Synthesis of a bilayered SDS/ionic liquid stabilized ferrofluid and magnetic cubic mesoporous silica using a long chain ionic liquid

Abstract

Bilayered sodium dodecyl sulfate (SDS)/ionic liquids (alkyl imidazolium type ionic liquid C_nmim⁺, n = 10, 12, 14, and 16) were first employed to modify the surface of Fe₃O₄ nanoparticles for the formation of stable aqueous ferrofluids. Subsequently, in the synthesized bilayered SDS/C₁₆mim⁺-stabilized ferrofluid (Fe₃O₄/SDS/C₁₆mim⁺), magnetic mesoporous silica with a cubic (Ia3d) mesostructure (Fe₃O₄@MCM-48) has been synthesized using tetraethylorthosilicate as the silicon source and the long chain C₁₆mim⁺ as a template again. The research results showed that the combination of SDS and long chain C_nmim⁺ (such as C₁₆mim⁺) is superior to that of SDS and short chain C_nmim⁺ (such as C₁₀mim⁺) for the production of stable ferrofluids in water. Moreover, Fe₃O₄@MCM-48 (0.1 g) with Fe₃O₄ particles embedded in the network of cubic mesoporous silica showed decolorization rates of up to ∼90% in 25 min for four dye (methylene blue, rhodamine B, malachite green, and methyl violet) solutions (50 mL, 100 mg L⁻¹). In addition, the malachite green-adsorbed Fe₃O₄@MCM-48 can be separated and recovered under an external magnetic field. This method in which the long chain ionic liquid C₁₆mim⁺ can be manipulated in turn not only as the modifier but also as the mesoporous templating agent provides important guidelines for the multifunctional applications of C₁₆mim⁺ in the synthesis of various nanostructured materials.