Facile synthesis of ordered magnetic mesoporous γ-Fe2O3/SiO2 nanocomposites with diverse mesostructures

On the basis of a sol-gel process, a facile, low cost, and one-step approach for preparing ordered magnetic mesoporous gamma-Fe2O3/SiO2 nanocomposites by an evaporation-induced self-assembly (EISA) approach is presented. Various mesostructured silica materials (P6mm or Im3m) incorporated with different amounts of iron oxide (n(Si)/n(Fe) = 9/1, 8/2, 7/3, respectively) were synthesized and characterized by XRD, TEM, N-2-sorption analyses, and superconducting quantum interference device (SQUID) magnetometer. The HCl-leaching experiments together with TEM micrographs and nitrogen sorption analysis suggested that most of the gamma-Fe2O3 domains of several nanometers were embedded in the silica walls, rather than dispersed in the mesopores, which could Cause the significant pore clogging reported in some studies. The release behaviors of lysozyme from these magnetic porous nanocornposites were investigated for the possible application of drug targeting and control release. The influence of iron precursors was also studied and a possible mechanism was proposed. The hydrolysis of Fe3+ ions under weakly acidic conditions and the induced formation of Si-O-Fe bonds may account for the synthesis of this kind of nanocomposite. These multi functional nanostructured materials would have a wide range of applications in toxin removal, catalysis, waste remediation, and biological separation as well as novel drug-carrier technologies. (C) 2008 Elsevier Inc. All rights reserved.