Green Preparation And Photocatalytic/Sers Performance Of Silver-based Micro-and Nanoparticles

The silver-based compound Ag₃PO₄has good photocatalytic activity under visible light irradiation.In recent years,researchers have designed many schemes to improve the photocatalytic activity and stability of Ag₃PO₄,including morphological control,construction of heterostructures,and ion doping.Porous Ag nanomaterials have a large specific surface area,excellent optical properties and good catalytic activity,etc,and show good application prospects in the fields of catalysis,optical sensing,surface enhanced Raman scattering,and biomedicine.In this thesis,a simple and green ion exchange method is proposed.In the experimental process,the concave structure octagonal Ag₃PO₄ particles are synthesized without adding any organic solvent or capper.Subsequently,the method using the concave octagonal Ag₃PO₄ as a sacrificial template for the preparation of porous Ag particles has the advantages of simple and mild experimental conditions.Moreover,no assistant solvent,such as surfactant,catalyst,is required to add during the whole experiment process,which is helpful to the preparation of porous Ag nanoparticles with high performance and purity.Based on the overall idea of this thesis,from the perspective of using hollow structure and improving the utilization of metal atoms,some new explorations have been made in the controllable synthesis of high index facets Ag₃PO₄ and porous Ag micro/nano materials.The specific work of this thesis is divided into the following two parts:1.First,Ag₃PO₄ particles with spherical shape were synthesized by simple ion exchange method with AgNO₃ and Na H₂PO₄ as the main raw materials.When[Ag（NH₃）₂]⁺and Na H₂PO₄ as the main raw materials,Ag₃PO₄ particles with cubic and concave octagonal shape were synthesized by adjusting the hydrothermal temperature of the reaction.The physical and optical properties of the three morphologies of Ag₃PO₄ particles were studied.The corresponding band gap of spherical,cubic and concave octagonal Ag₃PO₄ is 2.56 e V,2.50 e V and 2.46 e V,respectively.Under visible light irradiation,the degradation rate of methylene blue by concave octagonal Ag₃PO₄ particles can reach 99%within 60 min,indicating that it has high photocatalytic activity in the visible light region.This is attributed to the high index crystal plane exposed to the octagonal Ag₃PO₄ particles with concave structure.The exposed crystal plane can not only significantly improve the light absorption response and light utilization rate,but also has a low carrier recombination rate.At the same time,the surface with high index exposes more highly active atoms,which is more favorable to the occurrence of photocatalytic reaction,and ultimately greatly improves the photocatalytic efficiency and photocatalytic stability.2.In this work,the concave structure of octagonal Ag₃PO₄ particles were used as a sacrificial template to fabricate Ag submicron particles through a remarkably facile,rapid,inexpensive and green method in a completely green water solvent.In the reduction process,spongy porous and hollow cage porous Ag submicron particles with highly accessible surfaces were obtained by changing the initial concentration of Na BH₄without the aid of any surfactant.Both kinds of porous Ag particles have rough surface and sharp branch angle,and octagonal hollow cage porous Ag particles have hollow interior,which can be used to assemble SERS substrate.Moreover,the detection limits of the octagonal hollow cage porous Ag particles as SERS substrates for 4-ATP molecules and thiram molecules are 10^-11 M and 10^-8 M.The detection limits of the spongy porous Ag particles as SERS substrates for 4-ATP molecules and thiram molecules are10^-10 M and 10^-8 M.The excellent SERS activity was attributed to the presence of narrow and deep nanogaps on the spongy porous and hollow cage porous Ag submicron particles with highly rough surfaces.The porous Ag materials prepared have special morphology and excellent optical properties,and can be widely used in the fields of surface plasmon,SERS detection,drug delivery,photothermal therapy and catalysis.