Fabrication And Application Of Magnetic Iron Oxide Based Nanostructures

Nanotechnology has almost permeated into each branch of traditional natural science, and the nanoscience and nanotechnology has come into being the integration of multi-discipline. From the development view, the ultimate aim of the nanomaterial science and nanotechnology is to solve various problems occurring during the development of the human society.The magnetic iron oxide based nanomaterials have a good magnetic anisotropy, biocompatibility. biological degradation, low toxic behavior and large specific surface area, so they can be applied in the biomedicine and environmental sewage treatment, and are a kind of advanced functional materials. In this dissertation, the α-Fe2O3nanotubes, Fe2O3nanoparticles, magnetic Ni0.5Zn0.5Fe2O4nanoparticles and Ni0.5Zn0.5Fe2O4/SiO2nanocomposites were prepared by the electrospinning. citrate-gel, rapid combustion processes respectively with inorganic metal salts as the main raw materials, and they were characterized by the analysis methods of TG, XRD, SEM, TEM, BET, VSM and FTIR techniques. According to the characteristics of the as-prepared magnetic nanomaterials, the feasibility of their applications in the biomedicine and sewage treatment was studied, and the main results are as follows:1. Fabrication of magnetic iron oxide based nanostructures.(1) The α-Fe2O3nanotubes were prepared successfully by the sol-gel assisted electrospinning and subsequent heat treatment, with the precursor solution prepared from ferric nitrate, absolute ethyl alcohol and polyvinylpyrrolidone (PVP) as complexing agent. It is found that the water content in the precursor solution and the heating rate are the key factors affecting on the formation of the α-Fe2O3nanotubes, and the lower water content and larger heating rate are propitious to form the α-Fe2O3nanotubes. When the water content is about17wt%, heating rate is5"C/min and calcination temperature at500℃for2h, the α-Fe2O3nanotubes with diameters of400-700nm are obtained. The hollow formation mechanism of α-Fe2O3nanotubes is discussed, the controllable preparation of the α-Fe2O3nanotubes is realized.(2) Magnetic Ni0.5Zn0.5Fe2O4nanoparticles and Ni0.5Zn0.5Fe2O4/SiO2nanocomposites were synthesized by the facile citrate-gel process and the rapid combustion process, respectively. It is found that the grain size and the magnetism of Ni0.5Zn0.5Fe204nanoparticles calcined at400℃for2h with absolute ethyl alcohol of15mL were15nm and45Am2/kg, respectively, which is equivalent of Nio.5Zn0.5Fe2O4nanoparticles prepared by the facile citrate-gel process.(3) The Fe2O3nanoparticles were prepared via the rapid combustion process, and the preparation process is simple.2. The loading characteristics of nucleic acid molecules onto the magnetic iron oxide based nanostructures.(1) The surface of Fe2O3nanoparticles was modified by tetraethylorthosilicate and poly-l-lysine (PLL), and then the small interfering RNA (siRNA) was loaded onto them for the first time. The results show that the siRNA has been transferred successfully into primary rat neurons and then releases. The efficient silencing of the targeted gene with negligible cytotoxicity has been proved via the Western blot test, immunofluorescence experiments and the glial scar observations. The loading and transfer of siRNA into primary rat neurons have been achieved.(2) Based on the successful preparation of a-Fe2O3nanotubes, the adsorption of DNA onto a-Fe2O3nanotubes was determined at room temperature for the first time. The DNA adsorption onto the a-Fe2O3nanotubes can achieve a maximum value of4.19μg/g when the initial DNA concentration is50μg/mL, and the equilibrium time is90min. According to the adsorption kinetics and isotherms of DNA onto a-Fe2O3nanotubes, it is found that the pseudo-first-order kinetic model and the modified Temkin model can describe the DNA adsorption process and adsorption isotherm at room temperature, the adsorption mechanism of DNA onto a-Fe2O3nanotubes is generally revealed.3. The loading characteristics of proteins onto the magnetic iron oxide based nanostructures.(1) Tetraethylorthosilicate and l-Ethyl-3-(3-dimethyllaminopropyl) carbodiimide hydrochloride were used as the reagents to modify the surface of the magnetic Ni0.5Zno.5Fe2O4nanoparticles. The penicillin G acylase (PGA) was successfully immobilized on the surface-modified magnetic Ni0.5Zn0.5Fe2O4nanoparticles for the first time with the initial concentration of1mmol/L, and the activities of the immobilized enzyme and free enzyme under the various conditions were systematically examined. Compared to each other, it is found that the immobilized PGA is affected less by pH and temperature than the free PGA, and the immobilized PGA exhibits good chemical stability and thermal stability of enzyme catalyst. The relative activity of the immobilized PGA is about70%after11times cycling, which suggests a good recycling rate of the immobilization of PGA.(2) The Ni0.5Zn0.5Fe2O4/SiO2nanocomposites demonstrate a good adsorption capability of bovine serum albumin (BSA). The results show that with the increase of the silica content from0to0.05and the specific surface area from about49to57m2/g, the BSA adsorption capability of the Ni0.5Zn0.5Fe204/Si02nanocomposites calcined at400℃improves dramatically from22to49mg/g. However, with a further increase of the silica content from0.05to0.2, the specific surface area increase from about57to120m2/g, the BSA adsorption for the nanocomposites remains around49mg/g, which suggests that the silica coated onto the Ni0.5Zno.sFeiO4nanoparticles improve the BSA adsorption capability, but the thickness increase of the silica content is helpless to the adsorption capability.4. The adsorptions of arsenic and methyl blue onto the magnetic Ni0.5Zno.sFe2O4nanoparticles. Based on the successful preparation of Nio sZno5Fe2O4nanoparticles by the facile citrate-gel process and the rapid combustion process, the adsorption of arsenic and methyl blue onto the magnetic Ni0.5Zno.5Fe204nanoparticles were investigated for arsenic of3mg/L and methyl blue of50-300mg/L. It is found that the adsorption of arsenic onto the magnetic Ni0.5Zn0.5Fe2O4nanoparticles has a high selectivity, the remaining amount of arsenic in solution after the absorption can achieve zero, which can reach the standard for drinking water of the World Health Organization (WHO). Based on the simulation and calculation of the experiment data, it is found that the pseudo-second-order kinetic model is in a good agreement with the kinetics data for the adsorption of arsenic and methyl blue onto the magnetic Nio.sZn0.5Fe2O4nanoparticles, and the Temkin model and Redlich-Peterson model can be used to evaluate the adsorption isotherm of arsenic and methyl blue at room temperature, which suggests that the magnetic Nio.sZn0.5Fe204nanoparticles’ surfaces are heterogeneous, and the adsorption of arsenic and methyl blue onto the magnetic Nio.5Zn0.sFe204nanoparticles can be a hybrid of monolayer and multilayer absorption mechanism.