Pressure Argon Plasma Jet Research Articles

Evolution from a guided-streamer mode to a continuous-discharge mode in an atmospheric pressure argon plasma jet

Atmospheric pressure plasma jet (APPJ) has attracted much attention due to its versatile applications in various fields, which normally operates in either a guided-streamer mode or a continuous-discharge mode. In this paper, temporal evolution is observed from the guided-streamer mode to the continuous-discharge one in an argon APPJ excited by a sinusoidal voltage. Waveforms of voltage and current indicate that the voltage applied to the electrode is distorted severely from the ideal sine. For the guided-streamer mode, there is only one discharge pulse per half voltage cycle. For the mode transition or the continuous-discharge mode, there is only one discharge composed of a pulse and a hump per half voltage cycle. Fast photography implemented for the mode transition reveals that both the discharges in the positive and the negative voltage polarities evolve from the guided-streamer mode to the continuous-discharge one. In the guided-streamer mode of the mode transition, the discharge behaves as a positive streamer in the positive voltage polarity, while a negative streamer in the negative voltage polarity. In addition, the mode transition only occurs in a range of dissipated power and gap width. Based on optical emission spectroscopy, temporal evolutions of the mode transition are investigated for excited electron temperature, electron density, and field strength. Moreover, their spatial distributions along the argon stream are studied at different time instants. These results are of great importance for the discharge dynamics of APPJ.

A planar plume array emanating from an atmospheric pressure argon plasma jet employing floating electrodes

Large-scale plasma plumes downstream of plasma jets are in urgent need from a practical viewpoint. In this Letter, an argon plasma jet with floating electrodes is proposed to produce a large-scale planar plume array. Results indicate that with increasing peak voltage (Vp), the planar plume array elongates gradually and scales up in the lateral direction to an optimal value of 90.0 mm. There is only one discharge pulse per voltage half cycle, whose intensity and duration increase with increasing Vp. Moreover, there is a time lag between the initiations of individual plumes. Fast photography reveals that the planar plume array originates from the repeated process of some micro-discharge filaments stretching along the argon stream. By optical emission spectroscopy, the spatial distribution of plasma parameters is obtained, such as electron density, electron temperature, and gas temperature. At last, the planar plume array is employed to test the surface modification of polyethylene terephthalate, for which a uniform modification has been realized with a scan velocity of 1.0 cm/min. These results are of great significance for the development of large-scale atmospheric pressure plasma sources.

Physical and chemical diagnostics of cold atmospheric pressure argon plasma jet

AbstractThis article presents an experimental investigation of an argon plasma jet. It examines a commercial argon plasma jet device's physical, chemical, and biological impacts, comparing findings against global standards. The study focuses on electrical features ensuring safety for patients and consumers, finding all leakage current values within established standards. Chemical analysis of emitted gases shows no detectable levels of harmful compounds near treated skin. Optical emission spectroscopy reveals bioactive compounds within the plasma jet. UV radiation emission remains within safety thresholds. Hyperspectral imaging shows temporary increases in skin characteristics posttreatment, reverting to baseline over time. Overall, the study demonstrates the safety and potential of the argon plasma jet in skin treatment.

Dissociation of CO2 by Argon Atmospheric Pressure Plasma Jet

Dissociation of CO₂ by Argon Atmospheric Pressure Plasma Jet

Estimation of total forces of jets on liquid interfaces using image processing methods

Optical imaging is a fundamental method for detecting plasma phenomena, such as plasma bubbles, plasma streamers, and self-organized plasma patterns. Therefore, data mining of images is crucial in plasma diagnostics. This work presents image processing methods for extracting substructures in plasma bubbles, streamers, and patterns. In our experiment, plasma–liquid interfaces between atmospheric pressure argon-plasma jets and NaCl solutions are quantitatively captured. After extracting accurate plasma–liquid interfaces, traditional analytic functions and machine learning approaches are used to fit curves of interfaces. Regression of machine learning method based on Gaussian process reveals many details of interfaces, but neural networks present smooth and accurate regressions. The gravitational and surface tension forces are calculated using experimental plasma–liquid interfaces. The plasma forces are estimated to be several tens of Pa. However, they increased to several hundred Pa around the inflection points of interfaces. This study extends the application of image processing to plasma diagnostics and provides target data of gas–liquid interfaces for numerical simulations.

