Synthesis of Core-Shell Magnetic Nanoparticles Containing Ultrasmall Domains of Silicalite-1

Synthesis of core-shell nanostructures with magnetic core and zeolitic shell is an ongoing challenge. Herein, a strategy is presented for preparation of gamma-Fe2O3@mesoporous silica (mSiO(2)) core-shell nanoparticles containing ultrasmall domains of silicalite-1 in the shell (gamma-Fe2O3@mSiO(2)/silicalite-1). The strategy consists in a solid-state reorganization of the precursor amorphous mSiO(2) shell into silicalite-1 using a tetrapropylammonium hydroxide (TPAOH) as an organic structure-directing agent (OSDA) under mild hydrothermal (HT) conditions. The formation of silicalite-1 crystalline domains is investigated through the detailed characterization of products obtained at different times of HT treatment by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and nitrogen physisorption. By careful tuning the time of HT treatment, the gamma-Fe2O3@mSiO(2)/silicalite-1 nanostructures are prepared. Benefitting from the unique mesopores/microporous structure formed, the gamma-Fe2O3@mSiO(2)/silicalite-1 core-shell nanostructure shows superior adsorption capacity to remove aniline from aqueous solutions than the gamma-Fe2O3@mSiO(2). Moreover, the gamma-Fe2O3@mSiO(2)/silicalite-1 nanostructure is easily separated from aqueous solutions using magnetic separation technique within 1 min.