Engineering magnetic properties of nanoparticles for biomedical applications and magnetic thin film composite heterostructures for device applications.

• Main Author: Hunagund, Shivakumar
• Format: Others
• Published: VCU Scholars Compass 2019
• Subjects: Magnetic nanoparticles; MRI Contrast agents; Thin film; Bi-layer heterostructures; Materials Science and Engineering; Nanoscience and Nanotechnology; Other Engineering
• Online Access: https://scholarscompass.vcu.edu/etd/5943; https://scholarscompass.vcu.edu/cgi/viewcontent.cgi?article=7036&context=etd

The motivation of this study is to investigate the size dependent properties of Gadolinium silicide nanoparticles and their potential applications in Biomedicine. We use two approaches in our investigation - size dependence and possible exchange interaction in a core-shell structure. Past results showed Gd5Si4 NPs exhibit significantly reduced echo time compared to superparamagnetic iron oxide nanoparticles (SPION) when measured in a 7 T magnetic resonance imaging (MRI) system. This indicates potential use of Gd5Si4 ferromagnetic nanoparticles as T2 contrast agents for MRI. Until recently most contrast agents (CA) that are used in Magnetic Resonance Imaging (MRI) studies have been paramagnetic. However, ferromagnetic CAs are potentially more sensitive as T2 CAs than T1 paramagnetic compounds due to their large magnetic moments. Furthermore, the need for better MRI images without the need of upgrading to the higher magnetic field strength can be achieved using better CA such as Gd5Si4 NP. The quality of the image contrast in MRI is improved by shortening T1 and T2 relaxation times at the site or close proximity to the CA. In this study, effect of Gd5Si4 NP of varying sizes and with different concentrations are investigated on T1, T2 and T2* (effective/observed T2) relaxations times. Further study was carried out on possible exchange interaction between Fe3O4 and Gd5Si4 to enhance the magnetic properties of the Gd5Si4 which could be later used to synthesize core-shell structures. Exchange interaction / bias is a phenomena associated with the exchange anisotropy created at the interface between the two magnetic materials. Therefore, thin films of varying thickness was deposited and studied for their magnetic properties.