Document Type

Article

Publication Date

2025

Publication Title

Physica Scripta

Volume

100

Issue

7

Pages

075606 (1-17)

DOI

10.1088/1402-4896/adddf8

Abstract

Understanding plasma-liquid interactions and the impact of the electrical conductivity (σ) of liquid on plasma is important for plasma applications in water treatment and medicine. Ultrapure water, phosphate-buffered saline (PBS) solution, biological media, and sodium chloride (NaCl) solutions at various concentrations were used in this study to provide a broad range of conductivity values ranging from 0.055 μS cm−1 to 222 mS cm−1. A helium atmospheric pressure plasma jet (APPJ) impinging on liquid was generated in ambient air using a hollow-needle electrode that was powered by 200 ns, 7 kV pulses at a pulse repetition frequency of 1 kHz. Three regimes of the discharge energy consumption vs. σ were identified—low, high and transition, and are separated by two σ threshold values, 30.2 mS cm−1 and 69.5 mS/cm. For liquid with σ ⩽ 30.2 mS cm−1, the impinging plasma behaves as a typical guided streamer with a moderate energy per pulse (80 μJ) and a relative low H2O2 production rate (⩽ 0.22 nmol min−1 ml−1). For solutions with σ ≥ 69.5 mS/cm, the APPJ transitions to a different mode with 70 times more current peak and 4.8 times more energy per pulse compared with the low σ cases, and has enhanced production of excited species across the interelectrode gap. The H2O2 production rate was found increasing monotonically with σ and the maximum value of 0.435 nmol min−1 ml−1 was obtained for σ = 222 mS cm−1. Although the production rate increased, the energy efficiency decreased with σ. Solutions with σ ⩽ 35.0 mS cm−1 exhibited an energy efficiency of 47 nM J−1 , which was about 3 times that of σ ≥ 69.5 mS cm−1.

Rights

© 2025 The Authors.

Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License.

Data Availability

Article states: "All data that support the findings of this study are included within the article (and any supplementary files)."

Original Publication Citation

Oshin, E. A., Rahman, M. Z., & Jiang, C. (2025). The effect of liquid conductivity on a helium plasma jet and the hydrogen peroxide production. Physica Scripta, 100(7), 1-17, Article 075606. https://doi.org/10.1088/1402-4896/adddf8

ORCID

0000-0002-2932-9470 (Oshin), 0000-0001-8895-2580 (Jiang)

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