Plasma Radiation Research Articles

Cold plasma irradiation of chitosan: A straight pathway to selective antitumor therapy

Plasma-activated chitosan (PAC) colloids for cancer treatment were obtained by using the cold atmospheric plasma technique. Chitosan solutions were irradiated by plasma ignited in argon gas and in a mixture of argon with nitrogen and oxygen gases in certain ratios. The structural modifications of chitosan and the chemical species generated in plasma were investigated by EPR, LC-MS/MS, XRD, and NanoSight methods. The cell viability test showed a selective cytotoxic effect on human breast carcinoma cells (MCF-7), while the human mammary epithelial cells (MCF-10A) were left unharmed. The cytotoxic effect was attributed mainly to chitooligosaccharides, but also to a synergistic effect with other compounds generated in very low concentrations in plasma, such as glyceric acid, ethyl acetate, or tricarballylic acid. The plasma irradiation improved the antioxidant activity and mucoadhesivity, while not affecting the hemocompatibility investigated by a standard hemolysis ex vivo test on mice blood. Moreover, the in vivo biocompatibility investigation at intraperitoneal administration of PAC in mice showed no statistically significant changes in the hematologic, biochemical, and immune system parameters, and no morphologic alterations of the liver and kidney. All these data indicate the cold plasma activation of chitosan as a straight method to produce biocompatible, antitumor systems.

Influence of Hydrogen Additive on Electrophysical Parameters and Emission Spectra of Tetrafluoromethane Plasma

The influence of the addition of hydrogen on the electrophysical parameters and emission spectra of tetrafluoromethane under conditions of a direct current glow discharge has been studied. It has been established that gas temperature changes nonlinearly with increasing proportion of hydrogen in the plasma-forming mixture. The emission spectra of tetrafluoromethane plasma with hydrogen were obtained and analyzed. It is shown that plasma radiation is represented by atomic and molecular components, and the dependences of the line radiation intensities on the external conditions of the discharge are determined by the excitation of emitting states during direct electron impacts.

Effects of discharge parameters on plasma acceleration and transmission characteristics of a coaxial gun operated in gas-prefilled mode

The effects of discharge parameters on the discharge process and plasma transport characteristics of a coaxial gun in the gas-prefilled mode are studied. The plasma optical intensity and ejection velocity are measured by photodiodes, the optical emission spectrum is taken by a spectroscopic system, and the plasma evolution in the transport process is captured by a high-speed camera. The plasma acceleration characteristics under different discharge parameters show that the velocity and electron density of the ejection plasma are mainly determined by the pre-filled pressure and discharge current, which is consistent with the snowplow model. The kinetic energy of ejection plasma can be significantly increased by reducing the outer loop inductance, which is conducive to increasing the energy utilization efficiency. The time-varying images of plasma radiation and the plasma density at different transport locations illuminate the transmission characteristics of coaxial gun discharge plasma. The results show that the snowplow effect continues to play a role in the plasma transport process, and the plasma accumulation is induced by the combination of shock wave compression. The current-driven magneto hydrodynamics instability occurs during the transport process, and the luminous signal of the plasma current sheet oscillates periodically. In addition, the plasma impact effect is obvious and the gas retarding effect is enhanced with the increase in the gas pressure. These results give us a more comprehensive view of the coaxial gun discharge process and plasma transport and provide a certain reference for optimizing the parameters selection and physical design of coaxial gun discharge plasma characteristics.

Plasma-Activated AVC Hydrogel for Reactive Oxygen and Nitrogen Species Delivery to Treat Allergic Contact Dermatitis.

