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.