Preparation Of V₂O₅ With Different Morphologies And Its Surface Enhanced Raman Scattering Properties

Surface-enhanced Raman scattering（SERS）is an optical phenomenon and an effective tool for identifying molecular"fingerprints".Therefore,it is widely used in food safety,chemical,and medical inspections.A good SERS enhancement effect comes from a good SERS base,so it is the focus of current research to optimize the SERS base in various ways to improve its enhancement performance.In recent years,the it has attracted widespread attention to prepare hybrid materials of semiconductor and noble metal with special morphology for scientists because the metal-semiconductor composite not only has a charge transfer effect,but also the electromagnetic generated by the noble metal and the coupled electric field directly generated by the noble metal and semiconductor.In addition,compared with single precious metal nanoparticles,semiconductor/precious metal composites can generate more“hot spots”and can effectively avoid mutual agglomeration between precious metals.Therefore,semiconductor/precious metal composite substrates have a wide application for monitoring food safety.V₂O₅ is the most stable structure among vanadium oxides.Because of its wide application value in catalysis,supercapacitors,cathodes of lithium ion batteries,sensors and electronic switches,it has been at the forefront of basic research and applied research.However,V₂O₅ has little research on SERS performance.In order to expand the application of V₂O₅ in SERS performance,in this thesis,V₂O₅ flower-like materials（FLNMs）and V₂O₅ nanospheres（NSs）were prepared by a simple hydrothermal method.The Au nanoparticles（NPs）were sputtered on the surface of the V₂O₅ FLNMs by an ion beam sputtering,and annealed at 400°C to form a V₂O₅@Au FLNMs,and SERS measurement was performed.With the help of cetyltrimethylammonium bromide as a coupling agent,the V₂O₅ NSs were modified by Au NPs,obtained via in situ reduction of chloroauric acid（HAuCl₄）.The SERS properties of V₂O₅@Au composite flower-like material and V₂O₅/Au NSs as substrates were analyzed.The main results are as follows:The prepared V₂O₅ and V₂O₅@Au FLNMs were characterized by SEM and TEM.It is found that the prepared V₂O₅ FLNMs had a regular morphology and their surface is consisted of many sheet-shaped materials connected at one end.After sputtering plus annealing,the V₂O₅ FLNMs were modified by Au NPs successfully.The XRD analysis showed that the prepared V₂O₅ FLNMs have a monoclinic structure,no impurities were detected.The Au nanoparticles in the V₂O₅@Au FLNMs have a face-centered cubic structure.The sample did not undergo a phase change after heating.X-ray electron spectroscopy further proved that the prepared V₂O₅ and V₂O₅@Au FLNMs are relatively pure.On the properties of SERS,compared with the V₂O₅ FLNMs,the V₂O₅@Au FLNMs shows stronger SERS enhancement performance.The detection limit（LOD）of V₂O₅@Au FLNMs for R6G is 3.24×10^-9M and the LOD of V₂O₅ FLNMs is 3.01×10^-55 M（mol/L）.In addition,in order to extend its application,two carcinogen molecules of rhodamine B and malachite green were detected,and the corresponding LODs were 3.11×10^-8and 4.96×10^-9M,respectively.The V₂O₅ FNLMs has an enhancement factor of 10³,the enhancement factor of V₂O₅@Au FLNMs for various organics is¹0⁵,which indicates that V₂O₅@Au FLNMs has strong SERS performance.The RSD values obtained at characteristic peaks 610,1360 and 1649cm^-11 were 15.69%,15.51%and 13.21%,respectively.Higher EFs and lower RSD values indicate that V₂O₅@Au FLNMs substrate is an ideal SERS substrate.V₂O₅ nanospheres（NSs）prepared by hydrothermal method and V₂O₅/Au NSs reduced in situ were used for a series of characterizations.The SEM and TEM results show that the synthesized V₂O₅ and V₂O₅/Au NSs have uniform morphology,and the XRD and XPS characterization results show that the prepared samples do not contain other impurities.TheV₂O₅/Au NSs have good SERS performance,and the LOD for R6G solution is 3.60×10^-1111 M,reached single molecule level.In addition,in order to extendtheir application,we investigated the SERS properties of sudan III,CV,Rh B and MG.It revealed that their corresponding LODs of V₂O₅/Au NSs are 8.6×10^-8,7.9×10^-9,6.5×10^-10M,and 8.5×10^-1010 M respectively.The EFs reached¹0⁶.The RSDs at the characteristic peaks of R6G were 17.23%,17.17%,and 15.35%,and all RSD values were less than 20%.The substrate has good uniformity.The results illustrated that the V₂O₅/Au NSs exhibit an excellent SERS performance,compared to V₂O₅@Au FLNMs.