Reactive Plasma Species Research Articles

LC–ESI-MS/MS profile of phenolic and glucosinolate compounds in samh flour (Mesembryanthemum forsskalei Hochst. ex Boiss) and the inhibition of oxidative stress by these compounds in human plasma

Samh flour (Mesembryanthemum forsskalei) is a foodstuff with high protein content, which can be used as a replacement for wheat flour. It is often consumed by Bedouin tribes of northern Saudi Arabia. Very little is known about bioactive molecules present in samh flour, therefore we analyzed its extracts to evaluate the contents of secondary metabolites. A total of 43 secondary metabolites present in 60% MeOH extract of samh flour were tentatively identified using LC–ESI-MS/MS. These compounds represented five major categories: glucosinolates, sinapic acid and sinapoylglycosides, acylated flavonoids, flavonoids, and amide derivatives. Their effect on oxidative damage of proteins and lipids was determined in vitro by assessing levels of protein thiol groups and concentrations of thiobarbituric acid reactive species (TBARS) in human plasma. Obtained results indicated that samh flour is a rich source of compounds with antioxidant activity.

Single-electrode He microplasma jets driven by nanosecond voltage pulses

Excited by 5 ns, 8 kV voltage pulses, a 260 μm-diameter, 8 mm long helium plasma jet was generated with a single-electrode configuration in ambient air. Application of fast high voltage pulses (≥1012 V s−1) resulted in rapid acceleration of the microplasma plumes; within 5 ns the plume velocity reached 8 × 105 m/s, almost three times higher than that of the plasma jet generated with the pulsed voltage of the same amplitude but with a lower increase rate (1011 V s−1). Importantly, the ultrashort electric pulses were able to efficiently deposit energy in the plasma during the initiation process, which may be responsible for the rapid acceleration of the ionization wavefronts during the streamer onset, as well as efficient production of reactive plasma species including O(5P) and N2+(B2Σu+) via electron-induced processes. Emission spectral comparison between the plasma jets excited with 5 ns voltage pulses and with 140 ns voltage pulses showed enhanced O(5P) and N2+(B2Σu+) emission by the shorter pulses than the longer ones, while the vibrational and rotational temperature for both plasma jets are at 3000 K and 300 K, respectively.

Functionalization of graphene by atmospheric pressure plasma jet in air or H2O2 environments

The functionalization of graphene, which deforms its band structure, can result in a metal-semiconductor transition. In this work, we report a facile strategy to oxidize single-layer graphene using an atmospheric pressure plasma jet (APPJ) that generates a variety of reactive plasma species at close to ambient temperature. We systematically characterized the oxygen content and chemical structure of the graphene films after plasma treatment under different oxidative conditions (ambient air atmosphere or hydrogen peroxide solution) by X-ray Photoelectron Spectroscopy (XPS). Plasma-treated graphene films containing more than 40% oxygen were obtained in both oxidative environments. Interestingly, prolonged irradiation led to the reduction of graphene oxides. N-doping of graphene also occurred during the APPJ treatment in H2O2 solution; the nitrogen content of the doped graphene was dependent on the duration of irradiation and reached up to 8.1% within 40min. Moreover, the H2O2 solution served as a buffer layer that prevented damage to the graphene during plasma irradiation. Four-point probe measurement revealed an increase in sheet resistance of the plasma-treated graphene, indicating the transition of the material property from semi-metallic to semiconducting.

Aqueous Plasma Pharmacy: Preparation Methods, Chemistry, and Therapeutic Applications.

Plasma pharmacy is a subset of the broader field of plasma medicine. Although not strictly defined, the term aqueous plasma pharmacy (APP) is used to refer to the generation and distribution of reactive plasma-generated species in an aqueous solution followed by subsequent administration for therapeutic benefits. APP attempts to harness the therapeutic effects of plasma-generated oxidant species within aqueous solution in various applications, such as disinfectant solutions, cell proliferation related to wound healing, and cancer treatment. The subsequent use of plasma-generated solutions in the APP approach facilitates the delivery of reactive plasma species to internal locations within the body. Although significant efforts in the field of plasma medicine have concentrated on employing direct plasma plume exposure to cells or tissues, here we focus specifically on plasma discharge in aqueous solution to render the solution biologically active for subsequent application. Methods of plasma discharge in solution are reviewed, along with aqueous plasma chemistry and the applications for APP. The future of the field also is discussed regarding necessary research efforts that will enable commercialization for clinical deployment.

