“…1 mm above the edge of the insulating plastic blades). More details about the reactor and its geometry can be found in [12]. Here, we have performed the experiments in tap water with an initial conductivity of ∼450 µS cm −1 as well as in the DI water with an initial conductivity of ∼1.2 µS cm −1 .…”
Section: Methodsmentioning
confidence: 99%
“…Molecular radicals and atomic species are essential for post-discharge chemistry and converting the water into PAW [12]. Figure 11 shows typical emission spectra in the 300-340 nm wavelength range during the first tens of ns (a) and first microseconds (b), respectively.…”
Section: Emission Spectroscopymentioning
confidence: 99%
“…Gas temperature is a significant parameter in determining the discharge's underlying physical processes. The molecular rotational temperature T rot of the electronically excited state is often used to estimate the gas temperature, and N 2 SPS bands are often used for this purpose [12,[20][21][22][23]. Figures 14(a) and (b) shows the N 2 (SPS) normalised spectra at different times for the case of DI and tap water respectively.…”
Section: Parameters Obtained From N 2 Molecular Emissionmentioning
confidence: 99%
“…The disadvantage of all the configurations based on a powered metallic electrode located above the water surface is the possible erosion of the electrode surface with subsequent contamination of the water. This point has recently been addressed by designing a DBD-like configuration in which all the electrodes are immersed in a liquid so that there is no direct contact of the metal surfaces with the active plasma [12]. In this geometry, the discharge propagates over the water surface along the air-water interface and delivers nitrogen/oxygen radicals to the water surface, leading to effective nitrogen fixation in the water.…”
The characteristics of nanosecond discharge propagating along the water-air interface in a unique DBD-like configuration with coplanar electrodes submerged in deionized/tap water are studied by combining ultrafast imaging and emission spectra with electrical characteristics. Time-resolved images provide a clear signature of diffusive plasma excited on the water surface at either side of the blade (insulated plastic separating the anode/cathode) called streamer phase and propagating perpendicularly away from it towards the anode /cathode with different velocities. Later on, the diffusive plasma converts into a few discrete and bright plasma filaments due to ionization instability (spark phase). There is no distinctive dependence in the streamer phase on water conductivity, but in the spark phase, more numerous, brighter, and thicker filaments form in tap water. The time-resolved emission spectra reveal the dominance of the first and second positive system of $\mathrm{N_2}$ molecular bands in the streamer phase, followed by the appearance of atomic lines of hydrogen, nitrogen, and oxygen in the spark phase. The emission spectra are utilized to estimate plasma parameters (gas temperature ($T_d$), electric field ($E/N$), and electron density ($n_e$)) where a more dominant spark phase is formed in tap water with $T_d\sim1100$ K, $E/N$ $\sim800$ Td, and $n_e\sim10^{18}$ /$\rm cm^{-3}$.
“…1 mm above the edge of the insulating plastic blades). More details about the reactor and its geometry can be found in [12]. Here, we have performed the experiments in tap water with an initial conductivity of ∼450 µS cm −1 as well as in the DI water with an initial conductivity of ∼1.2 µS cm −1 .…”
Section: Methodsmentioning
confidence: 99%
“…Molecular radicals and atomic species are essential for post-discharge chemistry and converting the water into PAW [12]. Figure 11 shows typical emission spectra in the 300-340 nm wavelength range during the first tens of ns (a) and first microseconds (b), respectively.…”
Section: Emission Spectroscopymentioning
confidence: 99%
“…Gas temperature is a significant parameter in determining the discharge's underlying physical processes. The molecular rotational temperature T rot of the electronically excited state is often used to estimate the gas temperature, and N 2 SPS bands are often used for this purpose [12,[20][21][22][23]. Figures 14(a) and (b) shows the N 2 (SPS) normalised spectra at different times for the case of DI and tap water respectively.…”
Section: Parameters Obtained From N 2 Molecular Emissionmentioning
confidence: 99%
“…The disadvantage of all the configurations based on a powered metallic electrode located above the water surface is the possible erosion of the electrode surface with subsequent contamination of the water. This point has recently been addressed by designing a DBD-like configuration in which all the electrodes are immersed in a liquid so that there is no direct contact of the metal surfaces with the active plasma [12]. In this geometry, the discharge propagates over the water surface along the air-water interface and delivers nitrogen/oxygen radicals to the water surface, leading to effective nitrogen fixation in the water.…”
The characteristics of nanosecond discharge propagating along the water-air interface in a unique DBD-like configuration with coplanar electrodes submerged in deionized/tap water are studied by combining ultrafast imaging and emission spectra with electrical characteristics. Time-resolved images provide a clear signature of diffusive plasma excited on the water surface at either side of the blade (insulated plastic separating the anode/cathode) called streamer phase and propagating perpendicularly away from it towards the anode /cathode with different velocities. Later on, the diffusive plasma converts into a few discrete and bright plasma filaments due to ionization instability (spark phase). There is no distinctive dependence in the streamer phase on water conductivity, but in the spark phase, more numerous, brighter, and thicker filaments form in tap water. The time-resolved emission spectra reveal the dominance of the first and second positive system of $\mathrm{N_2}$ molecular bands in the streamer phase, followed by the appearance of atomic lines of hydrogen, nitrogen, and oxygen in the spark phase. The emission spectra are utilized to estimate plasma parameters (gas temperature ($T_d$), electric field ($E/N$), and electron density ($n_e$)) where a more dominant spark phase is formed in tap water with $T_d\sim1100$ K, $E/N$ $\sim800$ Td, and $n_e\sim10^{18}$ /$\rm cm^{-3}$.
“…Technologically relevant solid surfaces treated by APPs typically do not have homogenously smooth surfaces but rather may have complex shapes and/or compositions. Such complexities include metal catalysts embedded in dielectric supports [3], wrinkled or wounded skin [4], and liquid droplets on solid materials [5]. Sources of APPs for surface treatment include dielectric barrier discharges (DBDs) [6], surface dielectric barrier discharges (SDBDs) [7] and atmospheric pressure plasma jets (APPJs) [8].…”
Atmospheric pressure plasma jets (APPJs) are increasingly being used to functionalize polymers and dielectric materials for biomedical and biotechnology applications. Once such application is microfluidic labs-on-a-chip consisting of dielectric slabs with microchannel grooves hundreds of microns in width and depth. The periodic channels, an example of a complex surface, present challenges in terms of directly and uniformly exposing the surface to the plasma. In this paper, we discuss results from computational and experimental investigations of negative APPJs sustained in Ar/N2 mixtures flowing into ambient air and incident onto a series of microchannels. Results from 2-dimensional plasma hydrodynamics modeling are compared to experimental measurements of electric field and fast-camera imaging. The propagation of the plasma across dry microchannels largely consists of a sequence of surface ionization waves (SIWs) on the top ridges of the channels and bulk ionization waves (IWs) crossing over the channels. The IWs are directed into electric field enhanced vertices of the next ridge. The charging of these ridges produce reverse IWs responsible for the majority of the ionization. The propagation of the plasma across water filled microchannels evolve into hopping SIWs between the leading edges of the water channels, regions of electric enhancement due to polarization of the water. Positive, reverse IWs follow the pre-ionized path of the initial negative waves.
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