Non-equilibrium Pressure Plasma Research Articles

Degradation of isothiazolin‐3‐one’s from an aqueous solution via a multi‐pin nonthermal atmospheric pressure plasma and its toxicity analysis

Degradation of residuals of chemical compounds after use has attracted the attention of environmental scientists. In this work, the degradation of such a toxic biocide compound of isothiazolin-3-one from an aqueous solution using a novel multi-pin thermally nonequilibrium atmospheric pressure plasma reactor is reported. This investigation examined the impacts of different operating conditions on the decomposition of isothiazolin-3-one. Subsequently, the reactive excited plasma species formed and participated during the degradation processes were examined by optical emission spectrometer (OES), chemical dosimetry using terephthalic acid (TA), and spectroscopic determination involving potassium titanium (IV) oxalate. The efficiency of degradation of the plasma-treated isothiazolin-3-one from an aqueous solution was examined by UV–Vis spectrometry. The mineralization of isothiazolin-3-one was further examined by high-performance liquid chromatography (HPLC), determining conductivity, total organic carbon (TOC), and pH of the isothiazolin-3-one aqueous solution. Finally, nontoxicity of the plasma-treated isothiazolin-3-one solution was investigated by seed sprouting and germination tests using Vigna radiata L. Wildzek (Mung bean). The experimental results exhibit that a higher degradation percentage of 96.01% was attained for the isothiazolin-3-one treated at a longer treatment time and higher potential of 25 min and 31 kV, respectively. This may be attributed to the formation of various reactive oxygen and nitrogen species (RONS) as confirmed by OES and other spectroscopic analyses. The value of pH and TOC is found to be decreased, whereas the value of electrical conductivity of the isothiazolin-3-one aqueous solution is increased linearly with an increase in treatment time and applied voltage. This indicates the degradation of isothiazolin-3-one molecules and the formation of various ionic species in the solution. The toxicity investigation reveals that the plasma-treated isothiazolin-3-one aqueous solution is nontoxic in nature and useful for sprouting and germination of the Mung bean seeds compared with the untreated one. Overall, it can be concluded that the plasma-assisted process is ideally needed in various food, pharmaceutical, and textile industries as a highly efficient treatment of wastewater. Novelty impact statement The prime novelty of this manuscript is the degradation of isothiazolin-3-one from an aqueous solution using TNEAP plasma and exhaustively examined using various analytical techniques. Finally, the nontoxicity of the plasma-treated solution was also investigated.

Cleaning Methods of Ancient Chinese Murals Based on Atmospheric Pressure Non-Equilibrium Plasma and the Microscopic Investigation of the Dissociation Mechanism on Soot

Cleaning Methods of Ancient Chinese Murals Based on Atmospheric Pressure Non-Equilibrium Plasma and the Microscopic Investigation of the Dissociation Mechanism on Soot

Investigation of the relative reactivity of aromatic compounds in air under the action of pulsed discharge plasma

Based on the method of competing reactions, a method for determining the relative reactivity of aromatic vapors in relation to the plasma components of a pulsed corona discharge is developed. The parameters of the relative reactivity of aromatic compounds in the air and nitrogen stream were obtained using model mixtures based on benzene, toluene, and xylene with a content of 250-500 ppm. The effect of water vapor on the process is shown. The obtained data will be useful for optimizing the processes of plasma-chemical air purification from the vapors of toxic aromatic compounds. Keywords: Corona discharge, aromatic compounds, non-equilibrium atmospheric pressure plasma, air purification, volatile organic compounds, BTEX.

Influence of Ti3C2T x (MXene) on the generation of dielectric barrier discharge in air

The formation of homogeneous dielectric barrier discharge (DBD) in air is a key scientific problem and core technical problem to be solved for the application of plasmas. Here, we report the effect of two-dimensional (2D) nanomaterial Ti3C2T x (T x = –F, –O and/or –OH) on regulating the electrical discharge characteristics. The field emission and weak bound state property of Ti3C2T x can effectively increase the seed electrons and contribute to the generation of atmospheric pressure homogeneous air DBD. The electron avalanche development for the uneven electrode structure is calculated, and the discharge mode transition is modeled. The comparative analyses of discharge phenomena validate the regulation of Ti3C2T x on the discharge characteristics of DBD. The light emission capture and the voltage and current waveforms verify that the transition of Townsend discharge to streamer discharge is effectively inhibited. The optical emission spectra are used to characterize the plasma and confirm that it is in a non-equilibrium state and the gas temperature is at room temperature. This is the first exploration of Ti3C2T x on the regulation of electrical discharge characteristics as far as we know. This work proves the feasibility of Ti3C2T x as a source of seed electrons to form homogeneous DBD, establishing a preliminary foundation for promoting the application of atmospheric pressure non-equilibrium plasma.

