Theoretical Study On Several FCC Configuration Structural Evolution Of Gold And Silver Clusters Protected

Due to its excellent optical,electrical,mAgnetic and catalytic properties,nanoclusters have broad application prospects in materials,catalysis,optics,biomedicine and other fields.Thiolate-protected gold clusters and silver clusters are important inorganic nanomaterials.The controllable synthesis,structure analysis and characterization of these clusters cluster chemistry are one of the research hotspots in the field of material science and life science in recent decades.The research on the structure and properties of nano-clusters is a hot topic in the field of nanoscience.The structure rules of clusters are summarized based on the exploration of cluster structures.The structure-property law is one of the most important basic science problems in the study of the structure and properties of nano-clusters.In this paper,we have determined the growth mechanism between the face-centered cubic Au₂₁（SR）₁₅,Au₂₃（SR）₁₆^-and"positive icosahedral"Au₂₅（SR）₁₈^-clusters in a single crystal structure,the structural evolution between the core and the ligand layer structure of the surface-cube-stacked thiol/phosphine ligand-stabilized silver nanoclusters was discussed by using density functional theory.The main content of this article is divided into the following two parts:The first part of the research:The size conversion mechanism of Au₂₃（ER）₁₆ and Au₂₅（ER）₁₈ clusters（E=S and Se）was studied by using density functional theory method including dispersion correction.Thiolate and selenolate-protected Au₂₃3 and Au₂₅ clusters have attracted extensive attention in the past few years.Their precise atomic structures have been determined by single crystal X-ray diffraction analysis.In this part,the size conversion reaction between Au₂₃3 and Au₂₅5 clusters is mainly concerned and studied.Recent experimental studies have found that Au23 and Au25clusters can undergo reversible or irreversible precise size conversion reactions,such as the spontaneous transformation of Au₂₅（SeR）^–₁₈ clusters into Au₂₃（SeR）^–₁₆ clusters under the induction of external stimulus（for instance,in the presence of reductants）.This cluster reaction is very similar to the reaction of organic molecules,and the reactants and products have precise composition.However,the exact reaction mechanism and pathway are not clear because of the limitation of experimental methods.By means of density functional theory calculation,this part clarifies the reaction pathway and mechanism of Au₂₅（SeR）₁₈^–transformed into Au₂₃（SeR）^–₁₆by reducing agent NaBH₄ and water-soluble cluster Au₂₃（SR）₁₆^–size growth to form Au₂₅（SR）^–₁₈（R=SPhCOOH）.It is revealed that the growth and shortening of two symmetrical"staple"ligand units on the surface of clusters is the key to the size conversion reaction of clusters.The second part of the research:We summarize the structural properties,electronic properties and evolutionary laws of Ag₁₄（SR）₁₂（PR₃）₈,Ag₂₃（SR）₁₈（PR₃）₈,Ag₃₈（SR）₂₆（PR₃）₈,Ag₆₃（SR）₃₆（PR₃）₈⁺,Ag₄₆（SR）₂₄（PR₃）₈²⁺,Ag₆₇（SR）₃₂（PR₃）₈³⁺with face-centered cubic atom configuration nano-clusters structures.We found they were to be"structural homologous"clusters with"Ag₆ octahedron"as the basic core structural unit and Ag-SR-P as the ligand protection unit.Larger size Ag₂₃（SR）₁₈（PR₃）₈,Ag₃₈（SR）₂₆（PR₃）₈,Ag₆₃（SR）₃₆（PR₃）₈⁺clusters can be regarded as evolved from the structure of the smallest size Ag₁₄ cluster.The Ag₄₆（SR）₂₄（PR₃）₈²⁺can grow into Ag₆₇（SR）₃₂（PR₃）₈³⁺clusters.In this paper,Ag₁₄（SR）₁₂（PR₃）₈ and Ag₄₆（SR）₂₄（PR₃）₈ clusters were used as“growth seeds”to perform one-dimensional two-dimensional three-dimensional growth,summed up the two growth laws,and analyzed and discussed the properties of cluster energy,electrons and spectra during the growth process.