Preparation And Characterization Of Water-Soluble Fe₃O 4@Au Core-shell Nanoparticles

In this thesis, the research progress of preparation of magnetic nanoparticles and core-shell nanoparticles has been summarized first. One hand, superparamagnetic Fe₃O₄ nanoparticles are widely used in biomedical imaging as a contrast agent for magnetic resonance imaging （MRI）, environmental sciences and magnetism. Another hand, gold nanoparticles are also widely used in bioassay, optoelectronics, catalysis as well as biomedical imagings such as a contrast agent for computer tomography （CT）. An integration of both Fe₃O₄ nanoparticles and gold nanoparticles will benefit for the biomedical applications which could not offer only one component in general. Thus, it is also a hot research area that preparation and application of Fe₃O₄@Au. A simple preparation method of water souble Fe₃O₄@Au core-shell nanoparticles in aqueous solutions is uncovered in this dissertion. The relative physical properties such as size, mophorlogy, structure, magnetic and stability are investigated in detail. The research studies are as follows:1. A preparation method for Fe₃O₄ nanoparticles have been setup. First, the co-precipitation method and the modified co-precipitation method of preparation of Fe₃O₄ nanoparticles were described. Second, the prepared Fe₃O₄ nanoparticles by these two methods were characterized by TEM, XRD, PPMS and DLS for discovering their properties in morphology, size, structure, magnetic and stability. The experimental results showed that the Fe₃O₄ nanoparticles were with high monodispersity, and the morphology was spherical, and the average size was about 3-5 nm. In the modified preparation method of Fe₃O₄ nanoparticles, dispersion and stability of the Fe₃O₄ nanoparticles were modified in aqueous solutions by using citric acid, which inhibited the growth of Fe₃O₄ nanoparticles to a certain extent. So in the preparation process of Fe₃O₄@Au core-shell nanoparticles, Fe₃O₄ nanoparticles used for core were prepared by the modified co-precipitation method.2. The preparation and characterization of the water-soluble Fe₃O₄@Au core-shell nanoparticles have been investigated in detail. The superparamagnetic Fe₃O₄@Au core-shell nanoparticles were prepared by a general reduction of HAuCl4 using dispersed Fe₃O₄ nanoparticles for core in the aqueous solutions. Different reaction conditions were found to have influence on the preparation Fe₃O₄@Au nanoparticles in the morphology and size. It was shown that the hydroxyl amine solution used for reductant was 100mmol/L, the dosage of HAuCl4 （5 mmol/L） and Fe₃O₄ （20 mmol/L） was 1mL respectively, and the reaction time was 3h. The prepared Fe₃O₄@Au core-shell nanoparticles were characterized by TEM, XRD, PPMS, UV-vis and DLS for their properties in morphology, size, structure, magnetic and stability. It was shown that the morphology of Fe₃O₄@Au core-shell nanoparticles was spherical, and the average size was about 60nm with good crystalline and superparamagnetic at room temperature,the zeta potential for -30.2mV. According to the above-mentioned data, the as-prepared Fe₃O₄@Au core-shell nanoparticles were with good stability and water-solubility and good biocompatibility. It could be used as contrast agents in both MRI and CT based on these as-prepared Fe₃O₄@Au core-shell nanoparticles in biomedical imagings in future.