Synthesis of Core–Shell Magnetic Nanoparticles Containing Ultrasmall Domains of Silicalite‐1

Abstract

Abstract Synthesis of core–shell nanostructures with magnetic core and zeolitic shell is an ongoing challenge. Herein, a strategy is presented for preparation of γ‐Fe2O3@mesoporous silica (mSiO2) core–shell nanoparticles containing ultrasmall domains of silicalite‐1 in the shell (γ‐Fe2O3@mSiO2/silicalite‐1). The strategy consists in a solid‐state reorganization of the precursor amorphous mSiO2 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 γ‐Fe2O3@mSiO2/silicalite‐1 nanostructures are prepared. Benefitting from the unique mesopores/microporous structure formed, the γ‐Fe2O3@mSiO2/silicalite‐1 core–shell nanostructure shows superior adsorption capacity to remove aniline from aqueous solutions than the γ‐Fe2O3@mSiO2. Moreover, the γ‐Fe2O3@mSiO2/silicalite‐1 nanostructure is easily separated from aqueous solutions using magnetic separation technique within 1 min.

Keywords

• adsorption
• core–shell nanostructure
• crystallization
• magnetic properties
• zeolite