Mass spectrometric investigation of the ionic species in a dielectric barrier discharge operating in helium-water vapour mixtures

Abstract

Using advanced mass spectrometry the chemistry of ionic species present in an atmospheric pressure parallel plate dielectric barrier discharge (DBD) with a single dielectric on the powered electrode have been identified. The discharge was driven in helium with controllable concentrations of water vapour using an excitation frequency of 10 kHz and an applied voltage of 1.2 kV. Both negative and positive ions were identified and their relative intensity  , with n up to 9 in both cases. Negative and positive ions responded in a similar way to changes in the operating parameters, with the particular response depending on the ion mass. Increasing the inter-electrode spacing and the water concentration in the discharge led to an increase in the intensity of large mass ionic water clusters. However, increasing the residence time of the species in the plasma region and increasing the applied power resulted in fragmentation of large water clusters to produce smaller ions.

Time Behaviour of Helium Atmospheric Pressure Plasma Jet Electrical and Optical Parameters

“…Congruent results, concerning the ambient impurities present in the discharge effluent, were also reported by other research groups for various types of atmospheric pressure plasma jets [18][19][20][21]64]. This rich ion chemistry is only due to air impurities diffusion in the rare gas channel and it may be modified for desired applications if small amounts, less than 1% of additional gases (e.g., O 2 , N 2 , CO 2 or H 2 O), are mixed with the main working gas.…”

Non‐Thermal Plasma in Contact with Water: The Origin of Species

“…The interaction of these plasmas with ambient atmosphere results in the formation of a variety of reactive species that exhibit high biological activity (e.g., anti‐microbial, anti‐cancer, wound healing) . A range of spectroscopic techniques have been used to monitor different reactive species in these plasmas, for example, IR optical emission spectroscopy for 1 O 2 , diode laser absorption spectroscopy for metastable states of helium, vacuum ultraviolet (VUV) absorption spectroscopy and laser‐induced fluorescence for radical and atomic species, FTIR spectroscopy for hydrogen peroxide and mass‐spectrometry for ionic species …”

“…[5][6][7][8][9] Ar ange of spectroscopic techniques have been used to monitord ifferent reactive speciesi n these plasmas, for example, IR opticale mission spectroscopy for 1 O 2 , [10] diode laser absorption spectroscopy for metastable states of helium, [11] vacuum ultraviolet (VUV) absorption spectroscopya nd laser-induced fluorescence for radical and atomic species, [12,13] FTIR spectroscopy for hydrogen peroxide [14] and mass-spectrometry for ionic species. [15] Aqueous media is af undamentalp art of the biological milieu. The two main types of plasma applications in research and biomedical trials are the pre-treatmento fa queous media, which is subsequently appliedt ot issue or bacteria, andt he direct exposure of biological samples to ap lasma jet.…”

Mass Spectrometric Observations of the Ionic Species in a Double Dielectric Barrier Discharge Operating in Nitrogen

“…The material and geometry of the electrodes and the dielectric are easily adaptable for numerous applications. Properties of DBDs and their applications were explained in our previous work . The discharge properties of DBD's have been studied previously using a variety of diagnostic methods such as optical emission spectroscopy, Fourier transform infra‐red spectroscopy (FTIR), infra‐red laser absorption spectroscopy and electrical diagnostics .…”

“…The discharge properties of DBD's have been studied previously using a variety of diagnostic methods such as optical emission spectroscopy, Fourier transform infra‐red spectroscopy (FTIR), infra‐red laser absorption spectroscopy and electrical diagnostics . In our previous work we reported the first mass spectrometry study of ionic species generated in a single barrier DBD operating in helium and water vapor mixtures. However, the use of nitrogen gas instead of expensive noble gases such as helium is more attractive for several practical applications such as surface cleaning and polymer modification.…”