Allergic contact dermatitis (ACD) is a common inflammatory skin disease that accounts for approximately 20% of all occupational skin diseases. As an adverse and recurrent inflammatory dermatological agent, ACD shows insufficient response to current therapies largely owing to abnormal inflammatory activation and accompanying bacterial infection in lesions. Cold atmospheric plasma is a noninvasive fledgling reactive oxygen and nitrogen species (RONS)-based therapeutic technique for ACD treatment; however, its clinical adoption has been hindered due to the risk of electrical burns and insufficient delivery of the plasma-generated RONS. To address these limitations, we constructed plasma-activated AVC (PA-AVC) hydrogels loaded with plasma-generated RONS for ACD treatment as an alternative to the common direct plasma irradiation treatment. The proposed PA-AVC hydrogels were produced on a biodegradable acryloyldimethylammonium taurate/VP copolymer (AVC) with the aid of a novel air discharge plasma without the involvement of any catalyst. In vitro data showed that abundant RONS were produced and incorporated into the PA-AVC hydrogels via complex gas-liquid reactions between the air discharge plasma and hydrosolvent; additionally, the PA-AVC hydrogels exhibited excellent storage, slow release and transdermal delivery of RONS as well as good antibacterial effects. Moreover, in vivo experiments demonstrated that PA-AVC hydrogels effectively alleviated the ACD symptoms, such as skin redness and swelling, reduced epidermal thickening and inhibited mast cell infiltration and IL-9, TNF-α, and TSLP expression with no evident systemic toxicity. Our results revealed that long-acting plasma-activated AVC hydrogels could be effective therapeutic agents for local ACD treatment.

Thermal properties of MB2-WC (M = Ti, Zr, Hf) and tungsten and their stability after deuterium plasma exposure

The thermal properties of ultra-high temperature ceramics (UHTCs) in the MB2-WC (M = Ti, Zr, Hf) system and tungsten were studied for potential application as plasma-facing materials in fusion power plants. The sintered UHTC and tungsten samples were subjected to deuterium plasma or protons irradiation. Thermal diffusivity was measured using the laser flash method, and superficial thermal conductivity was analyzed through atomic force microscopy. Results showed that the thermal properties did not degrade when exposed to relevant environments and remained stable over a range of temperatures, unlike the reference tungsten material. Thermal conductivity ranged from 61 to 68 W m−1 K−1 for TiB2-2(WC-6Co), from 53 to 63 W m−1 K−1 for ZrB2-6WC, from 67 to 75 W m−1 K−1 for HfB2-6WC, and from 180 to 119 W m−1 K−1 for tungsten across the temperature range from room temperature to 1200 °C. The increasing trend of thermal effusivity, over 19000 J s−0.5 m−2 K−1 at 1200 °C, justifies further testing and of UHTC materials for fusion applications.

Cold plasma irradiation inhibits skin cancer via ferroptosis

Cold atmospheric plasma (CAP) has been extensively utilized in medical treatment, particularly in cancer therapy. However, the underlying mechanism of CAP in skin cancer treatment remains elusive. In this study, we established a skin cancer model using CAP treatmentin vitro. Also, we established the Xenograft experiment modelin vivo. The results demonstrated that treatment with CAP induced ferroptosis, resulting in a significant reduction in the viability, migration, and invasive capacities of A431 squamous cell carcinoma, a type of skin cancer. Mechanistically, the significant production of reactive oxygen species (ROS) by CAP induces DNA damage, which then activates Ataxia-telangiectasia mutated (ATM) and p53 through acetylation, while simultaneously suppressing the expression of Solute Carrier Family 7 Member 11 (SLC7A11). Consequently, this cascade led to the down-regulation of intracellular Glutathione peroxidase 4 (GPX4), ultimately resulting in ferroptosis. CAP exhibits a favorable impact on skin cancer treatment, suggesting its potential medical application in skin cancer therapy.

Real-time live imaging of cytosolic hydrogen peroxide and Ca2+ of Marchantia polymorpha gemmalings reveal immediate initial responses of plant cells triggered by nonthermal plasma irradiation

Cold atmospheric pressure plasma generators capable of generating plasma under normal pressure and temperature conditions have recently been developed, and their biological applications have been extensively studied. Plasma irradiation has been reported to affect plant germination and growth; however, the molecular mechanism underlying these effects and initial cellular responses to plasma irradiation remains poorly understood. To unravel the molecular and cellular mechanisms underlying the effects of plasma irradiation on plants, we have been establishing novel experimental systems using a model liverwort Marchantia polymorpha. We here focused on the initial responses of plant cells to plasma irradiation. To investigate immediate cellular responses following plasma irradiation, we developed a new plasma device that allows irradiation under a microscope. Through integration with live fluorescence imaging, we established an experimental setup to track, the dynamics of intracellular concentration of H2O2 and Ca2+ as representative initial cellular responses. We revealed that plasma irradiation induced a rapid and transient increase in intracellular concentration of H2O2 and Ca2+ in Marchantia gemmalings. Pharmacological analyses suggested that the long-lived reactive species, H2O2, generated by the plasma generator was directly delivered into the plant cells. Competitive inhibitors of Ca2+ channels abolished the Ca2+ rise, suggesting that plasma irradiation immediately activate plasma membrane Ca2+ channel(s) to induce Ca2+ influx. Importantly, this study marks the inaugural demonstration of real-time monitoring of cytosolic H2O2 and Ca2+ dynamics in plants, triggered by plasma irradiation.