Controlled accelerated oxidation of oleic acid using a DBD plasma: Determination of volatile oxidation compounds

Lipid oxidation is one of the main causes of food deterioration, resulting in the loss of nutritional properties and the formation of unwanted aroma properties. Both for scientific and industrial purposes there is a need for accelerated lipid oxidation tests in food research. The conventional thermally-based accelerated lipid oxidation protocols are known to insufficiently correlate to the realistic oxidation mechanisms. Recent studies have investigated the application of an innovative non-thermal plasma technique as a promising alternative approach. The produced reactive oxygen species in non-thermal plasma enabled to accelerate the lipid oxidation process, with a more accurate prediction of antioxidative properties, thus leading to a higher correlation with the product oxidized at room temperature. In order to obtain more profound insights in the plasma-induced chemistry, a profound parameter study was performed by studying the impact of applied voltage, plasma gas composition, distance between nozzle and sample surface, ambient gas composition and treatment time. Using analytical tools (HS–SPME–GC–MS) on one hand, combined with statistical interpretations (PCA/SIMCA/HCA) on the other hand, a selection of the most promising parameter settings was done. For this parameter study, pure oleic acid was used as a model matrix. In the sample oxidized at 25°C, typical oxidation products have been found, such as heptanal, octanal, nonanal, (E)-nonenal, etc.…Comparing the different plasma types (argon, argon/O2 and argon/H2O) in different surrounding gas compositions (air, argon) showed most promising results for Ar/O2 in Ar atmosphere. A correlation of up to 82% was found between the sample oxidized at 25°C and the plasma treated sample.

OPTICAL EMISSION SPECTROSCOPY ANALYSIS OF ATMOSPHERIC PLASMA JET PLUME ON BACTERIA INACTIVATION

In this paper, an atmospheric plasma jet plasma plume generated using Helium gas was investigated for reactive plasma species. The method of investigation is by using Optical Emission Spectroscopy analysis. Observation of the emission spectrum enables understanding of the influence of reactive species inside plasma plume to microbial inactivation process. The reactive species in plasma plume were detected using spectrometer without presence of bacteria. Escherichia coli and Methicillin-resistant staphylococcus aureus were used as inactivation targets. Bacteria were cultured in 10 Colony Forming Unit per milliliter in single colony and exposed to plasma at different time. It is found that, both bacteria were inactivated at 180 seconds. The result of emission line spectrum showed the presence of nitrogen and oxygen between line 300 nm until 700 nm. Nitrogen and oxygen are involved in oxidation process which is known as Reactive Nitrogen Species and Reactive Oxygen Species. These species are main key in bacteria inactivation.

Off-axis chemical crosstalk in an atmospheric pressure microplasma jet array

Developing arrays of parallel microplasma jets is an attractive route to scaling the area available for the treatment of surfaces with low temperature plasma. Increasing the packing density of the arrays may lead to electrical and gas kinetic jet–jet interactions, but previous work has focused almost exclusively on electrostatic coupling between the jets. Chemical interactions (‘crosstalk’) have received considerably less attention. We report here the results of an investigation of chemical crosstalk in 4 × 4 arrays of microplasma jets, produced in flowing helium at atmospheric pressure. Oxidation damage to an Escherichia coli lawn serves as a diagnostic of the spatial distribution of molecular radicals and other reactive plasma species, produced at the plasma jet/ambient background interface or between the jets, and incident on the surface. Spatial maps of bacterial inactivation by the microplasma jet array for 20 s show the destruction of E. coli at distances as large as 2.7 jet diameter from the nearest plasma perimeter, compared to typically less than 0.5 jet diameter in the single jet case. Extending to 30 s of plasma exposure leads to destruction of the entire bacterial sample. This ‘action at a distance’ effect, the production of long-lived species such as O, O2(a1Δg) and O3 that are responsible for bacterial deactivation, peaks along a line bisecting columns and rows of plasma jets. The data illustrate the synergistic effect of adjacent jets on off-axis formation of reactive species, and show that the chemical and biological impact of an array cannot be inferred from the plasma chemistry of a single jet.

