(697b) Photochemical Interaction Between Air Plasma Reactive Species and UV Photons | AIChE

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(697b) Photochemical Interaction Between Air Plasma Reactive Species and UV Photons

Authors 

Pavlovich, M. J. - Presenter, University of California - Berkeley
Graves, D. B., University of California - Berkeley
Clark, D. S., University of California



In this study, air plasma generated at ambient conditions by surface micro-discharge (SMD), and VUV photons at 172 nm produced by xenon microplasma, were used in combination to treat both gaseous and aqueous volumes. Quantitative FTIR, using standard spectra from the HITRAN database, was performed to measure gas-phase concentrations of reactive oxygen and nitrogen species (RONS) under plasma treatment, VUV treatment, and the combination of both treatments. We show how the concentrations of several important RONS, including ozone (O3), nitric acid (HNO3), nitrogen dioxide (NO2), nitric oxide (NO), and nitrous oxide (N2O) evolve over time in response to plasma and/or VUV treatment. In addition, we measure how the reactive species concentrations depend on both treatment time and discharge power density, in agreement with our earlier qualitative report of the gas-phase chemistry. [1]

Furthermore, the aqueous chemistry of the combined treatment is measured and compared to our earlier measurement of aqueous chemistry absent any UV treatment [1] and in combination with treatment by a 365 nm UVA LED [2]. Based on known photolysis reactions at particular wavelengths, mechanisms for the generation of aqueous RONS are proposed. Finally, the antimicrobial effects of the different UV exposures are compared, and we demonstrate that the interaction between plasma RONS and UV photons is synergistic in some cases and additive in others. The variation in combined effects of plasma treatment and UV photon exposure, as functions of plasma discharge parameters and UV photon wavelength, describes the potential for a dynamic and tunable plasma/photochemical system for the in situ, on-demand creation of reactive chemical species.

References

[1]         M. J. Pavlovich, H.-W. Chang, Y. Sakiyama, D. S. Clark, D. B. Graves, Journal of Physics D: Applied Physics 2013, 46, 145202.

[2]         M. J. Pavlovich, Y. Sakiyama, D. S. Clark, D. B. Graves, manuscript in preparation

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