Plasma Species Research Articles

ThunderBoltz: an open-source direct simulation Monte Carlo Boltzmann solver for plasma transport, chemical kinetics, and 0D modeling

Abstract Plasma-neutral interactions, including reactive kinetics, are often either studied in 0D using ODE-based descriptions, or in multi-dimensional fluid or particle-based plasma codes. The latter case involves a complex assembly of procedures that are not always necessary to test effects of underlying physical models and mechanisms for particle-based descriptions. Here we present ThunderBoltz, a lightweight, publicly available 0D direct simulation Monte Carlo code designed to accommodate a generalized combination of species and arbitrary cross sections without the overhead of expensive field solves. It can produce electron, ion, and neutral velocity distributions in applied AC/DC E-field and/or static B-field scenarios. The code is built in the C++ standard library and includes a convenient Python interface that allows for input file generation (including compatibility with cross section data from the LXCat database), electron transport and reaction rate constant post-processing, input parameter constraint satisfaction, calculation scheduling, and diagnostic plotting. These codes can be accessed at the repository: https://github.com/lanl/ThunderBoltz. In this work we compare ThunderBoltz transport calculations against Bolsig+ calculations, benchmark test problems, and swarm experiment data, finding good agreement with all three in the appropriate field regimes. In addition, we present example use cases where the electron, ion, and background neutral particle species are self-consistently evolved to model the background kinetics, a feature that is absent in fixed-background Monte Carlo and n-term Boltzmann solvers. The latter functionality allows for the possibility of particle-based chemical kinetics simulations of the plasma and neutral species as a new alternative to ODE-based approaches.

Effect of cold plasma treatment on physicochemical and functional properties of gelatin extracted from buffalo bone

The present investigation was carried out to evaluate the impact of cold plasma at various power levels (170, 200, and 230V) and for different times (5, 10, and 15 min) on gelatin extracted from buffalo bone to ascertain the difference in physicochemical and functional parameters of untreated and cold plasma treated gelatin. An increase in porosity and angle of repose, and decrease in flow characteristics were observed. The etching phenomenon of cold plasma enhanced surface area, and hence increased viscosity. An increase in the elastic behaviour of gelatin was detected from G' (Storage Modulus) and G" (Loss Modulus). The relative crystallinity dropped to 39.45% in the control sample and 36.9% in the treated samples on XRD as an effect of active plasma species. FTIR revealed minor differences in peak intensity, without a new chemical group. Gelatin's microstructure and surface topography were revealed via SEM investigation. The DSC analysis demonstrated an increase in glass transition (Tg) temperature of gelatin molecules due to alteration in chain dynamics and intermolecular interactions. Moreover, gelatin films prepared from cold plasma treated gelatin showed significant improvement in their tensile strength and mechanical properties suitable for development of packaging films.

XPS study of the nitridation of hafnia on silicon

We report a comprehensive quantitative ARXPS study of 20-cycle ALD-grown HfO2 films on Si (001) substrates with and without remote plasma nitridation. The films comprised a 0.6 nm HfO2 layer atop a 1 nm hafnium-rich silicate interlayer. A detailed analysis of the Hf 4f, Si 2p, O 1s, C 1s, and N 1s core level spectra is presented for samples with and without nitridation. The fitting of the Hf 4f spectra reveals four contributing components associated with silicate, hafnia, and their respective nitrided species. The Hf 4f, O 1s, and C 1s spectra exhibit a negative binding energy shift of about 0.2 eV upon nitridation induced by a Si2+-N dipole formed at the interface. Quantitative ARXPS analysis, employing the MultiLayer Model, enabled the determination of the thicknesses, and composition together with their associated uncertainties. The analysis showed that the composition of the nitrided hafnia is HfO1.66N0.33. There is a higher degree of nitridation in the silicate interlayer compared to the overlying hafnia layer. The degree of nitridation is found to increase with plasma power; N2+ is identified as the primary plasma species responsible for the nitridation of hafnia.

