Metrology of Ar–N₂/O₂ Mixture Atmospheric Pressure Pulsed DC Jet Plasma and its Application in Bio-Decontamination

Abstract

Atmospheric pressure plasma jets are gaining a lot of attention due to their widespread applications in the field of bio-decontamination, polymer modification, material processing, deposition of thin film, and nanoparticle fabrication. Herein, we are reporting the disinfection of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli bacteria using plasma jet. In this regard, Ar–O2, Ar–N2, and Ar–O2–N2 mixture plasma is generated and characterized using optical and electrical characterization. Variation in plasma parameters like electron temperature, electron density, and reactive species production is monitored with discharge parameters such as applied voltage and feed gas concentration. Results show that the peak average power consumed in Ar–O2, Ar–N2, and Ar–O2–N2 mixture plasma is found to be 4.45, 2.93, and 4.35 W respectively, at 8 kV. Moreover, it is noted that by increasing applied voltage, the electron temperature, electron density, and reactive species production also increases. It is worth noting that electron temperature increases with increase in oxygen concentration in the mixture ( , while it decreases with increase in nitrogen concentration in the mixture (Ar–N2). Similarly, a decreasing trend in electron temperature is noted for Ar–O2–N2 mixture plasma. On the other hand, a decreasing trend in electron density is noted for all the mixtures. Reduction in viable colonies of Pseudomonas aeruginosa, Staphylococcus Aureus, and Escherichia coli were confirmed by the serial dilution method. The inactivation efficiency of pulsed DC plasma generated, in the Ar–N2 mixture at 8 kV and 6 KHz, was evaluated against P. aeruginosa, S. aureus and E. coli bacteria by measuring the number of surviving cells versus plasma treatment time. Results showed that after 240 s of plasma treatment, the number of survival colonies of the mentioned bacteria was reduced to less than 30 CFU/mL.

Formation of reactive chlorine species in Cl− solutions treated by plasma-supplied O atoms and some implications for biological inactivation functions

“…A large number of high-energy electrons are generated during plasma discharge. The energetic electrons first excite the Ar atoms to some highly excited metastable state (reaction (3)), colliding with N 2 and O 2 molecules and producing the Penning ionization effect (reactions (4) and ( 5)), e * + Ar → Ar * + e (3) [32] Ar * + N 2 → Ar + 2N (4) [48] Ar * + O 2 → Ar + 2O.…”

“…(5) [32,48] H 2 O 2 is known to be a long-lived RONS, mainly generated by •OH in the gas and liquid phases through reaction (1) ,…”

“…Oxygen molecules have the potential to compete with argon atoms for energy transfer, thereby diminishing the excitation and ionization of argon atoms. As a consequence, this competition may lead to a reduction in the intensity of spectral lines observed in the Ar + O 2 plasma jet [32,33]. It is important to note that the specific reasons for the observed difference in spectral line intensity between the Ar and Ar + O 2 plasma jets would depend on the specific experimental conditions and the characteristics of the plasma discharge.…”