Measurement of hydroxyl radical (OH) concentration in an argon RF plasma jet by laser-induced fluorescence

Voráč, Jan; Dvořák, Pavel; Procházka, Vojtěch; Ehlbeck, Joerg; Reuter, Stephan

doi:10.1088/0963-0252/22/2/025016

Cited by 56 publications

(41 citation statements)

References 21 publications

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“…Therefore, at low Ar flow rates the active discharge did not reach the measurement point and the OH concentration in the effluent was low. The increase in Ar flow results in a sharp increase in OH concentration.This can be explained as follows[167]. When the RF power delivered to the plasma was 80 W, the visible active discharge reached the measurement point when the flow rate was approximately 0.3 L/min.…”

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confidence: 95%

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Reactive species in non-equilibrium atmospheric-pressure plasmas: Generation, transport, and biological effects

et al. 2016

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Non-equilibrium atmospheric-pressure plasmas have recently become a topical area of research owing to their diverse applications in health care and medicine, environmental remediation and pollution control, materials processing, electrochemistry, nanotechnology and other fields. This review focuses on the reactive electrons and ionic, atomic, molecular, and radical species that are produced in these plasmas and then transported from the point of generation to the point of interaction with the material, medium, living cells or tissues being processed. The most important mechanisms of generation and transport of the key species in the plasmas of atmospheric-pressure plasma jets and other non-equilibrium atmosphericpressure plasmas are introduced and examined from the viewpoint of their applications in plasma hygiene and medicine and other relevant fields. Sophisticated high-precision, timeresolved plasma diagnostics approaches and techniques are presented and their applications to monitor the reactive species and plasma dynamics in the plasma jets and other discharges, both in the gas phase and during the plasma interaction with liquid media, are critically reviewed. The large amount of experimental data is supported by the theoretical models of reactive species generation and transport in the plasmas, surrounding gaseous environments, and plasma interaction with liquid media. These models are presented and their limitations are discussed. Special attention is paid to biological effects of the plasma-generated reactive oxygen and nitrogen (and some other) species in basic biological processes such as cell metabolism, proliferation, survival, etc. as well as plasma applications in bacterial inactivation, wound healing, cancer treatment and some others. Challenges and opportunities for theoretical and experimental research are discussed and the authors' vision for the emerging convergence trends across several disciplines and application domains are presented to stimulate critical discussions and collaborations in the future. 4 3.5 Optical absorption spectroscopy 3.5.1 Ozone 3.5.2 UV broadband absorption of OH density 3.5.3 Cavity ring-down spectroscopy 3.5 Selected non-optical techniques 3.5.1 Mass spectrometry 3.5.2 Flow visualization 3.5.3 Electron paramagnetic resonance spectroscopy 4. Temporal and spatial behaviour of key reactive species 4.1 Electron density (n e) 4.2 O atoms 4.2.1 Effect of admixture of O 2 /air on O concentration 4.2.2 Diffusion effect of shielding gas on O production 4.3 OH radical 4.3.1 Effect of H 2 O admixture on OH concentration 4.3.2 Effect of gas flow on OH concentration 4.3.3 Effect of O 2 on OH production 4.3.4 Effect of the treated samples on OH concentration 4.3.4.1 Effect of humidity of treatment sample on OH distribution 4.3.4.2 Effect of sample conductivity on OH distribution 4.3.4.3. Effect of the amplitude of the applied voltage on OH distribution 4.3.4.4. The effect of gas flow on OH distribution 4.3.4.5. The effect of the surface characteristics on OH distribution 4.3.5 Effe...

