The Synthesis Of Fe₃O₄ Magnetic Nano-Structured Materials

Magnetic Fe₃O₄ nanoparticles are a kind of novel functional materials,which exhibit extensive application prospect.Compared with other nanomaterials,they are easier to aggregate with each other because of their small particle size and large specific surface area.So the modification of Fe₃O₄ nanoparticles becomes a problem confronting people.Modification means changing the physical and chemistry properties of nanoparticles by physical or chemical methods,including the surface chemistry properties,wettability,chemical adsorption and reaction characteristics. According to the surface properties of Fe₃O₄ nanoparticles,people usually adopt the method of coating organic or inorganic materials to improve the oxidation resistance, biocompatibility and stability,so that they are quite fit for application in biological system.In this paper,magnetic materials were prepared with monodisperse and strong magnetic responsively on the base of others'research.The main content of this paper is such as following:1.A facile method to synthesize carboxyl-functionalized magnetic polystyrene nanospheresMagnetic polystyrene nanospheres with high magnetite content and abundant surface carboxyl groups were prepared by emulsifier-free emulsion polymerization in the presence of aqueous magnetic fluid coated with oleic acid and 10-undecenoic acid as primary and secondary surfactants respectively.The effects of initiator concentration,initiator type(water-soluble or oil-soluble),monomer concentration and ferrofluid content on the particle characteristics such as the size,morphology, magnetic properties and the number of carboxyl groups were investigated.When water-soluble potassium peroxodisulfate was used as the initiator,magnetite nanoparticleswere uniformly encapsulated in polystyrene particles,while in the oil soluble benzoyl peroxide system,magnetite particles were located on one side of magnetic polystyrene nanospheres.The results showed that two mechanisms for the nucleation and growth of nanospheres were involved according to the kind of initiator used in the polymerization.The magnetic nanospheres were superparamagnetic with the highest saturation magnetization of 29.78 emu/g and the corresponding magnetite content of 41.67%.The maximum amount of surface carboxyls was 0.5594 mmol/g. BSA(bovine serum albumin)was used to test the immobilization capacity of proteins onto the magnetic spheres.The immobilization capacity was about 196.2mgBSA/g These carboxylated magnetic polystyrene nanospheres have extensive potential biomedical applications.2.Synthesis and preparation of polystyrene magnetic microspheres by ultrasonically assisted dispersion polymerizationUniform and superparamagnetic polystyrene microspheres were prepared by ultrasonically assisted dispersion polymerization of styrene in the presence of Fe₃O₄ coated with a bilayer of oleic acid.The effects of initiator concentration,stabilizer concentration,and the Fe₃O₄/styrene ratio on the microsphere characteristics were investigated.A comparison of dispersion polymerization with and without ultrasonic assistance was made to obtain a better understanding of the process.In the ultrasound-assisted synthesis,more iron oxide particles were encapsulated,so that more uniform superparamagnetic polystyrene microspheres with smooth polymer surfaces and higher magnetic saturation were obtained.In addition,a study of the kinetics of the polymerization with and without ultrasound treatment revealed that the ultrasound resulted in higher polymerization rate and yield.3.One-step synthesis of amine-functionalized thermo-responsive magnetite nanoparticles and single-crystal hollow structuresA high-temperature solution phase hydrolysis has been developed for the synthesis of amine-functionalized Fe₃O₄ nanostructures.The concentrations of the reagents and the reaction time have great influence on the morphologies of the products.Increasing the amounts of poly(propylene glycol) bis(2-aminopropyl ether)transformed the product morphology from hollow nanostructures to magnetite nanoparticles.Single-crystal solid spherical aggregates,hollow spheres,loose nanoclusters and polyhedral-like magnetite particles can be selectively synthesized by varying the synthesis parameters,including the reaction time or the weight ratio of iron precursors to polyetheramine.The morphological transformation could be attributed to the cooperation of oriented aggregation and Ostwald ripening mechanisms.By using poly(propylene glycol)bis(2-aminopropyl ether)as the capping agent,the amine-functionalized nanoparticles show high water dispersibility and thermo-Responsive.In addition,the Picketing emulsion stabilized by amine-functionalized nanoparticles was fabricated.One of the most promising applications of the as-prepared single-crystal hollow structures is as support materials for biological testing,catalysis and targeted drug delivery.4.A simple one-pot synthesis of single-crystalline magnetite hollow spheres from a single iron precursorThis part presents a facile route using a simple solvothermal reaction to synthesize monodisperse and single-crystalline Fe₃O₄ hollow spheres.Fe₃O₄ hollow spheres with a mean diameter of 200 nm are fabricated using the coordination compound[Fe(urea)₆]Cl₃ as the sole iron source,in the absence of any other additives. TEM,SEM and HRTEM results show that single-crystalline Fe₃O₄ hollow spheres are composed of well-aligned nanoparticles.The as-prepared hollow spheres have a Brunauer-Emmett-Teller(BET)surface area of about 16.251 m²/g with an average pore size of 3.537 nm.The hollow spheres display obvious ferromagnetism at room temperature with a saturation magnetization of 79.58 emu/g,a remanent magnetization of 19.1 emu/g and coercivity of 133.5 Oe.The growth mechanism of single-crystalline Fe₃O₄ hollow spheres is attributed to the cooperation of oriented aggregation and Ostwald ripening.5.Self-assembly of iron oxide nanoparticles into oriented nanosheets by one-pot template-free synthesis at low pHSingle-crystalline Fe₃O₄ nanosheets were obtained for the first time by simply adjusting the pH of a magnetite particle dispersion,using a hydrophilic terpolymer as stabilizer.We experimentally observed the magnetite nanoparticles spontaneous, template-free organization into nanosheets.This transformation occurs in an acidic environment at the zeta potential minimum by the abrupt,oriented self-assembly of polymer-stabilized magnetite particles at room temperature.The driving forces of the oriented self-assembly process includes the interplay of anisotropic dipolar forces, electrostatic interactions and isotropic van der Waals forces.