Experimental identification of the reactive oxygen species transported into a liquid by plasma irradiation

Abstract

Reactive oxygen species (ROS) supplied into liquids by plasma irradiation must be identified and controlled for the safe and effective use of plasmas in biomedical applications. This study aims to obtain information on the key ROS regarding ROS transportation through a liquid layer for realization of spatial ROS identification. Two-dimensional distributions of ROS after passing through liquids with and without ROS scavengers were visualized and compared to assess the suppression effects of each scavenger using a measurement system combined with a gel ROS detector. The plasma was generated under helium and 1% oxygen mixture gases. It was experimentally confirmed that a hydroxyl radical is not a key species, whereas, superoxide anion radicals and hydrogen peroxide play a key role for ROS transportation in our system. The results also suggested that the chemical processes for ROS transportation change at a liquid layer thickness of less than 1 mm.

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

“…The RONS formation is the resultant product of plasma chemistry that occurs during plasma-water interaction [3,15]. This plasma chemistry takes place between plasma and water influenced by various process parameters such as type of plasma (dielectric barrier discharge, spark discharge, gliding arc discharge, glow discharge and pulse discharge, etc), plasma forming gases, discharge power, electrode configuration, and plasma-water interaction time, etc [2,3,[15][16][17][18][19][20]. Among them, plasma forming gases mainly influence the plasma chemistry that results in the formation of RONS in PAW [2,3,15,16,18,19].…”

“…The most commonly used plasma forming gases for PAW production are air, argon, helium, nitrogen, oxygen, and their mixture [2,3,16,18,19,21]. PAW properties mainly depend on the type of gas used for its production.…”

Functional nitrogen science based on plasma processing: quantum devices, photocatalysts and activation of plant defense and immune systems

“…244) Kawasaki et al also examined the laminar-like and circulating flows from the plasma irradiation point into the bulk liquid. 245,246) Brubaker et al measured temporal changes in RONS concentrations throughout the depth of a liquid vessel and established that the plasma-induced liquid flow played an important role in determining reactive species concentrations at various locations in the liquid. 247,248) The flow of gases associated with the plasma irradiation forms a cavity on the liquid surface, and the depth of this cavity is determined by the balance between the electrohydrodynamic (EHD) force and the buoyancy of the liquid.…”

Relation between thresholds of free radical generation and atomization under ultrasound exposure

“…Iodine-starch reaction was used to determine the amount of free radicals generated by ultrasound irradiation. [24][25][26] Iodinestarch solution (0.01 M KI, 0.1 M CCl 3 CHO, 1 M NaCl and 0.3 g l −1 soluble starch) 17,27) of 13 g or 39 g was poured into the exposure chamber, and the height of the water surface from the transducer surface became 25 mm or 68 mm [Figs. 2(a)-2(c)].…”