Air spark-like plasma source for antimicrobial NO_x generation

We demonstrate and analyse the generation of nitrogen oxides and their antimicrobial efficacy using atmospheric air spark-like plasmas. Spark-like discharges in air in a 1 L confined volume are shown to generate NO_x at an initial rate of about 1.5 × 10¹⁶ NO_x molecules/J dissipated in the plasma. Such a discharge operating in this confined volume generates on the order of 6000 ppm NO_x in 10 min. Around 90% of the NO_x is in the form of NO₂ after several minutes of operation in the confined volume, suggesting that NO₂ is the dominant antimicrobial component. The strong antimicrobial action of the NO_x mixture after several minutes of plasma operation is demonstrated by measuring rates of E. coli disinfection on surfaces and in water exposed to the NO_x mixture. Some possible applications of plasma generation of NO_x (perhaps followed by dissolution in water) include disinfection of surfaces, skin or wound antisepsis, and sterilization of medical instruments at or near room temperature.