Fine-Tuning of Particle Size and Morphology of Silica Coated Iron Oxide Nanoparticles

Due to their unique properties such as superparamagnetism, easy surface functionalization, and colloidal stability among others, silica coated iron oxide nanoparticles (SIONPs) have received remarkable attention for biomedical applications such as in diagnostics or therapeutics. Tuning the particle size and size distribution of SIONPs as a function of solvent, catalyst, silica precursor, etc., in a modified Stöber’s method has been extensively studied. However, there has been no concerted effort to study the effect of the above parameters along with the surface chemistry of the iron oxide nanoparticles (IONPs) on the morphologies obtained and hence the resultant magnetic properties. Here, we report an in-depth investigation of the nature of solvent, concentration of catalyst, mass ratio of IONPs to silica precursor and surface groups of IONPs on the size and resultant morphology of SIONPs. We report here for the first time the evolution of different morphologies, namely, fused, irregular, aggregate, and spherical morphologies, by careful control of the reaction conditions. Controlling the sizes and morphologies exerts an influential effect on the resultant magnetic properties and, thus, their applications downstream.