Preparation And Characteristics Of SERS Substrate Based On Ag Nanostructure

Raman spectra,as the"fingerprint spectra"of molecules,can realize high-information analysis of various complex systems such as physics,chemistry and biology through detection of molecular vibration.Raman spectroscopy is widely used in the research of solid,liquid and gas samples and is a powerful chemical analysis spectroscopy technology.However,in the process of spontaneous Raman scattering,only about one in ten million photons interacting with molecules undergo Raman scattering,so that Raman scattering signals are usually very weak,and the detection sensitivity of Raman spectrum is greatly limited.In 1974,Fleischmann et al.discovered for the first time that pyridine molecules attached to the surface of rough silver electrodes have strong Raman signals.Later,this phenomenon was named surface enhanced Raman scattering?SERS?effect.The emergence of SERS technology provides an effective solution to the low sensitivity of spontaneous Raman spectroscopy.In addition,the continuous development of nanotechnology has laid a solid foundation for the application of SERS technology.In this paper,a new SERS substrate was prepared using silver nanomaterials,and the morphology and SERS characteristics of the substrate were carefully studied by scanning electron microscope,Raman spectrometer and other experimental instruments.At the same time,the FDTD method is used to study and discuss the substrate theoretically.We mainly prepared?PVDF/AgNWs?SERS substrates with piezoelectric effect and?ZnTiO₃/AgNPs?SERS substrates with photocatalytic effect.The specific research contents are as follows:1.Fabrication and Characteristics of PVDF/AgNWs Piezoelectric SERS SubstrateThe first discovery of piezoelectric effect in 1880 attracted extensive attention.Among many piezoelectric materials,polyvinylidene fluoride?PVDF?is widely studied as a representative material.We have prepared a SERS substrate with piezoelectric effect by a simple spin coating method.The experimental results show that the substrate not only has good SERS enhancement characteristics,but also can tune the SERS signal strength through the magnitude and position of the applied force.In addition,we simulated the local electric field of the substrate by FDTD numerical calculation.The substrate can be popularized and applied to other small intelligent sensing fields such as pressure sensors,audio responses and the like,and promotes the development of portable,fast and real-time detection technology to a certain extent.2.Fabrication and Characteristics of ZnTiO₃/AgNPs Photocatalytic SERS SubstrateIn recent years,semiconductor materials?such as TiO₂ and ZnO?have been used to fabricate reusable SERS substrates due to their good photocatalytic activity.However,the properties of the materials will affect the photocatalytic performance.Zinc titanate?ZnTiO₃?has narrower band gap and higher electron mobility than TiO₂ and ZnO,and theoretically has better photocatalytic performance.We use high temperature calcination to prepare ZnTiO₃,and drop AgNPs solution on it,thus preparing ZnTiO₃/AgNPs substrate.After comparing the experimental and theoretical simulation results,it is found that ZnTiO₃/AgNPs substrate not only has excellent SERS enhancement characteristics,but also can effectively degrade R6G under the irradiation of visible light.After 5 cycles,it can still show strong SERS enhancement effect.The corresponding results show that the substrate has high sensitivity and good photocatalytic performance,and is a SERS substrate with wide application prospects.This thesis is composed of the following five chapters:The first chapter is the introduction,which briefly introduces the development of Raman spectroscopy and the two main enhancement mechanisms of SERS.In the second chapter,computational electromagnetics and commonly used numerical methods are introduced.The FDTD method is mainly introduced,and the stability and boundary conditions of the solution of the equation are described.Chapters 3 and 4 introduce the preparation of two new SERS substrates based on silver nanomaterials and the research on their related properties.In the third chapter,PVDF/AgNWs piezoelectric SERS substrates are prepared.due to their flexibility and piezoelectric characteristics,the substrates will exhibit different SERS effects due to different pressures.In addition,the SERS strength of the substrate is also different under different bending degrees.The SERS can be adjusted by adjusting the bending force and pressure on the substrate.The material can also be bent and made into wearable material,which has a very wide application prospect.In chapter 4,ZnTiO₃/AgNPs photocatalytic SERS substrates were prepared.It can realize low concentration detection(10^-12 mol/L)of probe molecule?R6G?,and 5 cycles of detection prove that it can be repeatedly used and has good application prospect.The fifth chapter summarizes and prospects the work of this paper.