Production and characterization of long-term stable superparamagnetic iron oxide-shell silica-core nanocomposites

Highlights: • Synthesis of uniform loaded superparamagnetic iron oxide-shell silica-core nanocomposites. • Specific functionalization of nanocomposites allows broad use in nonpolar and aqueous matrices. • Raman and SQUID magnetometry analysis verify long-term stability of nanocomposites. - Abstract: Methods improving the chemical and physical stability of magnetic nanoparticles are important in diverse research disciplines such as catalysis, magnetic resonance imaging, biomedicine, and bioseparation. It is essential that defined nanomaterial characteristics remain unchanged from the start of the nanoparticle production to their final application. A simple, fast and reliable strategy based on a thermal decomposition approach was established to design highly and uniformly loaded iron oxide-shell silica-core nanocomposites. They are formed by maghemite nanoparticles (8.4 ± 1.0 nm) uniformly deposited on mesoporous silica nanoparticles (381 nm ± 111 nm). Their magnetic properties as well as chemical, and mechanical stability were verified by SQUID magnetometry, Raman microspectroscopy, and electron microscopy (SEM and TEM), respectively. The produced superparamagnetic nanocomposites were stable over several months. The coating with organosilanes enables the transfer from nonpolar to aqueous phase which makes the magnetic nanocomposites also applicable for life sciences.