A Research Of Fe₃O₄ Nanoparticles Modified By Hydroxyl Functional Compounds

Magnetic nanomaterials have many unique properties that are different from other conventional magnetic materials. Due to the simple and diverse preparation methods of ferric oxide magnetic particles, abundant source of raw materials, and their other special magnetic properties, such as low cytotoxicity, good biocompatibility and good adsorption, many magnetic materials have been widely used in the fields of biomedical,environmental management, and new materials.Naked iron oxide nanoparticles easily produce agglomeration and combine into larger particles owing to the large surface area, dipole-dipole interaction forces. In particular, the magnetic nanoparticles prepared in aqueous solution have the poor stability or low dispersibility, greatly limiting the application in biological materials,drug targeting tracking and other fields. In order to overcome these shortages, many materials are used to modify the surfaces of nanoparticles by physical adsorption or chemical bonds, such as inorganic substances, organic small molecules or polymers.The modifiers with strong hydrophility can improve the dispersibility and stability of nano-particles in aqueous solution. At the same time, the preparation condition can control the size and shape of obtained nanoparticle. Furthermore, the introduction of functional groups on the surface of nanoparticles, such as carboxyl groups, hydroxyl groups, etc., can increase the stability and provide the opportunity to connect with other molecules.Ferrous and ferric ions can be coordinated with a variety of functional groups, such as hydroxyl, carboxyl and ester bond, etc. In the case of hydroxyl groups, O can easily coordinate with ferrous and ferric ions. Molecules containing hydroxyl group are selected to modify iron oxide nanoparticles in order to improve the the stability of the nanoparticles in the water.In this thesis, various molecules containing different amounts of hydroxyl groups and different chain length were selected as modifiers and stabilizers to prepare magnetite by one-step coprecipitation method. The properties of obtained nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform' infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analyzer (TGA)vibrating sample magnetomer (VSM). The effects of hydroxyl group number, molecular structure and molecular weight of modifiers on the properties of the magnetic particles were discussed. The effects of heating time and modifier amount on the properties of product were also investigated. The possible formation mechanism of magnetite was speculated. Finally, the stability of product were detected.The results show that the magnetite nanoparticles can succesfully be modified by the molecules containg different hydroxyl groups and self-assembled into a flower-like three-dimensional structure and two-dimensional planete in special conditions. These obtained magnetite nanoparticles have good dispersibility and stability in physiological enviroment. These magnetite nanoparticles can be expected to be used in biomedical and wastewater treatment fields.