Syntheses And Structural Studies Of Au-Ag Bimetallic Nanoclusters Protected By Organic Ligands

Due to the unique size of noble metal nanoclusters protected by organic ligands,they show different properties from bulk materials and small molecules.The structures of nanoclusters can be easily determined at the atomic level by X-ray single crystal diffraction.Nanoclusters are regarded as good models to guide the synthesis of new nanomaterials and design more efficient catalysts.Therefore,nanoclusters protected by organic ligands have attracted more and more attention from researchers in recent years.The properties of nanoclusters could be regulated by introducing different metals.In this thesis,we reported the syntheses and structural determination of several Au-Ag bimetallic nanoclusters.Diverse nanoclusters with different sizes and surface ligands were obtained by regulating the ratio of metal and the kinds of the ligands.The structures of the obtained nanoclusters were characterized by X-ray single crystal diffraction,the synthetic strategies and properties of the nanoclusters were also discussed in this thesis.The main contents of this paper are summarized as follows:1.Au-Ag nanocluster protected by thiolate:A 45-atom trigonal-prismatic Au-Ag bimetallic nanocluster co-protected by thiolate and phosphine,formulated as Au9Ag36(SPhCl2)27(PPh3)6,was synthesized and characterized by X-ray single crystal diffraction successfully.The structure can be described as a core-shell structure with a tricapped trigonal prismatic Au9 core encaged in a larger tricapped trigonal prismatic Ag30 shell and further capped by six Ag(PPh3)moieties.Every 13 Ag atoms construct the nearly coplanar yet severely distorted"square" face of trigonal-prismatic,and arranged in a way reminiscent of the(100)face of a facecentered cubic(fcc)structure.Peculiar holes were found in the nanocluster,and the stability of the nanocluster could be caused by steric hindrance and magic electron count.2.Au-Ag nanoclusters protected by phenylalkynyl:A series of Au-Ag bimetallic nanoclusters protected by phenylalkynyl were synthesized through co-reduction of gold and silver precursors at a low temperature,the size and surface ligands of the nanoclusters are adjustable by modulating the ratio of metal,surface organic ligands in the reactants and the species of counter ions used in the syntheses.The structures of(AuAg)44,(AuAg)144 and(AuAg)135 protected by phenylalkynyl were characterized by X-ray single crystal diffraction successfully.Though the nanoclusters are mainly protected by phenylalkynyl with core-shell structures,they are co-protected by acetate radical,chloride ligands and bromide ligands,respectively.It is the first time we reveal the structure of the nanocluster with 144 metal atoms.In addition,we also discussed the synthetic strategy for the bimetallic nanoclusters protected by phenylalkynyl and made some improvements.