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confidence: 95%

“…Comparison of Rayleigh based approaches with chemical kinetics modelling show the advantage of using scattering for optical calibration [160,166,167].…”

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confidence: 99%

Reactive species in non-equilibrium atmospheric-pressure plasmas: Generation, transport, and biological effects

et al. 2016

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“…At atmospheric pressure, RET is sometimes so fast that the excited state is practically all the time in rotational equilibrium [20,34]. In such a case, each vibrational state can be treated as only one effective level, which simplifies the LIF data processing considerably.…”

Section: Collisional Processesmentioning

confidence: 99%

“…N Xi denotes the concentration of OH radicals in the particular rotational level of the ground vibronic state X 2 Π v 00 ¼ 0 ðÞ from which the excitation occurred, B is the absorption coefficient of the particular excitation transition, c is the speed of light and κ is the overlap term of the absorption and laser line [20], E f is the mean energy of laser pulses during the measurement of the fluorescence, τ is the lifetime of the relevant vibronic state, and…”

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confidence: 99%

Laser-Induced Fluorescence of Hydroxyl (OH) Radical in Cold Atmospheric Discharges

Voráč¹,

Dvořák²,

Mrkvičková³

2018

Photon Counting - Fundamentals and Applications

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The application of laser-induced fluorescence (LIF) to measurement of absolute concentration of hydroxyl radicals in cold atmospheric discharges is described. Though only the case of OH is presented, the method can be directly applied to other molecules as well. Starting from the rate equations for the LIF process, the main formulas for two-and multilevel excitation scheme are derived. It is also shown how to use partially saturated LIF in practice, enhancing the signal-to-noise ratio. Practical tips for automating the data evaluation are given, allowing processing large data sets, particularly suitable for planar measurements. Gas temperature estimation from fluorescence on different rotational absorption lines is shown as an attractive method for obtaining temperature maps with high spatial resolution. The important aspects of calibration are discussed, particularly the overlap of the laser line with the selected absorption line and the measurement of the Rayleigh scattering for sensitivity calibration, together with the common sources of errors. The application of OH(A, v 0 =0 X, v 00 = 0) excitation scheme to the effluent of atmospheric pressure plasma jet ignited in argon and of OH(A, v 0 =1 X, v 00 = 0) to the plasma of coplanar surface barrier discharge in air and in water vapor is shown.

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“…[9][10][11][12][13] It is a streamerlike propagation that produces reactive species while it propagates in an ambient air. [16][17][18][19][20][21][22][23][24] For instance, although it is known that the discharge polarity affects the shape, length, and emission profile of the plasma jet, 25 few studies have reported its effect on the reactive species production. 14,15 Although many studies have measured reactive species in the plasma jet, a lot of things are still ambiguous about the relation between the plasma bullet propagation and the production of reactive species.…”

Section: Introductionmentioning

confidence: 99%

Effect of discharge polarity on the propagation of atmospheric-pressure helium plasma jets and the densities of OH, NO, and O radicals

Yonemori

Ono

2015

Biointerphases

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The atmospheric-pressure helium plasma jet is an emerging technology for plasma biomedical applications. In this paper, the authors focus on the effect of discharge polarity on propagation of the discharge and the densities of OH, NO, and O radicals. The plasma jet is applied to a glass surface placed on a grounded metal plate. Positive or negative voltage pulses with 25 μs duration, 8 kV amplitude, and 10 kpps repetition rate are used for the plasma jet. The plasma propagation is measured using a short-gated ICCD camera. The light emission intensity of the discharge generated at the rising phase of the voltage pulse is approximately equivalent for both polarities, while that generated during the falling phase is much higher for the negative discharge than the positive one. The shape of the discharge changes with the discharge polarity. The OH, NO, and O densities in the plasma jet are also measured for both polarities. It is found that the OH density is almost the same regardless the discharge polarity. Conversely, the negative discharge produces more O atoms and the positive discharge produces more NO molecules. These results indicate that the polarity of the discharge affects the densities of some reactive species produced in the plasma jet.

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Measurement of hydroxyl radical (OH) concentration in an argon RF plasma jet by laser-induced fluorescence

Cited by 56 publications

References 21 publications

Reactive species in non-equilibrium atmospheric-pressure plasmas: Generation, transport, and biological effects

Reactive species in non-equilibrium atmospheric-pressure plasmas: Generation, transport, and biological effects

Laser-Induced Fluorescence of Hydroxyl (OH) Radical in Cold Atmospheric Discharges

Effect of discharge polarity on the propagation of atmospheric-pressure helium plasma jets and the densities of OH, NO, and O radicals

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