Optimal Power of Atmospheric Pressure Plasma Jet with a Simple DBD Configuration for Biological Application

The new strategy, non-thermal atmospheric pressure plasma (N-APP), as a ’physical’ method, could offer a simple, fast, effective, and economic way of disinfection of equipment, surfaces, a method that is unlikely to cause micro-organisms resistance, or allergic, and toxic reactions. Recently, cold physical plasma had been extensively studied by researchers as a possible therapy in dentistry and oncology, as well as the application of non-thermal plasma in biomedical researches such as wound healing. In clinical dermatology, cold plasmas are mainly used for the treatment of chronic wounds and pathogen-based skin diseases, in which stimulation of tissue repair and decontamination. In this research, the characterization of home-made Helium Non-Equilibrium atmospheric pressure plasma jet (He -NAPPJ), that had been generated using a dielectric barrier discharge (DBD) configuration for exceptional standardization protocol of this plasma source that meets medical requirements. The device equipped with two powered electrodes as well as a grounded electrode, driven by an (8 kVp-p) voltage, the frequency (12 kHz), and the distance between the nozzle of the plasma jet and the target were used as constant data. As a working gas, the Helium gas (He) was used in different flow rates (2, 4, 6, and 8) slm. The optical emission spectroscopy was used to measure the plasma parameters, of which the electronic excitation temperature and density of electrons were determined by the Boltzmann’s plot method and Stark broadening effect equation respectively. The result of the emission line spectrum showed the presence of nitrogen and oxygen between lines 300 nm until 700 nm. Nitrogen and oxygen are involved in the oxidation process which is known as Reactive Nitrogen species and reactive oxygen species. These species are the main key in bacteria inactivation and the wound healing process. Furthermore, the results had revealed, the optimal condition using the flow rate (6 slm) with 32 °C He gas temperature that had been stabilized for 20 min, plume length 40 mm, The distance is 15 mm from the distal end of the Pyrex tube (DBD) and the wound surface, the power density 44 mWatt/cm2, and plasma radiation energy dose: 76 J/cm2. These results were considered in this study as a safe operating condition for biomedical applications.

Brain cell proliferation in adult rats after irradiation with nonequilibrium atmospheric pressure plasma

Nonequilibrium atmospheric pressure plasma (NEAPP) has the potential for a wide range of medical applications, including wound healing, blood coagulation, and malignant cell apoptosis. However, its effect on the mammalian central nervous system remains unclear. We studied histological changes in the cerebral cortex of adult rats, following irradiation of the brain surface with NEAPP. NEAPP irradiation made three laminar tissue structures and induced high proliferation of brain-resident immature cells as well as bone marrow-derived cells. These observations indicate that NEAPP irradiation induced rearrangement of cellular and tissue organization, including cell proliferation in the central nervous system in vivo.

Atmospheric-Pressure Plasma Jet-Induced Ultrafast Construction of an Ultrathin Nonstoichiometric Nickel Oxide Layer with Mixed Ni3+/Ni2+ Ions and Rich Oxygen Defects as an Efficient Electrocatalyst for Oxygen Evolution Reaction

An approach, i.e., atmospheric-pressure nonequilibrium oxygen plasma jet technology, has been reported for the first time to in situ prepare ultrathin nonstoichiometric nickel oxide layers with mix...