Exploring the suppression methods of helium-induced damage in tungsten by investigating the interaction between beryllium and helium

Abstract Helium (He)-induced damage is a sensitive concern for the performance of tungsten plasma facing materials (W-PFMs). Recent experiments have revealed that trace impurities in He plasma can effectively prevent the formation of He bubbles and fuzz on W surfaces. To explore its plausibility and underlying mechanism, we performed a multiscale computational study that combines density functional theory calculations and object kinetic Monte Carlo simulations to investigate the effects of a small quantity of beryllium (Be) on the evolution of He bubbles. It is found that there is a strong attractive interaction between He and Be, which can be attributed to the decrease in electron density and the lattice distortion induced by embedded Be atoms. Therefore, the co-implantation of Be continuously introduces trapping centers for He. Due to the low implantation depth and high migration energy of Be, the Be atoms are located close to the surface, leading to the trapping of the majority of He within the near-surface region and the development of a shielding layer for He permeation. The presence of Be facilitates the dispersion of the trapped He, skewing the He clusters into smaller sizes. More importantly, the Be trapping centers bring the He clusters closer to the surface, significantly increasing the probability of bubble bursting and the release of He back to the vacuum. This ultimately leads to a lower retention of He in the case of He + Be co-irradiation, compared with the case of He-only irradiation. Consequently, our findings elucidate the suppressive effect of a low flux of Be atoms on the growth of He bubbles, highlighting the need to focus on synergetic effects between plasma species.

Numerical Simulation of Corona Discharge Plasma Affecting the Surface Behavior of Polymer Insulators

Corona discharge is a significant problem in the operation of high-voltage transmission and distribution systems, particularly for polymer insulators. Numerical simulation has become an effective tool for investigating the underlying physical mechanisms and optimizing the design of insulators. In this paper, we present a two-dimensional numerical simulation study on corona discharge plasma affecting the surface behavior of polymer insulators. The simulation was performed with the Comsol Multiphysic software and is based on the finite element method and the fluid plasma model, which considers ionization, recombination, and the transport of plasma species. The numerical results are analyzed to study the spatial and temporal characteristics of the corona discharge and its effect on the surface behavior of polymer insulators. The results show that the electric field is affected not only by the volume charge density but also by the surface charge density, which in turn depends on the densities of the charge carriers migrating on the insulator surface. However, the electric field drops drastically when one or two grading rings are installed. But one grading ring is not enough to limit the discharge.

Application of Diagnostic Stewardship to Fungal Polymerase Chain Reaction: Low Yield of Follow-up Testing on Plasma and Bronchoalveolar Lavage After a Negative Result.

Early diagnosis of invasive fungal disease is essential for optimizing management. Although the clinical utility of fungal polymerase chain reaction (PCR) testing on plasma and bronchoalveolar lavage (BAL) has been established, the role of follow-up testing remains unclear. This was a retrospective single-center study. The yield of follow-up PCR for Aspergillus species, Mucorales agents, Fusarium species, Scedosporium species, dimorphic fungi, Pneumocystis jirovecii, and Candida species on plasma and/or BAL was measured at intervals of 1, 2, 3, and 4 weeks following a negative result. A total of 1389 follow-up tests on 406 plasma specimens from 264 patients and 983 BAL specimens from 431 patients were evaluated. Overall, the positivity rate at 1, 2, 3, and 4 weeks was 2.7% (4/148), 3.3% (4/123), 5.1% (4/78), and 3.5% (2/57), respectively, on plasma, and 0% (0/333), 0.3% (1/288), 0.4% (1/228), and 0.7% (1/134), respectively, on BAL. Conversions occurred with Aspergillus species, Mucorales agents, and Fusarium species PCR on plasma and Aspergillus species and P jirovecii PCR on BAL. All patients who converted were immunocompromised. Within 1 week of a prior negative test, 2 Aspergillus and 2 Mucorales PCRs were positive on plasma, and zero tests were positive on BAL. In week 1, only 1 Aspergillus species that was positive on day 7 was classified as probable fungal disease. Fungal PCR follow-up testing on plasma and BAL within 4 weeks of a prior negative result was of low yield and rarely generated a positive result considered clinically significant in the first week.

