Quantitative Investigation Of Plasmonic Hot-electron Injection By KPFM

Plasmonic photocatalysis,which combines metal nanoparticles with semiconductor materials,can absorb both ultraviolet and visible light from sunlight.It significantly broadens the light response band of traditional photocatalytic materials?TiO₂?and greatly improves the photocatalytic efficiency.The generation and injection of hot electrons is an important part of plasmonic photocatalysis.It is very important to research the generation and transfer of hot electrons between metal semiconductors to enhancing the photocatalytic efficiency and solar efficiency.In this thesis,the Au-TiO₂ with a particle size of about 60 nm was prepared by photochemical reduction method.The surface potential of Au-TiO₂ under different illumination was measured by KPFM.The hot electron transfer at the interface of Au-TiO₂ was studied by comparing the changes of surface potential difference between Au particles and TiO₂ film.Specific works are as follows:Firstly,the influence of filter order,sensitivity and driving voltage on the surface potential measurement was studied with high-oriented HOPG as the standard sample,and the KPFM measurement parameters of the experiment was optimized.Then,the Au-TiO₂ samples were prepared by photochemical reduction method.The samples were characterized by SEM,AFM and ultraviolet-visible spectrophotometer.Meanwhile,the surface potential of Au-TiO₂ under ultraviolet and visible light was compared by KPFM,and the qualitative law of hot electron migration was obtained.Finally,the surface potential of Au-TiO₂ under different illumination conditions was measured by KPFM.It was found that the surface potential of Au NPs had the same change trend with the absorption spectrum.Based on the theories of Schottky junction solar cell,we develops a theoretical model for quantitative interpretation.The model can well fit the measureing data of KPFM under different wavelengths of light and obtain the injection efficiency of hot electrons.The research in this paper provides an effective quantitative test method for the hot electron injection efficiency and lays a foundation for improving the photoelectric conversion efficiency and photocatalytic efficiency of plasmonic photocatalytic composite materials.