Investigation of Novel Nanoparticles for Biomedical Applications

The aim of the work presented here is to investigate the oxidation behaviour of nanoparticles produced using novel physical vapour deposition methods with magnetic moments and saturation greater than commercially available Fe-oxide nanoparticles. The production of such nanoparticles is tailored towards usage in biomedical applications, where, due to health and safety concerns the strength and frequency of magnet fields is limited. As such the goal is to produce highly optimised and tailored nanostructures that offer the best magnetic performance possible under the medical constraints. This necessitates building a detailed understanding of the oxidation pathways and processes that nanoparticles undergo as the formation of oxide layers on nanoparticles hinders their magnetic performances. Furthermore, while the oxidation of bulk materials is well-studied and documented applying this understanding at the nanoscale presents many challenges as oxidation behaviour at this level differs greatly based on the physical properties of the samples. Fe was used throughout this study due to the materials desirable magnetic properties and current use in medical applications. The study presented here examines the mechanisms behind the oxidation of spherical Fe/FexOy particles with the oxidation process enhanced through annealing at 200°C as well as attempts to create protective metal shells around pure Fe particles to preserve the iron core from oxidation. To this end investigation into the production of Fe@Cu, Fe@Ag, Fe@Al and Fe@Mg is given. Particle analysis was carried out using the wide variety of characterisation techniques available through electron microscopy using a JEOL 2011 TEM and JEOL 2200 FS (S)TEM. It was found that diffusion through iron oxide grain boundaries in the particle shell had a significant effect with the diffusion coefficient estimated to be 4.67×〖10〗^(-11) 〖cm〗^2 〖 s〗^(-1). While the best performing metallic coating was Fe@Cu with particle exhibiting vastly different physical properties due to the addition of copper.