Synthesis And Application Of Graphene Oxide And Surface Coating Fe₃O₄ Nanoparticles

In the last few years, graphene with unique structure and novel properties has attracted much attention from physical, chemical and material scientists. Superparamagnetic Fe₃O₄ nanoparticles coated with different functional materials, which have high magnetic permeability, low loss and high saturation magnetization, have been widely applied in various fields, such as magnetic memory, biomedicine, environmental protection, magnetic separation and so on. This dissertation deals primarily with the synthesis of graphene oxide and superparamagnetic Fe₃O₄ nanoparticles modified with various functional agents, and then carries out their applications research. The main points are summarized as follows:The graphene oxide is exfoliated by the ultrasonic from graphite oxide which is synthesized by a chemical method. Atomic Force Microscope （AFM） verifies that most of the graphene oxide are multilayer and flake structure. Zeta potential and Fourier Transform Infrared （FT-IR） spectrum indicate that the graphene oxide has a lot of oxygen-containing groups and is electronegative. In the present study, graphene oxide is used as an adsorbent for the removal of methylene blue which is an organic cation dye from its aqueous solutions. The influences of experimental conditions such as adsorption rate, pH, MB concentration, temperature, ionic strength and desorption solution are investigated in detail. The results show that the adsorption process is fast, pH sensitive, and consistent with Langmuir adsorption model and exothermic reaction.Fe₃O₄ nanoparticles are embedded on the surface of the as-prepared graphene oxide via a modified co-precipitation procedure. Scanning Electron Microscopy （SEM） , Fourier Transform Infrared （FT-IR） spectrum and X-Ray Diffraction pattern are obtained for the as-prepared Fe₃O₄/GO. The results indicate that the Fe₃O₄ nanoparticles are cubic phase structure and spherical appearance （about 20 nm in diameter）, however, the graphene oxide is flake-like and has a lot of oxygen-containing groups. Using the electronegative groups of graphene oxide as the adsorbent spots, the research of methylene blue adsorbed on it is carried out. We investigate the influences of experimental conditions, such as adsorption rate, pH, MB concentration, temperature and ionic strength in detail. The results indicate that Fe₃O₄/GO could adsorb considerable methylene blue quickly. The desorption process is easy to achieve, so the recycle capability is perfect. At the same time, the separation process can be easily completed by magnetic separation of Fe₃O₄ nanoparticles.The Fe₃O₄ nanoparticles could be coated with 3-aminopropyl-3-ethoxyl silane （APTES）. The results show that APTES has been successfully modified onto the surface of Fe₃O₄ nanoparticles, the crystal is cubic phase structure by X-Ray Diffraction （XRD） analysis, the size is about 8 nm by Transmission Electron Microscopy （TEM）, the hydrated diameter of the nanoparticles is 25.0 nm by Dynamic Light Scattering （DLS）, the saturation magnetization is about 56 emu/g Fe by Vibrating Sample Magnetometer （VSM）. Using the magnetic fluid as the marker of cells, the results show that Fe 3 O4 nanoparticles modified by amino and atibody can enter the stem cells and the rhinopharyngeal cancer cells respectively, and improve the magnetic resonance imaging （MRI） imaging signal, is conducive to cell marker, tracing and targeting test.