Hydrogen peroxide in lactate solutions irradiated by non-equilibrium atmospheric pressure plasma

A mechanism of hydrogen peroxide (H2O2) generation in plasma-activated lactated Ringer’s solution (PAL) has been analyzed. PAL was produced by irradiating a sodium lactate solution, a class of hydroxy acid, with non-equilibrium atmospheric pressure plasma (NEAPP). The concentration of H2O2 generation was dependent on the initial lactate concentrations, which ranged from 0–28 mM. However, the generation of H2O2 was inhibited by higher lactate concentration. The formation of H2O2 is proposed by catalyzed lactate and radicals in aqueous solution, such as ⋅OH, ⋅H and ⋅OO, during the plasma treatments.

Studying of Plasma- Polymerized Pyrrole at Variable Gas Flow Rates Via Plasma Jet

In this manuscript has investigated the synthesis of plasma-polymerized pyrrole (C4H5N) nano-particles prepared by the proposed atmospheric pressure nonequilibrium plasma jet through the parametric studies, particularly gas flow rate (0.5, 1 and 1.5 L/min). The plasma jet which used operates with alternating voltage 7.5kv and frequency 28kHz. The plasma-flow characteristics were investigated based on optical emission spectroscopy (OES). UV-Vis spectroscopy was used to characterize the oxidization state for polypyrrole. The major absorption appears around 464.1, 449.7 and 435.3 nm at the three flow rate of argon gas. The chemical composition and structural properties of the contained samples which synthesized at 0.5 L/min as a argon flow rate were analyzed by scanning electron microscopy (SEM), Fourier transformation infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD). SEM point to a uniform distribution of polypyrrole (PPY) nanoparticles matrix. XRD technique showed a semicrystalline pattern for PPY)thin film. It is expected, that the high-quality plasma polymer grown by atmospheric pressure plasma jet method contributes to serving as conducting materials.

Measurement of electron temperature and density of atmospheric-pressure non-equilibrium argon plasma examined with optical emission spectroscopy

The electron temperature T e and density N e of atmospheric-pressure non-equilibrium dielectric barrier discharge argon (Ar) plasma are measured with optical emission spectroscopy. Continuum emission due to bremsstrahlung is applied to the analysis of the electron temperature and density with the spectrometric system in the visible wavelength range calibrated absolutely. The assumption of the Maxwellian electron energy distribution function (EEDF) results in T e ≃ 0.29 eV and N e ≃ 1.1 × 1016 cm−3, whereas the Druyvesteyn EEDF leads to the result T e ≃ 0.79 eV and N e ≃ 1.4 × 1014 cm−3. To confirm the validity of these values, several line intensities of the excited states of the Ar atom are observed experimentally and compared with the theoretical population densities calculated by the Ar collisional–radiative (CR) model that includes atomic collisional processes. It is confirmed that the order of the observed excited-state number densities agrees well with that calculated numerically by the CR model with the Druyvesteyn EEDF, while the Maxwellian EEDF gives poor results.

Discharge characteristics of argon brush plasma plume operated at atmospheric pressure

Atmospheric pressure non-equilibrium low-temperature plasma has been widely used in biomedicine, surface treatment and other fields, which has attracted the attention of researchers extensively. As one of the important methods to generate such a plasma, the plasma jet has become a popular method, which can generate a remote plasma plume at the nozzle through introducing a rare gas flow. However, plasma plume has a small diameter, which results in deficiency for the large-scale surface treatment. A dielectric barrier discharge device with three electrodes is utilized to produce a large brush-shaped plasma plume (50.0 mm × 40.0 mm) downstream of flowing argon under the combined excitation of an alternate current (AC) voltage and a negative bias voltage, thereby increasing the plume scale. The results show that the luminescence intensity of the plasma plume increases with AC peak voltage increasing. By fast photography implemented with an intensified charge coupled device (ICCD), it is found that the plasma plume is composed of temporally superposed branched-streamers. The ICCD images also reveal that the number of branches increases with AC peak voltage increasing. Moreover, the waveforms of AC voltage and light emission signal recorded simultaneously indicate that the plasma plume initiates once per AC voltage cycle, which occurs in the positive half cycle of the applied voltage. With AC peak voltage increasing, the duration and intensity of discharge pulse increase, which results from more branches of the branched streamer. Besides, optical emission spectrum in a range from 300 nm to 850 nm mainly includes OH (A<sup>2</sup>Σ<sup>+</sup>–X<sup>2</sup>Π) peaked at 308.0 nm, the second positive system of N<sub>2</sub> (C<sup>3</sup>Π<sub>u</sub>–B<sup>3</sup>Π<sub>g</sub>), Ar I (4p–4s), and O I (3p<sup>3</sup> P–3s<sup>3</sup> S) at 844.6 nm. Based on the optical emission spectrum, the plasma parameters such as vibrational temperature and intensity ratio of spectral lines (correlated with electron density and electron temperature) are investigated. Besides, the variation of concentration of oxygen atoms in the plasma plume with experimental parameters is investigated by optical actinometry. The results indicate that the concentration of oxygen atoms first increases and then decreases with the distance increasing along the argon flow direction or with oxygen content of the working gas increasing. In addition, the concentration of oxygen atoms increases with AC peak voltage increasing. All these results are discussed qualitatively. These results are of great importance in modifying the plasma surface on a large scale.