Investigating the Effects of Gliding Arc Plasma Discharge’s Thermal Characteristic and Reactive Chemistry on Aqueous PFOS Mineralization

Per-and Polyfluoroalkyl substances (PFASs) are recalcitrant organofluorine contaminants, which demand urgent attention due to their bioaccumulation potential and associated health risks. While numerous current treatments technologies, including certain plasma-based treatments, can degrade PFASs, their complete destruction or mineralization is seldom achieved. Extensive aqueous PFAS mineralization capability coupled with industrial-level scaling potential makes gliding arc plasma (GAP) discharges an interesting and promising technology in PFAS mitigation. In this study, the effects of GAP discharge’s thermal and reactive properties on aqueous perfluorooctanesulfonic acid (PFOS) mineralization were investigated. Treatments were conducted with air and nitrogen GAP discharges at different plasma gas temperatures to investigate the effects of plasma thermal environment on PFOS mineralization; the results show that treatments with increased plasma gas temperatures lead to increased PFOS mineralization, and discharges in air were able to mineralize PFOS at relatively lower plasma gas temperatures compared to discharges in nitrogen. Studies were conducted to identify if GAP-based PFOS mineralization is a pure thermal process or if plasma reactive chemistry also affects PFOS mineralization. This was done by comparing the effects of thermal environments with and without plasma species (air discharge and air heated to plasma gas temperatures) on PFOS mineralization; the results show that while GAP discharge was able to mineralize PFOS, equivalent temperature air without plasma did not lead to PFOS mineralization. Finally, mineralization during treatments with GAP discharges in argon and air at similar gas temperatures were compared to investigate the role of plasma species in PFOS mineralization. The results demonstrate that treatments with argon (monoatomic gas with higher ionization) lead to increased PFOS mineralization compared to treatments with air (molecular gas with lower ionization), showing the participation of reactive species in PFOS mineralization.

Unraveling NO Production in N2-O2 Plasmas with 0D Kinetic Modeling and Experimental Validation.

This work presents a detailed investigation aimed at understanding the key mechanisms governing nitric oxide (NO) production in N2-O2 discharges by systematically comparing experimental results to modeling data. The experimental phase capitalizes on radiofrequency (13.56 MHz) discharges, sustained at 5 mbar pressure conditions, featuring varying concentrations of oxygen, ranging from pure N2 plasma to air-like mixtures. On the modeling front, we adopt an integrated approach that combines the solution of the Boltzmann equation for electrons with a system of rate balance equations for heavy species. To account for ground state NO(X) generation at the reactor wall, we combine the volume chemistry with a mesoscopic description of the surface, taking into account adsorption sites and various elementary surface phenomena. Comparisons between experiments and modeling demonstrate very good agreement, extending beyond NO(X) formation to encompass other species in the plasma such as N2O(X) and atomic nitrogen N(4S). Noteworthy findings include (i) the pivotal role of surface mechanisms in NO(X) production, particularly at low oxygen content values; (ii) the significance of accurately describing the postdischarge phase, where depletion of plasma species occurs at different time scales (millisecond range); and (iii) the importance of vibrationally and electronically excited states (e.g., O2(b)) in elucidating NO(X) formation dynamics, crucial for unraveling reaction pathways and energy transfer processes. This work makes an important step toward formulating a comprehensive reaction mechanism for N2 and N2-O2 plasmas applied to nitrogen fixation, covering both volume and surface mechanisms, and lays a robust foundation for future research on plasma-based NO(X) production, particularly in the presence of catalysts.

