Polyvinyl alcohol–potassium iodide gel probe to monitor the distribution of reactive species generation around atmospheric-pressure plasma jet

Abstract

Reactive species in the gas-phase region are of great interest for biomedical, agricultural, and industrial applications. At the same time, assessment of the concentration and distribution of reactive species and treatment area control need to be further understood. Visualization of reactive species concentration and distribution has been studied for decades based on a variety of methods. This study proposes polyvinyl alcohol–potassium iodide (PVA–KI) as a novel gel chemical probe. The probe uses the reactions among PVA, KI, water, borax, and oxidative species to visualize the distribution of reactive species. This method provides information regarding the distribution of reactive species by coloration on the gel surface. The effects of the surrounding gas phase on the distribution and diffusion of the reactive species are also investigated using the PVA–KI gel probe. Further, the relationship between the irradiation distance and reactive species diffusion is determined on the surface of the PVA–KI probe with and without plastic shielding. Adjusting the irradiation distance appropriately leads to an increase in the modified area as detected by the PVA–KI gel probe analysis. The relative reactive species concentration distributions are also obtained from visualized color distributions measured using a colorimeter. Further, reactive species generation by long-scale line plasma is confirmed by the color reaction on the PVA–KI gel surface, with a greater area being covered by an atmospheric-pressure pulsed microwave line plasma source.