This paper experimentally discusses roles of dinitrogen pentoxide (N ₂ O _5gas ) in the air plasma effluent gas on the effluent gas exposed liquid water, through nitrate ( ) generation and nitration processes in the liquid phase. The generation from N ₂ O _5gas is suppressed approximately up to 50% by a competing reaction with a p -hydroxyl-phenyl-acetate ( p -HPA) at pH = 11. This indicates a near-surface generation of an intermediate species derived from N ₂ O _5gas , which turns to . Also, it is found that the nitration reaction rate observed with NiSPY-3N can be of the order of the generation rate. From experimental results on the air plasma effluent gas and the liquid phase species, the role of the N ₂ O _5gas exposure to the liquid surface is interpreted as an intermediate species supply to the liquid surface, such as the solvated nitronium ion ( ). This deduced roles of N ₂ O _5gas can contribute to developments and understanding of the N ₂ O _5gas -involved plasma biological applications.

Nitrogen is a very common element, comprising approximately 78% of Earth’s atmosphere, and is an important component of various electronic devices while also being essential for life. However, it is challenging to directly utilize dinitrogen because of the highly stable triple bond in this molecule. The present review examines the use of non-equilibrium plasmas to generate controlled electron impacts as a means of generating reactive nitrogen species (RNS) with high internal energy values and extremely short lifetimes. These species include ground state nitrogen atoms, excited nitrogen atoms, etc. RNS can subsequently react with oxygen and/or hydrogen to generate new highly reactive compounds and can also be used to control various cell functions and create new functional materials. Herein, plasma-processing methods intended to provide RNS serving as short-lived precursors for a range of applications are examined in detail.

Increase of the water flow rate into atmospheric pressure air discharge plasma for humidification can significantly improve suppressing conidium germination of a plant pathogenic fungus in the liquid phase by its effluent gas exposure. The role of the introduced water includes enhancement of hydrogen supply to the plasma and cooling of the plasma effluent gas. The hydrogen‐containing precursors for antibacterial species generation are experimentally increased. The gas cooling by the latent heat assists dinitrogen pentoxide density in the gas phase, a suggested precursor for antibacterial species generation near the liquid surface. This suggested near‐surface reaction is a second‐order reaction, generally requiring lower precursors concentrations and leading to less residues, thus it can be an important process for agricultural applications.