Etch characteristics of cobalt thin films using high density plasma of CH3COCH3/Ar gas mixture

Co thin films masked with SiO2/Si3N4 layers were etched using a high-density plasma of a CH3COCH3/Ar gas mixture. As the concentration of CH3COCH3 increased, the etch rate of the Co thin films and etch selectivity decreased. Optimal etch profiles of the Co films without redeposition were achieved owing to the formation of Co compounds and a passivation layer, which facilitated a high degree of anisotropy. Moreover, the etch characteristics of the Co films were examined using the ICP RF power, dc-bias voltage to the substrate, and process pressure. The active species in plasmas and Co compounds formed during etching were investigated using optical emission spectroscopy and X-ray photoelectron spectroscopy. Finally, the Co thin films patterned with 300 nm lines were etched using a CH3COCH3/Ar gas mixture under optimized etch conditions. The findings suggest that a CH3COCH3/Ar gas mixture can serve as an effective etch gas for fabricating dry-etched Co thin films.

Ammonia Decomposition By Microwave Plasma Discharges

The global discourse focuses on future energy vectors, with hydrogen emerging as a robust candidate owing to its established industrial applications. However, a current challenge lies in storing and transporting hydrogen-based fuels. This research focuses on advancing efficient and environmentally friendly techniques for large-scale hydrogen production, leveraging its widespread industrial presence. Ammonia, identified as a promising energy vector, offers advantages in storage and transport over hydrogen. It capitalizes on existing global infrastructures, with approximately 20 million metric tons traded annually, contributing to a total production of 150 million tons annually. If many works focus on producing ammonia by electrical discharges [1], only a few are devoted to ammonia cracking and generally concentrate on catalysis [2]. In this study, we propose an investigation into the decomposition of ammonia by applying microwave (MW) plasma. Utilizing a MW cavity that confines an electromagnetic field excited at 2.45 GHz, we induce electrodeless plasma within a fused silica tube where pure ammonia (NH3) gas flow. At first, the plasma discharge was characterized with Fourier Transform Infrared Spectroscopy (FTIR). This preliminary part of the study exhibited that, for fixed input power (300 W) and fixed working pressure (100 mbar), NH3 decomposition decreased with a flow rate ranging from 0.4 to 2.4 SLM. It also showed that for fixed input power (300 W) and fixed flow rate (2.4 SLM), the NH3 dissociation increased with pressure ranging from 40 to 140 mbar. These experiments exhibited the predominant role of the residence time of ammonia but also reactive species in plasma. To further understand the NH3 cracking mechanisms, we performed optical emission spectroscopy (OES). This technique allowed us to determine the various light-emitting species produced during NH3 dissociation in the discharge and their physical parameters, such as temperatures and relative densities, as a function of different experimental parameters. We study the influence of gas flow rate ranging from 1 to 15 SLM, input power and near-atmospheric pressure on NH3 cracking and hydrogen (H2) recombination mechanisms. Gas chromatography (GC) was employed to measure the dissociation yield of NH3 and assess the efficiency of the H2 production process. In parallel, we synthesize iron (Fe) and nickel (Ni) nanoparticles through a plasma solution process. Both metals are abundant and inexpensive; hence, they are good candidates as catalysts for potential industrial applications. In the experimental setup, a pair of tungsten electrodes, connected by a high-voltage cathode, was submerged in an aqueous solution containing Fe and Ni chlorides. One electrode was the high-voltage cathode, while the other was the grounded anode. Pulsed discharges were generated to produce Fe and Ni compounds. The resulting Fe-Ni nanoparticles (NPs) were characterized by transmission electron microscopy (TEM) to determine their shape, size and composition, which depends on the concentrations of the metal chlorides in the electrolyte solution. Those NPs were then coated on silica tubes inserted in the MW reactor at various positions to establish their influence on the NH3 decomposition and H2 recombination processes. The primary goal of this study is to compare the dissociation of NH3 with and without catalysts, aiming to achieve optimal results for H2 production. This study investigates the impact of experimental parameters on ammonia cracking efficiency within a microwave plasma combined with catalysis. We compare these factors with ruthenium-catalyzed and non-catalyzed thermal processes, recognized as leading methods for ammonia cracking. The goal is to gain insights into the mechanisms of ammonia decomposition in microwave plasmas and evaluate the efficiency of our proposed methodology relative to established thermal processes, contributing to the advancement of sustainable and optimized ammonia cracking practices and decarbonated hydrogen production. Acknowledgements The authors would like to thank the Department of Physics, College of Science, Jazan University, Jazan 45142, Saudi Arabia, for the financial support to M. Awaji and SAKOWIN for the financial support to L. Pentecoste.

