(705b) 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] Kovaèík P., Kremláèková Z., ?tìpánek 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.