Innovative hydrothermal microwave synthesis of supermagnetic iron oxide nanoparticles suitable for catalytic applications

Magnetic iron oxide nanoparticles, in particular magnetite (Fe3O4) and maghemite (γ-Fe2O3), with a ferromagnetic behavior at room temperature, find many technological employments, not only as sensors, optical devices, medicine applications but also in the synthesis of magnetically separable catalysts. In fact, catalysts separation and recycle represent fundamental steps for the overall economy of industrial processes. The use of solid catalysts with magnetic properties allows efficient separation from the reaction medium by simple application of an external magnetic field. Many methodologies have been reported for the preparation of superparamagnetic iron oxide nanoparticles (SPION), generally working in the presence of different stabilizing agents in order to prevent their agglomeration. Now we report two novel sustainable single-step approaches for the microwave-assited synthesis of maghemite (γ-Fe2O3) and magnetite (Fe3O4) respectively, involving a simple procedure, the use of a green solvent such as aqueous ethanol, short reaction times, good energy efficiency and the absence of any high-boiling stabilizing agent or organic surfactant. The obtained SPIONs were characterized by FT-IR, TEM, powder XRD, BET and their magnetic properties were studied. They show particularly promising magnetic properties and work is in progress on their use as supports for the synthesis of Ru, Pd and Pt magnetic catalysts.