(Invited) Low Temperature Plasma Synthesis and Functionalisation of Carbon Nanostructures for Energy Conversion and Storage

Low-temperature plasmas are nowadays widely developed and used for synthesis and functionalization of various materials with applications in areas ranging from microelectronics and aeronautical industry to energy conversion and storage. The focus of the research and applications has lately shifted towards carbon and carbon-based materials synthesis. The materials of interest vary from nanoparticles, nanotubes, nanowalls, free standing graphene flakes, vertical graphene rods, sponge structures, nanostructured surfaces, to composites (with conductive or non-conductive polymers, or MoS2, to mention some of the examples that will be presented herein). The interest for direct applications of plasma processes as well as nanostructures in the field of energy conversion and storage has been present since a long time. Recently, however, several interesting fundamental breakthroughs have been observed in terms of better control of processes, diagnostics and several other benefits that are attracting more and more attention: lower temperatures of surfaces needed for synthesis and functionalization (due to active plasma species interacting with surfaces), dry processes (diluted precurors or liquid monomers introduced in processes, without use of solvents), decreased overall pollution, fast processes, to mention just some of the advantages. However, our work must not forget the disadvantages and problems that can occur during application tests, such as stability, adhesion, loss of conductivity, reproducibility, general ageing or recyclability.Different factors can affect the function of the final setup (from photocatalytic elements, to batteries or fuel cells/HER systems, in our case) – from production of the starting materials to the assembly. Therefore, careful synthesis and control of the process (including the chamber and surface conditions for example) is necessary. We present herein several examples of carbon materials developed or in development (as mentioned 1D-3D carbons, carbon in organic and inorganic composits, mesoporous carbons). These materials were synthesized at surface temperatures between room temperature and up to 550°C.We emphasize, for example, the importance of in-situ control of processes, the importance of precise process conditions, the control of the synthesized materials with regard to their electrical conductivity, adhesion, thermal stability or sensitivity to photon irradiation.Acknowledgments:Authors acknowledge the EU Graphene Flagship FLAG-ERA III JTC 2021 project VEGA (PR-11938) and the project PEGASUS (funded by the European Union's Horizon research and innovation programme under grant agreement No 766894. UC and NMS acknowledge the Slovenian Research Agency for the program ARRS No. P1-0417 and project Z2-4467. TS, EK and JB want to thank HZB for the allocation of synchrotron radiation beamtime at the HE-SGM beamline of BESSY II. Thanks goes also to Prof. Wöll from KIT for providing the HE-SGM endstation used for the XPS and NEXAFS measurements. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 730872 (Nr. 18207084-ST and 18207393- ST). EK and JB acknowledge also support obtained via ARD MATEX Region Centre.

The Pharmacokinetics, Metabolism, and Clearance Mechanisms of Ritlecitinib, a Janus Kinase 3 and Tyrosine-Protein Kinase Family Inhibitor, in Humans.

