnuclearity metal clusters are synthesized by modulating the amount of nitrate ions.We get three novel gold/silver mixed metal clusters:Au24Ag22(PhC=C)24(PPh3)2Cl4,Au46Ag41(PhC ? C)44(NO3)2Cl5 and Au43Ag38(PhC?C)35(NO3)4Cl8(CH3CN)2.The structure of Au24Ag22(PhC=C)24(PPh3)2Cl4 is similar to that of Au24Ag20 with two additional silver atoms connected to the metal core..Single crystal X-ray structural analysis revealed that the Au46Ag41 core can be viewed as being generated from two Au12@Ag20@Au11 Agi clusters via vertex sharing and the Au43Ag38 core is generated from the fusion of two Au12@Ag19Au1@Au9Ag3 via sharing seven atoms.The optical properties have been investigated.This work indicates that Au24Ag20 can be an elementary unit for building high-nuclearity mixed-metal clusters.The nitrate ions play a critical role in the formation of large cluster aggregates.?:Phosphine and alkynyl protected gold and silver nanoclustersTwo gold/silver mixed metal clusters,[Au26Ag18(C8H5)24(PC18H15)2Cl](BF4)2 and[Au28Ag16(C8H5)24(PC18H15)4](BF4)2 have been prepared by modulating the ratio and order of reactants.Their crystal structures have been determined by single crystal X-ray diffraction.We found these two metal cluster cores are doped M44 with structures similar to that of Au24Ag20.The optical properties have been investigated.?:Thiolate and phosphine protected gold and silver nanoclustersWe obtained a bimetallic nanocluster[Au19Ag6(MeOPhS)17(PPh3)6]2+ with mixed ligands of thiolates and phosphines.The structure of An19Ag6 retains the characteristics of Au25,with six gold atoms on the icosahedron Au12 being replaced by silver,which is confirmed by mass spectrometry.Mixed gold and silver nanoclusters have good performance in luminescence and catalysis.There are a lot of active site on the surface of Au19Ag6,so it provides a structural model for the catalytic study.