DOI
https://doi.org/10.25772/J5XY-W536
Defense Date
2025
Document Type
Thesis
Degree Name
Master of Science
Department
Mechanical and Nuclear Engineering
First Advisor
Jessika Rojas Marin
Abstract
Orthovoltage X-ray beams are attractive for surface and intra-operative radiotherapy. Yet, their clinical utility is constrained by rapid attenuation and the limited dose that can be delivered without harming healthy tissue. High-Z hafnium oxide (HfO2) nanoparticles can boost local energy deposition through the photoelectric effect, while catalytic surface defects accelerate water radiolysis. Harnessing both mechanisms in a single nano-heterostructure could enable potent radiosensitization at diagnostic-range energies.
This thesis develops and evaluates HfO2-based nanoheterostructures, both bare and Au-decorated, as catalytic radiosensitizers.
Two types of HfO2 were evaluated, one was synthesized following a specific route and the other commercially available. Afterward, each HfO2 was decorated with Au nanoparticles via a wet-chemical route. Crystallite size, phase, morphology, Au loading, and surface chemistry were investigated by XRD, TEM and XPS. Cat- alytic radiosensitization was assessed by monitoring pseudo–first-order degradation of methylene blue under 70kV, 100kV, 150kV and 225kV X-rays, varying nanoparticle concentrations (0.10, 0.25, 0.50, 0.75, and 1 mg mL−1).
The hydrothermally synthesized HfO2 rose the rate constant k by up to 0.110 min−1 and delivering a 43% enhancement at 225 kV; even at 70 kV it achieved a 30% gain. Au decoration passivated active sites on this support, adding no more than 6%. In contrast, the commercial powder showed minimal benefit, < 10 %, unless augmented with Au, which restored activity to 19 % at the lowest energy tested.
Performance correlates with lattice disorder and surface defect chemistry rather than Au loading alone. By tailoring synthesis to maximize oxygen-vacancy density while controlling noble-metal coverage, catalytic dose amplification approaching 40 % can be achieved across the entire 70 kV to 225 kV window. Together, these insights set the stage for HfO2 nanomaterials that maximize therapeutic gain at low kilovoltage energies with minimal collateral toxicity.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
5-9-2025
Included in
Nanomedicine Commons, Nanoscience and Nanotechnology Commons, Nuclear Engineering Commons, Other Materials Science and Engineering Commons