Nanosecond Pulse-Driven Oxygen Bubble Plasma Activation of Low-Concentration Alcohol Solutions and its Sterilization Mechanism

To address the current use of high-concentration (70-75%) alcohol solutions as disinfectants, which are known for their drawbacks such as flammability and strong odor, a new approach based on nanosecond pulse-driven bubble discharge in low-concentration ethanol solutions is proposed. Research findings indicate that O₂ bubble plasma activated ethanol solution (PAES) exhibits superior sterilization efficacy. A 3 min treatment using 10% alcohol eliminated all bacteria (reducing the bacterial count by 7 orders of magnitude) with an energy requirement of only 10.9 J/ml, whereas the same treatment with air PAES achieved less than a one-order reduction and O₂/N₂/air plasma activated water (PAW) achieved even less. Furthermore, to delve deeper into the key factors of PAES sterilization, concentrations of inorganic reactive species (H₂O₂, NO₂ ^-, NO₃ ^-, ONOO^-, pH) and organic components resulting from alcohol decomposition (CH₃CHO, CH₃CH₂OH, CH₃COOH, and CH₃COOOH) were analyzed using assay kits and GC-MS. Their variations at different storage temperatures (4 °C and -20 °C) were compared with the corresponding bactericidal effects. The results identified peroxyacetic acid (CH₃COOOH) as a key bactericidal factor in PAES, showing that CH₃COOOH over time at different storage temperatures correlated with their bactericidal effects. The study also revealed that O₂ PAES stored at -20 °C maintained complete bacterial elimination even after 4 days. Therefore, PAES has the potential to replace high-concentration alcohol solutions for sterilization.