Investigation of radiofrequency induced release kinetics from magnetic hollow silica microspheres

Composite hollow silica microspheres containing embedded iron oxide nanoparticles for radiofrequency heating have been synthesised by a soft templating route. The influence of nanoparticle concentration on the microspheres size distribution, shell thickness, and heating rate was investigated. The structure of the hollow microspheres was characterised by SEM, confocal microscopy and BET analysis, and the temperature-dependence of release kinetics of a model substance (vitamin B12) from the microspheres was measured by time-resolved UV/Vis spectrophotometry. A mathematical model of the release process, based on simultaneous diffusion and adsorption/desorption of the solute in the mesoporous shell, has been developed and used to evaluate the dependence of the effective diffusivity in the mesoporous silica shell on temperature and preparation conditions. (C) 2012 Elsevier Inc. All rights reserved.