Surfactant-free preparation and drug release property of magnetic hollow core/shell hierarchical nanostructures

We report the preparation of a novel kind of nanoporous hollow core/shell hierarchical nanostructures of iron oxide (gamma-Fe2O3 or Fe3O4) with a high specific surface area, whose morphological feature is characterized as hierarchically nanostructured complex architectures self-assembled by nanosheets of the same kind of iron oxide with the spherical core inside the hollow sphere and circular empty space in between the core and hollow sphere. The precursor with the similar hollow core/shell hierarchical morphology is synthesized using FeCl3 and urea in ethylene glycol in the absence of any surfactant by a solvothermal method at 160 degrees C for 15 h. The precursor is used to prepare gamma-Fe2O3 and Fe3O4 with well-preserved morphological architectures by a thermal transformation strategy. The formation mechanism of the precursor and the effects of the reactant concentration and reaction temperature are discussed. The BET surface areas and the magnetic properties of as-prepared iron oxides are investigated. The drug storage and in vitro release property of the PEG-modified Fe3O4 sample are studied. The PEG-modified Fe3O4 sample has a high drug loading capacity and favorable drug release property.