Bactericidal effect of surface plasma under different discharge modes

Abstract

Plasma-activated water (PAW) with reactive species produced by plasma in water can efficiently inactivate bacteria and has potential biomedical applications. Surface dielectric barrier discharge (SDBD) is extensively used for the preparation of PAW, and the bactericidal effects of PAW are highly related to the discharge mode. In previous studies, saline was directly placed under surface plasma within a short distance, and the gaseous reactive species diffused into the saline. In this study, the gaseous reactive species flowed into the saline by airflow, which was outside the treatment distance and accelerated the diffusion rate. The gaseous reactive species were compared at different power levels and flow rates, and three discharge modes were classified, namely, ozone, transition, and nitrogen oxides modes, based on the characteristic peaks in the spectra. Long-lived and short-lived species were detected in the saline, and short-lived species were more associated with the bactericidal effect. The results suggest that the bactericidal effect of the transition mode is the most prominent and the scavenger results show that nitric oxide (•NO), singlet oxygen, and peroxynitrite play a more crucial role in bacterial inactivation. This study provides a potential strategy for modulating the discharge mode to generate selective reactive species in plasma-activated saline to promote bactericidal application.