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Plasma Medicine
SJR: 0.271 SNIP: 0.316 CiteScore™: 1.9

ISSN Druckformat: 1947-5764
ISSN Online: 1947-5772

Plasma Medicine

DOI: 10.1615/PlasmaMed.2013005816
pages 1-18

Active Species Concentrations in Pure N2 and Ar/x%N2 Flowing Late Afterglows at Reduced Pressure: Implications for the Sterilization of the Medical Instrumentation

Hayat Zerrouki
Universite de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d'Energie), Bat. 3R2, 118 route de Narbonne, F-31062 Toulouse cedex 9, France; CNRS, LAPLACE, F-31062 Toulouse, France
Laure Barreyre
Universite de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d'Energie), Bat. 3R2, 118 route de Narbonne, F-31062 Toulouse cedex 9, France; CNRS, LAPLACE, F-31062 Toulouse, France
Gerald Ledru
Universite de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d'Energie), Bat. 3R2, 118 route de Narbonne, F-31062 Toulouse cedex 9, France; CNRS, LAPLACE, F-31062 Toulouse, France
Sarah Cousty
Universite de Toulouse, UPS, Laboratoire Parodontites et Maladies Generales, Faculte de Chirurgie Dentaire de Toulouse, 3 Chemin des Maraichers, 31062 Toulouse cedex 9, France
Andre Ricard
Universite de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d'Energie), Bat. 3R2, 118 route de Narbonne, F-31062 Toulouse cedex 9, France; CNRS, LAPLACE, F-31062 Toulouse, France
Jean-Philippe Sarrette
Universite de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d'Energie), Bat. 3R2, 118 route de Narbonne, F-31062 Toulouse cedex 9, France; CNRS, LAPLACE, F-31062 Toulouse, France

ABSTRAKT

The present paper is devoted to the characterization of the late afterglow region of N2 and Ar−N2 flowing discharges. Optical emission spectroscopy is used to quantify the concentrations of the chemical species able to interact with microorganisms in the treatment chamber. Herein, we show that the production of nitrogen atoms in the afterglow of a reduced-pressure flowing microwave discharge can be increased using Ar−N2 mixtures instead of pure nitrogen. At 45 cm from the discharge, the maximum concentration of atoms, obtained for the Ar−15%N2 mixture, is 2.2 × 1021 m−3 at 9 Torr with an injected microwave power PMW of 100 W and 2.9 × 1021 m−3 at 200 W. Compared with the maximum N atom concentrations obtained in pure nitrogen at 4 Torr, this result corresponds to an increase of 120% at 100 W and 45% at 200 W.
We have verified that these results can be obtained while conserving full late afterglow conditions at a temperature equal to the room temperature at 100 W and not exceeding 35°C at 200 W. Under such conditions, the concentrations of the NO(A and B) excited states, formed from the impurities of the flowing gas, are low. For pure nitrogen, the concentration of the N2(A) metastable state was also measured at the end of the pink afterglow, where it is assumed to be maximal; it was 2.5 × 1016 m−3.
Nitrogen atoms are the major reactive species in the late afterglow region. They are believed to be responsible for the antibacterial properties of pure N2 and Ar−N2 flowing afterglows. To verify this assumption, the Ar−15%N2 flowing afterglow was applied to inactivate Escherichia coli bacteria, and the results were compared with previous studies performed in pure nitrogen and using the same microbiological protocol. With 40 min of exposure to Ar−15%N2 afterglow ([N] = 2.9 1021 m−3) at 32°C, a 6 log decrease of the initial bacteria population was obtained, while the same 6 log reduction could only be reached at 60°C with pure nitrogen afterglow ([N] = 1.0 × 1021 m−3).


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