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

Abstract

Radio-frequency driven atmospheric pressure plasmas are efficient sources for the production of reactive species at ambient pressure and close to room temperature. Pulsing the radio-frequency power input provides additional control over species production and gas temperature. Here, we demonstrate the controlled production of highly reactive atomic oxygen and nitrogen in a pulsed radio-frequency ( MHz) atmospheric-pressure plasma, operated with a small % air-like admixture (/ at ) through variations in the duty cycle. Absolute densities of atomic oxygen and nitrogen are determined through vacuum-ultraviolet absorption spectroscopy using the DESIRS beamline at the SOLEIL synchrotron coupled with a high resolution Fourier-transform spectrometer. The neutral-gas temperature is measured using nitrogen molecular optical emission spectroscopy. For a fixed applied-voltage amplitude (234 V), varying the pulse duty cycle from 10% to 100% at a fixed 10 kHz pulse frequency enables us to regulate the densities of atomic oxygen and nitrogen over the ranges of – and – , respectively. The corresponding 11 K increase in the neutral-gas temperature with increased duty cycle, up to a maximum of K, is relatively small. This additional degree of control, achieved through regulation of the pulse duty cycle and time-averaged power, could be of particular interest for prospective biomedical applications.

Chemical kinetics and density measurements of OH in an atmospheric pressure He + O2 + H2O radiofrequency plasma

“…These are in good agreement with the experimental results presented in [8,45,47]. In [8] and [45], nitrogen was also included in the gas mixture at a 4:1 ratio. This comparison may suggest that 0.1% nitrogen has a moderate impact on the atomic oxygen density in dry conditions.…”

Chemical kinetics in an atmospheric pressure helium plasma containing humidity

“…The plasma jet used in this work is shown in Fig. 1 and is the same as described by Dedrick et al 23 The jet has a plane-parallel electrode configuration. One electrode with an area of 2.4 × 0.86 cm 2 is powered by a sinusoidal voltage at a frequency of 13.56 MHz while the other electrode, which is the housing of the source, is grounded.…”

“…However, atomic species, in particular O and N, have previously been quantified in an APP using synchrotron radiation and a spectrometer with an ultra-high spectral resolution, so-called VUV high-resolution Fourier-Transform Absorption Spectroscopy (VUV-FTAS). 22 , 23 …”

Applications of the COST Plasma Jet: More than a Reference Standard

“…The applicability of an APPJ to specific purposes is largely defined by the induced chemistry. The aforementioned tunability of the COST jet (and COST jet-based modified plasma setups) allows controlled generation of RONS in the gas phase [19,23]. Specifically, when operated with a feed gas of He with O 2 admixtures, the main 'output' reactive oxygen species (ROS) are atomic oxygen O, singlet oxygen 1 O 2 , and ozone O 3 [24,25].…”