7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Gas-liquid interfacial plasmas: Controlled generation of short-lived
reactive species and its applications
Toshiro Kaneko, Kazuki Takeda, Shota Sasaki, and Keisuke Takashima
Graduate School of Engineering, Tohoku University
e-mail: kaneko@tohoku.ac.jp
Atmospheric pressure plasmas (APPs) in contact withliquid, which are defined as “gas-liquid interfacial
plasmas (GLIPs)”, are widely used in medical,agricultural, and public health fields. In these applicationsof GLIPs, the reactive species generated by the plasma in
the gas and liquid phases, especially those with short
lifetimes, are considered to play an important role (Fig. 1).
In this study, the controlled generation of short-lived
reactive species using several lab-built GLIP devices andthe elucidation of their chemical reaction mechanisms are
realized [1,2], and applications such as sterilization [3],virus inactivation [4,5], cell membrane permeabilization(molecular transfer to biological cells) [6], andenhancement of plant immunity [7], using these shortlived reactive species are demonstrated.

hydroxyphenylacetic acid), a scavenger of nitrite andnitrate precursors. The nitrite precursors were detected
whereas nitrate precursors were below the detection limit,
and the half-life of nitrite precursors was approximately 3ms, which is obviously longer than 0.1 ms of OH.
These findings will contribute to the fully controlled
generation of short-lived reactive species at the plasmaliquid interface, and the resulting selectively generated
short-lived reactive species will be extended to a wide
range of applications in environmental science, plantscience, drug discovery science, material science, andother fields.

Fig. 2: Schematic drawing of the GLIP system withhigh-speed liquid-column flow.

Fig. 1: Transport of reactive species generated by air
plasma to the liquid phase and generation of short-lived
reactive species in liquid.
In addition, GLIP experiments using high-speed
liquid-column flow [8] are conducted to investigate indetail the spatio-temporal dynamics of the short-lived
reactive species in the liquid phase irradiated by a helium
plasma. As a result, very fast decay (a half-life of ~ 0.1msec) of OH radical was detected for the first time andexplained with a numerical model assuming surfacelocalization of OH radical.
Furthermore, we are trying to measure not only OH
radicals but also short-lived reactive nitrogen species(RNS). To achieve this purpose, we attempted to measure
short-lived RNS, which are precursors of long-lived RNS
such as nitrate and nitrite, using a GLIP system equippedwith a high-speed liquid column flow as shown in Fig. 2.
As a result, we have successfully measured the time
decay of precursors of RNS using the reagent p-HPA (p-References[1] Y. Kimura, K. Takashima, S. Sasaki, and T. Kaneko,J. Phys. D: Appl. Phys. 52, 064003 (2019).
[2] S. Sasaki, K. Takashima, and T. Kaneko, Ind. Eng.
Chem. Res. 60, 798 (2021).
[3] K. Shimada, K. Takashima, Y. Kimura, K. Nihei, H.
Konishi, and T. Kaneko, Plasma Process. Polym. 17,e1900004 (2020).
[4] S.E. Hanbal, K. Takashima, S. Miyashita, S. Ando,K. Ito, M.M. Elsharkawy, T. Kaneko, and H.
Takahashi, Arch. Virol. 163, 2835 (2018).
[5] S. Sasaki, S. Osana, T. Kubota, M. Yamaya, H.
Nishimura, R. Nagatomi, and T. Kaneko, J. Phys. D.
Appl. Phys. 55, 295203 (2022).
[6] S. Sasaki, Y. Zheng, T. Mokudai, H. Kanetaka, M.
Tachikawa, M. Kanzaki, and T. Kaneko, Plasma
Process. Polym. 17, e1900257 (2020).
[7] D. Tsukidate, K. Takashima, S. Sasaki, S. Miyashita,T. Kaneko, H. Takahashi, and S. Ando, PLOS ONE
17, e0269863 (2022).
[8] K. Takeda, S. Sasaki, W. Luo, K. Takashima, and T.
Kaneko, Appl. Phys. Express 14, 056001 (2021).