radical using air plasmas and its agricultural applications*

Atmospheric-pressure plasmas (APPs) have been of great interest and are widely used in medical, agricultural, and environmental applications. In particular, air APP can convert nitrogen (N₂), oxygen (O₂), and water (H₂O) molecules on site into gaseous reactive species H_xN_yO_z [for example, ozone (O₃), nitric oxide (NO), nitrogen dioxide (NO₂), and hydroxyl radical (OH)], which can play key roles in those applications, potentially increasing the utilization of air to a great extent. The control of the H_xN_yO_z gas composition is very important for the further development of air APP technology, however, is still challenging. We have ever engaged in composition control and quantification of H_xN_yO_z generated in air APP-activated gas and developed a new APP system for the selective synthesis of dinitrogen pentoxide (N₂O₅) [1]. In addition, we recently found that the plasma-generated N₂O₅ has many beneficial effects (e.g., bactericidal/virus-inactivating [2], activation of plant immunity [3], nitrogen fertilization [4,5]) in agricultural fields. More recently, we developed a new technology of high density (~ 10¹⁴ cm^-3) NO₃ radical generation from air, extended from the N₂O₅ synthesis technology. In the presentation, strategy and detailed setup for the composition control of the H_xN_yO_z species, quantification technique, and investigation of the biological effects will be discussed with specific examples in agricultural application.

[1] S. Sasaki, K. Takashima, and T. Kaneko, Ind. Eng. Chem. Res. 60, 798 (2021).

[2] T. Kaneko, K. Takashima, and S. Sasaki, Plasma Chem. Plasma Process. in press (2024). https://doi.org/10.1007/s11090-024-10461-z

[3] D. Tsukidate, K. Takashima, S. Sasaki et al., PLOS ONE 17, e0269863 (2022).

[4] T. Yamanashi, S. Takeshi, S. Sasaki et al., Plant Mol. Biol. 114, 35 (2024).

[5] S. Takeshi, K. Takashima, S. Sasaki et al., Plasma Process. Polym. in press (2024). https://doi.org/10.1002/ppap.202400096