Ritlecitinib is an oral once-daily irreversible inhibitor of Janus kinase 3 and tyrosine-protein kinase family being developed for the treatment of moderate-to-severe alopecia areata. This study examined the disposition of ritlecitinib in male participants following oral and intravenous administration using accelerator mass spectroscopy methodology to estimate pharmacokinetic parameters and characterize metabolite profiles. The results indicated ritlecitinib had a systemic clearance of 43.7 L/h, a steady state volume of distribution of 73.8 L, extent of absorption of 89%, time to maximum plasma concentration of ∼0.5 hours, and absolute oral bioavailability of 64%. An observed long terminal half-life of total radioactivity was primarily attributed to ritlecitinib binding to plasma albumin. Ritlecitinib was the main circulating drug species in plasma (∼30%), with one major pharmacologically inactive cysteine conjugated metabolite (M2) at >10%. Oxidative metabolism (fractional clearance 0.47) and glutathione-related conjugation (fractional clearance 0.24) were the primary routes of elimination for ritlecitinib with the greatest disposition of radioactivity shown in the urine (∼71%). In vitro phenotyping indicated ritlecitinib cytochrome P450 (CYP) fraction of metabolism assignments of 0.29 for CYP3A, 0.09 for CYP2C8, 0.07 for CYP1A2, and 0.02 for CYP2C9. In vitro phenotyping in recombinant human glutathione S-transferases indicated ritlecitinib was turned over by a number of cytosolic and microsomal enzyme isoforms. SIGNIFICANCE STATEMENT: This study provides a detailed understanding of the disposition and metabolism of ritlecitinib, a JAK3 and TEC family kinase inhibitor for alopecia areata in humans, as well as characterization of clearance pathways and pharmacokinetics of ritlecitinib and its metabolites. As an AMS-based ADME study design, we have expanded on reporting the standard ADME endpoints, providing key pharmacokinetic parameters, such as clearance, volume of distribution, and bioavailability, allowing for a more comprehensive understanding of drug disposition.

Effect of liquid surface depression size on discharge characteristics and chemical distribution in the plasma-liquid anode system

Atmospheric pressure plasma-liquid interactions exist in a variety of applications, including wastewater treatment, wound sterilization, and disinfection. In practice, the phenomenon of liquid surface depression will inevitably appear. The applied gas will cause a depression on the liquid surface, which will undoubtedly affect the plasma generation and further affect the application performance. However, the effect of liquid surface deformation on the plasma is still unclear. In this work, numerical models are developed to reveal the mechanism of liquid surface depressions affecting plasma discharge characteristics and the consequential distribution of plasma species, and further study the influence of liquid surface depressions of different sizes generated by different helium flow rates on the plasma. Results show that the liquid surface deformation changes the initial spatial electric field, resulting in the rearrangement of electrons on the liquid surface. The charges deposited on the liquid surface further increase the degree of distortion of the electric field. Moreover, the electric field and electron distribution affected by the liquid surface depression significantly influence the generation and distribution of active species, which determines the practical effectiveness of the relevant applications. This work explores the phenomenon of liquid surface depression, which has been neglected in previous related work, and contributes to further understanding of plasma-liquid interactions, providing better theoretical guidance for related applications and technologies.

Dust particle surface potential in an argon-helium plasma using the (r,q)-distribution function

Abstract In this paper, the dust particle surface potential for argon-helium plasma is evaluated analytically and numerically in the context of negatively charged dust particles by employing a power-law r , q -distribution function. Recent studies have reported the argon-helium plasma and conducted a brief theoretical and experimental survey. To deepen our understanding further, this study aims to analyze the argon-helium plasma comprehensively using the same pattern but with the r , q -distribution function. For this purpose, the current balance equations are derived for electron, helium and argon ions, when these charge species attain the quasineutrality condition. We numerically examined the currents of plasma species for a broad range of effective distribution function parameters r and q . It is revealed that the surface potential of dust particles is significantly affected by the parameters r and q , helium ion-to-electron temperature ratio, argon ion-to-electron temperature ratio, and helium ion to argon ion number density ratio. By incorporating the multi-ion (argon-helium) species, the significance of low-temperature non-Maxwellian dusty (complex) plasma is briefly examined.

