Fabrication And Research Of TiO₂-based Surface Enhanced Raman Scattering Substrates

TiO₂ NPs are regarded as one of the most widely investigated and used inorganic semiconductor materials because of their chemical and thermal stability,availability,nontoxicity,and biocompatibility,also it is a relatively large band gap semiconductor material with its affluent and various surface states.Due to the weak Raman enhancement of TiO₂,the application of SERS is limited.In this paper,the application of TiO₂ in raman detection field was investigated by doping nonmetallic elements and considerd it can improve the SERS performance.The main research contents and results are as follows:1.P doping TiO₂ were synthesized by using H₃PO₄ as phosphorus source via a facile sol-hydrothermal process.We choose 4-Mercaptobenzoic acid?4-MBA?as the probe molecule to build TiO₂/MBA structures as active substrates for surface-enhanced Raman scattering?SERS?.The samples were characterized for morphology,structure,optical property and surface chemical composition by Transmission Electron Microscope?TEM?,X-Ray Diffraction?XRD?,(X-Ray Photoelectron Spectroscopy?XPS?,UV–visible diffuse reflectance spectra?DRS?and Raman spectroscopy.It shows that the crystal size of TiO₂was about 6-12 nm and P doping could not influence the phase of the crystal.XPS revealed that P⁵⁺replace Ti⁴⁺and doping into the crystal lattice by forming O-P-O.The Raman result shows that P doped TiO₂ has a higher intensity of Raman signals in P-TiO₂/MBA structures than that in pure TiO₂/MBA,the 2%P-TiO₂ own the strongest Raman signals than any other samples,this is due to phosphorus doping which narrow the energy band gap of TiO₂ and abundant the surface states,these were profitable for TiO₂ to MBA molecule charge transfer process.2.N doping TiO₂ NPs were synthesized by a sol-hydrothermal process using NH₄Cl as nitrogen source and build N-TiO₂/MBA structures as active substrates for surface-enhanced Raman scattering?SERS?.The samples were characterized for morphology,structure,surface chemical composition and spectroscopic properties by TEM,XRD,XPS,DRS and Raman spectroscopy.TEM and XRD shows that TiO₂ and N-TiO₂ were mainly anatase phase nanoscale particles with the crystal size about 11 nm and N doping could not influence the phase of the crystal.XPS revealed that N was doped by two forms:N replace O by building Ti-O-N or Ti-N-O oxynitride and the N-H or NH₃adsorbed on the surface of TiO₂ NPs.The Raman result shows that the N doped TiO₂ NPs have a higher intensity and sensitivity of Raman signals in N-TiO₂/MBA structures than that in pure TiO₂/MBA,the 1%N-TiO₂ own the strongest Raman signals than any other samples.This was attribute to the nitrogen doping energy level that profitable TiO₂ to MBA molecule CT process.3.The silver sol was prepared by Lee and Meisel method,and the SERS active substrate of doped TiO₂/MBA/Ag sandwich structure was constructed by coupling with P and N doped TiO₂ prepared in the previous two chapters.In the doped TiO₂/MBA/Ag structure,2%P-doped TiO₂ and 1%N-doped TiO₂ own the most obvious enhancement of the Raman peak signal.The sensitivity of 1%N-TiO₂/MBA/Ag substrate was magnitude higher than that of pure TiO₂/MBA/Ag substrate.4.Researched the SERS spectra of norfloxacin adsorbed on 1%N-doped TiO₂.Under the combined action of Ag nanoparticles,the Raman signal intensity of norfloxacin was enhanced.When the p H is nearly 6-7,the Raman signal with the best strength can be obtained.