One of the most central scientific questions for plasma applications in healthcare and environmental remediation is the chemical identity and the dose profile of plasma-induced reactive oxygen and nitrogen species (ROS/RNS) that can act on an object inside a liquid. A logical focus is on aqueous physicochemical processes near a sample with a direct link to their upstream gaseous processes in the plasma region and a separation gap from the liquid bulk. Here, a system-level modeling framework is developed for indirect interactions of surface air plasma and a deionized water bulk and its predictions are found to be in good agreement with the measurement of gas-phase ozone and aqueous long-living ROS/RNS concentrations. The plasma region is described with a global model, whereas the air gap and the liquid region are simulated with a 1D fluid model. All three regions are treated as one integrated entity and computed simultaneously. With experimental validation, the system-level modeling shows that the dominant aqueous ROS/RNS are long-living species (e.g. H ₂ O _{2 aq} , O _{3 aq} , nitrite/nitrate, H ⁺ _aq ). While most short-living gaseous species could hardly survive their passage to the liquid, aqueous short-living ROS/RNS are generated in situ through reactions among long-living plasma species and with water molecules. This plasma-mediated remote production of aqueous ROS/RNS is important for the abundance of aqueous HO _{2 aq} , HO _{3 aq} , OH _aq and _aq as well as NO _{2 aq} and NO _{3 aq} . Aqueous plasma chemistry offers a novel and significant pathway to activate a given biological outcome, as exemplified here for bacterial deactivation in plasma-activated water. Additional factors that may synergistically broaden the usefulness of aqueous plasma chemistry include an electric field by aqueous ions and liquid acidification. The system-modeling framework will be useful in assisting designs and analyses of future investigations of plasma-liquid and plasma–cell interactions.

Plasma-liquid interaction is a critical area of plasma science and a knowledge bottleneck for many promising applications. In this paper, the interaction between a surface air discharge and its downstream sample of deionized water is studied with a system-level computational model, which has previously reached good agreement with experimental results. Our computational results reveal that the plasma-induced aqueous species are mainly H⁺, nitrate, nitrite, H₂O₂ and O₃. In addition, various short-lived aqueous species are also induced, regardless whether they are generated in the gas phase first. The production/loss pathways for aqueous species are quantified for an air gap width ranging from 0.1 to 2 cm, of which heterogeneous mass transfer and liquid chemistry are found to play a dominant role. The short-lived reactive oxygen species (ROS) and reactive nitrogen species (RNS) are strongly coupled in liquid-phase reactions: NO₃ is an important precursor for short-lived ROS, and in turn OH, O₂⁻ and HO₂ play a crucial role for the production of short-lived RNS. Also, heterogeneous mass transfer depends strongly on the air gap width, resulting in two distinct scenarios separated by a critical air gap of 0.5 cm. The liquid chemistry is significantly different in these two scenarios.

Phosphorene is a promising candidate for gas sensing materials. This letter describes our study of the adsorption of SF ₆ and SF ₆ decomposition gases (SO ₂ and H ₂ S) on phosphorene. We used first principles calculations to explore phosphorene's potential applications as gas sensor to diagnose the state of online gas insulated switchgear (GIS). The calculation results showed that only the adsorption of SO ₂ induced a moderate adsorption energy and apparent charge transfer. We further investigated the current-voltage (I-V) relationships before and after gas absorption through the non-equilibrium Green's function method. It was found that only SO ₂ induced a dramatic change in the I-V relationships. Therefore, phosphorene appears to be a promising candidate for highly sensitive and selective SF ₆ decomposition gas sensors for online GIS diagnosis.