Multifunctional amphiphilic ionic liquid pathway to create water-based magnetic fluids and magnetically-driven mesoporous silica

Abstract

Amphiphilic ionic liquids, 1-alkyl-3-methylimidazolium chloride (C_nmimCl with n = 10, 12, 14, 16) were firstly used as modifiers to construct a self-assembly bilayer on the surface of iron oxide nanoparticles for generation of highly stable, water-based magnetic fluids. Subsequently, a magnet-driven mesoporous silica was synthesized by in situ self-assembly in the bilayer C_nmimCl-stabilized magnetic fluid using the C₁₆mimCl as template and tetraethylorthosilicate (TEOS) as silicon source via a hydrothermal synthesis and following calcination procedure. A systematic study was carried out addressing the influence of the alkyl chain length of C_nmimCl in the primary and secondary layers on the stability of magnetic fluids. The characterization of TEM, XRD, VSM, electrophoresis experiments, TGA and DTA showed that stable water-based magnetic fluids can be synthesized based on the assembly of the well-defined bilayer-C_nmimCl structure with long-chain C₁₆mimCl as secondary layer on the magnetite (Fe₃O₄) nanoparticles. The results of small and wide-angle XRD, TEM, VSM, and N₂ absorption experiments indicated that the nano-scale magnetic Fe₃O₄ particles were inlayed into hexagonal p6mm mesoporous silica (MCM-41 type) framework. Importantly, it was found that the obtained Fe₃O₄/MCM-41 was an appropriate adsorbent for the adsorption of rhodamine B and methylene blue from their aqueous solution. In addition, the adsorbent could be separated and reclaimed fleetly from the solution under external magnetic field.