The role of different plasma forming gases on chemical species formed in plasma activated water (PAW) and their effect on its properties

Abstract The present work showed the role of plasma-forming gases (air, nitrogen (N 2 ), argon (Ar), helium (He), and their mixture with oxygen (O 2 )) on the properties of plasma-activated water (PAW). Electrical diagnosis and optical emission spectroscopy were performed to characterize plasma and identify plasma radicals/species. The PAW is characterized by studying its physicochemical properties and dissolved reactive oxygen-nitrogen species (RONS) concentration in it. The results showed introducing O 2 in N 2 , Ar and He plasma suppresses the emission lines intensity of NO ϒ band in N 2 plasma, OH band in Ar and He plasma, and N 2 second positive system in He plasma. Also, adding O 2 to Ar and He plasma changes the plasma discharge characteristic from glow discharge to filamentary micro-discharge. The PAW prepared by air and its mixture with O 2 showed improved physicochemical properties and RONS concentration in it compared to other plasma forming gases and their mixture with O 2 . In addition, increasing plasma-water exposure time significantly affects the physicochemical properties and RONS concentration in PAW. Therefore, plasma forming gas and plasma-water exposure time gives better control over the properties of PAW. Hence, these parameters play a significant role in deciding the applications of PAW.