Atmospheric pressure argon plasma jets I – Measurements of spatial distribution for visible emission spectrum and vacuum ultraviolet

AbstractThis paper describes the observed position dependent emission spectrum and vacuum ultraviolet (VUV) to clarify the optical structure of argon atmospheric pressure plasma jets (APJs). Visible emission spectra of argon, nitrogen, and OH molecules were measured as a function of position from the nozzle of plasma jet generator to gas flow direction. From the results, we realized that a certain electric field is required for producing high energy excited atoms of argon in the jet from the high voltage electrode in the device to the ground positioned at downstream side. Moreover, VUV was detected along the plasma jet through the downstream direction. Thus, we could picture that the light pattern of plasma jet of which intensity weaken depend to the distance from the nozzle is sustained by the above two factors with the present steady state experiments.

Development of a pulse modulated sub-radio frequency power supply for atmospheric pressure plasma devices.

The effect of pulse-modulated sub-RF range (100 kHz-1MHz) excitation on atmospheric pressure argon plasma jet characteristics is studied. For this, a suitable power supply is developed, offering a sub-µs rise time with control of different parameters, such as voltage amplitude, pulse modulation frequency in the range of 1-30kHz, and an oscillation frequency of ∼520kHz, which can affect the plasma behavior. Plasma characteristics, such as reactive species generation, ionic composition, plasma plume length, and gas temperature, are evaluated qualitatively and quantitatively by employing diagnostics such as optical emission spectroscopy, molecular beam mass spectrometry, and optical imaging. Experimental observations indicate that the gas temperature of the plasma jet and plume length increase with the applied voltage for all pulse modulation frequencies, with a maximum value of ∼(325 ± 2K) and a maximum length of ∼(23 ± 3mm), respectively, at 30kHz and 9 kVpp. The emission intensities of OH• and O• lines show an incremental behavior with the applied voltage across all pulse modulation frequencies. The relative yield of different positive (OH+, O+, etc.) and negative (OH-, O-, etc.) ions also increases with the applied voltage for all pulse modulation frequencies with maximum values of ∼(7.6%, 9.9%) and (3.9%, 9.4%), respectively; these are relatively close to RF excited ionic concentrations reported previously. Attaining a high plasma length and species yield signify the features of both kHz and RF atmospheric plasmas. This study offers significant insights and flexibility into exploring the impact of different RF frequency regimes on plasma characteristics.

Analysis of plasma plume parameters in physio-chemical processes of RF plasma jet plume direct in water for the inactivation of Enterococcus bacteria

The contamination of Enterococcus bacterium is widely observed in the living environment and water. The decontamination of drinking water from the bacterial pollution is an important issue in water treatment. Here, the inactivation of Enterococcus bacteria is studied by placing the dielectric barrier discharge structure, with the RF discharge frequency of 13.56 MHz atmospheric pressure argon plasma jet, directly in water, whereas the water around the plasma plume was seething and the bubbles produced stirring all liquid volume. The ability to place a plasma jet nozzle directly in water for 10 min while maintaining a steady and uniform plasma plume, besides water temperature, provides the effectiveness enhancement in the inactivation of bacteria. The absorption of UV radiation in water is effective, and the role of UV radiation of plasma plume was mainly responsible for the destruction of peptidoglycan, which is the outer layer of Enterococcus. Then, the presence of electrons and plasma plume in water leads to the formation of hydroxyl, hydrogen peroxide, and other reactive radicals that are involved in chemical reactions, which lead to the inactivation of micro-organisms. The number of bacteria decreases from the initial value of 16 × 105 MPN/100 ml to less than 1.2 MPN/100 ml. The spectra of the plasma radiation, with the plume length 2 cm within the water, have been analyzed via the first nitrogen negative system N2+B−X. The plume temperature was calculated to be about 64 °C, which has a good agreement with water temperature measured by using a thermometer at about 67 °C after 15 min at maximum 200 W input power of the plasma jet.

