Development of Novel Synthetic Methods for Size-Tunable Synthesis of Superparamagnetic Iron Oxide Nanoparticles

The properties of magnetic nanoparticles vary dramatically with size, so reproducibly controlling size is critical for practical applications. This is particularly true when moving into clinical settings, where regulatory approval requires demonstrated reproducibility in efficacy that can only be achieved with excellent size control. A number of methods for the synthesis of magnetic nanoparticles have been published, although the thermal decomposition of iron(III) precursors in organic solvents has been shown to yield high quality particles with low shape and size dispersity. Currents methods lack reproducibility resulting from non-stoichiometric starting materials, and reliance on reaction parameters, such as temperature ramp rate, that are nearly impossible to replicate between syntheses. Limited control of particle size has been demonstrated, though no truly size-tunable synthetic method has been proposed. Here, we endeavor to remove the sources of reproducibility in the existing methods and achieve size control of synthesized particles while maintaining narrow shape and size dispersity. Further, we endeavor to understand the physical mechanisms by which the control of size is achieved. Here, we detail two alternative approaches to the synthesis of an iron(III) precursor containing a known quantity of iron. These materials are further evaluated for use in the preparation of high quality iron oxide nanoparticles with high magnetic saturation values. Existing synthesis methods are also evaluated, leading to the development of a novel synthetic method that yields tunability of sizes over a broad range with nanometer precision and nearly uniform size and shape dispersity. By manipulating reaction parameters such as temperature and reagent concentration, the kinetics of the reaction can be controlled, revealing new insights into the growth of particles in a highly supersaturated monomer solution. We expect that our approach will resolve the challenges associated with the reproducible synthesis of spherical magnetite nanoparticles with low shape and size dispersity, and provide scalability required to meet commercial demand