Effects of pulse width on He plasma jets in contact with water evaluated by OH(A–X) emission and OH_aq production

Abstract

Nanosecond pulsed helium plasma jets impinging on water produce hydroxyl radicals both in gas- and liquid-phase. In this study, the effects of pulse width on a repetitively pulsed plasma jet in contact with water are evaluated via OH(A–X) emission and OHaq production in water for various pulse widths ranging from 200 to 5000 ns. The maximal energy efficiency of OH(A–X) emission is obtained for pulse widths of 600–800 ns whereas the maximal efficiency of OHaq production is at 200 ns. Temporally-resolved emission spectroscopy shows that more than 40% of OH(A–X) emission is produced during the first 200 ns of the voltage pulse regardless of the pulse width. An equivalent circuit model of the plasma jet impinging on water is compiled to understand the charge transfer process, which is important for OHaq production via charge exchange reactions.

Plasma activated water: a study of gas type, electrode material, and power supply selection and the impact on the final frontier

“…Varying the pulse width modifies the time in which molecules may solvate into the water before interacting with additional plasma species, and thus controls the concentration of reactive species. 20,21 Electrode materials are an important consideration for most plasma treatments, but even more so when using PAW. Common electrode materials are stainless steel, copper, tungsten, and aluminum.…”

Combination of ICCD fast imaging and image processing techniques to probe species–specific propagation due to guided ionization waves

“…Ultimate aims of these works are the enhancement of the reactive species production and the understanding of their propagation mechanisms. Cases of plasma jets that expand freely in air or impinge on substrates [7][8][9][10][11][12], have both been considered. Key results based on (i) ICCD and bandpass optical filters [8,[12][13][14], (ii) LIF [7,8,[15][16][17], (iv) ICCD and LIF combination [9][10][11][18][19][20][21], ICCD and two-photon absorption LIF (TALIF) combination [11,21], and (v) OES [9,12,[22][23][24] have been reported.…”

“…Cases of plasma jets that expand freely in air or impinge on substrates [7][8][9][10][11][12], have both been considered. Key results based on (i) ICCD and bandpass optical filters [8,[12][13][14], (ii) LIF [7,8,[15][16][17], (iv) ICCD and LIF combination [9][10][11][18][19][20][21], ICCD and two-photon absorption LIF (TALIF) combination [11,21], and (v) OES [9,12,[22][23][24] have been reported. These works highlight the interest and progress in the field.…”

“…On the contrary, the present work refers to pulsed helium plasma jet, and presents a systematic combination of wavelength filtered fast imaging and LIF fast imaging with digital image processing techniques. It is admitted that both techniques have been applied to plasma jets since at least one decade (see for instance [8,[12][13][14] and [9][10][11][18][19][20][21], respectively), but their combination with image processing algorithms becomes the main claim of the present work. It is argued that the naked eye observations of the ICCD snapshots-raw images of 'plasma bullets', regularly presented in the literature-may lead to loss of information or even mistaken conclusions.…”

Microsecond pulse gas–liquid discharges in atmospheric nitrogen and oxygen: Discharge mode, stability, and plasma characteristics

“…[ 8 ] As such, it is well‐accepted that the electrical characteristics and physiochemical properties of the plasma directly determine the type and concentration of aqueous RONS, thus regulating the bioactivities of plasma‐activated water. In the gas–liquid discharge, the plasma characteristics are affected by various factors [ 9–11 ] of which the type of working gas is one of the most critical.…”