Preparation And Sers Effect Of Au And Ag Modified WO₃ Composite Substrate

Surface-Enhanced Raman Scattering(SERS)refers to the phenomenon that when molecules are adsorbed on the rough surface of some metal,semiconductor,carbon materials and other nano materials,the Raman scattering intensity is greatly enhanced.SERS can provide the information of molecular content and structure to be measured,and realize rapid nondestructive and ultrasensitive detection.At present,the widely accepted SERS mechanism is Electromagnetic enhancement and chemical enhancement.The enhancement of the former mainly depends on the resonance process between the surface plasmon and the excitation field,and the localized surface plasmon resonance(LSPR)of the nanomaterials will be stimulated when the molecules are close to or adsorb the surface of the nanomaterials.As a result,the intensity of local electric field increases,which affects the Raman signal positively.The local electric field intensity is related to the size and morphology of the particles.The latter enhancement is caused by the resonance transition between the substrate and the adsorbed molecule.It's a charge transfer that leads to chemical enhancement,when the excited energy satisfies the transition from the ground state to the excited state.With the development of the current SERS substrate research,some new SERS substrate problems have emerged to be solved urgently.For example,the method of expressing pollutant concentration only by Raman signal strength is not accurate,and the precious metal particles such as gold and silver have been affected by the environment for a long time,resulting in oxidation and failure of the surface part.There were also some SERS substrations with strong adsorption capacity.After the test,there were still target molecules remaining in the SERS substrate,which was difficult to clean up and would cause secondary pollution.This paper studied the problems of the above SERS substrate,and the main research contents and results were as follows:1.WO₃ nanosheets were prepared by dealloying method,and oxygen defects were introduced in 100 Pa H₂ reduction atmosphere to enhance the SERS performance and photocatalytic activity of semiconductor substrate.The WO_3-x SERS substrate modified with Au nanoparticles was prepared by ion sputtering on the surface of nanoplates.The vacuum was 4-5 Pa,the sputtering current was 5-6 m A,the sputtering time was 5-40 s and spheroidization annealing was carried out.The results show that the substrate can effectively detect R6G molecules of 10^-8mol/L,It has the ability of surface self-cleaning and recycling,and can realize the quantitative detection of target pollutant molecules in the electrode system through the degradation of photocurrent density.2.Ag nanoparticles were deposited on tungsten surface in situ by laser printing technology and in situ ion exchange method,and high throughput and rapid preparation could be achieved.In Raman performance test,10^-8 mol/L concentration of R6G could be detected.3.Using the excellent photoelectric properties and large specific surface area of TiO₂ nanotube array,the SERS active electrode of Ag/WO₃/TiO₂ substrate was prepared by means of electrochemical adsorption,in-situ ion exchange and UV irradiation precipitation of silver nanoparticles on the TiO₂ substrate,and the methylene blue(MB)molecules were detected.The minimum detection limit is 10^-11mol/L.Also due to the more prominent photoelectric performance of this substrate,the SERS active electrode of Ag/WO₃/TiO₂ substrate also shows the ability of surface self-cleaning and recycling,and the accurate quantitative detection of MB molecules within a certain concentration range can be realized through the electrode system.