Si modified aluminide coatings on a Ni-base superalloy prepared using Al-Si plasma irradiation: Growth mechanism and oxidation behavior

The growth mechanism and high temperature oxidation behavior of Si-modified aluminide coatings prepared on a Ni-base single crystal superalloy DD98M using vacuum plasma irradiation were investigated. The growth of the coatings under plasma irradiation was much faster than thermal diffusion-controlled process. The coatings comprised an aluminide outer zone, where Si existed as solid-solute, and an inter-diffusion zone where silicide particles precipitated in aluminide matrix. The crystalline structures of the aluminides were found dependent on the irradiation power. β-NiAl was formed at higher irradiation power while δ-Ni2Al3 was formed at lower irradiation power. The β-NiAl coatings had higher oxidation resistance than the δ-Ni2Al3 ones usually, with an exception of one β coating which was prepared at the highest substrate bias which underwent severe internal oxidation. The presence of numerous voids in the oxide scale of Ni2Al3 may be related to the large number of Kirkendall voids present in the as-prepared coating.

Experimental study on the formation and evolution of unconfined counter-helicity spheromaks merging using magnetized coaxial plasma gun

The formation and evolution of unconfined counter-helicity spheromaks merging have been experimentally investigated by using a magnetized coaxial plasma gun. By comparing the time-dependent photodiode signals and plasma radiation images of counter-helicity spheromaks merging and plasma jets merging, it is found that the field-reversed configuration (FRC) plasma formed by counter-helicity spheromaks merging has a distinct contour and a long maintenance time. For plasma jets merging, the resulting plasma has no discernible contours and a shorter lifetime. In addition, it is inferred from these data that stagnation heating and magnetic reconnection events occur during the counter-helicity spheromaks merging, causing a rapid rise in plasma pressure at the merging midplane and sharp kinks in the field lines near the merger region. By changing different operating parameters and observing the impact on the merger characteristics, it is suggested that the qualitative dynamics of the FRC plasma depends on the balance between the plasma pressure and the magnetic pressure. The high discharge voltage breaks the equilibrium in the merged body, while the large gas-puffed mass just weakens the compression effect of the merged body. These results give us an intuitive understanding of the counter-helicity spheromak merger process and its dependence on discharge parameters, and also provide a distinct perspective for the optimal design of FRC.

Dataset of aquatic insects acquired using field-emission scanning electron microscopy and the NanoSuit method

A simple surface modification, called NanoSuit, by electron beam or by plasma irradiation can form a nanoscale layer, allowing to keep small animals alive and hydrous under the high vacuum required for field-emission scanning electron microscopy (FE-SEM). We previously applied NanoSuit to aquatic insects, Dixa longistyla larvae (Diptera: Dixidae), which always lie on their ventral surface just under the water surface. We found that the crown-like structures on the ventral side of the hind segments enable the larvae to reside in such ecological niche. Moreover, fine structures in the crown protected with NanoSuit appeared intact, unlike those subjected to conventional sample fixation. However, a fundamental understanding of these structures (living and/or not treated with conventional fixation) interacting directly with water should be established using FE-SEM. This data descriptor introduces a rich dataset of images acquired using NanoSuit for various aquatic insects. The image data can be accessed and viewed through Figshare.

Radiation Effects in Tungsten and Tungsten-Copper Alloys Treated with Compression Plasma Flows and Irradiated with He Ions.

The paper presents the results of studying the structure and phase state of tungsten and tungsten-copper alloy after pulsed action of compression plasma flows and irradiation with helium ions. The compression plasma flows were used to modify the surface layer of tungsten, as well as to create an alloy based on tungsten and copper. Using scanning electron microscopy and X-ray structural analysis, the formation of radiation defects on the tungsten surface was detected in the form of local areas of exfoliation and destruction, which begin to form at helium ion irradiation doses of 2 × 1017 cm-2. It is shown that preliminary plasma treatment of the surface in the melting mode leads to the complete disappearance of surface radiation defects up to a dose of 2 × 1017 cm-2, which may be associated with the formation of a fine-crystalline grain structure, the intergranular boundaries of which serve as effective sinks for primary radiation defects.

