Facile synthesis of silica–manganese oxide nanocomposites with core–shell structure using surfactant and cosurfactant

In this study, silica–manganese oxide (Mn3O4) nanocomposites with core–shell structure were synthesized using surfactant and cosurfactant in the sol–gel reaction medium for the formation of spherical silica nanoparticles at basic condition using NH4OH as a catalyst. In order to prepare the composites of silica and Mn3O4, the aqueous solution of manganese nitrate, cetyltrimethylammonium bromide (CTAB) and tert-butanol (t-butanol) was added into the sol–gel reaction solution after the formation of silica particles which would be negative-charged at basic condition. CTAB and t-butanol as binders induced the attractive interaction between silica and Mn(OH)2 by their adsorption onto the surface of Mn(OH)2 formed by the reaction between Mn nitrate and NH4OH. After the Mn(OH)2 particles were prepared, they were transformed into Mn3O4 through the oxidation in air due to its very high reactivity. Through this process, the silica–Mn3O4 nanocomposites with controllable core–shell structure were synthesized with the variations of volume of Mn solution and concentrations of Mn nitrate, CTAB, and t-butanol. The characterizations of the silica–Mn3O4 nanocomposites were performed using FE-SEM, TEM, EDS, XRD, and TGA. The magnetization of composites was studied using a vibrating sample magnetometer (VSM) at room temperature in the range of −5000 to 5000 Oe.

TEM image of silica–Mn3O4 nanocomposites prepared in sol–gel reaction medium with cationic surfactant and cosurfactant.Figure optionsDownload as PowerPoint slideHighlights
► Silica-manganese oxide nanocomposites of core–shell type were prepared by one-step process in aqueous surfactant solution.
► Cationic surfactant at the surface of Mn3O4 nanoparticles induced the attractive interaction with negatively charged silica particles in basic solution.
► Composites showed the enhanced magnetic properties.