Momentum, heat, and neutral mass transport in convective atmospheric pressure plasma-liquid systems and implications for aqueous targets

There is a growing interest in the study of plasma-liquid interactions with application to biomedicine, chemical disinfection, agriculture, and other fields. This work models the momentum, heat, and neutral species mass transfer between gas and aqueous phases in the context of a streamer discharge; the qualitative conclusions are generally applicable to plasma-liquid systems. The problem domain is discretized using the finite element method. The most interesting and relevant model result for application purposes is the steep gradients in reactive species at the interface. At the center of where the reactive gas stream impinges on the water surface, the aqueous concentrations of OH and ONOOH decrease by roughly 9 and 4 orders of magnitude respectively within 50 m of the interface. Recognizing the limited penetration of reactive plasma species into the aqueous phase is critical to discussions about the therapeutic mechanisms for direct plasma treatment of biological solutions. Other interesting results from this study include the presence of a 10 K temperature drop in the gas boundary layer adjacent to the interface that arises from convective cooling. Though the temperature magnitudes may vary among atmospheric discharge types (different amounts of plasma-gas heating), this relative difference between gas and liquid bulk temperatures is expected to be present for any system in which convection is significant. Accounting for the resulting difference between gas and liquid bulk temperatures has a significant impact on reaction kinetics; factor of two changes in terminal aqueous species concentrations like H2O2, NO, and NO are observed in this study if the effect of evaporative cooling is not included.

Treatment of methyl orange by nitrogen non-thermal plasma in a corona reactor: The role of reactive nitrogen species

Methyl orange (MO) azo dye served as model organic pollutant to investigate the role of reactive nitrogen species (RNS) in non-thermal plasma (NTP) induced water treatments. The results of experiments in which MO aqueous solutions were directly exposed to N2-NTP are compared with those of control experiments in which MO was allowed to react with nitrite, nitrate and hydrogen peroxide, which are species formed in water exposed to N2-NTP. Treatment of MO was also performed in PAW, Plasma Activated Water, that is water previously exposed to N2-NTP. Both direct N2-NTP and N2-PAW treatments induced the rapid decay of MO. No appreciable reaction was instead observed when MO was treated with NO3− and H2O2 either under acidic or neutral pH. In contrast, in acidic solutions MO decayed rapidly when treated with NO2− and with a combination of NO2− and H2O2. Thorough product analysis was carried out by HPLC coupled with UV–vis and ESI–MS/MS detectors. In all experiments in which MO reaction was observed, the major primary product was a derivative nitro-substituted at the ortho position with respect to the N,N-dimethylamino group of MO. The reactions of RNS are discussed and a mechanism for the observed nitration products is proposed.

Reactive oxygen species in plasma against E. coli cells survival rate**Project supported by the Natural Science Foundation of Fujian Province, China (Grant No. 2014J01025), the National Natural Science Foundation of China (Grant No. 11275261), and the Funds from the Fujian Provincial Key Laboratory for Plasma and Magnetic Resonance, China.

In this paper, we report on the contrastive analysis of inactivation efficiency of E. coli cells in solution with different disinfection methods. Compared with the hydrogen peroxide solution and the ozone gas, the atmospheric-pressure He plasma can completely kill the E. coli cells in the shortest time. The inactivation efficiency of E. coli cells in solution can be well described by using the chemical reaction rate model. X-ray photoelectron spectroscopy (XPS) analysis shows that the C–O or C=O content of the inactivated E. coli cell surface by plasma is predominantly increased, indicating the quantity of oxygen-containing species in plasma is more than those of two other methods, and then the C–C or C–H bonds can be broken, leading to the etching of organic compounds. Analysis also indicates that plasma-generated species can play a crucial role in the inactivation process by their direct reactions or the decompositions of reactive species, such as ozone into OH radicals in water, then reacting with E. coli cells.

