Enhanced SERS Of TiO₂ Substrates Via Synergistic Effect Between AgNPs And Oxygen Vacancies

After Industrial Revolution,people have to confront with the energy crisis and environmental pollution.As a common method of detection of contaminants in water,Raman based material with high sensitivity and low cost is what many researchers are seeking.The very research subject is of great theoretical and practical significance.Due to its localized surface plasmon resonance which is able to induce the change of bandwidth of material,optical property and increase performance of Raman enhancement,Ag nanoparticles are often used as composite raw material of semiconductors.However,high oxidability of Ag and the narrow scope of photoresponse of TiO₂ limit their application.Therefore we have to do some modification.Self-doping?oxygen vacancy?is an ideal method of modifying which will keep purity of elements,but it is easy for oxygen vacancy to recombine with oxygen.Therefore,this article mainly focuses on solving above-mentioned problems.Our article mainly focuses on the growth of TiO₂ crystal on the FTO conductive glass,getting TiO₂ film of rutile phase.Ag nanoparticles were deposited on the surface of TiO₂ nanorods arrays by chemical precipitation and cold plasma and the surface intrinsic defects were introduced by ethanol impregnation treatment.And we explore the influence of temperature,time and solution ratio in the process of chemical precipitation.In this article,SEM,TEM,EDS,XRD,XPS,EPR and UV-vis are used to characterize materials and research the SERS performance by R6G detection.1)FTO glass that is washed by mixed solution is as the substrate to grow the nano-array of rutile TiO₂ film.And diameter of the Ag nanoparticles is below 20 nm with good microstructure and high dispersion.Compared with pristine TiO₂,the composite substrate has better Raman performance,and enhancement factor and relative enhancement factor reach 2.56 and 2.8×10⁶,whose ability is comparable with metal.2)By comparing physicochemical property of samples with different operation sequence,we found there exists synergy between Ag nanoparticles and oxygen vacancy,so we raised a presumption of synergy mechanism:newly formed defect level?Ess?acting as a new valence band that leads to redistribution of electron transportation;the free electron in Ag can balance the positive charge of oxygen vacancy,destroying metastable state.3)We focused on the inoxidizability by collecting physicochemical parameters of samples placed in air for two months.The results indicate that the test outcome won't be affected by storage,and the synergy can improve the antioxidant ability of both of them.So we build relaxation effect hypothesis:Ag nanoparticles can slow down the speed of oxygen vacancy oxidation;bulk oxygen vacancy can diffuse to the surface of the material,making up a deficiency.4)Based on the time decay law of self-diffusion coefficient,we build Fick diffusion model of Vo parameter.We conclude that geometrical parameter of Vo controls the decay law,determing rate of decay,and then change form of decay curve.