Date of Award

August 2021

Document Type


Degree Name

Doctor of Philosophy (PhD)


School of Materials Science and Engineering

Committee Member

Thompson Mefford

Committee Member

Marek Urban

Committee Member

Jiro Nagatomi

Committee Member

Igor Luzinov


Metal substituted ferrite nanoparticles (MxFe3-xO4, M = Mn, Co, Ni, or Zn) have been synthesized and applied for a variety of biomedical applications, including magnetic hyperthermia treatment, drug delivery, and tunable MRI contrast agents. To better understand the structure-property relationship of such materials, nonstoichiometric manganese ferrite was computationally modeled with density functional theory (DFT). Detailed XRD and HRTEM analysis suggest that substitution-induced crystalline defects cause a discrepancy between the computational results and the experimental results. To improve the control of the size, and composition of the ferrite nanoparticles, a seed-mediated drip synthesis method and post-synthesis oxidation method were developed. Manganese-cobalt substituted ferrite nanoparticles were synthesized and characterized. The results showed an insufficiently oxidized core-oxidized shell structure leading to a shell-dominated magnetic property. To solve the insufficient oxidation issue and to better control the crystalline structure of the ferrite nanoparticles, a post-synthesis annealing method was developed. The results indicated that the wüstite rich nanoparticles can be oxidized by post-synthesis annealing without the addition of oxidizing agents. For 20 nm iron oxide nanoparticles, the saturation magnetization increased from 35 Am2/kg to 72 Am2/kg and exhibited a specific absorption rate of 240 W/g under a 212 kHz, 33 mT AC field. To study the structure-property relationship of the 4-arm polypropylene oxide (PPO)–polyethylene oxide (PEO) block copolymers, a series of polymer hydrogels with various molecular weights, block molar ratios, and solution concentrations were prepared via anionic ring-opening polymerization. The chemical structures were determined by nuclear magnetic resonance (NMR) and the thermal properties were tested by differential scanning calorimetry (DSC). The resulting data were statistically analyzed, and a corresponding empirical model was developed. The empirical model indicated the thermoresponsive temperature is positively correlated with the EO/PO ratio and negatively correlated with the molecular weight and concentration. The empirical model was then challenged through the synthesis of 3 targeted polymers and resulted in an RDS of less than 5%. Particles with high heating efficiency were surface modified with thermoresponsive PEO-b-PPO ligands via ligand exchange and silica surface chemistry. The polymer-particle complex showed magneto-thermoresponsiveness that is potentially used in magnetically triggered drug release in the future.



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