Efficient Nebulization of Argon Plasma-Jet-Activated Water via Surface Acoustic Waves for Surface Bacterial Inactivation.

Plasma-activated aerosols produced via surface acoustic wave (SAW) nebulization have the potential for improving surface disinfection processes by providing wider distribution coverage due to the dispersibility of the aerosols. Motivated by previous studies showing that increasing the electrical conductivity of air plasma-activated water led to a significant reduction in the SAW nebulization rate, which poses a severe limitation to the efficiency of the technology, we evaluate here the use of argon plasma-jet-activated water as an alternative to air plasma jets. Compared to the higher electrical conductivity of air plasma-jet-activated water (0.3 mS/cm ≤ σe ≤ 4 mS/cm), argon plasma-jet-activated water has substantially lower conductivity (4 μS/cm ≤ σe ≤ 40 μS/cm) and thus more efficient nebulization (103% higher nebulization rate compared to that for deionized (DI) water, in contrast to 65% lower nebulization rate with air plasma jets). Nevertheless, despite its lower electrical conductivity, the argon plasma-jet-activated water was observed to maintain Escherichia coli inactivation efficacy even after four days of storage due to the high hydrogen peroxide (H2O2) concentrations that were produced. This is in sharp contrast to air plasma-jet-activated water, which yielded only limited bacterial inactivation efficiency (approximately 10.5% reduction) even when fresh and surprisingly promoted E. coli growth after one day of storage. In particular, we found that 2.4 g of the argon plasma-jet aerosols, equivalent to just 10 min of nebulization, was capable of achieving 100% bacterial inactivation, thus alluding to the platform's potential for efficient and effective spray-based surface disinfection.