Synthesis of ellipsoidal hematite/polymer/titania hybrid materials and the corresponding hollow ellipsoidal particles

Ellipsoidal tri-layer hematite/poly(N,N'-methylenebisacrylamide-co-methacrylic acid)/titania (Fe2O3/P(MBA-co-MAA)/TiO2) hybrid materials were prepared by a three-stage reaction process, which included the combination of the controlled hydrolysis of inorganic salt to afford ellipsoidal hematite core and titania shell layer and distillation precipitation copolymerization of N,N'-methylenebisacrylamide (MBA) and methacrylic acid (MAA) in acetonitrile for the formation of a P(MBA-co-MAA) sandwiched mid-layer. The corresponding hollow ellipsoidal hematite-sphere-in-titania-spheres were afforded by selective removal of the sandwiched P(MBA-co-MAA) mid-layer via calcination. Hollow titania ellipsoids were further obtained by selectively etching the hematite core in aqueous hydrofluoric acid (HF) solution from the ellipsoidal hematite-sphere-in-titania-sphere. The resultant ellipsoidal tri-layer Fe2O3/P(MBA-co-MAA)/TiO2 and the corresponding hollow ellipsoidal particles were confirmed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, X-ray diffraction (XRD), thermogravimetric (TGA) analysis and vibrating sample magnetometery (VSM).