The Concepts Of The Superatomic Molecule Theory And Their Applications In The Ligands-protected Metal Nanoclusters

Nanomaterials are the basis of the modern science and technology,and very im-portant for the nanotechnology.According to the spatial dimension,nano-materials can be divided into zero-dimensional,one-dimensional,two-dimensional and three-dimensional nano-materials.Among OD nanomaterials,the smaller ones are named nanocluster,and the bigger ones are named nanoparticle.Nanocluster or cluster has become an important subject named " cluster science".In the field of cluster science,metal clusters are very important branches.Start-ing from the magic numbers of sodium clusters are found by mass spectrometry,to the jellium model and superatom concept,and then to the assumption of 3D periodic table of elements,there are many kinds of theory models and ingenious experiments reported.Among these research works,one of the most important and challenging is-sues is the superatom assembly,including assemble superatoms to form supermolecule or supercrystal material.However,there is no proper theory to guide superatoms assem-bly.Researchers have no idea on how to assemble superatoms,and difficult to guarantee the stability and the reasonableness of the superatoms stacking structures.Therefore,it is important to understand the interactions between superatoms,and establish the bonding rules and assembly models.Those significant works can form a theoretical framework which can be used to guide superatom-ssembly,new structures design and experimental synthesis.The purpose of this thesis is to explore bonding types and assembly models among superatoms,and to construct the superatomic molecule theory.We hope the super-atomic molecule theory can be used for new clusters design and synthesis.There are five chapters in this thesis:Chapter 1 contains the background of the cluster research.First,main theoretical methods named density functional theory are introduced.Some important theoretical models and theorems of the density functional theory are included.Then,some theories on the stability and the structures of clusters are introduced,including the jellium model which mainly used for metal cluster,the polyhedral skeletal electron pair theory which mainly used for borane and transition metal complex,and the aromaticity rule.Chapter 2 is the main contents of the superatomic molecule theory.Based on the super valence bond model,the chemical bonds between superatoms can be summarized as three categories,e.g.super covalent bond,super hybrid bond and super non-bonding.Those knowledges together with the isosuperatom concept and hybrid superatom net-work model are new understandings on the chemical bonds,building blocks and assem-ble models of superatoms.The isosuperatom concept and the hybrid superatom network will be introduced detailly in the chapter 3 and 4.Chapter 3 contains the isosuperatom concept which based on the deeply thinking on the building blocks.The new concept is illustrated by the synthesized clusters,and the decision method also will be illustrated.Based on the experimental results,the isosuperatom can be used to form supermolecule.Then,different isosuperatoms can form isosupermolecules.The isosuperatom concept not only can be used to understand the stability of the clusters,but also can be used for the new clusters prediction.Chapter 4 mainly illustrates the superatom network model.In this model,the su-peratoms are assembled by the super non-bonding to form a superatom-network.Then the superatom networks are connected by ligands to form a bigger cluster.The stabil-ity of many ligands-protected gold clusters can be understood by this model.At the same time,a structural evolutional rule named Au13topological rule is proposed based on the structural analysis.The results in this chapter are important both for the stability understanding and the structure predictions.Chapter 5 contains four works which all combined with experiments.In the first work,the structure and optical properties of Ag2@Au25 are investigated.The second work focuses on the possible location of the Hg atom in the Hg@Au25 nanocluster.In the third work,the structures,chemicla bonds and optical properties of Pdn(SR)2n clus-ters are investigated.The fourth work focuses on the structures and chemical properties of Au@Pdn(SR)2n clusters.Theoretical results and analysis of these works give a good explanation and complement of the experimental results.