2024 report

Absolute Reactive Oxygen Species Densities in the Effluent of the COST Reference Source and Plasma-generated Atomic Oxygen Density Measurements in Liquid using TALIF

By: K. Stapelmann n 

UN Sustainable Development Goal Categories
6. Clean Water and Sanitation (OpenAlex)
Source: ORCID
Added: April 22, 2024

Reactive oxygen species are one of the most important species produced in a plasma. In particular the role of atomic oxygen and the hydroxyl radical OH has attracted many studies ranging from plasma medicine to plasma-driven biocatalysis and water treatment. Atomic oxygen and the hydroxyl radical OH are very reactive and react unselectively with many different substrates. The quantification of atomic oxygen and OH is challenging because of their reactivity and unknown reactions and rate constants. Absolute densities of reactive oxygen species in the effluent of a microscale atmospheric pressure plasma jet, the reference plasma source COST jet, were determined. The goal of this research was to quantify absolute OH, hydrogen peroxide, and O densities using laser induced fluorescence (LIF), photofragmentation LIF (pf-LIF), and two photon absorption laser induced fluorescence (TALIF) to gain a better understanding of the role of these reactive oxygen species for biomedical applications of plasmas. In addition, we measured absolute atomic oxygen densities directly in liquid exposed to the effluent of an atmospheric pressure plasma jet using two-photon absorption laser induced fluorescence (TALIF), as the first group attempting to employ TALIF in liquids. The spatial resolution of the laser measurements allowed the penetration depth and Henry's law constant of atomic oxygen to be determined, providing better information on the transport and lifetime of oxygen atoms in liquid. It also provides essential data for plasma chemistry models and may help optimization processes for applications. Performing these measurements on a reference source provided other research groups working with the COST Jet and similar plasma jets with vital information on some of the most important reactive species generated in APPJs. This will inform other experiments and simulations that will continue to advance the field for years to come.