Synthesis, surface characterization and electrokinetic properties of colloidal silica nanoparticles with magnetic core

Abstract

In order to obtain functionalized silica colloids with magnetic properties, the three-step reaction, was carried out. The aqueous suspension of iron oxide nanoparticles as magnetic core (maghemite—γ-Fe2O3) was synthesized according to the Massart’s method (Massart in IEEE Trans Magn 17:1247–1248, 1981). A silica shell was obtained onto maghemite employing a modified sol–gel method by Salgueirino (Salgueirino-Maceira et al. in Adv Mater 19:4131–4144, 2006). As-synthesized magnetic silica core/shell nanocomposites were further functionalized by the post-grafting approach, using (3-Aminopropyl)-trimethoxysilane (APTMS) (Pham et al. in Langmuir 18:4915–4920, 2002). The obtained materials were characterized by nitrogen adsorption/desorption measurements, X-ray powder diffractometry (XRD), transmission electron microscopy (TEM). Particle sizes were measured by diffraction laser (DL). In order to establish colloidal stability of the system, zeta potential were measured. The syntheses routes led to obtain both, good purity of maghemite particles (more than 90 %) and their good coverage by outer silica shell. Thanks to their nanometer size and surface properties (especially, presence of amino groups which can ensure the electrostatic interaction between surface of adsorbent and adsorbate molecules), as-prepared nanocomposites can be considered as promising adsorbents. It can be found in the literature, that such systems are used in medicine as targeted drug delivery systems (Chen et al. in J Magn Magn Mater 322:2439–2445, 2010; Bele et al. in J Chromatogr B 867:160–164, 2008) or in environment protection as magnetically removable adsorbents (Giakisikli and Anthemidis in Anal Chim Acta 789:1–16, 2013; Tural et al. in J Phys Chem Solids 72:968–973, 2011).