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

• We first report lifetimes of nitric oxide in a plasma reactor. • A simultaneous measurement of 7 reactive species is a merit of our study. • The NO lifetime of 214 s occurred with 20 % O 2 , exceeded the value in air (∼ sec ). • The increase in NO lifespan by sixfold when O 2 was reduced from 20 % to 5 %. 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 (O 2 ) and/or ozone (O 3 ), 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 O 3 and nitrogen oxides (NO x =1–3 ) in a surface dielectric barrier discharge (sDBD) reactor with respect to the O 2 content of the controlled atmosphere (N 2 +O 2 ). In situ optical absorption spectroscopy enabled the observation of the dynamics of O 3 and NO x under gas-tight conditions. In these plasma reactors, NO became a dominant species after the chemical mode transition from O 3 to NO occurred. We found that a lower O 2 content correlated to a faster appearance of NO in the plasma reactor. The NO lifetime significantly increased as the O 2 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 O 2 content is essential in atmospheric plasma reactors dependent on O 3 and/or NO x applications.