Atmospheric Pressure Humid Argon DBD Plasma for the Application of Sterilization - Measurement and Simulation of Hydrogen, Oxygen, and Hydrogen Peroxide Formation

Hydrogen, oxygen, and hydrogen peroxide have been measured downstream of an atmospheric pressure humid argon dielectric barrier discharge. The yield of the three species was studied as a function of the discharge power and gas flow rate. Hydrogen peroxide was measured after dissolution into water downstream of the discharge, while hydrogen and oxygen were measured in the gas phase. The production rates of both hydrogen and oxygen were found to be at least one order of magnitude greater than that of hydrogen peroxide. In all cases, the molar rate of molecular hydrogen production was more than twice that of molecular oxygen. At various total gas flow rate, and over a range of energy density of 0 to 1500 J/L, the concentration of hydrogen found at the reactor outlet varied from 0 to 1000 ppm, while oxygen reached a maximum concentration of about 400 ppm. The corresponding concentration of hydrogen peroxide that was calculated to have been in the reactor outlet gas did not exceed 11 ppm. Mechanisms for this system based on experiments and a numerical model are presented. The results of experiments on the use of post-discharge effluent gas of humid argon plasma for sterilization purposes (inactivation of E. Coli) bacteria are also presented and discussed in relation to the results of the chemical measurements and simulations

BIOLOGICAL APPLICATIONS OF ATMOSPHERIC PRESSURE DIELECTRIC BARRIER DISCHARGES

International audienceA reduction of more than 4 orders of magnitude of survivors was obtained by exposing a Bacillus Stearothermophilus spores - contaminated surface to an atmospheric pressure DBD post-discharge for 20 minutes. Decontamination mechanisms are investigated assuming that (i) inactivation is obtained when the bacteria DNA is fragmented, (ii) the protein coats are the main protection of the cell core DNA in the case of bacteria spores. The degradation of DNA (plasmid) and protein (RNAse A) samples submitted to the postdischarge is evaluated according to the operating conditions: gas composition, treatment time and sample state, i.e. hydrated or dried samples

RADIATION KINETICS AND CHEMICAL REACTIVITY OF BARRIER DISCHARGES IN HUMID ARGON

International audienceThe technique of spatially resolved cross-correlation spectroscopy was used to record two-dimensional luminosity distributions for the selected spectral bands of molecular nitrogen (λ=337.1 nm), OH-radical (λ=308 nm), and two spectral lines of excited Ar (λ=750.4 nm and λ=763.5 nm) emitted by the microdischarges of the barrier discharge in flowing humid argon at atmospheric pressure. Concentrations of two stable reaction products of H2O decomposition (H2 and O2) in argon plasma were determined experimentally as functions of humidity. Comparison of these results with the corresponding measurements of radiation kinetics permitted a detailed analysis of the influence of the discharge mechanism on its chemical reactivity in humid argon to be accomplished

Etude des propriétés oxydantes de mélanges gazeux activés par décharge électrique à pression atmosphérique (interaction avec un matériel biologique)

Depuis plusieurs années, des procédés plasma froid sont étudiés et développés pour des applications dans le domaine de la santé, par exemple pour la décontamination de surface. Dans ce travail de thèse, des réacteurs de type décharge sur barrière diélectrique à pression atmosphérique ont été utilisés pour étudier les propriétés oxydantes du milieu gazeux en post-décharge. En particulier, les investigations ont porté sur les mécanismes réactionnels menant à la formation de peroxyde d'hydrogène. La production optimum de H2O2 a été obtenue avec un gaz plasmagène constitué d'argon et de vapeur d'eau, impliquant les métastables de l'argon dans les mécanismes de dissociation de la molécule d'eau pour former les radicaux OH. Un rendement énergétique de 4 g(H2O2) / kWh a ainsi été obtenu. L'efficacité de décontamination de ce type d'effluent a été testée avec succès sur différents types de macromolécules d'intérêt biologique (acides nucléiques et protéines). De plus, l'interaction des effluents du plasma avec le matériel biologique a également constitué un outil de diagnostic indirect des espèces produites par la décharge : le traitement de solutions d'ADN et de protéines a mis en évidence le radical HO2 et son rôle dans les mécanismes de dégradation de ces macromolécules. De même, l'inactivation de micro-organismes, les spores bactériennes, par les effluents d'une décharge dans un gaz contenant de l'oxygène moléculaire, a montré qu'une espèce à durée de vie limitée, l'oxygène singulet O2 (1 Đg), conduisait à une réduction significative du nombre de spores. Enfin, l'étude des modifications induites sur le matériel biologique par les espèces issues du plasma a permis d'appréhender.In recent years, non-thermal plasma processes have been studied and developed for medical applications such as surface decontamination. The work presented here deals with the study of the oxidative properties of atmospheric pressure dielectric barrier discharge effluents. Investigations were mainly focused on hydrogen peroxide formation mechanisms. An optimum production of H2O2 has been obtained using an argon/water vapour mixture as a discharge feed gas; excited argon atoms are implied to be responsible in water vapour dissociation and thereby for OH radical formation. A maximum energy yield value of 4 g(H2O2) / kWh has been reached under these conditions. The decontamination efficiency of such atmospheric discharge effluents was found to be quite high when tested by treating surfaces bearing nucleic acids and proteins. Furthermore, results from the interaction of the discharge effluents with biologic materials could be used as non direct diagnostic tools for the identification of the active species; DNA and protein degradation results raised the HO2 radical as a specie that was significantly involved in their degradation processes. In a similar way, bacteria spore inactivation treatment with discharge feed gas containing oxygen showed that a short lived species, O2 (1 Đg) singlet oxygen, was efficient for this inactivation. Results from the discharge effluent interaction with proteins and DNA were finally used to propose fundamental mechanisms occurring during the inactivation of bacteria spores using the same process: combined action of oxidative species and acidification lead in aqueous phase to spore coat permeation; these oxidative species coming from dissolution of...ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Atmospheric Pressure Humid DBD Plasma for the Application of Sterilization – Measurement and Simulation of Hydrogen, Oxygen, and Hydrogen Peroxide Formation

International audienc