Effects of electrode geometry on the physicochemical properties and antimicrobial efficacy of plasma-activated water generated by surface dielectric barrier discharge.

Abstract

This study investigates the impact of electrode geometry on the physicochemical properties and bactericidal efficacy of plasma-activated water (PAW) generated using surface dielectric barrier discharge. PAW with a hexagonal electrode (PAW-H) was compared to that of a square electrode (PAW-S). PAW-H showed significantly higher reactive oxygen species (ROS) concentrations than PAW-S at the same power level (200 W; p < 0.05). After 1 min, PAW-H achieved a 3.55 log reduction in E. coli O157:H7 and a 3.24 log reduction in S. Typhimurium, significantly outperforming than PAW-S (p < 0.05). PAW-H also inactivated L. monocytogenes and S. aureus more effectively, with 3.61 and 1.89 log reductions after 30 min, respectively. Also, under the same voltage conditions, PAW-H exhibited higher bactericidal efficacy compared to PAW-S (220 V; p < 0.05). Optimizing power levels proved essential for maximizing antimicrobial efficacy, as the 175 W achieved the most effective results where the highest levels of ROS detected primarily at this power level. Scavenger assays confirmed that hydroxyl radicals and singlet oxygen were key contributors to the bactericidal effect. These findings demonstrate the importance of both electrode geometry and operational parameters to microbial inactivation of PAW.