Minimally destructive laser-induced breakdown spectroscopy of brass assisted by a low-power atmospheric pressure plasma jet

Minimizing sample damage is crucial in laser-induced breakdown spectroscopy (LIBS) for applications involving valuable samples and elemental mapping. In this study, we introduced a low-power atmospheric pressure plasma jet (APPJ) to reduce sample damage by obtaining LIBS signals at significantly lower laser fluences. The proposed technique, APPJ-assisted LIBS (APPJ-LIBS), utilized an argon APPJ to provide seed electrons and enhance the excitation. The APPJ was generated by a 10 kHz alternating current power supply and made contact with the surface of a brass sample at a 30° angle. An infrared nanosecond Nd:YAG laser was focused onto the contacting zone, allowing the resulting laser-induced plasma to evolve within the surrounding APPJ and produce optical emission. The optimized APPJ-LIBS system reduced the laser fluence threshold for spectral detection of the brass sample by 97 %, from 1.43 J/cm2 to 0.05 J/cm2, which represented the lowest laser fluence threshold reported in LIBS studies on copper-based materials. Micrographs of the sample surface showed no visible damage after the APPJ-LIBS measurement at a near-threshold laser fluence and an APPJ input power as low as 6.0 W. Furthermore, gated images showed the plasma evolution in APPJ-LIBS and confirmed the excitation capability of the APPJ for the laser-ablated materials.

A comprehensive study on the synthesis, characteristics, and catalytic applications of submerged hydrogen-mixed argon plasma-synthesized silver nanoparticles

This research studied the effects of hydrogen addition on the structural, optical, and catalytic properties of silver nanoparticles (AgNPs) synthesized by an atmospheric-pressure argon plasma jets with a submerged nozzle. A 3% hydrogen-mixed argon (H2–Ar) plasma jet rapidly and efficiently produced more AgNPs than a pure argon (Ar) plasma jet. Moreover, a submerged plasma jet enhanced the synthesis of AgNPs compared to an atmospheric-pressure plasma jet with its nozzle above the solution. Electrical conductivity, acidity, and hydrogen emission measurements suggested that the efficient and rapid synthesis of AgNPs was due to an increase in the aqua-electron and atomic-hydrogen concentrations caused by the interaction between the H2–Ar plasma and the silver precursor solution. The H2–Ar plasma jet-synthesized AgNPs exhibited strong catalytic effects for rhodamine-B dye and Saccharomyces cerevisiae cells. The H2–Ar plasma synthesis of AgNPs is rapid, low cost, and environmentally friendly. We hope that this research will promote the broader use of metal nanoparticles.

Cold Physical Plasma-Mediated Fenretinide Prodrug Activation Confers Additive Cytotoxicity in Epithelial Cells.

Cold physical plasma is a partially ionized gas operated at body temperature and utilized for heat-sensitive technical and medical purposes. Physical plasma is a multi-component system consisting of, e.g., reactive species, ions and electrons, electric fields, and UV light. Therefore, cold plasma technology is an interesting tool for introducing biomolecule oxidative modifications. This concept can be extended to anticancer drugs, including prodrugs, which could be activated in situ to enhance local anticancer effects. To this end, we performed a proof-of-concept study on the oxidative prodrug activation of a tailor-made boronic pinacol ester fenretinide treated with the atmospheric pressure argon plasma jet kINPen operated with either argon, argon-hydrogen, or argon-oxygen feed gas. Fenretinide release from the prodrug was triggered via Baeyer-Villiger-type oxidation of the boron-carbon bond based on hydrogen peroxide and peroxynitrite, which were generated by plasma processes and chemical addition using mass spectrometry. Fenretinide activation led to additive cytotoxic effects in three epithelial cell lines in vitro compared to the effects of cold plasma treatment alone regarding metabolic activity reduction and an increase in terminal cell death, suggesting that cold physical plasma-mediated prodrug activation is a new direction for combination cancer treatment studies.

