Magnetically-assisted synthesis of porous sol-gel magnetite matrices with structural anisotropy

Here we describe the first example of magnetite based sol-gel matrices with structure anisotropy. The materials were synthesized by magnetic structuring of magnetic fluids based on pristine magnetite nanoparticles with a subsequent formation of magnetite hydrogels and drying in mild conditions. The corresponding ferrofluid was synthesized by an ultrasonically-assisted co-precipitation procedure and consisted of 10 nm pristine magnetite nanoparticles (MNPs) dispersed in deionized water. Colloidal stability of the system was maintained by the high value of zeta potential valued + 33 mV at pH 7.0. Under the influence of propylene oxide, the surface of MNPs was partially dehydrated and inter-particle Fe-O-Fe bonds were formed leading to gelation of the system. The produced materials had a linear periodic structure with its parameters, such as periodicity, relative surface area, pore diameter, total pore volume, dependent on the magnetic fields applied during their synthesis. Thus, the change of the magnetic field from zero to 515 G led to the elevation of the materials surface area from 125 to 209 m epsilon(2)/g.