Loading channels of SiO 2 mesoporous matrices with Fe oxides

After embedding hematite nanowires (15 wt.% Fe) into a MCM-41 hard template, we have explored alternative routes to induce the structural transformations that lead from hematite to maghemite and magnetite embedded nanowires. The impregnation media (ethanol or water) and the calcination atmosphere (air and NO/He) on the hematite nanowires production play a significant role at the time of reducing and re-oxidizing the embedded hematite nanoparticles. The solids were characterized by X-ray diffraction, nitrogen adsorption, and Mössbauer spectroscopy. The results indicate that the effect of the solvent on the structural properties of the iron species is more important than the calcination atmosphere. The best conditions for iron magnetic nanowires not to get outside of the MCM-41 channels over the treatments are reached using water as the solvent and air as the calcination atmosphere. When ethanol is the solvent used over the preparation step, the end iron oxides are in the form of nanotubes spread out on the amorphous silica walls of the matrix.