Synthesis And Application Of Surface Coating Superparamagnetic Fe₃O₄ Nanoparticles

Magnetic nano-materials have gained a tremendous amount of attention due to their novel physical and chemical properties which are different from their corresponding bulk materials. Supermagnetic nano-materials coated with different functional molecular agents have been application in various fields such as biomedicine, environmental protection, magnetic seperation, magnetofluid, lithium-ion batteries and photonic crystals. This dissertation deals primary with the synthesis of superparamagnetic Fe₃O₄ nanoparticles coated with various functional molecular agents and their applications in various fields. The main points are summarized as follows:1. The supermagnetic Fe₃O₄ nano-fluids coated with small molecule---fulvic acid were prepared through a co-precipitation method and used as magnetic resonance imaging （MRI） contrast agents. Their efficacy for liver MRI contrast agent was investigated by using live Wistar rat and VX2 tumor-bearing rabbit models. The experimental results showed that fulvic acid coated Fe₃O₄ nanopartical hydrosol could enhance the contrast between normal and pathologic tissue in the liver with increasing sensitivity and differentiation. This technique will be beneficial to discover the liver pathological changes and cancer cells in its early stage. Moreover, Fe₃O₄ nanoparticles could be conjugated with Hab 18 monoclonal antibody via coupling agents and go into the cancer cells by the antibody binding to its antigen. The efficacy of cancer cell marking in male Wistar rats as animal model was studied. The experimental results showed that antibody modified magnetic naoparticles could enter into liver cancer cells and reduce the MRI contrast of lumor. This is convenient for marking of cancer cells and discovering of cancer cells during its early stage.2. The Fe₃O₄ nanoparticles could be coated with inexpensive and eatable folic acid. They could enter into lumor cells by specifically binding of folic acid and receptor of folic acid. The efficacy of cancer cell marking was investigated by using male Wistar rats as animal model. The experimental results showed that folic acid coated magnetic naoparticles could enter into liver cancer cells and reduce the MRI contrast of lumor. This technique is beneficial for marking cancer cells and discovering cancer cells in its early stage.3. The Fe₃O₄ nanoparticles could be coated with humic acid, which is of regenerative resources. They could be used as adsorbents for removal of cational organic dye methylene blue in wasterwater through the functional groups of humic acid molecules. The experimental results showed that humic acid coated magnetic nanoparticles possess fast adsorbing rate and large adsorbing capacity. Furthermore, the desorbing process of dye from magnetic adsorbents was very easy and the magnetic adsorbents could be reused. The even important thing for this process is its magnetic seperation.4. After using for adsorbing methylene blue dye, the humic acid coated magnetic nanoparticles could be turned into carbon coated magnetic nanoparticles by high temperature carbonization. The latter could be used as anode materials for lithium-ion batteries, with high reversible capacity and significantly enhanced cycling performance as compared with commercial carbon products.5. The poly （acrylic acid） coated Fe₃O₄ nanoparticles with self-assembly structure were prepared by solvent-thermal method. They could be dispersed in water and turn into magnetic colloid. Under the magnetic field, this magnetic colloid could form photonic crystals to modulate the light they reflected. Through tuning the magnetic field strength, the band gap of photonic crystals could change easily and the color of diffraction lights could be seen by nake eyes.