Formation and behaviour of plasma spots on the surface of titanium film

Numerous studies have shown that dielectric barrier discharge (DBD) and DBD-like plasma jets interact with a treated surface in a complex manner. Eroded traces after treatment cannot be explained by conventional plasma-surface interaction theory. The mechanisms of a controlled formation of these plasma objects is still unclear. In this work, the authors show that the formation rate and characteristics of eroded traces, treating a titanium surface, can be controlled by process design and the combination of materials used. A thin (0.45 µm) layer of titanium film is deposited onto a glass substrate and is then treated in the effluent of a non-equilibrium atmospheric pressure plasma jet (N-APPJ) operated with argon or krypton flow. Plasma spots with diameters ranging from 100–700 µm are observed using an intensified digital camera on the titanium film surface. These plasma objects are strongly inhomogeneous, forming a core with a very high current density and leave erosion holes with diameters of about 1 µm. By using krypton as a working gas, effective erosion of the titanium substrate can be shown, whereas by using argon no traces are detected. For the latter case, traces can be provoked by deposition of a thin aluminum layer on top of the titanium substrate, by creation of artificial scratches or by an additional swirling flow around the discharge. Based on the experimental results presented in this and previous papers, it is assumed that plasma spots with dense cores are produced by an interaction of micro-vortices within the plasma channel and by the formation of an extremely high axial magnetic field. This assumption is confirmed by destruction of the treated surface material, extraction of paramagnetic atoms and toroidal substrate heating, which is most likely caused by a helical current of the plasma spot.

Genotypic and Phenotypic Changes in Candida albicans as a Result of Cold Plasma Treatment.

We treated Candida albicans cells with a sublethal dose of nonequilibrium (cold) atmospheric-pressure He plasma and studied alterations in the genome of this fungus as well as changes in the phenotypic traits, such as assimilation of carbon from carbohydrates, hydrolytic enzyme activity, and drug susceptibility. There is a general problem if we use cold plasma to kill microorganism cells and some of them survive the process—whether the genotypic and phenotypic features of the cells are significantly altered in this case, and, if so, whether these changes are environmentally hazardous. Our molecular genetic studies have identified six single nucleotide variants, six insertions, and five deletions, which are most likely significant changes after plasma treatment. It was also found that out of 19 tested hydrolytic enzymes, 10 revealed activity, of which nine temporarily decreased their activity and one (naphthol-AS-BI- phosphohydrolase) permanently increased activity as a result of the plasma treatment. In turn, carbon assimilation and drug susceptibility were not affected by plasma. Based on the performed studies, it can be concluded that the observed changes in C. albicans cells that survived the plasma action are not of significant importance to the environment, especially for the drug resistance and pathogenicity of this fungus.

Steering of surface discharges on through-glass-vias combined with high-density nonequilibrium atmospheric pressure plasma generation

The concept of using a glass substrate with fine through-holes filled with metal, called through-glass-vias (TGVs), for an inner wall of an enclosure of a nonequilibrium atmospheric pressure plasma source was validated to extend its processing area with high plasma densities maintained. When applying the TGV substrate into an inner wall of the plasma source, the generated discharge was less likely to drift along with the gas flow, which resembled the behavior of locally high electric fields of the plasma source, called the creeping mode. The decrease in breakdown voltage was also observed. These phenomena are caused by the TGV areas acting as a steering control material in the enclosure of the plasma source. The location of the TGV areas affected the behavior of the generated plasma. The shape of the plasma was accomplished to arbitrarily and locally control by the placement of TGVs.