Nanosecond time-resolved microscopic spectroscopy for diagnostics of an atmospheric-pressure discharge plasma formed in aqueous solution

Glow discharge plasma formed in solution under atmospheric pressure has been expected to provide reaction fields with characteristic physical and chemical properties owing to the frequent collisions and reactions of reactive particles inside and the rapid quenching of the products by the surrounding cold solutions. In particular, when an aqueous solution is utilized as the surrounding solution, the atmospheric-pressure in-solution glow (ASG) plasma contains hydrogen and hydroxyl radicals showing large activities for reduction and oxidation, respectively. In addition, because the ASG plasma is formed under atmospheric pressure, the collision frequencies between the particles contained in the plasma are higher than those in other plasmas ordinarily formed under low pressure. This feature should result in rapid energy redistribution among particles contained in the plasma. In the present study, time-resolved optical emission spectroscopy with nanosecond time resolution was applied for the diagnostics of the ASG plasma with chemical species selectivity. The time-resolved measurements revealed that the temporal evolutions of the temperatures of blackbody, hydrogen radical, and hydroxyl radical contained in the ASG plasma consist of two stages: initial rise within 0.15 µs (rising stage) and fluctuation around certain values for about 1 µs (fluctuating stage). In the time region corresponding to the rising stage, the electron number density is about ten times larger than the value temporally averaged during the plasma emission. The initial rise should result from frequent collisions between charged particles accelerated by the applied voltage and unexcited particles. In the fluctuating stage, the electron number density strongly correlates with the increase in the radical temperatures. It is concluded that the electron number density, rather than the electron temperature, is a key parameter determining the temperatures of reactive species in the ASG plasma.

Experimental investigation on plasma-assisted combustion characteristics of premixed propane/air mixture

A detailed study on the plasma-assisted combustion (PAC) characteristics of premixed propane/air mixture is presented. The PAC is measured electrically, as well as optically with a multichannel spectrometer. The characteristics are demonstrated by stable combustion temperature and combustion stability limits, and the results are compared with conventional combustion (CC). Stable combustion temperature measurements show that the introduction of PAC into combustion system can increase the stable combustion temperature, and the increment is more notable with an increase of discharge voltage. Besides, the rich and weak limits of combustion stability are both enlarged when plasma is applied into the combustion process and the increase of discharge voltage results in the expansion of combustion stability limits as well. The measurements of temperature head and emission spectrum illustrate that the kinetic enhancement caused by reactive species in plasma is the main enhancement pathway for current combustion system.

Compact High-Velocity Atmospheric Pressure Dielectric Barrier Plasma Jet in Ambient Air

In this paper, a non-thermal atmospheric pressure plasma jet at high streaming velocity operating with ambient air is highlighted. In the present technological approach, the employment of air poses a significant challenge. The high oxygen concentration in air results in a reduced concentration of reactive species in combination with a short species lifetime. The plasma jet assembly presented here contains a special dielectric barrier with a high secondary emission coefficient. In this way, the electron density and in turn the density of reactive species is increased. In addition, the plasma jet assembly is equipped with a short electrode. This leads to a higher voltage across the discharge gap and in turn to an increased density of reactive plasma species. The plasma jet is formed within and emitted by a small conical nozzle. A high-speed gas flow with gas velocity of 340 m/s was achieved at the end of the nozzle. In the jet the concentration of toxic and unwanted neutral plasma species like O3 or NOx is significantly reduced because of the shorter residence time within the plasma. The range of short-lived active plasma species is in turn considerably enhanced. The jet efficiency and action range measured through the oxidation of a test surface were determined by measuring the increase of surface tension of a polypropylene substrate via contact angle measurements after plasma treatment. Numerical modeling of the plasma plume indicates that oxygen atoms are in fact the main active species in the plasma plume.

