Fabrication of Ordered Mesoporous Silica Films with Encapsulated Iron Oxide Nanoparticles using Ferritin-Doped Block Copolymer Templates

Abstract

Ordered mesoporous silica glasses containing encapsulated magnetic nanoparticles were fabricated by the 3D replication of preorganized block copolymer templates doped with ferritin. Solutions of Pluronic F127 (PEO105-PPO70-PEO105) containing horse spleen ferritin and p-toluene sulfonic acid were spin-coated onto silicon test wafers. Phase selective deposition of silica within the ferritin-containing block copolymer was conducted by exposure of the template films to solutions of tetraethylorthosilicate in supercritical carbon dioxide. Silica network formation occurs exclusively in the hydrophilic block due to partitioning of the acid catalyst to the PEO rich domains during spin coating. Calcination of the resultant composite at 400 °C removes the polymer template and protein shell of the ferritin nanoparticles, yielding a robust mesoporous film as evidenced by electron microscopy. X-ray diffraction showed that after processing the crystalline structure of the iron oxide ferritin core was maintained. Magnetization measurements indicate that the magnetic properties of the ferritin cores are unaffected by the silica infusion and calcination steps. This approach provides a simple and general way to fabricate functionalized mesoporous materials with defined pore structures.