Study On Preparation And Properties Of Magnetic Nanocomposites

The synthesis of magnetic nanocomposites is a very important research field in new nano-materials at present. In the thesis, we have first demonstrated a simple method to construct Fe3O4/Au composite microspheres by using L-cysteine as a linker to modify Fe3O4 nanoparticles; the solvothermal method was used to synthesize 3D flowerlike hierarchical Fe3O4@Bi2O3 core-shell architectures and Fe3O4@SiO2@CeO2@Au composite with multi-shell. The composition, construction and properties of the products have also been investigated.The main contents are summarized as follows:1. In the solution, the surface of Fe3O4 nanospheres was modified by L-cysteine. The gold nanoparticles were successfully adsorbed on the surface of Fe3O4 spheres due to strong coordinative interactions between the NH2 and SH groups of L-cysteine and Au nanoparticles. The results indicated that the Fe3O4/Au composite spheres showed a strong absorption in the NIR region and novelty tuned optical properties from the visible to the NIR by simply controlling the diameter of Fe3O4. This Fe3O4/Au hybrid nanostructure will be used as potential photothermal therapeutic agents and for catalysis, biological sensing, probing, and so on. Furthermore, this experiment also suggested a simple way to synthesize various bifunctional or multifunctional composite nanomaterials through simply linking two or several kinds of nanomaterials by chemical bonds.2. The 3D flowerlike Fe3O4@Bi2O3 core-shell structure composite photocatalyst was fabricated by a solvothermal method in the component solvent of glycol and ethanol (Vglycol/Vethanol=1:2). The size of these flowerlike hierarchical microspheres is about 420 nm, and the shells are composed of several nanosheets with a thickness of 4-10 nm and a width of 100-140 nm. These composite microspheres are superparamagnetic at room temperature. It is worth noting that the obtained composite photocatalysts can not only be easily recycled by applying an external magnetic field, but also exhibit powerful visible-light photocatalytic activity for the degradation of RhB. The photodegradation rates of the as-synthesized Fe3O4@Bi2O3 hierarchitectures are much higher (7-10 times) than the commercial Bi2O3 particles. Moreover, it is important to point out that the RhB degradation reaches about 100% for the as-prepared Fe3O4@Bi2O3 composite microspheres under visible-light irradiation after 50 min. In addition, due to their unique architectures, the as-obtained products may have potential applications in water treatment, sensors, microelectronics, energy storage, and other related micro- or nanoscale devices.3. The Fe3O4@SiO2 core-shell microspheres were prepared through a modified Stober process. Then, CeO2 colloids were adsorbed on the surface of Fe3O4@SiO2 microspheres by means of the hydrolyzation of Ce4+ under alkaline solution, and the above mixed solution was sealed in a Teflon-lined stainless-steel autoclave and maintained at 160℃for 5 h, the Fe3O4@SiO2@CeO2 multi-shell magnetic composite were obtained. The gold nanoparticles were successfully adsorbed on the surface of APTS-functionalized Fe3O4@SiO2@CeO2 spheres due to strong coordinative interactions between the NH2 of APTS and Au NPs. This Fe3O4@SiO2@CeO2@Au hybrid nanostructure will be used as catalyst for CO oxidation, sensors and so on.