Description of the physicochemical properties of a gas–liquid phase discharge under the Ar—N2 environment

H I A Qazi,L Zhou,Y.-Y Xin,J J Huang

doi:10.1063/5.0014656

Abstract

AC-excited Ar—N2 gas–liquid phase discharges, operating at constant AC amplitude, are investigated as a function of the N2 concentration from 0 vol. % to 100 vol. % in an Ar—N2 mixture. Immediately after discharge initiation, increasing the N2 concentration in Ar significantly affects discharge voltage characteristics, optical-emission intensity, and rotational and vibrational temperatures. At a later stage, increasing the N2 concentration stimulates significant temporal behavior in discharge electrical characteristics such as the voltage and power input; discharge channel length in liquid; liquid properties such as pH and conductivity; and instantaneous concentrations of H2O2, NO2−, and NO3− in the liquid phase. Moreover, a temporal study of the aforesaid important experimental parameters indicates that in a given gas mixture, the length of the discharge channel and species concentrations are sensitive to the liquid properties. On the one hand, present experimental results are helpful in improving the understanding of physical–chemical processes of discharge in the gas–liquid phase. On the other hand, these are important to extend the practical applications of gas–liquid phase discharge in the field of environmental safety, plasma medicine, hydroponics, and so on.

Highlights

It is well known that discharges sustained in contact with or in liquid are rich sources of many short-lived reactive nitrogen– oxygen species (SRNOS) (e.g., OH, NO, N2, and O), many longlived reactive nitrogen–oxygen species (LRNOS) (e.g., H2O2, NO−2, and NO−3 ), and UV radiation.[1,2]
The produced SRNOS penetrate into the liquid and initiate various chemical processes depending upon the nature of the liquid; as a consequence, a number of LRNOS are formed in the liquid phase
A detailed analysis of the nature of the Ar−−N2 discharge can be obtained by using fast imaging with an intensified charge-coupled device (ICCD)

Summary

Introduction

It is well known that discharges sustained in contact with or in liquid are rich sources of many short-lived reactive nitrogen– oxygen species (SRNOS) (e.g., OH, NO, N2, and O), many longlived reactive nitrogen–oxygen species (LRNOS) (e.g., H2O2, NO−2 , and NO−3 ), and UV radiation.[1,2] there is great interest in these discharges due to their abundant technological applications in the field of environmental safety, plasma medication, hydroponics, and fabrication of nano-materials.[3,4,5,6,7,8] According to the discharge type (plasma-assisted gases), discharge conditions (polarity and peak applied voltage and electrode curvature), and surrounding environment (ambient air and vapor of the liquid electrode), many types of plasma reactions are initiated and a number of SRNOS are formed by these discharges in the gas phase. Plasma-treated water, containing reactive species, such as NO−2 and H2O2, is effective for inactivating cancer cells;[3] plasma-treated water with NO−3 is capable of improving seed germination and plant growth rate.[6,7]

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Conclusion