Fluid models calculation of Ar/CF4 radiofrequency capacitively coupled plasmas

A fluid model is used to calculate plasma density in radiofrequency capacitively coupled plasmas (RF-CCPs), assuming geometrically symmetric Ar/CF4. Electrodes are powered by a 200 V sinusoidal wavefront at 13.56 MHz. The gap between the electrodes is 5 cm. The plasma species density is calculated as a function of the gas pressure, electron temperature, and gas composition. As expected from recent experiments, CF3+ and F are dominant for all simulation parameters (Plasma Chemistry and Plasma Processing, 2022; 42: 989-1002, 2013 Pulsed Power Conference (PPC), 19th IEEE, DOI:10.1109/PPC.2013.6627595). The results explain the pathways to perform atomic layer etching and nanolayer deposition processes. In order to reveal the effect of electron heating on the discharge dynamics, the spatiotemporal electron energy equation is coupled with the fluid model. Tailoring the driven potential has been found to control the concentration of some plasma species. When the plasma is driven by the fundamental frequency, ohmic and stochastic heating allow electrons to be heated symmetrically. Higher harmonics give rise to an electrical asymmetry and an electron heating asymmetry between the powered and grounded sheaths. The electron temperature depends on the driven harmonics; it adjusts gain and loss rates and some plasma species densities.

Analysis of short-term treatment effects of dielectric barrier discharge plasma to improve germination characteristics of wheat seeds

In this work, an effort has been made to show that a cold atmospheric pressure plasma (CAPP) can be applied to promote the growth and development of wheat seedlings. A dielectric barrier discharge (DBD) plasma-based reactor has been developed having two-roller conveyor rollers running on sprockets to generate cold plasma. Wheat seeds (Triticum aestivum) are treated with cold plasma for shorter durations to examine their germination parameters. In the cold plasma, reactive oxygen and nitrogen species (RONS) are generated which alter the surface of the seeds. This results in enhanced germination, growth, and enduring vitality of the plants enhance seed germination. After plasma treatment, the germination rate was enhanced from 84% to 98%. Also, after treatment surfaces of wheat seeds became more hydrophilic, as confirmed by a decrease in the water contact angle which results in higher seed germination. It is inferred that plasma is a viable alternative to the conventional pre-sowing seed treatment for germination due to its uniform treatment without degradation and the use of pesticides.

Studying species distribution in laser-induced plasma by molecular and atomic fluorescence

The spatial distribution profiles of particles in plasma sources push forward our understanding of plasma evolution and physicochemical processes occuring inside. Optical probe methods, such as laser-induced fluorescence, are advanced tools for spatially resolved plasma studies. In our work, we focused on investigation of distribution of neutral Ca and Fe atoms and CaO and FeO molecules in laser-induced plasma by means of laser-induced fluorescence. The development of excitation-emission schemes for Fe and FeO and the practical implementation of schemes for Ca and CaO allowed us to construct distribution maps of these species in laser plasma at 10 and 100 Torr pressures. Both atomic and molecular fluorescence were observed much further from the plasma formation point than the region of bright spontaneous atomic emission. Additionally, by comparing fluorescence intensity distributions with plasma imaging data, we explain the origin of some pecularities in observable plasma inhomogeneity. Distributions of Ca and CaO fluorescence intensity, as well the distribution of CaO/Ca intensity ratio, demostrate that the monoxide is distributed within the plume by the shock wave, but its concentration in the outer layers of plasma is influenced by recombination with atmospheric oxygen.

The impact of atmospheric air plasma treatment on the polyfunctional end-use polyester fabric using new synthetic pyrazole dye

