Interacting kinetics of neutral and ionic species in an atmospheric-pressure helium–oxygen plasma with humid air impurities

Abstract

We unravel the complex chemistry in both the neutral and ionic systems of a radio-frequency-driven atmospheric-pressure plasma in a helium-oxygen mixture (He-0.5%O 2 ) with air impurity levels from 0 to 500 ppm of relative humidity from 0% to 100% using a zero-dimensional, time-dependent global model. Effects of humid air impurity on absolute densities and the dominant production and destruction pathways of biologically relevant reactive neutral species are clarified. A few hundred ppm of air impurity crucially changes the plasma from a simple oxygen-dependent plasma to a complex oxygen-nitrogen-hydrogen plasma. The density of reactive oxygen species decreases from 10 16 to 10 15 cm −3 , which in turn results in a decrease in the overall chemical reactivity. Reactive nitrogen species (10 13 cm −3 ), atomic hydrogen and hydroxyl radicals (10 11 -10 14 cm −3 ) are generated in the plasma. With 500 ppm of humid air impurity, the densities of positively charged ions and negatively charged ions slightly increase and the electron density slightly decreases (to the order of 10 11 cm −3 ). The electronegativity increases up to 2.3 compared with 1.5 without air admixture. Atomic hydrogen, hydroxyl radicals and oxygen ions significantly contribute to the production and destruction of reactive oxygen and reactive nitrogen species.

Improvement in ionization efficiency of direct analysis in real time-mass spectrometry (DART-MS) by corona discharge

“…1b. [19][20][21][22][23] The physicochemical behavior of He* in the plasma jet, related to the formation and subsequent energy transition of He*, is discussed below. S1 in the ESI †) indicates that this glow includes He atoms in various excited states (He*), including the high-Rydberg states 3 1 D (internal energy Q = 23.1 eV), 3 3 D (Q = 23.1 eV) and 3 3 S (Q = 22.7 eV), a resonance state 2 1 P (Q = 21.2 eV), and an optically allowed state 2 3 P (Q = 21.0 eV).…”

Controlled production of atomic oxygen and nitrogen in a pulsed radio-frequency atmospheric-pressure plasma

“…Atomic oxygen and nitrogen have been shown to play key roles in the chemical kinetics of these systems [26][27][28][29][30][31]. In this study, we have therefore combined the use of rf pulse modulation with an air-like admixture (0.1% N 2 /O 2 at 4:1) to a helium-fed APPJ to more closely match the conditions of prospective applications.…”

Interactions of a Non‐Thermal Atmospheric Pressure Plasma Effluent with PC‐3 Prostate Cancer Cells

“…Relatively recently non‐thermal plasmas produced at atmospheric pressure have shown great potential for having a similar impact in biomedicine . They offer a unique chemically reactive environment, producing high densities of a range of different reactive species very efficiently . Furthermore, their properties can be changed in order to tailor their chemical composition for the particular application required …”