Selective generation of reactive oxygen species in plasma-activated water using CO2 plasma

In this study, we discuss a process for selectively generating reactive oxygen species (ROS), such as H2O2 and dissolved O-3, in plasma-activated water (PAW) using pure CO2 as a plasma-forming gas. A detailed comparison of the gas species/radicals present in plasma and the properties of PAW when using CO2 and air as plasma-forming gases is presented. Our results show that PAW generated with CO2 has a significantly higher pH and lower oxidizing potential and electrical conductivity compared to PAW generated with air. Species formed in PAW (CO2) due to CO2 plasma-water interaction include dissolved O-3, H2O2, dissolved CO2, CO 3 2 - ions, etc. Moreover, the concentration of NO 2 - and NO 3 - ions in PAW (CO2) is beyond the detection limit. PAW (CO2) has a substantially higher concentration of H2O2 than PAW (air). Furthermore, increasing the plasma treatment time with water significantly increases the concentration of H2O2 and dissolved O-3 in PAW (CO2). In conclusion, our study demonstrates that selective generation of ROS in PAW is possible using CO2 as a plasma-forming gas, leading to a higher H2O2 concentration compared to air.

Automated summary

This study discusses the selective generation of reactive oxygen species (ROS) in plasma-activated water (PAW) using pure CO2 as a plasma-forming gas. A detailed comparison of gas species/radicals in plasma and the properties of PAW generated with CO2 and air is presented. The results show that PAW (CO2) has a higher pH, lower oxidizing potential, and lower electrical conductivity compared to PAW (air). The species formed in PAW (CO2) include dissolved O-3, H2O2, dissolved CO2, CO 3 2 - ions, etc. The concentration of NO 2 - and NO 3 - ions in PAW (CO2) goes beyond the detection limit. Moreover, PAW (CO2) has a significantly higher concentration of H2O2 than PAW (air), and increasing the plasma treatment time with water increases the H2O2 and dissolved O-3 concentration in PAW (CO2).