Biological and Chemical Reactivities of Plasma-Activated Water Prepared at Different Temperatures

In this study, plasma activated water (PAW) has been prepared by using atmospheric pressure air dielectric barrier discharge (DBD) at the PAW temperature of 3–90 °C. The effects of PAW temperature, pH values and O 3 concentration on the E. coli inactivation have been studied, and the chemical reactivity of PAW has been analyzed by using the chemical probe. It is found that both the biological and chemical reactivities of PAW are strongly dependent on the PAW temperature, however, their dependences on temperature are not consistent. When the PAW temperature decreases from 90 to 3 °C, the chemical reactivity of PAW is significantly increased due to an increase in the concentration of activated oxygen in PAW. Decreasing the temperature from 30 to 3 °C or increasing the temperature from 45 to 90 °C leads to an obvious increase in the biological reactivity of PAW. Our analysis shows that an obvious increase in the biological reactivity of low-temperature (≤ 15 °C) PAW is due to the synergistic effect of acidic solutions and a high concentration of activated oxygen in PAW. The high biological reactivity of PAW at the temperature of ≥ 60 °C can be attributed to the synergistic effect of acidic solutions, heat and the activated oxygen, such as O 3 and HOONO.