Generation of Chemically Active Species in Hydrogen Peroxide (H2O2) Discharge Plasma and Their Role in the Eradication of Microorganisms

Abstract

Electrical impulse voltage discharges using hydrogen peroxide (H₂O₂) are of increasing interest for eradicating biological species. Pulsed power is beneficial in addressing the problem of overheating the cathode surface due to successive collisions of energetic plasma species. The present study demonstrates the generation of active species of oxygen (O, O-, and O₂), hydrogen (H_-α, H_-β), and hydroxyl radicals (OH⁻) in pulsed hydrogen peroxide discharge. The level of active species is directly or indirectly related to the emission intensity by varying the applied current and filling pressure. The discharge is generated between two annular electrodes powered by a 50-Hz pulsed direct current source. The aqueous hydrogen peroxide solution is sucked into the stainless steel reactor by creating a pressure gradient. The experiment is carried out for different discharge currents (0.2–0.5 A) and filling pressures (0.1–0.5 mbar). Optical emission spectroscopy (OES) is performed using McPherson (0.01 nm) and Ocean (0.75 nm) spectrometers to record spectra. Following the optimal discharge conditions, Pseudomonas aeruginosa samples (N × 10⁴ CFU/0.1 ml per sheet) are treated at a filling pressure of 0.5 mbar and a current density of 2.2 mA/cm² for different treatment times. Inactivation is achieved by counting the viable number of colonies before and after plasma treatment using the serial dilution method. Scanning electron microscopy (SEM) was accomplished for Pseudomonas aeruginosa, which confirms the inactivation of the pathogens.