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

Abstract

By choosing an appropriate duty cycle and modulation frequency, the pulse-modulated RF discharge can be optimized to provide a high-density atmospheric plasma with a reduced power consumption but without the risk of gas heating in pure helium. In this paper, we presented a fluid model to investigate the generation of reactive oxygen species (ROS) in an atmospheric pulse-modulated RF discharge with He/O 2 mixtures. The numerical results show that modulated by a pulse the electrons could not fully interact with the oxygen molecules, then leading to a less consumption of electrons. Thus, the production of ground state atomic oxygen, excited atomic oxygen and single delta oxygen (SDO) are suppressed, however, due to the reduced power dissipation under pulse modulation, the production of ground state atomic oxygen and excited atomic oxygen are still effective. Consequently, the duty cycle and modulation frequency can also be used to manipulate the generation of ROS in an atmospheric RF discharge.

Influence of pulse modulation frequency on helium RF atmospheric pressure plasma jet characteristics

“…These relatively high emissions from the oxygen species were observed without admixing any external oxygen content to the main discharge gas, which is usually obtained by gas admixture. [ 30,41 ] Electron impact excitation of ground‐state molecular and atomic oxygen leads to the emission at 844.6 and 777.4 nm, which is predicted by the dissociative excitation, given as, and direct impact excitation mechanisms, where O * refers to the O (3p 5 P) state, which emits at 777.4 nm, and the O (3p 3 P) state, which emits at 844.6 nm. [ 48–50 ] The generation of oxygen metastable is predominantly caused by electron impact dissociation of O 2 , and electron‐induced processes dominate the generation of ground‐state atomic oxygen.…”

“…[ 23 ] In another finding, He et al presented a fluid model to investigate the generation of reactive oxygen species in an atmospheric pulse‐modulated RF discharge with He/O 2 mixtures by varying the duty cycle from 30 to 60% at a low modulation frequency <50 kHz. [ 30 ] They also found that the electron density in a pulse‐modulated RF discharge even becomes more significant than that in a continuous RF discharge at some duty cycles (30–60%).…”

Numerical study on interactions of atmospheric plasmas and peptides by reactive molecular dynamic simulations

“…Actually, it is well accepted in MD simulations to ensure adequate reactivity of the whole molecular system in such a small computational domain. [ 27 ] Before the particle impacts, the system is equilibrated at room temperature (300 K) for 50 ps in the NVT ensemble (a constant number of atoms under a constant volume and constant temperature system) using the Berendsen thermostat. The velocity directions of reactive species are chosen randomly.…”

Numerical study on interactions of atmospheric plasmas and vegetable oils by reactive molecular dynamic simulations

“…Usually, the ROS density in the simulation domain is much larger than the true density generated in the experimental plasmas. [8][9][10]42] Actually, it is well accepted in MD simulations to ensure adequate reactivity of the whole molecular system in such a small computational domain. Periodic boundary conditions are applied in all three directions to mimic a larger system in our simulations.…”

“…[1][2][3][4] A large number of experiments have demonstrated the effect of low-temperature plasma treatment in applications ranging from decontamination of medical equipment and disinfection of tissue to the regeneration of chronic wounds and even cancer treatment, [5][6][7] and the reactive oxygen species (ROS) and reactive nitrogen species (RNS) produced in atmospheric plasmas are believed to play essential roles in plasma medicine. [1,[8][9][10][11] Moreover, the plasma-activated solution (PAS) has attracted increasing attention as a promising tool in plasma medicine, even showing therapeutic effects in cancer treatment, [7,12] which have suggested some differences from the direct cold plasma treatment. [13] PAS can be carried to places where plasma generation is not possible, such as in small organs that are difficult to reach.…”