Synthesis of Macroporous Magnetic Fe3O4 Microparticles Via a Novel Organic Matter Assisted Open-Cell Hollow Sphere Assembly Method

Abstract

Macroporous magnetic Fe3O4 microparticles, which might act as both drug carriers and magnetocaloric media, were expected to have broad application prospects on magnetocaloric-responsively controlled drug release systems. A kind of macroporous magnetic Fe3O4 microparticle was prepared by an organic matter assisted open-cell hollow sphere (hollow sphere with holes on shell) assembly method in this study. 1-vinyl-2-pyrrolidinone (NVP) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS) were selected as the template and the binder, respectively. Ferrous ions were specifically bound to carbonyl groups on NVP and were then reduced by NaBH4. The reduced irons underwent heterogeneous nucleation and grain growth to form Fe0/Fe3O4 microspheres consisting of a lot of nano-Fe0 grains, and were then assembled into Fe0/Fe3O4 microparticles wrapped by AMPS. Results indicate that NVP binding with ferrous ions can promote a self-polymerization process and the formation of Fe0/Fe3O4 microspheres, while AMPS enwrapping around the resultant microspheres can facilitate their assembly into larger aggregates. As a result, macroporous Fe3O4 microparticles composed of several open-cell hollow Fe3O4 microspheres can be obtained under a Kirkendall-controlled oxidation. Moreover, these as-prepared macroporous Fe3O4 microparticles possess a narrow particle size distribution and exhibit ferromagnetism (Ms = 66.14 emu/g, Mr = 6.33 emu/g, and Hc = 105.32 Oe). Our work, described here, would open up a novel synthesis method to assemble macroporous magnetic Fe3O4 microparticles for potential application in magnetocaloric-responsively controlled drug release systems.