Development of iron modified MCM-41 as promising nano-composites with specific magnetic behavior

Abstract

MCM-41 type mesoporous silica materials were synthesized and modified with different iron loadings by the wet impregnation method and exhaustively characterized by different instrumental techniques, including XRD, TEM, N2 adsorption, UV–Vis DRS, XPS, TPR and Mössbauer spectroscopy. The relation between the iron loadings in the samples and their structural, textural and magnetic properties were studied. The curves of room temperature magnetization vs. field were measured using a maximum magnetic applied field of l0Ha = 1 T. Depending on the dispersion and size of the different iron species, the nanocomposites showed different magnetic behaviors. Thus, a predominant superparamagnetic behavior was found for the samples with the lower iron loadings; this feature was assigned to oxide species finely dispersed such as the oligonuclear (FeO)n clusters and nanoparticles, both of very small size and located preferably inside the channels. Meanwhile, a lineal behavior was observed for the samples with the higher Fe loadings, attributed to the hematite nanoparticles of larger size, located on the external surface.