Sandwich Fe2O3@SiO2@PPy ellipsoidal spheres and four types of hollow capsules by hematite olivary particles

Hematite@ silica@ polypyrrole (Fe2O3@ SiO2@ PPy) ellipsoidal sandwich composite spheres as well as SiO2, SiO2/PPy, PPy hollow capsules and PPy ellipsoidal hollow capsules with movable hematite cores were successfully fabricated by hematite (alpha-Fe2O3) olivary particles. Monodispersed alpha-Fe2O3 olivary particles were firstly prepared via hydrolysis of ferric chloride solutions. Then Fe2O3@SiO2 core - shell particles were synthesized based on base-catalysed hydrolysis of TEOS (tetraethylsiloxane) using steric agent PVP [ poly(N-vinylpyrrolidone)] as anchor-molecule. Furthermore, polymerization of pyrrole monomers was preformed around as-prepared Fe2O3@ SiO2 composite spheres to form sandwich multilayer core - shell particles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that both the middle layer silica shell and the outer layer polypyrrole sheath are uniformly coated over the hematite cores. In addition, SiO2, SiO2/PPy, PPy ellipsoidal hollow capsules and PPy ellipsoidal hollow capsules with movable hematite cores were obtained after the selective removal of the hematite, Fe2O3@ SiO2 cores or silica middle shell of the sandwich ellipsoids respectively.