Frequency effects on the production of reactive oxygen species in atmospheric radio frequency helium-oxygen discharges

Abstract

Several experimental and computational studies have shown that increasing frequency can effectively enhance the discharge stability in atmospheric radio-frequency (rf) discharges, but the frequency effects on the reactivity of rf discharges, represented by the densities of reactive oxygen species (ROS), are still far from fully understood. In this paper, a one-dimensional fluid model with 17 species and 65 reactions taken into account is used to explore the influences of the driving frequency on the production and destruction of ROS in atmospheric rf helium-oxygen discharges. From the computational results, with an increase in the frequency the densities of ROS decrease always at a constant power density, however, in the relatively higher frequency discharges the densities of ROS can be effectively improved by increasing the input power density with an expanded oxygen admixture range, while the discharges operate in the α mode, and the numerical data also show the optimal oxygen admixture for ground state atomic oxygen, at which the peak atomic oxygen density can be obtained, increases with the driving frequency.

Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet

“…(2) (the electron density n e is cancelled with the one in the numerator), increases actually with increase in the oxygen concentration. Therefore, if this contribution is considered, the ground state O-density is likely to behave as indicated by the dot line in Figure 5C , which is in accord with the experimental results of rf-driven atmospheric pressure plasmas 39 48 .…”

“…Ozone's damaging effect of the cell can be mediated via an induction of ROS within cells 38 . Since the reaction O + He + O 2 → He + O 3 is believed as the main way to produce ozone in the discharge region 39 , it is expected that the ozone density correlates with the densities of atomic oxygen and oxygen molecule. Thus, the ozone density keeps growing with increase in the concentration of O 2 40 .…”

Electrode-Gap Effects on the Discharge Structure in Atmospheric Radio-Frequency Microplasmas With He/O₂ Mixtures

“…Therefore, the underpinning physical and chemical processes of the generation of ROS have raised more attention in low-temperature plasma community, and the experimental and computational investigations have contributed to the further understandings of the evolution of ROS [8], [12]. The recent simulation shows that although increasing the frequency can improve the uniformity of atmospheric plasmas, the ROS generation is suppressed [16].…”

Numerical Simulation on the Production of Reactive Oxygen Species in Atmospheric Pulse-Modulated RF Discharges with He/O2 Mixtures

“…[17][18][19] The simulations based on the fluid description also have been developed, usually with simplified reaction set that selected by the global model, to greatly reduce the computational load. [14,15,20] In our previous report, we have presented a fluid model to tailor and optimize the pure helium plasmas generated in a pulse-modulated RF discharge. [12] In this study, the fluid model incorporated with a simplified He/O 2 reaction set is explored to examine the generation of ROS in a pulsemodulated RF discharge, we focus on the influences of duty cycle and modulation frequency on the generation of ROS, which would provide interesting and useful information for many applications.…”

“…Due to the high computational efficiency by neglecting the spatial gradients, global model always is adopted to study the plasma chemistry even with tens of species and hundreds of reactions, to further clarify the key reactive species and reactions . The simulations based on the fluid description also have been developed, usually with simplified reaction set that selected by the global model, to greatly reduce the computational load …”