Atmospheric pressure plasma treatment of polyurethane foams with He–O2 fed dielectric barrier discharges

The atmospheric pressure non-equilibrium plasma treatment of open-cell polyurethane foams is carried out using dielectric barrier discharges fed with helium and oxygen mixtures. During plasma processes, the discharge is ignited both outside the foam and within its porous structure to achieve the three-dimensional surface modification of the entire substrate. X-ray photoelectron spectroscopy results reveal the uniform functionalization of both the exterior and interior surfaces of the porous material with oxygen-containing groups. In addition, nuclear magnetic resonance spectroscopy analyses confirm that surface chemical modification occurs with preservation of the foam polymeric skeleton. Scanning electron microscopy observations and water contact angle measurements show that the plasma-treated foams exhibit increased surface roughness and wettability, respectively. It is also observed that aging of the plasma-treated foams is more pronounced in water than in air, due to the inevitable dissolution of oxidized polymer fragments formed during plasma exposure. Finally, it is found that a simple post-processing step improves the capability of the plasma-treated foams to remove heavy metal ions from water, as demonstrated through Cd2+ adsorption experiments.

TRPA1 and TRPV1 channels participate in atmospheric-pressure plasma-induced [Ca2+]i response

Despite successful clinical application of non-equilibrium atmospheric pressure plasma (APP), the details of the molecular mechanisms underlying APP-inducible biological responses remain ill-defined. We previously reported that exposure of 3T3L1 cells to APP-irradiated buffer raised the cytoplasmic free Ca2+ ([Ca2+]i) concentration by eliciting Ca2+ influx in a manner sensitive to transient receptor potential (TRP) channel inhibitors. However, the precise identity of the APP-responsive channel molecule(s) remains unclear. In the present study, we aimed to clarify channel molecule(s) responsible for indirect APP-responsive [Ca2+]i rises. siRNA-mediated silencing experiments revealed that TRPA1 and TRPV1 serve as the major APP-responsive Ca2+ channels in 3T3L1 cells. Conversely, ectopic expression of either TRPA1 or TRPV1 in APP-unresponsive C2C12 cells actually triggered [Ca2+]i elevation in response to indirect APP exposure. Desensitization experiments using 3T3L1 cells revealed APP responsiveness to be markedly suppressed after pretreatment with allyl isothiocyanate or capsaicin, TRPA1 and TRPV1 agonists, respectively. APP exposure also desensitized the cells to these chemical agonists, indicating the existence of a bi-directional heterologous desensitization property of APP-responsive [Ca2+]i transients mediated through these TRP channels. Mutational analyses of key cysteine residues in TRPA1 (Cys421, Cys621, Cys641, and Cys665) and in TRPV1 (Cys258, Cys363, and Cys742) have suggested that multiple reactive oxygen and nitrogen species are intricately involved in activation of the channels via a broad range of modifications involving these cysteine residues. Taken together, these observations allow us to conclude that both TRPA1 and TRPV1 channels play a pivotal role in evoking indirect APP-dependent [Ca2+]i responses.

Atmospheric plasma VUV photon emission

Owing to its distinctive photon energy range, vacuum ultraviolet (VUV) emission plays a key role in diverse photo-induced natural and technological processes. Atmospheric-pressure plasma produced VUV is central to resolve long-held issues in dynamics of natural (e.g., lightning) and laboratory (e.g., streamer) plasmas. Challenging the seemingly unavoidable vacuum systems used to prevent VUV emission quenching by ambient gases, here we report the first observation of vacuum-free generation of stable sub-110 nm VUV emission from atmospheric-pressure plasmas jetted into open air and atmospheric air plasma. Emission from atomic helium at 58.4 nm is observed from a nonequilibrium atmospheric pressure plasma jet (N-APPJ), jetted directly into ambient air. In a similar experiment, we also report VUV emission from excited nitrogen species in an atmospheric pressure discharge in ambient air. The photon emissions detected expand the window of photo-induced processes beyond ∼10 eV commonly achievable by existing non-excimer VUV plasma sources, and enables direct photo-excitation and ionization of molecular species such as CO2 and many others. The thus-enabled direct photoionization of O2, O, and N species further justifies the role of direct photoionization in the dynamics of natural and laboratory atmospheric-pressure plasmas and informs the development of the relevant plasma photoionization models, which currently largely sidestep the sub-110 nm domain. These findings can make contribution to the complement of photoionization model of lightning, streamer, and other plasmas, open new avenues to quantify the yet elusive role of photoionization in the plasma dynamics.

