Generation and loss of reactive oxygen species in low-temperature atmospheric-pressure RF He + O₂ + H₂O plasmas

Abstract

This study focuses on the generation and loss of reactive oxygen species (ROS) in low-temperature atmospheric-pressure rf (13.56MHz) He+O 2 +H 2 O plasmas, which are of interest for many biomedical applications. These plasmas create cocktails of ROS containing ozone, singlet oxygen, atomic oxygen, hydroxyl radicals, hydrogen peroxide, and hydroperoxyl radicals, i.e. ROS of great significance as recognized by the freeradical biology community. By means of 1-dimensional fluid simulations (61 species, 878 reactions), the key ROS and their generation and loss mechanisms are identified as a function of the oxygen and water content in the feed gas. Identification of the main chemical pathways can guide the optimization of He+O 2 +H 2 O plasmas for the production of particular ROS. It is found that for a given oxygen concentration, the presence of water in the feed gas decreases the net production of oxygen-derived ROS, while for a given water concentration, the presence of oxygen enhances the net production of water-derived ROS. Although most ROS can be generated in a wide range of oxygen and water admixtures, the chemical pathways leading to their generation change significantly as a function of the feed gas composition. Therefore, care must be taken when selecting reduced chemical sets to study these plasmas.

Hydrogen Peroxide Production in an Atmospheric Pressure RF Glow Discharge: Comparison of Models and Experiments

“…These are incorporated in the third model, a 1-dimensional fluid model. The fluid model is based on the model used in references [11,29] and briefly it solves the continuity equation for each plasma species, the electron energy equation and Poisson's equation. Due to the large collisionality of atmospheric pressure plasmas (ν >> ω r f where ν is the neutral collision frequency and ω r f the angular driving frequency), the particle inertia is neglected and the drift-diffusion approximation is used to determine the mean velocity for each species.…”

“…Due to the large collisionality of atmospheric pressure plasmas (ν >> ω r f where ν is the neutral collision frequency and ω r f the angular driving frequency), the particle inertia is neglected and the drift-diffusion approximation is used to determine the mean velocity for each species. A few modifications have been made to the model used in [11] for this study:…”

“…The measurements are complemented with accurate gas temperature (T gas ) measurements and plasma dissipated power measurements. In addition the experimental results are compared with a previously published global model [10] and 1D fluid model [11]. An analysis of the production and destruction mechanisms of H 2 O 2 is made with a simplified analytical balance equation of the H 2 O 2 production based on extensive chemistry models.…”

Corrigendum on ‘OH Density Measurements by Time-Resolved Broad Band Absorption Spectroscopy in a He-H2 O Dielectric Barrier Discharge With Small O2 Addition’

“…We remind that our measurements and the calculations of Ref. [6] are obtained at the same power density of 1 W cm…”

“…No direct comparison with the calculations of Ref. [6] is then possible, but numbers seem to be very similar. Differences in the OH concentration as a function of oxygen addition are instead unchanged, and are even more striking due to the improved agreement in the no oxygen case.…”