Structure and Properties of Surface Modified Magnetic Hollow Silica Spheres

Structure and properties of surface modified magnetic hollow silica spheres

Kovacik Pavel, Kremlackova Zuzana, Soltys Marek, Stepanek Frantisek

ICT Prague, Department of Chemical Engineering, Laboratory of Chemical Robotics

kovacikp@vscht.cz

The aim of this work was to prepare composite hollow magnetic silica spheres via the soft templating method. Depending on the method and its parameters we prepared hollow spheres with a mean size ranged from tens of nanometers to tens of micrometers. The spheres had a porous silica (SiO₂) shell containing embedded iron oxide nanoparticles for radiofrequency heating (Fe₃O₄/Fe₂O₃). Coating applied to the surface of the silica spheres can ensure the controlled diffusion of encapsulated substances from the hollow core across the silica shell. Two coating approaches were used: i) so-called polymer brushes systems and ii) covering the surface of spheres by a phase change material (Fig. 1). The structure of the spheres was characterised by SEM, TEM, confocal and FTIR microscopy and BET analysis. The heating rate of prepared spheres was measured in alternating magnetic field (PowerCube 32/400, 2.5 kW). The temperature-dependence of release kinetics of a model substance (vitamin B12, methylene blue) from the spheres was measured by time-resolved UV/Vis spectrophotometry. Remotely induced radiofrequency heating was found to be an effective mechanism for controling the release kinetics from the composite capsules.

Figure  SEQ Figure \* ARABIC 1: The diffusion across a silica shell can be controlled by using polymer brushes (A) or phase change material (B).

Reference

[1] Kovačík P., Kremláčková Z., Štěpánek F., "Investigation of radiofrequency induced release kinetics from magnetic hollow silica microspheres", Micropor. Mesopor. Mater., in press (2012), http://dx.doi.org/10.1016/j.micromeso.2012.04.019.