Date of Award

7-28-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Applied Science

First Advisor

Gregory Guisbiers

Second Advisor

Qingfang He

Abstract

This study aimed to synthesize selenium nanoparticles (Se NPs) by Pulsed Laser Ablation in Liquids (PLAL) and investigate their antibacterial and biological effects, particularly their impact on cell viability and related biological responses. Spherical amorphous Se NPs were produced by irradiating a selenium target using a combination of bottom- and top-ablation protocols. After autoclaving, the amorphous Se NPs were converted into trigonal Se NPs. Se NPs were characterized by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR). The biological effects of Se NPs were quantitatively assessed through evaluations of cell viability and associated biological markers, consistent with the analyses discussed in the dissertation. The experimental results showed that amorphous Se NPs revealed enhanced antibacterial activity compared to the trigonal phase because of the atomic structure's amorphous nature, Reactive Oxygen Species (ROS) formation, and the high surface area to volume ratio. Notably, the Se NPs showed a dose-dependent response and the higher the concentrations of the NPs, the lower the concentrations of the photosynthetic pigments. While the results are promising, especially regarding the antibacterial activity of amorphous Se NPs at concentrations as low as 10 µg/mL, further studies are necessary to fully validate their potential for large-scale production and biomedical application. Nonetheless, this research underscores the important role of synthesis conditions—such as the use of PLAL—in shaping nanoparticle properties and bioactivity. The chemical-free nature of PLAL and the observed antibacterial effects suggest that Se NPs may be suitable candidates for future applications in antimicrobial coatings, drug delivery, and wound treatment, offering a step toward eco-friendly nanomedicine. Keywords: Nanoparticles, Pulsed Laser Ablation in Liquids, Selenium, Antibacterial, Reactive Oxygen Species (ROS).

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