Second grounded electrode non-equilibrium atmospheric pressure argon plasma jet impact on germination of basil (Ocimum basilicum) seeds

In this article, we investigated the impact of a two electrodes argon atmospheric pressure plasma jet with a second grounded electrode (SGE) on the basil (Ocimum basilicum) seeds germination rate. The SGE enhanced the axial electric field in the direction of the treated sample. The plasma operated with two current pulses per each halve a cycle of an applied voltage. The second plasma jet current pulsed increased from 0.7 mA to 3.6 mA and the emission of the O (777.2 nm) increased 3.85 times when the jet operated with the SGE compared to that operated without SGE. The germination rate increased by eight times at 5 min of exposure using the SGE. The SEM images proved a clear etching of the basil (O. basilicum) seed surface by plasma jet with more pronounced etching and cracks by using SGE specially at higher exposure times.

Mitigating the allergenicity of peanut allergen Ara h 1 by cold atmospheric pressure argon plasma jet.

Peanut allergy is recognized as a major food allergy that triggers severe and even fatal symptoms. Avoidance of peanuts in the diet is the main option for current safety management. Processing techniques reducing peanut allergenicity are required to develop other options. Cold plasma is currently considered as a novel non-thermal approach to alter protein structure and has the potential to alleviate immunoreactivity of protein allergen. The application of a cold argon plasma jet to peanut protein extract could reduce the amount of a 64 kDa protein band corresponding to a major peanut allergen Ara h 1 using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but the overall protein size distribution did not change significantly. A decrease in peanut protein solubility was a possible cause that led to the loss of protein content in the soluble fraction. Immunoblotting and enzyme-linked immunosorbent assay elucidated that the immunoreactivity of Ara h 1 was significantly decreased with the time treated with plasma. Ara h 1 antigenicity reduced by 38% after five scans (approximately 3 min) of cold argon plasma jet treatment, and the reduction was up to 66% after approximately 15 min of treatment. The results indicate that cold argon plasma jet treatment could be a suitable platform for alleviating the immunoreactivity of peanut protein. This work demonstrates an efficient, compact, and rapid platform for mitigating the allergenicity of peanuts, and shows great potential for the plasma platform as a non-thermal technique in the food industry. © 2023 Society of Chemical Industry.

Spectral diagnosis of atmospheric pressure AC argon plasma jet at constant power

In the application of atmospheric pressure plasma jet, because the frequency of AC power supply is limited in the kHz range, the research on the influence of power supply electrical parameters on discharge is basically aimed at the variation of plasma jet characteristics with a single driving electrical parameter ( such as voltage and frequency). However, the discharge power usually changes with a single electrical parameter changing, which can undoubtedly affect the discharge performances including the plasma physical parameters and generated reactive species, resulting in the failure to reflect the influence of the single driving parameter on the discharge. In this study, an atmospheric pressure argon plasma jet is driven by a home-made AC power supply with adjustable pulse modulated duty cycle. And combining the diagnosis of the optical emission spectrum and the optical absorption spectrum, the influences of the voltage, frequency and pulse modulated duty cycle parameters on the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, electron density <i>n</i><sub>e</sub>, and OH radical particle number density of the plasma jet are studied under a constant discharge power of 2 W. The results show that at the constant power, the electron density n<sub>e</sub> does not change with the variation of electrical parameters as the linkage change of electrical parameters will offset the influence of a single parameter on the electron density, while the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, and OH radical particle density are most affected by the pulse modulated duty cycle, followed by driving voltage, and the frequency effect is the smallest. Under the constant power, as the frequency decreases, the voltage will increase, and also the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, and OH radical particle number density will increase. On the contrary, although the voltage also increases as the pulse modulated duty cycle decreases, the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, and OH radical particle number density are all reduced. In addition, the results indicate that reducing the duty cycle of AC power can make the atmospheric pressure plasma jet produce more OH radicals at lower gas temperature. This study provides a new insight into the influence of electrical parameters on the characteristics of atmospheric pressure plasma jets under constant power, and also presents a guidance for choosing power parameters of plasma jets with low gas temperature and high density of reactive species, which is conducive to the development of atmospheric pressure plasma jets in biomedicine and other fields.

