Synthesis And Study Of Magnetite Nanoparticles And Composites

Magnetic nanoparticles (MNPs) have been of great interests because of their extensive applications. Their magnetic properties are size- and shape-dependent, and therefore, the synthesis of well-controlled shapes and size of MNPs is important for their applications. Recently, shape-control studies are actively being pursued on the semiconductor and metal nanocrystals but little work exists for MNPs system despite their unique nanomagnetism and important technological applications. This study focused on the synthesis of magnetite nanoparticles and investigation the mechanism of their morphology control. With the as-synthesized magnetite nanoparticles, Ag–Fe₃O₄ heterodimeric nanoparticles and periodic mesoporous organosilica (PMO) magnetic hollow sphere (PMO-MHS) were prepared and studied profoundly. The content of this thesis is as following:1. Different sizes of magnetite nanoparticles were synthesized by using 6 nm magnetite nanoparticles as"seeds"and Fe(acac)₃ as precursor in the thermal decomposing reaction. Growth kinetics of magnetite nanoparticles was studied by analyzing the morphology of the products during the progress of reaction. The surface of the as-synthesized Fe₃O₄ nanoparticles was studied by FTIR, XPS and TGA. It showed that he cover density of OA molecules on the particle surface was significantly various with the size of Fe₃O₄ nanoparticles.2. Starlike and flowerlike Fe₃O₄ nanoparticles were synthesized by the pyrolysis method using 1- adamantanecarboxylic acid (ACA) and oleylamine (OLA), ACA and 1-adamantaneamine (AA) as the combined surfactants, respectively. XRD, TEM, HRTEM, PPMS are used to characterize the structure and magnetic property of the as-synthesized nanostructures. Control over the morphology of these nanoparticles was realized by using different surfactants under otherwise similar reaction conditions. Triangular, cubic and cuboctahedron magnetite nanocrystals have been synthesized by thermal decomposition Fe(acac)3 in the presence of oleic acid under various reaction rate. The result suggests the shape-controlled growth mechanism that the role of the surfactant selective capping and external reaction rate are important to determine the final shape of nanocrystals.3. We reported a general synthetic method for construction of size-controlled Ag–Fe₃O₄ heterodimeric nanoparticles using the Fe₃O₄ nanoparticles as the seeds. The Ag–Fe₃O₄ heterodimeric nanoparticle can be controlled by tuning the size of the Fe₃O₄ seed and reaction conditions for synthesis of the Ag nanoparticles grown on it. The as-synthesized nanoparticles can be readily converted into aqueous-soluble form with newly introduced functional groups on the surface of Ag–Fe₃O₄ heterodimeric nanoparticles.4. We reported the preparation of a novel periodic mesoporous organosilica (PMO) magnetic hollow sphere (PMO-MHS) by embedding the monodispersed magnetite nanocrystals into the cage of the highly ordered PMO hollow sphere. Small particle size, low density, high surface area and large pore volume as well as high saturation magnetization value may make this material have high drug loading capacity and easily move with the aid of a low-moderate strength magnetic field. Functionalized PMO surface displays an easily modifiable chemistry with a variety of drug molecules.