The Preparation Of The Fe₃O₄/SiO₂ Magnetic Composite Particles In St(?)ber Process And Surface Modification

Magnetic nanoparticles have their potential applications in bioseparation, immunochromatography assay, enzyme immobility, target drug, magnetic fluid hyperthermia and magnetic resonance imaging etc. But in generally, magnetic nanoparticles will aggregate by magnetic dipole-dipole interaction; the surface of great variety of magnetic nanoparticles (such as Fe3O4) usuallycan be oxidated and bioconsistion of that is poor. Modification of the magnetic nanoparticles forming magnetic composite particles will screen magnetic dipole-dipole interaction, improve resistoxidation and bioconsistion. In generally, there are organic small molecule, polymer and inorganic materials(such as SiO₂)used modifying surface of magnetic nanoparticles. The magnetic composite particles modified with organic small molecule and polymer will be destroyed by force or organic solvent, and the organic molecule usually is toxic. However, Modified with inorganic SiO₂ not only have better chemical stability and bioconsistion, but also facility in modification because of mature silicon chemistry technology. Thereby, Fe₃O₄/SiO₂ magnetic composite particles is one of hotspots in international investigation. In traditionally, there are Sol-Gel and emulsion process to control the shape, surface property and quantity of magnetic materials of Fe₃O₄/SiO₂ magnetic composite particles. This decade, aerosol pyrolysis and combustion process have been appeared with developing in investigation. It is very significant to realize syntheses of the composite particles, that to improve technics currently, devise new materials and apply in variety of fields. In this thesis we prepare the Fe₃O₄/SiO₂ magnetic composite particles in St?ber process that is the most classical Sol-Gel process, control the the extent of aggregate of the particles in various conditions, and then modify the surface of the composite particlesThe main achievements of this thesis is totally divided into three parts:In chapter 2, firstly we prepare Fe₃O₄ magnetic nanocomposite in coprecipitate methed, and then synthesize FFSi composite particles in Na2SiO3 solution. Finally, we package FFSi composite particles in St?ber process by TEOS. In this process, we change the effecting factor to control the extent of aggregate of FFSi composite particles. Ammonia can ionize in the ethanol/water solution, and the ions from ammonia affect double-electronic layer of the surface of FFSi composite particles. Colloid stability of the composite particles is destruct that makes the composite particles more congregate. There are a mass of Si-OH groups on FFSi composite particles, the Si-OH groups can easily form hydrogen bond with polar solvent, and that the ability of water forming hydrogen bond is stronger than alcohol, when the alcohol/water ratio rises, the amounts of hydrogen bond on surface of the composite particles will decrease, and colloid stability of the composite particles is destruct that makes the composite particles more congregate. Simultaneity,we constitute a characterization that estimate the extent of aggregate of the composite particles, foresee the whole size of the final composite particles by the average hydrated diameter of the final composite particles. In the end, we confirm the dependability of this characterization through accord between the ability of magnetic response and the average hydrated diameter of the final composite particles measuring by DLS.In chapter 3 of this thesis, we modify the surface Fe₃O₄ with oleic acid (OA), then prepare Fe₃O₄/SiO₂ magnetic composite particles in St?ber process with Fe₃O₄/OA composite particles as basic particles, and form better monodispersity than that of FFSi composite particles. Because Fe₃O₄/OA composite particles can not disperse in alcohol/water, we package the particles in St?ber process with toluene (toluene can be soluble in ethanol as random ratio) as cosolvent to disperse composite particles in alcohol/water. Monodispersity of Fe₃O₄/OA composite particles is rather better, so that of the final Fe₃O₄/SiO₂ magnetic composite particles is also better. Simultaneity,we do research in some solvent, and find only ethanol that toluene can be soluble in as random ratio is the optimal solvent.In chapter 4, at first we modify the surface of Fe₃O₄/SiO₂ magnetic composite particles with 3-aminopropyl triethoxysilane (APS) in alcohol/water, and then with glutaric anhydride (GA) in anhydrous dimethylformamide (DMF) obtained amino and carboxyl functionalized Fe₃O₄/SiO₂ magnetic composite particles, respectively. We characterize the functionalized composite particles using Zeta potential,IR and Organic element analysis, confirm and primary quantificationally analyze the amino and carboxyl on the surface of composite particles, discover the amounts of the amino more than that of the carboxyl. Therefor, the functionalized layer of APS is multilayered, a majority of aminos are buried inside the composite particles. We also do research about the property of functionalized Fe₃O₄/SiO₂ magnetic composite particles. First of all, we make the composite particles hydrolyzing accelerated in aqueous, then quantificationally analyze the amount of the carboxyl hydrolyzed from the composite particles in aqueous conditions using gas chromatography (GC); subsequently we conjugate bovine serum albumin (BSA) with the carboxylic composite particles, that grope for conjugating the protein and enzyme primarily.