The Structure And Properties Of Ligand-protected Gold And Silver Nanoclusters

Ligand-protected coin metal nanoclusters are attracting wide interests owing to their potential applications in catalysis,nanotechnology and biology.As a bridge between organic metal complexes and nanoparticles,zero-valent nanoclusters possess a certain amount of valence electrons which are important to effect metal-metal bond formation.It is well known that surface organic ligands not only help to stabilize the cluster from aggregation,but also play important role in structural modification and function.In this regard,it is highly desirable to obtain a gold nanocluster protected by different organic ligands and study their electronic structures and catalytic properties,which not only enrich the structure and properties of the nanoclusters,but also has crucial importance for the recognition of the interface of nanoparticles.So far,one of the challenges with nanocluster catalysis is the low catalytic activity.In general,removing of the peripheral protecting ligands can increase the activity of the clusters,but the clusters are often unstable and easy to agglomerate.Moreover,unambiguous determination of the obtained structure of the model catalysts is still a challenge for fundamental understanding.Therefore,the controlled synthesis and structure determination of nanoclusters with uncoordinated surface sites are of great significance for the improvement of catalytic activity and the understanding of the catalytic reaction mechanism.We look forward to synthesize more stable and more active nanocluster catalysts.Based on the aboving problems and emergency,this dissertation mainly focuses on the controlled synthesis and structure determination of nanoclusters as well as their properties.Specifically,the following results are included and discussed:(1)Two unique silver nanoclusters protected by alkynyl and diphosphine ligands have been synthesized by direct reduction method.Single crystal structural determination reveals that they have a centered anticuboctahedral Ag13 kernel.Such a kernel is observed for the first time in a coinage metal nanocluster.And the dominating factor of the cluster kernel in affecting the electronic and optical properties was also discussed;(2)Hydrido gold nanoclusters have been synthesized and structurally determined.They represent the first examples of ligand-protected gold nanoclusters containing hydrides.In addition,the structures and electronic and catalytic properties relationship between Ag25Cu4 hydride cluster and nanocluster were also revealed;(3)The novel amido-protected gold clusters with uncoordinated surface sites are the first example of structurally characterized.There are no staple structures existing in the amido-protected gold clusters and the entire constituent Au atoms merge into a metal core with strong electronic interactions.This is an effective method for the direct synthesis of access granted nanocluster catalysts;(4)Homoleptic amido-protected metal nanoclusters have been synthesized.The efficient and flexible protection of amine ligands enables the diversity of nanocluster structure and the regulation of surface atomic arrangement;(5)The access granted Au23 nanocluster has been controlled synthesis with the steric repulsion of amine ligands,which showing excellent performance toward selective oxidation catalysis of benzyl alcohol.