The Synthesis, Characterization And Applications Of Magnetic Iron Oxide Materials With Core/Shell Structure

In recent years, magnetic nanoparticles with core/shell structure have attracted more and more attentions. In this paper, several magnetic composites with core/shell structure have been successfully prepared, characterized in detail and further applied in catalysis areas etc..Firstly, core/shell structured y-Fe2O3@Ti-tmSiO2(tm means tunable mesoporous) nanoparticles with good activity for the degradation of dyes and the capability of fast magnetic separation have been successfully prepared by a sol-gel process followed with calcination. The obtained core/shell structure is composed of a superparamagnetic core with a strong response to external fields, and an outer layer of porous titanium silicate with a tunable porous sizes. y-Fe2O3core not only facilitate separation of composite from solution, but also serve as a Fenton-like catalyst to catalyze the degradation of methylene blue (MB) and Rhodamine B (RhB). The convenient control over the pore size of porous silica containing titanium species may make it possible to adsorb and catalyze molecules with different sizes. Meanwhile, the framework Ti species exsiting in shell layer also are efficient active sites. This kind of composite exhibits good activity and regenerability in the degradation of pollutants such as MB and RhB.Secondly, a magnetic chemosensor Fe3O4@SiO2-Au-RhB-Tren@PSiO2has been prepared and applied to the detection of Hg+in water. The typical preparation procedure is as following:Fe3O4particles are firstly coated with a compact SiO2layer, then deposited a layer of Au nanoparticles through-NH2groups. Finally, a porous SiO2as the outer layer to excapulate the probe molecules is prepared and it can protect the inner cores. This chemosensor Fe3O4@SiO2-Au-RhB-Tren@PSiO2exhibits good sentivity and high selectivity for Hg2+in water, and can be conveniently separated from the solution.A multifunctional magnetic molecular sieve composite y-Fe2O3@TS-1has been prepared through hydrothermal synthesis using cationic polymer PDDA as a medium between magnetite core and the outer layer of TS-1seeds. Magnetite transfers into maghemite later and imparts this composite highly super-paramagnetic property. As-obtained material y-Fe2O3@TS-1presents good performance in thiophene oxidation and photocatalytic-assisted degradation of phenol. In thiophene oxidation, the composite retains the high catalytic activity of TS-1, meanwhile it can be easily recycled by applying an external magnetic field. In photocatalytic-assistant degradation of phenol, the y-Fe2O3core and TS-1shell have a synergistic effect to some extent. The embedded y-Fe2O3particles serve as Fenton-like catalyst during the reaction. TS-1molecular sieve in outer layer can adsorb the reactants in the solution and protect the y-Fe2O3core.