Study On The Preparation And Properties Of Hollow Superparamagnetic Fe₃O₄Submicrosphers

Fe3O4hollow spheres have shown great applications in the fileds of biomedicine,biosensor, magnetic fluid, magnetic resonance image and so on. To promote theapplications of Fe3O4hollow spheres in those areas, it is necessary to synthesizemonodisperse superparamagnetic ferrites particles with chemical stability, goodbiocompatibility, high saturation magnetization. Among the approaches to fabricatethe Fe3O4hollow spheres, hard template methods usually suffer from time consumingpost-treatments, uneconomic and are not easy to control the shape of hollow parts andsize. Thus, the application of hard template methods has been limited. Besides, it isvery difficult to fabricate Fe3O4hollow spheres with uniform morphology by softtemplates because of its high mobility. At the same time, the agents as soft templatesare almost organic snbstances, so the as-prepared samples are easily contaminated bythese soft templates and may contain toxic residues. This study aims to preparaedisperse superparamagnetic Fe3O4hollow spheres with good biocompatibility，gooddispersion，high saturation magnetization by a simple free-template, one-pot method.Besides, the preparation process of the Fe3O4hollow spheres and effects of rawmaterials on the reaction systems were investigated. Moreover, the influence of thereaction time and the amount of PAM on the thickness of shell and magneticproperties were also studied. Finally, the surface modification of the Fe3O4hollowspheres will be conducted to be combined with organics subatances. The main pointsof this dissertation are summarized as follows:1. Monodisperse Fe3O4hollow spheres with average diameter of250nm wereprepared by a one-pot hydrothermal process. In the process, FeCl3.6H2O andpolyacrylamide was used as iron sources and dispersing agent respectively. And thecitrate is one kind of reducing agent and stabilizer. Moreover, urea provided thealkaline environment. Through the study, we found that the as-prepared Fe3O4exhibited the hollow structure, superparamagnetism, high saturation magnetization.2.In order to improve the property of dispersion, the effect of the alkalisources(NH4AC、NaHCO3、NH4HCO3) and the dispersant PEG,SDBS, PVP on thestructure and properties and properties of ferroferric oxide were investiagted. Theresults revealed that the Fe3O4with good dispersion, high saturation magnetization, high specific surface area and the shell having a mesoporous structure could beprepared when using polyacrylamide and polyethylene glycol as a surfactant, sodiumcitrate as the reductant, and urea as alkali source. In terms of the effects of thedifferent surfactants and different alkali sources on the properties of hollow structuralferroferric oxide, we further analyzed the effects of raw materials such aspolyacrylamide, polyethylene glycol, sodium citrate and urea in the preparation ofhollow Fe3O4and the effects of reaction time and the amount of PAM on thethickness of shell and magnetic properties. The result of dissolution experimentindicated that the amount of ferric ion dissolution in the body had no effect on thehuman.3. To make the Fe3O4hollow spheres easily combined with macromolecule,theFe3O4hollow spheres were modified with3-aminopropyl–triethoxysilane (APTTS).The results indicate that there are chemical bonds between the surface of f Fe3O4hollow spheres and amino silane coupling agent when the mol ratio of amino-silanecoupling agent and ferrite is1:1, and there is one hydroxyl on the surface of everyferrite nanoparticle. Besides, after modification, the ferrite hollow nanoparticle stillexhibited superparamagnetism and the saturation intensity decreased to a certaindegree.The innovation of this dissertation was that we used a simple and quickfree-template approach to fabricate superparamagnetic Fe3O4hollow spheres withgood dispersion, high saturation magnetization, high specific surface area, discussedthe amount of ferric ion dissolution about the Fe3O4hollow spheres in thePhysiological saline.