Improving electrochemical sensitivity of screen‐printed carbon electrodes by atmospheric pressure plasma jet treatment and electrochemical detection of dopamine

AbstractScreen‐printed carbon electrode (SPCE) has various crucial applications as biosensors. The binders used in the ink formulation of the SPCEs reduce the electron transfer from an electrolyte to it. In this study, we used an argon atmospheric pressure plasma jet (APPJ), a cost‐effective device, to modify the SPCE surface. Scanning electron microscopy and X‐ray photoelectron spectroscopy results show binder removal and oxidation of the APPJ‐treated SPCE surface. Due to binder removal and exposure of graphitic surface, the hydrophilicity of the APPJ‐treated SPCE surface enhances significantly. Moreover, oxidation makes the electrode more suitable for dopamine adsorption, resulting in enhanced sensitivity. The detection limit for the APPJ‐treated electrode is 1 μm, as observed in this study. Cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy have been performed on APPJ‐treated and untreated SPCEs.

Combined toxicity of indirubins with cold physical plasma in skin cancer cells in vitro

Cold physical plasma is a partially ionized gas that generates various components identified as potential anticancer compounds. Due to its topical application, cold plasmas are suitable, especially in dermatological applications. We, therefore, tested the cold plasma effects in skin cancer cells in vitro. An atmospheric pressure argon plasma jet was used as the plasma source. The plasma exposure alone reduced the metabolic activity and induced lethal effects in a treatment time-dependent fashion in both cell lines investigated. This was accompanied by executioner caspases 3 and 7, cleavage indicative of apoptosis and reduced cell migration and proliferation. Recent research also indicated roles of novel indirubin derivatives with potent anticancer effects. Three candidates were tested, and reduced metabolic activity and viability in a dose-dependent manner were found. Strikingly, one compound exerted notable synergistic toxicity when combined with plasma in skin cancer cells, which may be promising for future in vivo experiments.

The shift in the laminar‐to‐turbulent transition flow mode in atmospheric pressure plasma jet

AbstractNonthermal equilibrium atmospheric pressure plasma jet gained great interest due to its multidisciplinary applications. This work is focused on studying the characteristics of an argon atmospheric pressure plasma jet and the laminar‐to‐turbulent flow mode transition. By increasing the applied voltage from 10 to 25 kV, the plasma can run in four operational modes depending on the number of current pulses per half a cycle of the applied voltage. The plasma jet gas temperature increases from 310 to 370 K and the laminar‐to‐turbulent transition value shifts toward lower flow rate values from 3.75 to 2.6 slpm as a result of increasing the applied voltage. A clear border between the laminar and the turbulent regions has been resolved at different applied voltages and flow rates at a fixed applied frequency of 24 kHz.

