Depth-resolved potentiometric detection of active species near the surface of an aqueous solution under atmospheric pressure plasma

Near the plasma/water interface, highly active species such as ·OH are formed, providing unique reaction fields. To develop interfacial reaction systems that utilize them, it is important to conduct in-situ quantitative analysis of their supply and consumption kinetics. In this study, depth- and time-resolved in-situ potentiometric measurements were performed to detect redox-active species, such as OH radicals. A Pt electrode was employed as an indicator electrode and showed a large potential shift to 1.5 V vs SHE only when the depth was less than 10 µm, suggesting the presence of ·OH.