Brayden Myers successfully defends PhD dissertation

On November 3, 2021, Brayden Myers successfully defended his PhD dissertation, Production and Transport of Plasma-Generated Reactive Oxygen Species in the COST Reference Source. Brayden’s committee consisted of his advisor, Katharina Stapelmann, and members, Alexander Bataller, Steven Shannon, Tatyana Smirnova, and Amy Grunden.

Abstract

MYERS, BRAYDEN GRAHAM. Production and Transport of Plasma-Generated Reactive Oxygen Species in the COST Reference Source. (Under the direction of Dr. Katharina Stapelmann).

Atmospheric pressure plasmas have become the focus of intense research for a litany of biomedical applications. Their utility arises from the unique capacity to deliver high concentrations of reactive oxygen and nitrogen species to a target substrate. The basis of research into plasma for biomedicine is identifying a mode of action responsible for an observed outcome. A major impediment to advancing understanding in the field is the complex and interdependent reactions that occur as a result of the plasma-induced chemistry. To address this, the COST Reference Microplasma Jet was introduced to provide a standard source capable of highly tunable reactive species production.With this, researchers can contextualize results with the shared knowledge of the community, expedite understanding, and optimize sources for application.

In this work, the COST jet is employed to investigate the formation and transport of reactive oxygen species of interest. Significant attention is devoted to two particularly potent species: hydroxyl radicals and atomic oxygen. Focuses include accurate characterization of hydroxyl radicals and atomic oxygen in the active plasma and plasma effluent, as well as distinguishing their respective induced chemistries in plasma-treated liquid. Gas-phase studies are performed with absolutely-calibrated optical emission spectroscopy, laser-induced fluorescence, and two-photon laser-induced fluorescence. In liquid, chemifluorescence assays and EPR spectroscopy are applied. Limitations in current techniques are established and novel methods are developed to address shortcomings. The first direct detection of ground-state atomic oxygen in liquid using two-photon absorption laser-induced fluorescence is presented. Considerable effort throughout is devoted to maintaining conditions relevant for applications. Continuity in experimental parameters is emphasized to develop a complete picture of reactive species formation, transport, and extinction. Self-consistent agreement is noted throughout this work and results are concurrent with other studies utilizing the COST jet, when applicable.