Measurement of short-lived reactive oxygen species generated by an atmospheric-pressure plasma jet with the quartz-coated internal electrode

The atmospheric-pressure helium plasma jet (APPJ) is a capable plasma source for generating and irradiating short-lived reactive oxygen and nitrogen species (RONS) through its interaction with ambient air. The gas temperature is around room temperature; thus, it can be exposed to the living organisms. When RONS are supplied to living organisms, various changes are induced inside the body. Szili et al. introduced the APPJ for cancer therapy and revealed that RONS can be delivered into the tumor [1]. The results suggested that RONS are the most important factor in plasma cancer therapy. We investigated a new plasma jet with a quartz-coated inner electrode to provide more ROS than conventional plasma jets, a fully capillary dielectric discharge system with a single external electrode. In this study, we focused on short-lived ROS (•OH, O₂^-•) and evaluated the ROS using the decomposition of methylene blue aqueous solution. The distance, flow rate and driving frequency were varied in this study. The distance-dependent is mainly carried out by comparing a conventional plasma jet.

[1] E. Szili et al, Plasma Sources Science and Technology 27, 014001 (2017).