Magnetic Micro-/Nanomaterials:Synthesis,Charaterization And Application

The microspheres with various functionalities possess a series of novel properities. The further control of their composition and morphology may result in a range of microspheres with some special functionality. These microspheres exhibited some promising applications such as catalysis, drug release, and gene delivery etc. In this paper, we will introduce the preparation, function and morphology control, mechanism of the magnetic microspheres and their application in catalysis and biomedicine.A facile and general method was afforded to prepare magnetite/polymer core-shell microspheres via a one-pot in-situ distillation-precipitation polymerization. Various functional shells such as carboxyl, hydroxyl, amide and ester were provided via the tune of the monomer during the polymerization. The P(MBAAm-co-MAA) shell coated magnetic microspheres were loaded with a series of metal nanoparticles like Au, Ag and Pd. Due to their high saturation magnetization values and easy preparation, these microspheres may be promising materials for catalysis. Maghemite@SiO2rattle type microspheres (MSRMs) with mesoporous shells and strong magnetic cores were synthesized through the sol-gel process performed on the templates of Fe3O4@P(MBA-co-MAA) core-shell microspheres for the synthesis of Fe3O4/Polymer/SiO2tri-layer microspheres together with the subsequent calcination, during which the magnetite was transferred to maghemite. Importantly, MSRMs kept the superparamagnetic property and had a high saturation magnetization value and big BET surface area. Further, this rattle-type microsphere was studied in vitro and in vivo to assess their toxicity, which exhibited good biocompatibility. The surface functionalization of the rattle-type microspheres with PEG and folic acid was performed through the silica coupling reaction. The functionalized rattle-type microspheres revealed a better drug release process. At last, a facile method based on the electrostatic self-assembly was developed for preparation of polymer/magnetite composite core/shell microspheres and corresponding hollow magnetic microspheres. The shell thickness (18-35nm) and void size (110-300nm) of the hollow microspheres can be easily controlled through tuning Fe3O4feed and the polymer template size. The acquired microspheres were porous and owned high saturation magnetization values. These hollow magnetic microspheres exhibited a controlled release process when it was used as a drug carrier. Based on these good properties, the hollow magnetic microspheres can be potentially used for drug delivery. Furthermore, this electrostatic self-assembly method over the surface of the template microspheres provided a facile way for preparation of other organic-inorganic composites and hollow inorganic microspheres.