How do plasma-generated OH radicals react with biofilm components? Insights from atomic scale simulations

The application of nonthermal atmospheric pressure plasma is emerging as an alternative and efficient technique for the inactivation of bacterial biofilms. In this study, reactive molecular dynamics simulations were used to examine the reaction mechanisms of hydroxyl radicals, as key reactive oxygen plasma species in biological systems, with several organic molecules (i.e., alkane, alcohol, carboxylic acid, and amine), as prototypical components of biomolecules in the biofilm. Our results demonstrate that organic molecules containing hydroxyl and carboxyl groups may act as trapping agents for the OH radicals. Moreover, the impact of OH radicals on N-acetyl-glucosamine, as constituent component of staphylococcus epidermidis biofilms, was investigated. The results show how impacts of OH radicals lead to hydrogen abstraction and subsequent molecular damage. This study thus provides new data on the reaction mechanisms of plasma species, and particularly the OH radicals, with fundamental components of bacterial biofilms.

One-step argon/nitrogen binary plasma jet irradiation of Li4Ti5O12 for stable high-rate lithium ion battery anodes

Atmospheric pressure Ar/N2 binary plasma jet irradiation has been introduced into the manufacturing process of lithium ions batteries as a facile, green and scalable post-fabrication treatment approach, which enhanced significantly the high-rate anode performance of lithium titanate (Li4Ti5O12). Main emission lines in Ar/N2 plasma measured by optical emission spectroscopy reveal that the dominant excited high-energy species in Ar/N2 plasma are N2*, N2+, N∗ and Ar∗. Sufficient oxygen vacancies have been evidenced by high resolution X-ray photoelectron spectroscopy analysis and Raman spectra. Nitrogen doping has been achieved simultaneously by the surface reaction between pristine Li4Ti5O12 particles and chemically reactive plasma species such as N∗ and N2+. The variety of Li4Ti5O12 particles on the surface of electrodes after different plasma processing time has been examined by grazing incident X-Ray diffraction. Electrochemical impedance spectra (EIS) confirm that the Ar/N2 atmospheric plasma treatment facilitates Li+ ions diffusion and reduces the internal charge-transfer resistance. The as-prepared Li4Ti5O12 anodes exhibit a superior capacity (132 mAh g−1) and excellent stability with almost no capacity decay over 100 cycles under a high C rate (10C).

Characterization of Kilohertz-Ignited Nonthermal He and He/<inline-formula> <tex-math notation="TeX">${\rm O}_{2}$ </tex-math></inline-formula> Plasma Pencil for Biomedical Applications

In this paper, an atmospheric pressure low-temperature plasma pencil generated in helium and helium/ oxygen gas mixtures was characterized in detail for its discharge characteristics, plasma power, reactive plasma species produced, plasma density, and plasma temperatures using electrical and optical emission spectroscopy (OES) diagnostics, and its efficacy for biomedical application. A visible plasma plume length of approximately 27 mm was generated using a 60-kHz ac HV power supply. The OES results showed the most intensive plasma emission lines of OH transition A <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Σ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> (v = 0, 1)→X <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Π(Δν = 0) at 308 nm and OH transition A <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Σ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> (v = 0, 1)→X <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Π(Δν = 1) at 287 nm, O I transition 3p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> P→3s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> at 777.41 nm, O I transition 3p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> P→3s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> at 844.6 nm, and N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (C-B) second positive system with electronic transition C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> →B <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> in the range 300-450 nm. The effects of controlled oxygen content on the plasma pencil and on various helium plasma emissions and electrical properties are studied. A spatial distribution of reactive plasma species produced by the plasma pencil is presented. The electron density of plasma jet was estimated to be in the order of 2.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> using Stark broadening line profile of the hydrogen alpha emission. The temperatures of afterglow plasma pencil were evaluated using OH rotational temperatures, and the results demonstrate temperatures of 316 and 362 K for pure He and He/O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas mixtures (0.1% O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), respectively. Preliminary results on inactivation of Streptococcus pneumoniae on a solid surface and in liquid suspension were carried out using the plasma pencil for biomedical applications.