On Plasma Activated Acetyl Donors: Comparing the Antibacterial Efficacy of Tetraacetylethylenediamine and Pentaacetate Glucose

The study compares how acetyl donor molecules tetraacetylethylenediamine (TAED) and pentaacetate glucose (PAG) improve the antibacterial efficacy of solutions activated with a low-temperature atmospheric-pressure argon plasma jet. Plasma activation of solubilised TAED and PAG produce solutions with different chemical compositions and oxidative potentials. Both acetyl donor molecules enhance the hydrogen peroxide (H2O2) concentration in solution with TAED being more effective compared to PAG. However, PAG is more effective at forming peracetic acid (PAA) from reaction of its acetyl donor groups with plasma generated H2O2. The enhanced oxidative potential of plasma activated TAED and PAG solutions were shown to significantly improve bactericidal activity against common wound pathogens Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus compared to plasma activated water produced without acetyl donors. Furthermore, the oxidative capacity of plasma activated PAG was least affected by the bacterial oxidative defence enzyme catalase, attributed to the high concentration of PAA produced in this formulation. Overall, the above data show that acetyl donors may help improve next generation of antimicrobial formulations produced by plasma, which might help combat increasing problems of antimicrobial resistance.

(Invited) On Several Atmospheric Pressure Plasma Sources

In this talk, firstly, several plasma jets developed in our group are presented, including a nobble gas plasma jet for root canal treatment and four air plasma jet devices [1, 2] . Secondly, several interesting physics phenomena of plasma jets are introduced, such as the repeatability of the plasma bullet, the plasma interruption behavior, the plasma transfer dielectric phenomenon, and the appearance of multiple plasma bullet per voltage pulse [2-4] . Thirdly, the state-of-the-art on the measurement of VUV emission of atmospheric pressure air plasma is discussed and our results by using differential pumping system as EUV window are presented [5] . Fourthly , several different configurations of nonequal gap distance DBD are described [6, 7] . Finally, an atmospheric pressure glow discharge in air stabilized by a magnetic field and its application on nitrogen fixation are rep orted. Li, J. Liu, X. Lu, A large atmospheric pressure nonequilibrium open space air plasma based on a rotating electrode,P lasma Sources Sci. Technol. 29, 045015 (2020)Lu*, G. Naidis, M. Laroussi, K. Ostrikov, Guided ionization waves: Theory and experiments. Physics Reports , 540,123-166 (2014)Lu*, and Kostya (Ken) Ostrikov, Guided ionization waves: The physics of repeatability, Appl. Phys, Rev ,5, 031102 (2018)Liu, L. Nie, Y. Xian, X. Lu*, The twisted behavior of a rotating electrode atmospheric-pressure argon plasma jet, J. Phys. D: Appl. Phys. 54, 185201 (2021)F Liu, L Nie, X Lu, J Stephens and K Ostrikov, Atmospheric plasma VUV photon emission, Plasma Sources Sci. Technol. 29, 065001(2020)Li, S. Jin, Y. Xian, L. Nie, D. Liu, X. Lu*, A non-equal gap distance dielectric barrier discharge: between a wedge-shaped and a plane-shaped electrode, Plasma Sources Sci. Technol. 30, 065026 (2021)Jin, Z. Li, Y. Xian, L. Nie, X. Lu*, A non‐equal gap distance dielectric barrier discharge: Between cone‐shape and cylinder‐shape electrodes, High Voltage , 1-9 (2021)

Surface decontamination by atmospheric pressure plasma jet: key biological processes

In this work, surface decontamination of bacteria by argon atmospheric-pressure plasma jet was systematically studied. The chemical modifications and etching characteristics of Gram-positive and Gram-negative bacteria under direct plasma jet exposure were inspected by in-situ Fourier transform infrared spectroscopy. Etching rather than chemical modifications dominates the infrared spectral variations. The etching rate of bacteria is comparable to the cell wall constituents. By using the green fluorescence protein-expressing Escherichia coli, it is found that cellular envelope destruction by plasma etching is the main cause of bacterial inactivation. The tailing phenomenon of the survival curve is more pronounced when the initial bacterial density is higher than ∼1 × 107 CFU cm−2, indicating the limited penetration depth of reactive species into bacterial deposits. Finally, three dominant biological processes key to surface decontamination were put forward according to our results.