Lifetime of nitric oxide produced by surface dielectric barrier discharge in controlled atmospheres: Role of O2 content

Abstract

Nitric oxide (NO) is an invaluable multifunctional chemical in agri-food applications; for example, it plays a role in plant growth, development, and stress tolerance. One of the interesting implications of NO is the suppression of fruit ripening and the resulting increase in shelf life. Since a high concentration of NO is producible in atmospheric plasmas, increasing attempts in plasma agriculture have been made to study several types of plasma reactors operated in air. However, as NO is rapidly oxidized by oxygen (O₂) and/or ozone (O₃), the use of NO produced in atmospheric plasmas is naturally nontrivial, and the lifetime of NO is highly sensitive to the reactor environments. Here, we investigated the time development of O₃ and nitrogen oxides (NO_x=1–3) in a surface dielectric barrier discharge (sDBD) reactor with respect to the O₂ content of the controlled atmosphere (N₂+O₂). In situ optical absorption spectroscopy enabled the observation of the dynamics of O₃ and NO_x under gas-tight conditions. In these plasma reactors, NO became a dominant species after the chemical mode transition from O₃ to NO occurred. We found that a lower O₂ content correlated to a faster appearance of NO in the plasma reactor. The NO lifetime significantly increased as the O₂ content decreased from 20 to 5 % in the plasma reactor, while the maximum concentration of NO decreased. Our findings indicated that the appropriate control of the O₂ content is essential in atmospheric plasma reactors dependent on O₃ and/or NO_x applications.