Green, LAW; (2014) Synthesis and Characterisation of FePt Magnetic Nanoparticles. Doctoral thesis , UCL (University College London).

Abstract

Magnetic nanoparticles (MNPs) are intensively researched due to their high potential in biomedicine, catalysis and high density information storage. FePt NPs are a potential alternative magnetic material to commonly used magnetite NPs for biomedical applications and the synthesis of FePt NPs is an active area of research. The purpose of this thesis has been to develop wet chemical synthetic methods to tune and improve the properties of FePt magnetic nanoparticles. The morphology of magnetic nanoparticles affects the way they interact with each other, and with their surroundings. Changes in shape and composition with varying synthetic conditions can also give clues to the mechanism of formation. Changes in volume, solvent and the nature of the stabiliser have been shown to yield varying morphology in the FePt system. Multicore FePt nanoparticles up to 44 nm in diameter and composed of Pt rich FePt nanocrystals within an iron rich FePt matrix not previously seen in the literature are presented here. Magnetic properties of multicore nanoparticles are size dependent; in dioctyl ether and dibenzyl ether and with decreasing amount of oleic acid, saturation magnetisation and blocking temperature increase with size. The results indicate that coordination of Fe and Pt intermediates with oleic acid and oleylamine respectively hinders deposition of each respective metal in the growth of discrete and multicore nanoparticles. L-glutathione and albumin immediately transferred 20 nm multicore nanoparticles into water and show that large FePt nanoparticles may be stable under physiological conditions following stability tests. The use of an autoclave is shown to increase the Fe content, crystallinity and subsequent magnetic properties of FePt pseudo cube nanoparticles compared to those synthesised under atmospheric pressure. Decreasing amount of oleic acid is also shown to increase the iron content and can lead to elongated FePt nanoparticles under normal pressure. Infra-red studies indicate mono and bi dentate coordination with oleic acid, however shifts of spectra show that the strength of the bi-dentate interactions weaken with increasing oleic acid amount.

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