Synthesis of a hydrothermally stable, periodic mesoporous material containing magnetite nanoparticles, and the preparation of oriented films

Magnetite nanoparticles modified covalently with triethoxysilane having a quaternary dicetyl ammonium ion are used together with tetraethylorthosilicate as building blocks to prepare a mesoporous material. Cetyltrimethylammonium bromide is used as a structure-directing agent under conditions typically used for mesoporous MCM-41 silicas. The resulting mesoporous material (MAG-MCM-41), containing up to 15 wt % of magnetite is characterized by transmission electron microscopy (TEM), isothermal gas adsorption, and X-ray diffraction. In contrast to siliceous MCM-41, mesoporous MAG-MCM-41 exhibits a remarkable hydrothermal stability. The magnetic properties of MAG-MCM-41 are characterized by DC and AC magnetic susceptibility, and by isothermal hysteresis cycles, confirming the long-range magnetic ordering above 400 K. As evidenced by atomic force microscopy and TEM, the ability to respond to magnetic fields is used to orient films of MAG-MCM-41 with the channels perpendicular to a support.