Before gluing, bonding, and painting, a variety of materials' surfaces can be modified using the widely used plasma treatment technique. These materials include plastics, glass, metals, and wood. Materials' physical and chemical properties are changed in an environmentally responsible way to enhance or confer particular qualities. The recently used technology known as low-temperature atmospheric pressure plasma (LTAPP) allows heat-sensitive materials to be surface modified in a simple, one-step process. Polymer-based materials are frequently surface modified using LTAPP treatment to improve adhesion, printability, and surface sterility. Polyester's superior mechanical and physical qualities have led to its widespread use as a technical textile and garment material in the form of fibers, films, and plastics. Its limited versatility in terms of end use has been caused by its poor surface properties as the hydrophobic nature of polyester surface, roughness, the crystallinity, and lack of dyeability which are the main drawback restricting its use in different textile applications especially during wet treatments unlike natural fibers. In order to increase the fabric's hydrophilicity and dyeability, the surface of a polyester fabric was altered in this study using atmospheric pressure plasma treatment with atmospheric plasma jet and dielectric barrier discharge (APJ-DBD) technology in air. The primary obstacles in making dielectric barrier discharge (DBD) plasma treatment suitable for industrial purposes are the extended duration of treatment and the utilization of elevated voltage levels. The combination between the atmospheric plasma jet and the dielectric barrier discharge reduces the optimal treatment time to 1 min and the applied voltage to 3.3 kV. After being exposed to oxygen plasma species for a brief period of time (between 30 and 300 s), and were analyzed using an X-ray diffraction machine, an X-ray photoelectron spectroscopy (XPS), static contact angle, and a scanning electron microscope (SEM) to investigate changes in the morphology and chemical nature of the surface, respectively. Fabric wettability increased as a result of plasma treatment, which also increased the fabric's surface roughness, as demonstrated by SEM and X-ray diffraction. The contact angle decreases by increasing the treatment time. The dyeability of untreated and plasma-treated samples was examined with respect to washing, rubbing, perspiration, sublimation, and light fastness. Additionally, color strength was examined. Adequately, compared to the untreated fabric, polyester treated with plasma showed improved dyeing performances. The technical reactivity of poly (ethylene-terephthalate) (PET) fabrics was found to be effectively increased by atmospheric air plasma treatment, creating new avenues for surface modification in light of the expanding environmental and energy-saving concerns.

Experimental investigation of styrene destruction by DBD plasma and its conversion pathways

AbstractThis work was devoted to the investigation of the contribution of various species in plasma to styrene decomposition. Different background gases (air, argon, nitrogen, and oxygen) and plasma reactor (in‐plasma, post‐plasma, and post‐plasma with buffer tube) were employed in this experiment. The results showed that degradation and polymerization of styrene occur simultaneously in the plasma treatment process. In the discharge zone, the bombardment of electrons and energetic particles on styrene and its degradation intermediates played a role in breaking its weak bond energy and promoting their conversion. The short‐lived reactive species with high oxidation potential in plasma were the prerequisite for complete degradation of styrene, due to its ability of breaking bonds with large bond energies, such as benzene ring. Away from the discharge zone, long‐lived reactive oxygen species further oxidized and degraded styrene, and its intermediates outside the discharge zone, promoting their mineralization.

Pseudo-Wet Plasma Mechanism Enabling High-Throughput Dry Etching of SiO2 by Cryogenic-Assisted Surface Reactions.

Manufacturing semiconductor devices requires advanced patterning technologies, including reactive ion etching (RIE) based on the synergistic interactions between ions and etch gas. However, these interactions weaken as devices continuously scale down to sub-nanoscale, primarily attributed to the diminished transport of radicals and ions into the small features. This leads to a significant decrease in etch rate (ER). Here, a novel synergistic interaction involving ions, surface-adsorbed chemistries, and materials at cryogenic temperatures is found to exhibit a significant increase in the ER of SiO2 using CF4/H2 plasmas. The ER increases twofold when plasma with H2/(CF4 + H2) = 33% is used and the substrate temperature is lowered from 20 to -60°C. The adsorption of HF and H2O on the SiO2 surface at cryogenic temperatures is confirmed using in situ Fourier transform infrared spectroscopy. The synergistic interactions of the surface-adsorbed HF/H2O as etching catalysts and plasma species result in the ER enhancement. Therefore, a mechanism called "pseudo-wet plasma etching" is proposed to explain the cryogenic etching process. This synergy demonstrates that the enhanced etch process is determined by the surface interactions between ions, surface-adsorbed chemistry, and the material being etched, rather than interactions between ion and gas phase, as observed in the conventional RIE.