Activation of deionized water by atmospheric plasma jet in helium gas flow

A dielectric barrier discharge operated at 7-9 kV (peak-to-peak value) and 28 kHz was used to produce plasma jets with helium as feed gases. For the plasma activation treatment, 20 ml of deionized (DI) water was placed in direct contact with the extruded plasma jet for the duration of 2 to 15 min. The conductivity and the acidity of DI water were found to increase with treatment time. Reactive species generated in the gaseous phase at the plasma-liquid interface were identified from the optical emission spectra and were correlated qualitatively to the changes in conductivity and acidity of the plasma-activated water.