# Water Modification by Cold Plasma Jet with Respect to Physical and Chemical Properties
## Appendix A  
[PERSON] et al. [60] demonstrated that an atmospheric pressure micro-plasma can act as a gaseous, metal-free electrode to mediate electron transfer reactions in aqueous solutions. Ferricyanide was reduced to ferrocyanide by plasma electrons, and the reduction rate was found to depend on discharge current. They stated that the ability to initiate and control electrochemical reactions at the plasma-liquid interface opens a new direction for electrochemistry based on interactions between gas-phase electrons and ionic solutions. [PERSON] et al. [61] used cell electrochemical setups consisting of direct current, atmospheric pressure micro-plasma jets sustained in a flow of argon gas. Micro-plasma was formed on the surface of the solution and operated as the cathode. Experimental evidence was presented that, in the case of water, plasma electrons are involved in electrolytic reactions leading to the conversion of protons (H\({}^{+}\)) to hydrogen gas. Reactions associated with water electrolysis were indirectly characterized by pH measurements that showed qualitatively and quantitatively that the liquid at the plasma interface increased in basicity, consistent with the reduction of protons by plasma electrons. Mass spectrometry measurements confirmed the evolution of hydrogen gas, directly providing evidence of water electrolysis. This work highlighted the critical role that plasma electrons can play in plasma-liquid interactions with broad implications for any plasma system involving an aqueous electrode. [PERSON] et al. [52] elucidated the mechanism of hydroxyl radicals (OH\({}^{\bullet}\)) generation and its lifetime measurements in bio-solution. They observed that plasma-initiated ultraviolet photolysis was responsible for the continuous generation of OH\({}^{\bullet}\) species which resulted in OH\({}^{\bullet}\) being major reactive species in the solution. The density and lifetime of OH\({}^{\bullet}\) species acted inversely proportional to one another with increasing depth inside the solution. The cause of increased lifetime of OH\({}^{\bullet}\) inside the solution is predicted using theoretical and semiempirical calculations. Further, to predict the mechanism of conversion of hydroxide ion (OH\({}^{-}\)) to OH\({}^{\bullet}\) or H\({}_{2}\)O\({}_{2}\) (hydrogen peroxide) and electron, they determined the current inside the solution of different pH values. Additionally, they investigated the critical criterion for OH\({}^{\bullet}\) interaction on cancer cell inducing apoptosis under effective OH\({}^{\bullet}\) exposure time. [PERSON] et al. [53] reviewed a compilation of the work conducted between 2010 and 2015 in the field of plasma-liquid-tissue interaction, to reveal both the actual knowledge and the parts still missing for a complete understanding. They stated that, in general, independent of the atmospheric pressure plasma sources and the liquid system investigated, hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)), as well as nitrite (NO\({}_{2}^{-}\)) and nitrate (NO\({}_{3}^{-}\)), were detected as stable reactive oxygen and nitrogen species (ROS, RNS/RONS). In non-buffered systems, pH decrease was found. They noted that, as most important precursors of hydrogen peroxide, as well as nitrite and nitrate, hydroxyl radicals(\({}^{\bullet}\)OH), superoxide anion radicals (O\({}_{2}^{\bullet-}\)), singlet oxygen (\({}^{1}\)O\({}_{2}\)), and nitric oxide(\({}^{\bullet}\)NO) have been identified and partially detected in different plasma-treated liquids. Finally, they mentioned that above all, peroxynitrite (ONOO\({}^{-}\)) has been identified as playing a crucial role for biological effects of plasma-treated liquids. [PERSON] et al. [62] studied the interactions of a helium plasma jet (atmospheric ionization waves produced in a He:1%N\({}_{2}\) mixture) with a commonly used physiological liquid in biology, i.e., phosphate buffered saline solution (PBS) at pH 7.4.