Thermal, Stability, and Morphological Effects of Multicore Surface-Functionalized Magnetic Nanoparticles

Multicore magnetic nanoparticles are composed of multiple single-core magnetic nanoparticles packaged together into a mosaic (aggregate) core that is encapsulated by a shell to form an overall core-shell structure.  The mosaic nanoparticles utilized in this work were comprised of multiple magnetite (Fe₃O₄) single-core nanoparticles encapsulated within a silicate shell, with the shell surface-functionalized with amine, chitosan, or hydroxyl groups.  Magnetic nanoparticles have been used for a wide range of applications, including drug delivery, material separations, energy harvesting and electronic displays.  The stability of these mosaic-core type magnetic nanoparticles is important to determine processing and usage specifications; therefore, it is important to understand the effects of the thermal conditions to which they are subjected.  In this study, thermal stress experiments were performed: reflux heating/condensation, differential scanning calorimetry (DSC), temperature-controlled dynamic light scattering (DLS), and sonication with heating.  Maximum operating condition prior to these mosaic magnetic nanoparticles undergo breakage were determined, including temperature, time at temperature, and thermal cycling.  Samples were characterized before and after thermal treatments using transmission electron microscopy, dynamic light scattering, and FTIR spectroscopy to evaluate the stability of these core-shell magnetic nanostructures. This study evaluates optimum processing and usage conditions for magnetite mosaic nanoparticles to guide in their application.