Study On The Characteristics And Application Of Discharge Plasma In Contact With Water

Discharge plasma in contact with water has attracted a lot of interest in recent years due to its rapid developments for different environment and biomedical applications.In plasma applications,plasma is applied onto a wet surface?human skin,wet tissue,water,culture medium?,therefore,the interaction between gas plasma and aqueous solution plays the dominant role.In this paper,the discharge plasma in water is studied.The research work is carried out in the aspects of its related properties and application.?1?A plasma device driven by high voltage pulse is designed,which is capable of generating safe,stable,dispersive non-equilibrium He plasma at atmospheric pressure.Its core discharge part of the structure is simple,with a strong practical value.First,the discharge pattern and its voltage and current parameters are studied.When the discharge occurs in contact with the water,the discharge is gradually weakened from the nozzle to the water surface.But near the water,the jet becomes a lot stronger,and even a bright spot appear.During a period,the discharge current has two opposite peak.And then,we analyze the emission spectrum of the plasma jet by spectrometer and find the plasma the OH radicals that we want.The subsequent study reveals that elevated oxygen content will consume more high-energy electrons and thus affects the formation of OH radicals.Finally,the temperature of the plasma was studied by using the infrared thermometer and the best fitting method of the measured spectrum and the simulated spectrum.?2?Hydroxyl radicals?OH?plays an important role in plasma-related biology and medical applications.In this study,the dynamic of atmospheric-pressure plasma jet?APPJ?above water and the OH radicals produced by the APPJ were investigated experimentally.The distributions of OH both in free space and above the liquid surface were recorded by a laser-induced fluorescence?LIF?technique.It was observed that for the latter case,OH LIF intensity would rise above the liquid surface,potentially leading to an increase of OH radical flux diffused from the gas phase to dissolve in the liquid.Dynamic process recorded by the high speed intensified charge-couple device?ICCD?camera showed that after the primary discharge,a secondary discharge would form and propagate backward from the gas-liquid interface towards the nozzle.The evaporation of water vapor and formation of secondary discharge was possibly the reason for the increase of OH LIF intensity above the water surface.It was also found that the influence region of OH radicals was much larger than the size of the plasma jet.?3?The third part of the study is mainly about the plasma in the solution of the active particles and the induction of cancer cell apoptosis effect.When discharging on the surface of water,the most important active particles in the solution are hydrogen peroxide and some active nitrogen components.In this paper,the effect of different conditions on the concentration of hydrogen peroxide in the 1640 complete medium solution was studied by the colorimetric-spectrophotometric method.The effects of discharge voltage,air velocity,the distance from nozzle to liquid surface,plasma treatment time and pore area of the substrate were studied.The effects of each influencing factor were obtained.It is found that,Within a certain range,higher discharge voltages,larger airflow rates,closer distances,longer plasma treatment times,and larger pore sizes contribute to the formation of higher concentrations of hydrogen peroxide?H₂O₂?.The apoptosis rate of esophageal squamous cell carcinoma cell line ECa109 was verified by trypan blue staining.In addition,it has been proved that the hydrogen peroxide plays a major role in the induction of apoptosis in the plasma,but it is not the only active particle,the active nitrogen is NO?NO2^-+NO3^-?)also played a role.Finally,this was further verified by the nitrate reductase method.