Reactive Molecular Dynamics Simulations for a Better Insight in Plasma Medicine

AbstractIn this review paper, we present several examples of reactive molecular dynamics simulations, which contribute to a better understanding of the underlying mechanisms in plasma medicine on the atomic scale. This includes the interaction of important reactive oxygen plasma species with the outer cell wall of both gram‐positive and gram‐negative bacteria, and with lipids present in human skin. Moreover, as most biomolecules are surrounded by a liquid biofilm, the behavior of these plasma species in a liquid (water) layer is presented as well. Finally, a perspective for future atomic scale modeling studies is given, in the field of plasma medicine in general, and for cancer treatment in particular.

Peroxiredoxin I in sperm and reactive oxygen species in seminal plasma in patients with idiopathic asthenozoospermia

To explore the relationship between peroxiredoxin I expression and seminal reactive oxygen species (ROS) in patients with idiopathic asthenozoospermia. Twenty-six infertile male patients were selected from the Reproductive Medical Center, Xiangya Hospital, from September to December in 2012. Fresh semen was collected from an experimental group (26 idiopathic asthenozoospermia patients) and a control group (15 men with fertility history and normal semen). Luminol chemiluminescence method was applied to detect the seminal ROS level. Western blot was used to detect the peroxiredoxin I expression. 1)The seminal ROS level in the experimental group was significantly increased compared with that in the control group (P<0.05), and the seminal ROS level was negatively correlated with mobility of the sperm (r=-0.777, P<0.01). 2) Compared with the control group, the peroxiredoxin I expression was significantly downregulated in the experimental group (P<0.05). The content of sperm peroxiredoxin I in the 2 groups was negatively correlated with the seminal ROS level (r=-0.474, P<0.01). 3) The content of peroxiredoxin I had a positive correlation with human sperm motility(r=0.779, P<0.01). The decline of peroxiredoxin I expression may be one of the crucial factors that leads to idiopathic asthenozoospermia. High level of ROS may be one of the main reasons for sperm vitality decline in patients with idiopathic asthenozoospermia.

Temporal modulation of plasma species in atmospheric dielectric barrier discharges

The atmospheric pressure dielectric barrier discharge in helium is a pulsed discharge in nature and the moment of maximum species densities is almost consistent with peak discharge current density. In this paper, a one-dimensional fluid model is used to investigate the temporal structure of plasma species in an atmospheric He-N2 dielectric barrier discharge (DBD). It is demonstrated that there exist microsecond delays of the moments of the maximum electron and ion densities from the peak of discharge current density. These time delays are caused by a competition between the electron impact and Penning ionizations, modulated by the N2 level in the plasma-forming gas. Besides, significant electron wall losses lead to the DBD being more positively charged and, with a distinct temporal separation in the peak electron and cation densities, the plasma is characterized with repetitive bursts of net positive charges. The temporal details of ionic and reactive plasma species may provide a new idea for some biological processes.

Plasma-catalytic degradation of anthraquinonic acid green 25 in solution by gliding arc discharge plasma in the presence of tin containing aluminophosphate molecular sieves

In this paper, the plasmacatalytic removal of an anthraquinonic dye type acid green 25 (AG 25) in aqueous solutions has been investigated in the presence of microporous tin containing aluminophosphates as catalysts under a gliding arc discharge plasma.The catalysts have been synthesised in AEL and AFI structure types by static hydrothermal crystallisation. These materials were characterised by elemental analysis, X-ray diffraction, scanning electron microscopy, N2 adsorption measurements (BET) and Mössbauer spectroscopy. These analyses showed significant catalytic properties of these materials.The degradation process has been monitored during the experimental runs through UV/visible spectroscopy and chemical oxygen demand (COD). The results showed a good synergetic effect between the tin-containing aluminophosphate particles and the highly reactive plasma species. Moreover, it was found that these catalysts can be reused several times.Kinetics of the dye removal has also been investigated on the basis of the Langmuir–Hinshelwood (L–H) model.