Diffusion And Doping Behavior Of Noble Metal Atoms In Nanomaterials

Atom diffusion and doping processes govern the structure and composition of solid material,which play a key role in determining their properties.How diffusion takes place at the atomic scale in nanomaterial is a significant issue and crucial step in crystallization and catalysis.In addition,diffusion-based element doping is considered to be effective for precisely tuning the optical,electrical or magnetic properties of materials.Especially,as noble metal nanomaterials have been widely used in photocatalysis,it is imperative to deepen our understanding of the diffusion mechanism to promote the ability to control the synthesis of materials with desired properties.In this dissertation,we focused on the diffusion and doping behavior of noble metal atoms in nanomaterials.By the construction and characterization of atom diffusion process,the structural evolution phenomena in nanomaterials were discovered.Moreover,we have well investigated the relationship between atom doping and band structure,which will aid the ability to design and synthesis materials with improved performance.The main contents are listed below:1.We briefly summarizes the recent research progress and background knowledge about the atomic diffusion and doping.This is followed by introducing the research significance and master's projects.2.The Au@Ag2S nanocrystals were used as a model system to investigate Au atom diffusion behavior.By using aberration corrected high-resolution transmission electron microscopy and X-ray absorption near edge structure in combination with In situ X-ray diffraction,we confirm that single atom diffusion of Au in Ag2S occurs and structural evolution from Au@Ag2S core-shell nanostructure to AuAgS-AuAgx or Ag3AuS2-AuAgx hetero-structure were observed.The transition from amorphous Ag2S to crystal AuAgS or Ag3AuS2 occurs selectively on the basis of Ag/Au atom ratio,leading to a significant difference in the performance of photocatalytic activity.3.We have developed a simple method for preparing amorphous GaOx nanosheets and studied in-situ Pt-doping effect of on its properties.Alkali salts were used as template to access amorphous GaOx nanosheets by calcining gallium acetylacetonate at 200?.By using aberration corrected high-resolution transmission electron microscopy and synchrotron radiation photoelectron spectroscopy in combination with UV/Vis/IR diffuse reflectance spectroscopy,we confirmed that Pt-doping led to a raised conduction and valence band position and narrow band gap,indicating the improved conductivity.