Synthesis, Assembly And Applications Of Magnetic Nanospheres

With rapid advances in nanoscience and nanotechnology, more and more researches focus on developing more novel nanomaterials with distinctive mechanical, optical, magnetic or electrical properties and finding their potential applications in information technology (IT), energy, biomedical, catalyst, etc. The outstanding properties of nanomaterials depend on their novel structures and preparation procedures. In nano-fabrication, there are two common routes, bottom-up and top-down, both of which show their advantage and disadvantages.The magnetic nanomaterials have attracted a lot of interest in nanotechnology field due to their promising applications in Giant Magnetoresistance, magnetic fluid, bio-diagnostics, etc. Hitherto, researches have already obtained a series of routes to fabricate different structures of magnetic nanomaterials. However, there are few reports about synthesis of superparamagnetic double shell nanoparticles. Comparing with magnetic core particles, the magnetic shell structured particles have advantages in magnetic property (e.g. magnetically responsive), huge core volume for loading other components (especially for the ones that are not expected outside of particles), etc. therefore, we developed a new method to synthesize the magnetic shell particles through a template method, and their applications in the fields of photonic crystals and drug delivery systems were investigated.1. Photonic Crystal ApplicationSilica microspheres were coated with Fe₃O₄ and carbon by decomposition of ferrocene in an acetone system containing hydrogen peroxide. The as-prepared superparamagnetic colloids of SiO₂@Fe₃O₄@C were dispersed in acetone and efficiently self-assembled into centimeter-sized 3D magnetic colloidal crystals under the induction of a 0.2 T magnetic field. Both optical microscope image and reflection spectrum show a blue color of the colloidal crystals, demonstrating photonic crystal features. Because of the thinness of the shell and large difference in reflective index between the core and shell, a new pseudogap whose reflection cannot be predicted by Bragg's law was generated.2. Drug Delivery System The hollow Fe₃O₄@C nanoapheres were synthesized by removing silica core in SiO₂@Fe₃O₄@C colloids. The porous hollow magnetic nanocapsules showed a BET (the Brunauer-Emmett-Teller) surface area of 159.8 m²/g, which is about 4 times higher than that of SiO₂@Fe₃O₄@C colloids. The as-prepared nanocapsules were evalued as nanocapsules for drug uptake, such as Cisplatin, Ibuprofen, and Doxorubicin (DOX). In Cisplatin loading, the drug uptake rate was about 3 % and 5 8 % in two different loading process. And the drug release process was carried out in a 150 mL PBS solution (PH = 7.4) at the temperature of 37°C and the PBS suspension was collected 1 mL every predetermined time for further measurement. Finally, the mechanism of drug release was discissed.