| Magnetic Fe3O4@SiO2 composites nanoparticles (NPs) are widely applied in the field of chemical separation, environment detection, and biological sensors due to its large surface area, easy separation, and repeatable recycling. The magnetism of Fe3O4@SiO2 NPs can conveniently separate heavy metal ions from aqueous solutions. The silica coating layer outside the surface of Fe3O4 NPs not only can improve the chenmical stability and dispersion in solution, but also has good biocompatibility. In this thesis, the Fe3O4@SiO2 NPs are modified by chemical covalent coupling to form oganic/inoganic hybrid nanomaterials, which have the potential applications in the detection, enrichiment, and removal of heavy metal ions in aqueous solution.In the thesis, the Fe3O4 nanoparticles were prepared based on the chemical co-precipitation, and then the magnetic nanoparticles werecoated with SiO2 via the sol-gel process by the hydrolysis and polycondensation of TEOS. Based on the design and tailoring of organic or biological ligand molecules, organic/inorganic hybrid magnetic SiO2 nanomaterials were synthesized by using chemical covalent coupling. In this thesis, two kinds of oganic/inoganic hybrid magnetic Fe3O4@SiO2 fluorescence nanomaterials were synthesized for the detection and removal of heavy metal ions. And the microstructure, surface properties, optical response characteristics and adsorption behavior to heavy metal ions were systematically investigated. In addition, fluorescence change mechanism to heavy metal ions is analyzed by quantum chemical calculation. The as-synthesized nanomaterials are as follows:(1) The Fe3O4 NPs were coated with silica nanoparticles based on the sol-gel process and modified with fluorescence probes after the Fe3O4 NPs were synthesized through the chemical co-precipitation. The saturated magnetism of Fe3O4 NPs can reach up to 64.9 emu/g. Neither remanence nor coercivity indicated these were superparamagnetic nanoparticles. The saturated magnetism of Fe3O4@SiO2 NPs (19.8 emu/g) decrease obviously due to the nonmagnetic silica coating layer. There is almost no change about the saturated magnetism of Fe3O4@SiO2 NPs between the pristine and modified with fluorescence probes.(2) Fe3O4@SiO2 NPs functionalized with di (2-picolyl) amine were synthesized as a fluorescent sensor for detection and removal of Zn2+. The fluorescence photograph showed that the organic/inorganic hybrid Fe3O4@SiO2 NPs were able to sensor to Zn2+ selectively among other metal ions. A significant visual color change from colorless to pink-red was observed under the irradiation of 365 nm UV lamp as the Zn2+could reduce the electron-donating ability of the nitrogen atom so that the PET process was inhibited. In contrast, no significant change in emission was observed in the presence of other metal ions. According to the Langmuir isotherm adsorption model, the removal efficiency of Zn2+ can reach as high as 97.1% and the saturated adsorption amount of Zn2+ is 161.6 mg/g.(3) The organic/inorganic hybrid Fe3O4@SiO2 magnetic NPs were synthesized and.functionalized with rhodamine derivates (RhoB-NCS) for selective detection and removal of Hg (Ⅱ) The fluorescence photograph showed that significant visual color change from orange to rufous was observed by naked-eye and the jacinth was also obtained by irradiating with 365 nm UV lamp in water/methnol media. The obvious color change on the Fe3O4@SiO2 nanoparticles surface was also observed through separating and drying from aqueous solution after mercury ions was adsorbed by the rhodamine derivates functionalized organic/inorganic hybrid Fe3O4@SiO2 nanoparticles. The fluorescence spectra indicated that rhodamine derivates functionalized Fe3O4@SiO2 nanoparticles were highly sensitive and selective to mercury ions in aqueous solution. Adsorption results indicated that the removal efficiency for mercury ions can reach as high as 92%. |
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