Synthesis, Characterization And Property Study Of Magnetic Fe₃O₄ Micro-and Nanocomposites

Magnetic micro-nano-materials have attracted intense interest due to their unique physical and chemical properties that different from bulk magnetic materials. The development and application of magnetic micro-nano-materials with unique structure and composition are of great significance. However, magnetic micro-nano-materials tend to aggregate, and they are lack of functional groups on their surfaces, which limits their applications. Now, the magnetic nanocomposites have been a hot-spot in materials research because they can overcome these disadvantages. In this dissertation, we studied the preparation of Fe3O4 magnetic composites, and synthesized Fe3O4@silica, Fe₃O₄@SiO₂-Ag, and Fe₃O₄@SiO₂@PbS micro- and nanocomposites. The formation mechanism and the application of these composites in areas such as ion-adsorbanceas and pollutant detection have been stidued. The main results are summarized as follows:1. Through using Fe₃O₄ microspheres that synthesized via a hydrothermal method as raw material, we prepared Fe₃O₄@SiO₂ composites. The adsorption ability of the composites to heavy metal ions was studied by inductively coupled plasma atomic emission spectrometer and UV-Vies spectrophotometer. We found that adsorption ability of the composites to Pb²⁺ and Hg²⁺ are very strong. Due to the magnetic property of the composites, it can be removed from the solution conveniently, and thus these composites have potential valuation of application.2. By using Fe₃O₄ microspheres and ethyl orthosilicate (TEOS) as starting materials, magnetic Fe₃O₄@SiO₂ composite microspheres were prepared at room temperature. Then, these compostes were applied to the synthesis of Fe₃O₄@SiO₂-Ag three-ply composites through using the Ag-mirror reaction. The composites were characterized by XRD, SEM and TEM, the results show that a layer of Ag nanoparticles with size of about 20 nm were coated on the surfaces of the Fe₃O₄@SiO₂ composite microspheres. The three-ply magnetic composites were applied as as a SERS substrate to detect Rhodamine 6G and melamine, and we found that the detection limits of Rhodamine 6G and melamine were 10^-9 M and 10^-6 M, respectedly.3. On the basis of our previous works, we prepared Fe₃O₄@SiO₂@PbS three-ply magnetic composites through a simple wet-chemical route. Although the property of Fe₃O₄@SiO₂@PbS composites needs further exploring, this work may provide useful information on the synthesis of magnetic micro- and nanocompounds with core-shell structure and other inorganic micro-nano-materials with core-shell structure.