Water activated by the atmospheric air streamer‐to‐spark transition discharge over its surface

Abstract

Here, we report on the optimized design for the needle‐to‐plane electrode geometry to generate the atmospheric air streamer‐to‐spark transition discharge over the surface of the water at the pulsed voltage of ±30 kV. This design contributes to an increase in the electric field at the head of air surface streamers during their propagation, which eventually evolves into a spark over water. The length of streamer‐to‐spark transition discharge is up to 150 mm, which is affected by the conductivity of water, the electrode polarity, and the horizontal distance between the high‐voltage pin electrode and the grounded plane electrode. Water is quickly activated by the streamer‐to‐spark transition discharge, which can be attributed to the dissolution of plasma‐generated species including long‐lived and short‐lived reactive species in the gas phase. Compared to the negative streamer‐to‐spark transition discharge, the positive one is more effective in increasing the biological reactivity of water. Analysis indicates that the positive ions in the positive surface streamers can dissolve in water, which contributes to the formation of reactive species in water, thus an increase in the biological reactivity of water.