Incorporation of silica coated Magnetic iron oxide nanoparticles in a phosphate glass matrix

This thesis reports the incorporation of silica coated magnetic iron oxide nanoparticles (IONPs) within a phosphate glass matrix. The motivation was to create a novel composite material with potential applications in magnetic hyperthermia cancer treatment, based on NPs of Fe3O4 and

g-Fe2O3 being superparamagnetic. A silica coating can prevent agglomeration, and transformation to a-Fe2O3 during heat treatment, and glass as a host matrix is a chemically inert and able to be shaped. Characterisation was completed at each experimental stage, including TGA/DSC, IR, XRD, TEM, and XANES. Magnetic IONPs were synthesised (Chapter 3) through two different large-scale methods: co-precipitation (CP) and thermal decomposition (TD). CP NPs showed particle agglomeration and wide size distribution (TEM 7-22 nm) which was expected from this method. TD NPs had a hydrophobic oleic acid capping which allowed for a narrower size distribution and no agglomeration (TEM 7-17 nm). The Fe-oleate and solvent used influenced the final NP product. To prepare TD NPs for the silica coating process, phase transfer through oxidative cleavage was performed. Both CP and TD (after phase transfer) NPs were coated in a protective silica shell (Chapter 4) through a sol-gel method, using sodium silicate as the silica source. TD NPs were found to be better coated in silica than CP NPs. To increase the coatings effectiveness, further densification of silica coating was performed through heat treatments. It was found that silica coated NPs of both types (CP and TD) generally showed no transformation to a-Fe2O3 at 500 °C, partial transformation at 700-825 °C, and would undergo full transformation when exposed to 1000 °C. Hence, a low melting temperature 45P2O5-10CaO-45Na2O glass was used as a matrix to synthesise a novel nanocomposite material (Chapter 5). The glass was first synthesised through a melt-quenching process, and then coated NPs were incorporated through a flash melting procedure. Both CP and TD glass nanocomposites showed that the NP structure has been altered through the incorporation process. NPs also altered glass structure. Only nanocomposites produced with TD NPs showed response when exposed to an external magnet. These show promise for further

development to achieve applications in magnetic hyperthermia.