Fluorescence measurement of atomic oxygen concentration in a dielectric barrier discharge

Abstract

Concentration of atomic oxygen was measured in a volume dielectric barrier discharge (DBD) ignited in mixtures of Ar + O 2 (+ H 2 ) at atmospheric pressure. Two-photon absorption laser induced fluorescence (TALIF) of atomic oxygen was used and this method was calibrated by TALIF of Xe in a mixture of argon and a trace of xenon. The calibration was performed at atmospheric pressure and it was shown that quenching by three-body collisions has negligible effect on the life time of excited Xe atoms. The concentration of atomic oxygen in the DBD was around 10 21 m −3 and it was stable during the whole discharge period. The concentration did not depend much on the electric power delivered to the discharge provided that the power was sufficiently high so that the visible discharge filled the whole reactor volume. Both the addition of hydrogen or replacing of argon by helium led to a significant decrease of atomic oxygen concentration. The TALIF measurements of O concentration levels in the DBD plasma performed in this work are made use of e.g. in the field analytical chemistry. The results contribute to understanding the processes of analyte hydride preconcentration and subsequent atomization in the field of trace element analysis where DBD plasma atomizers are employed.

Atmospheric plasma oxidative polymerization of ethylene dioxythiophene (EDOT) for the large‐scale preparation of highly transparent conducting thin films

“…The mist created, with most of the droplets below 10 μm in size, was directed toward the dielectric barrier discharge thanks to a gas flow, which played the role of both carrier gas and plasma gas. In contrast with most of the PEDOT synthesis routes, the present work does not involve the use of oxidants other than the reactive oxygen species (ROS) formed by the open air Ar/O 2 dielectric barrier discharge, including long lifetime species such as hydrogen peroxide and ozone and short lifetime species such as hydroxyl radical, superoxide, and atomic oxygen (Figure S1) . Thus, the proposed approach is halogen‐free.…”

“…Thus, pulse frequencies in the range of 1–10 kHz were investigated to generate a sufficient amount of ROS over an appropriate duration. Optical emission spectroscopy analysis of the Ar/O 2 dielectric barrier discharge highlights the presence of ROS such as ● OH and atomic oxygen (Figure S1), which are both believed to play a major role in the dehydrogenation of organic monomers. Interestingly, the addition of oxygen to an argon dielectric barrier discharge has also been reported to significantly reduce electron density …”

“…2.5–3 eV in the proposed AP‐DBD approach), some electrons can gain energies up to tens of eV and break any of the chemical bonds of EDOT, with bond‐dissociation energies ranging from 2.4 to 4.9 eV . On the other hand, the reactive oxygen species (ROS), with a lifetime from several tens to hundreds of nanoseconds, may be promoted in order to achieve the targeted reaction. In the first part of the present work, we investigate several Ar/O 2 plasma gas mixtures and demonstrate the occurrence of oxidative polymerization in an AP‐DBD process using ultraviolet‐visible spectroscopy (UV‐vis) and Raman spectroscopy.…”

The temporal behavior of O atom of a nonequilibrium atmospheric pressure plasma driven by kHz nanosecond voltage pulses

“…Figure 11b Each discharge cycle can be divided into Phase Ⅰ and Phase Ⅱ. As can be seen from Figure 13a, in Phase Ⅰ, the O atoms are mainly produced by the dissociation of Reactions ( 6) and (7) and are consumed by Reactions ( 8) and (12). According to Figure 13b, in Phase Ⅱ, (10), ( 11), ( 13), ( 14) are the main consumption reactions.…”

Plasma-assisted agriculture: history, presence, and prospects—a review

“…In such a case, the state-of-the-art diagnostics of plasma filaments have to be applied during the treatment process with adequate spatio-temporal resolutions (a few micrometres in space and (sub)nanoseconds in time). The required diagnostics include the direct monitoring of the treatment 'morphology' through intensified charge-coupled device microscopic imaging [260,315] and the determination of basic plasma parameters via emission/laser-induced fluorescence (LIF)/two-photon absorption laser-induced fluorescence (TALIF) spectroscopy [225][226][227][316][317][318][319][320][321][322][323][324][325][326].…”