Synthesis,Characterization And Photocatalysis Of Plasmonic Metal-Semiconductor Core-Shell Nanomaterials

In recent years,photocatalysis technology,as a technology that can solve the environmental problems and energy problems,which hinder the development of human beings,has been widely concerned.However,the low solar energy conversion and poor photocatalyst stability always restrict the development of photocatalysis technology,so the design and synthesis of new nano catalyst with excellent quantum efficiency and catalytic performance is of great significance for photocatalysis technology.Noble metal nanomaterials have high photosensitivity because of their special surface plasmon resonance characteristics,so it is a hot research direction to combine the principle of noble metal surface plasmon resonance with semiconductor photocatalysis technology to build surface plasmon.metal semiconductor heterostructure nanomaterials,which can also solve the two major problems human beings facing.In this thesis,we use two typical semiconductors(TiO2,CeO2)as shells and three different morphologies of gold nanoparticles(nanorods,nanospheres,nanocubes)as cores to prepare noble metal@semiconductor core-shell nanostructures with excellent properties.At the same time,combined with related characterization methods,we explore the surface plasmon metal for semiconductor photocatalysis mechanism of action.Finally,we also study the method and characterization of the preparation of Au@SnO2 and Au@Cu2O by electrostatic adsorption.The details are as follows:1.Firstly,gold nanoparticles,gold nanorods and gold nanocubes with good dispersion and regular morphology were prepared by seed mediated method.Then,SDS(sodium dodecyl sulfate)is used as the surface modifier of gold nanoparticles and TiCl3 is used as titanium source.By adjusting the pH of solution to control the rate of hydrolysis of titanium source,the core-shell structure of Au@TiO2 and other exciton photocatalytic materials is constructed.Three main factors(SDS residue,solution pH,TiCl3)that affect the formation of core-shell structure are discussed.Au@TiO2 photocatalytic materials with different shell thickness are synthesized.The performance and mechanism of photocatalytic degradation of methylene blue are explored by combining various characterization methods and high-temperature annealing treatment.The results show that annealing crystallization can greatly improve the catalytic activity of the materials;among the three kinds of Au core,gold nanorods have better catalytic activity;with the increasing thickness of the shell,the catalytic activity gradually decreases.Through this work,we can provide a simple strategy of annealing crystallization to improve the photocatalytic activity of amorphous TiO2 photocatalyst,and verify that the photocatalytic activity of semiconductor titanium oxide is mainly affected by the surface plasmon resonance effect of noble metals.2.Ce(NO3)3 is used as Ce source,EDTA-NH3 is used as amphiphilic modifier,mixed with three kinds of prepared gold core,EDTA-NH3 is coupled with Ce3+on one side and CTAB on the other side.Ce3+ is hydrolyzed to CeO2 by water bath heating,so as to achieve the coating of CeO2 shell.Three key factors(reaction time,EDTA/Ce ratio,NH3 content)that affect the synthesis are discussed,and the core-shell structure materials with different thickness of ceria coated gold are synthesized.The core-shell nanostructures of Au@CeO2 are characterized by UV-vis,TEM,SEM,HRTEM and XRD.The photocatalytic activity of photocatalyst is verified by the photocatalytic oxidation of benzyl alcohol to benzaldehyde under visible light and monochromatic light.The results show that the annealed Au@CeO2 has better photocatalytic activity than pure CeO2.The results show that the photocatalysis of Au@CeO2 core-shell nanomaterials result from the photogenerated electrons and holes produced by semiconductor CeO2 absorbing light and hot electrons produced by surface plasmon resonance of Au core.This structure can not only promote the separation of electron hole pairs,but also greatly expand the light absorption range of the catalyst.In addition,the photocurrent signal of core-shell nanomaterials under visible light is higher than that of pure CeO2 nanomaterials,and the charge mobility is higher,which also proves that the core-shell structure has better light response ability.3.By controlling the reaction temperature,SnO2 and Cu2O were generated from sodium stannate and copper sulfate respectively.Au@SnO2 and Au@Cu2O core-shell nanostructures are prepared by electrostatic adsorption.The morphology and composition of the two core-shell nanostructures are characterized using UV-vis,TEM,SEM and XRD.