Preparation, Funcation And Mechanism Study Of Magnetic Hollow/Porous Nanocomposite Microspheres

Magnetic hollow(porous) materials not only process the unique characters of magnetic materials such as superparamagnetism but also their hollow or porous structure make them have large surface area,small density,large internal space and good surface permeability etc.Therefore,the materials have potential applications in bio-medicine,catalysis,sewage treatment etc.The research emphasis of this paper is on exploring the novel and facile synthesis methods of magnetic hollow(porous) materials,studying their properties and modifying them with multifunctional properties.Meanwhile,the applications of them in catalysis and the removal of pollutants in water are investigated also.The main contents of this paper comprise six parts as follows:1.The amphiphilic magnetic nanoparticles(MPs) whose surface coexist hydrophobic oleic groups and hydrophilic hydroxyl groups are prepared through the co-precipitation method.The content of oleic acid at the surface of MPs which is able to impact the surface properties of MPs can be controlled by changing the reaction conditions.In the presence of the MPs,the superparamagnetic hollow nanocomposite microspheres are prepared in the miniemulsion system through radiation induced the interfacial polymerization of styrene.The polymerization is initiated by the free radicals on the surface of MPs located on the interface of water and oil.These radicals are produced by the attack of.OH etc.in the water against the active hydroxyl groups of MPs.The experimental results indicate that MPs are a key for the formation of magnetic hollow nanocomposite microspheres.Moreover,the content of oleic acid at the surface of MPs has effect on the formation of magnetic hollow spheres also.The experimental conditions such as the ultrasonication time,the added amount of MPs and the dose rate have effect on the size and the size distribution of magnetic hollow spheres.The approach to magnetic hollow nanocomposite microspheres is free to the core template and can be carried out at room temperature and under ambient pressure. Especially,the products synthesized byγ-ray are beneficial to their bio-applications because the contamination of chemical initiators is avoided and the final products are sterilized. 2.We report a facile route to prepare hollow superparamagnetic magnetite/polystyrene nanocomposite microspheres via irradiation induced inverse miniemulsion polymerization at room temperature and under ambient pressure.Water droplets act as a soft template for the formation of hollow structure.The free radicals produced from the radiolysis of water initiate the polymerization of styrene at the interface of oil and water,which lead to the formation of magnetic hollow spheres. The amount of styrene is a key to the formation of hollow spheres.Magnetic hollow spheres with different wall thickness are obtained through changing the amount of styrene in oil phase,and the more styrene can lead to the formation of solid magnetic nanocomposite microspheres.The volume of water phase,the amount of surfactant and the dose rate all have effect on the size and the size distribution of magnetic hollow spheres.According to the results,we further discuss the formation mechanism of magnetic nanocomposite microspheres.3.Because the uniformity and monodispersity of magnetic hollow spheres in first two parts is not enough good,which is disadvantageous to downstream applications,we develop a facile approach to uniform and nearly monodisperse magnetic nanocomposite microspheres with controllable structure via irradiation induced inverse emulsion polymerization at room temperature and under ambient pressure.12-acryloxy-9-octadecenoic acid(AOA,containing part of sodium salts Na-AOA) as a surfactant can also copolymerize with the styrene.Moreover,its unique structure increases the stability of inverse emulsion,leading to the better uniformity and monodispersity of final products.It is interesting that just by changing the added amount of styrene,the magnetic hollow spheres with different wall thickness and various sizes of core,up to the magnetic solid spheres,can be obtained.4.We offer a simply method to the preparation of multihollow magnetic nanocomposite microspheres via water-in-oil-in-water double emulsions.Amphiphilic magnetite nanoparticles act as an oil-soluble emulsifier and sodium dodecyl sulfate (SDS) acts as a water-soluble surfactant in the system.The method is novel,facile and template-free to the formation of porous structure.The results show that the added amount of MPs impacts the pore size of multihollow magnetic nanocomposite microspheres.In addition,the experimental conditions during the course of polymerization such as stirring and temperature are also two key factors to the formation of multihollow structure. 5.Combining the as-synthesized magnetic hollow nanocomposite microspheres and the superiority of the facile preparation of inorganic nanomaterials viaγ-ray,we prepare multifunctional CdS/magnetite/poly(styrene-co-methyl methacrylate) microspheres,which possess superparamagnetic,fluorescent and hollow properties.CdS nanoparticles are chelated on the surface of magnetic hollow spheres through the carbonyl groups located at the surface of them.The Uv-vis and photoluminescence spectrum show that the multifunctional nanocomposite spheres have the quantum-confined effect.In this section,we offer a facile and mild method to the synthesis of multifunctional magnetic nanocomposite microspheres.6.Using porous activated carbons as carriers,we prepare superparamagnetic porous carbons materials,in which superparamagneticγ-Fe₂O₃ nanoparticles are randomly dispersed in the porous carbons.The magnetic porous carbon materials have large surface area(844 m²/g) and large pore volume(0.86 cm³/g).Meanwhile, the saturation magnetism can be tunable by changing the initial amount of iron salt. We also study the application of magnetic porous carbon materials in the removal of organic pollutants in water.After the pollutants are absorbed by magnetic carbon materials,they can be separated from the water easily by the magnet.The experimental results display the magnetic porous materials have high capacity of removing the pollutants.On the other hand,Ag nanoparticles which possess catalysis are loaded in magnetic porous carbon materials,which can apply in the catalytic area and be recycled by the magnet.The experimental results show that they still have better catalytic activity after being used many times.