Fabrication Of Magnetic Iron Oxide/Noble Metal Composite And Its Aplication In SERs Substrates

As its high sensitivity and it can provide the characteristic fingerprint peak of the substance at single-molecule level which can achieve rapid and non-destructive testing,Surface-Enhanced Raman Spectroscopy?SERS?has attracted much attention in the fields of biomedicine,environmental monitoring and food safety.The preparation of SERS active substrate has been one of the hotspots in related research area.However,the aggregation state of SERS active substrate is difficult to control,which directly affects the reproducibility and stability of SERS performance.Magnetic iron oxide/noble metal composites have been extensively studied in sensing,imaging,catalysis,and drug release due to their magnetic and plasmonic properties.Since magnetic iron oxide/noble metal composites can be controlled to assemble metal nanostructures to generate mass SERS active hot spots by magnetic field,they have been used as excellent SERS active substrates.Based on the electromagnetic field enhancement mechanism,the ideal SERS substrates can be prepared by using the magnetic iron oxide nanoparticles with specific morphology as the template.Then the Fe₃O₄@SiO₂@Ag nanospindles were synthesized and characterized.Due to the excellent performances of both TiO₂ and mesoporous structure,the Fe₃O₄@mTi02@Ag nanocomposites were prepared.This paper includes the following chapters.In the first chapter,the magnetic properties,preparation methods and applications of magnetic iron oxide nanomaterials were systematically introduced.Then,the contents of SERS were described,including development process,mechanism,and the progress of SERS.Finally,the current research progress of magnetic iron oxide-based SERS active substrates was summarized.In the second chapter,?3-FeOOH nanospindles were synthesized.Then they were coated with the SiO₂ layer about 10 nm thick.And ?-FeOOH@SiO₂ nanospindles were reduced to Fe₃O₄@SiO₂ nanospindles under hydrogen atmosphere.The Ag nanoparticles anchored on Fe₃O₄@SiO₂ were successively introduced via in-situ reduction of AgNO3.The FDTD simulation results indicate that the tips of each nanospindle exhibit strong electromagnetic field enhancement.The experiment results show that Fe₃O₄@SiO₂@Ag nanospindles which had stable and good SERS performance can be used for label-free detection of thiram when they were in the magnetic aggregation state.In the third chapter,Fe₃O₄@TiO₂ nanocomposites were synthesized and Fe₃O₄@mTiO₂ nanocomposites with mesoporous structures were prepared by hydrothermal treatment of Fe₃O₄@TiO₂.The experimental results show that mass Ag nanoparticles can be introduced into mesoporous structures of Fe₃O₄@mTiO₂ nanocomposites.The Fe304@ mTi02@Ag nanocomposites had excellent SERS properties about the dectection of crystal violet and thiram.Finally,the work of this paper was summarized and forecasted.