No abstract

Non-thermal atmospheric pressure plasmas are known to be an effective method for the inactivation of microorganisms. However, yeasts have proved to be more resistant to provided treatments. We investigated the influence of an Argon plasma jet on the inactivation of four different yeasts; Saccharomyces cerevisiae, Schizosaccharomyces pombe, Candida parapsilosis and Magnusiomyces magnusii. Results from direct plasma treatment on the yeasts in distilled water, as the most effective technique we found, are presented here. The surviving yeasts after 5, 7, and 10 min plasma exposures were evaluated visually and quantitatively. Quantitative results showed strong reductions in the survival rates after the plasma treatment. The longest plasma exposure time yielded the least survival. Moreover, how long the inactivations lasted was evaluated by assessing the treated samples after 1 h and again after 2 h. The survival rates were further decreased within these storage times. In the 10 min treated-2 h stored samples, the rates dropped to 5% or even below, depending on the yeast species. High concentrations of reactive oxygen and nitrogen species in the plasma-air-water interacting system were detected by optical emission spectroscopy of the plasma jet and also by measuring concentrations of H2O2, NO2 − and NO3 − in plasma activated water (as the surrounding liquid for the yeasts). The conductivity and pH of the treated water was measured as well. The level of the conductivity increased along with the decrease in pH. Synergistic effects of these chemical reactive species in acidified water resulted in the yeast inactivation.

The aim of this work was to determine the effect of plasma on the substrate and on the nanofibers themselves. The PA6 nanofibrous material and the PP carrier were exposed to the effects of dielectric barrier plasma generated in air at atmospheric pressure. Changes in chemical composition, the effect on adhesions to the support substrate and especially the plasma effect on the filtration efficiency of the nanofiber material were studied.

Nanofiber membranes are made of synthetic polymers mainly by electrospinning technology. The key point for creating a functional nanofiber membrane for water and air filters is to meet basic key properties such as filtration efficiency, mechanical resistance, and resistance to fouling and chemicals. Design and manufacturing of the advanced nanofiber-based filters urgently require new environment-friendly and cost-effective surface treatments without the use of organic solvents and caustic solutions. To address this need, as an alternative, the atmospheric-pressure plasma treatment offers to be used for surface activation of polymer textile materials serving as a substrate for electrospun nanofiber. Nanofiber carriers represented by polypropylene non-woven were pre-treated by dielectric barrier discharge in continuous mode to improve the adhesion between the produced nanofibers and substrate. The increased adhesive forces to carrier substrate were confirmed by two peeling tests. The fact that the robust and effective atmospheric-pressure diffuse coplanar surface barrier discharge technology, primarily developed and optimized for the plasma treatment of textile and fibrous material, can be easily implemented in the industrial production lines predetermines this technology for in-line a large throughput manufacturing of advanced nanofiber-based filters.