Continuous release of O2−/ONOO− in plasma‐exposed HEPES‐buffered saline promotes TRP channel‐mediated uptake of a large cation

AbstractAlthough the externally controllable extracellular supply of the short‐lived reactive oxygen and nitrogen species, such as O2•−, •NO, and ONOO−, could potentially manipulate cellular functions, their simple administration to cells is likely to be ineffective due to their rapid deactivation. In this study, we found a method of a continuous supply of O2•−/ONOO− over a few minutes, which is triggered by irradiation of a nonequilibrium atmospheric pressure plasma to commonly used organic buffers (e.g., 4‐(2‐hydroxyethyl)‐1‐piperazineethanesulfonic acid, HEPES). In addition, a continuous low‐dose O2•−/ONOO− supply was shown to induce a physiologically relevant Ca2+ response and subsequently the uptake of a large cation mediated by transient receptor potential channel family member(s). Our results provide a novel approach to the continuous O2•−/ONOO− supply, requiring controllable and mass‐volume treatments.

Effects of nonequilibrium atmospheric-pressure O2 plasma-assisted annealing on anatase TiO2 nanoparticles

Anatase TiO2 nanoparticles (NPs) immobilized on glass substrates were annealed with the assistance of nonequilibrium atmospheric-pressure O2 plasma. The plasma-assisted annealing greatly enhanced the photodecomposition and photobactericidal activity as compared with electric-furnace annealing. The plasma-assisted annealing reduced the TiO2 NP agglomerate size and increased the optical absorption, the photoinduced electrical conductivity, the amounts of bridging and terminal oxygen groups, and the (1 1 2)/(1 0 1) plane intensity ratio, causing the lattice oxygen deficiency that formed partially Ti-rich surface portions. The enhanced photobactericidal activity would arise from the bridging and terminal oxygen groups. The enhanced photodecomposition would arise from the increased concentration of photogenerated carriers due to the following three factors. The first is the optical absorption increased by the agglomerate size reduction and the (1 1 2) plane growth or appearance, which exert scattering more incident photons. The second is the charge separation of photogenerated carriers facilitated by the bridging and terminal oxygen groups, which originate from oxygen vacancies via oxygen ion impact from the plasma. The third is the charge transfer of plasmon-excited electrons from the partially Ti-rich portions to TiO2. The enhanced photodecomposition would also arise from more reactive oxygen species generated from the bridging and terminal oxygen groups by the photogenerated carriers.

Direct Exposure of Dry Enzymes to Atmospheric Pressure Non-Equilibrium Plasmas: The Case of Tyrosinase.

The direct interaction of atmospheric pressure non-equilibrium plasmas with tyrosinase (Tyr) was investigated under typical conditions used in surface processing. Specifically, Tyr dry deposits were exposed to dielectric barrier discharges (DBDs) fed with helium, helium/oxygen, and helium/ethylene mixtures, and effects on enzyme functionality were evaluated. First of all, results show that DBDs have a measurable impact on Tyr only when experiments were carried out using very low enzyme amounts. An appreciable decrease in Tyr activity was observed upon exposure to oxygen-containing DBD. Nevertheless, the combined use of X-ray photoelectron spectroscopy and white-light vertical scanning interferometry revealed that, in this reactive environment, Tyr deposits displayed remarkable etching resistance, reasonably conferred by plasma-induced changes in their surface chemical composition as well as by their coffee-ring structure. Ethylene-containing DBDs were used to coat tyrosinase with a hydrocarbon polymer film, in order to obtain its immobilization. In particular, it was found that Tyr activity can be fully retained by properly adjusting thin film deposition conditions. All these findings enlighten a high stability of dry enzymes in various plasma environments and open new opportunities for the use of atmospheric pressure non-equilibrium plasmas in enzyme immobilization strategies.