Ion energy dependence of helium plasma irradiation effects on the photoelectrochemical properties of tungsten oxide

Abstract Tungsten samples with fuzz nanostructures on the surface were generated using helium plasma with different incident ion energies, and then fuzz tungsten oxide electrodes were prepared by calcination. The photoelectrochemical (PEC) properties and stability of the samples were measured, and the dependence on the incident ion energy was discussed. The mechanism of the fuzz structure to enhance the PEC performance of tungsten oxide was analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). The results show that fuzzy sample fabricated with higher ion energy has greater PEC performance, which is mainly caused by the increase in active surface area.

The effect of target material concentration on EUV near 6.7 nm and out-of-band radiation of laser-produced Gd plasma

We have prepared various low-density Gd targets to investigate the effect of concentration on the extreme ultraviolet (EUV) radiation near 6.7 nm and out-of-band emission from laser-produced plasma source. Results show that an increased EUV radiation intensity and narrow-band spectra from the low-density target was obtained. Comparing with the original solid Gd target, the intensity and spectral purity of the 6.7 nm EUV radiation from the 40 % mass concentration Gd target are enhanced 45 % and 74.5 %, respectively. And the FWHM of the spectra are decreased to one-half of that from the solid target. The measurements of the plasma electron density for various concentration targets shown that the low-density target exhibited lower plasma electron density, which reduced the self-absorption effect and the yield of the low-charge ions in the plasma, resulting in the enhancement of EUV radiation intensity as well as narrower band spectra output. Finally, the out-of-band radiation in the range of 325–385 nm from the 40 % concentration Gd target is decreased to approximately 60 % of the solid target case, while the angular distribution profile was significantly uniform. Our findings are beneficial to the Gd target as a new promising source candidate for the EUV nanolithography in the future.

The Effect of Cold Plasma and Low-Level Laser Therapy on Oral Fibroblast Proliferation

Background: Wound healing is a complex physiological process involving multiple phases and cellular mechanisms that restore damaged tissue. The oral cavity presents unique challenges for wound healing due to the presence of microorganisms and the impact of various diseases and treatments. Recent advancements, including low-level laser therapy (LLLT) and cold plasma, offer promising approaches to enhance wound healing by promoting cell proliferation and reducing inflammation. This study aimed to investigate the effects of cold plasma and low-level 980nm laser on the growth of oral fibroblasts and compare their respective impacts on wound healing. Methods: Human gingival fibroblasts were divided into nine study groups, including a control group. Two groups were exposed to low-level 980nm diode laser irradiation for 15 and 30 seconds, while six groups received cold plasma irradiation with helium gas at flow rates of 1.85, 2.78 and 5.56 cm3/s for the same durations. Fibroblast proliferation was evaluated on days 1, 3, and 5 after treatment using the MTT assay. Results: The results showed that on the 5th day after irradiation, 30 seconds of 980 nm laser irradiation significantly increased fibroblast proliferation compared to the other groups. In contrast, 15 seconds of plasma irradiation at a flow rate of 1.85 cm3/s had the least effect on promoting fibroblast proliferation. On the 1st day after radiation, plasma irradiation at flow rates of 2.78 and 5.56 cm3/s exhibited a greater impact on fibroblast proliferation compared to the other five test groups. Conclusion: The 980nm diode laser demonstrated a greater capacity to enhance the proliferation of oral fibroblasts compared to cold plasma using helium gas.

Data streaming infra-red video bolometer (IRVB) of Korea Superconducting Tokamak Advanced Research (KSTAR).

Due to the increasing demands for active plasma control operations, in situ diagnostics are highly sought after. Tungsten plasma-facing components have been utilized in the Korea Superconducting Tokamak Advanced Research (KSTAR) lower divertor since the 2023 campaign. Plasma radiation is a key parameter for plasma control, especially in radiation front control experiments. Therefore, the KSTAR infra-red video bolometer (IRVB) needs to be reconfigured into an in situ data streaming diagnostic. This requires comprehensive changes in both infra-red camera control and data analysis compared to the previous system. To ensure the stability of the reconfigured system, functional parts are grouped and separated into individual processes to protect camera acquisitions from errors in other processes. In addition, to enhance the speed of data streaming analysis, the analysis code has been optimized and converted into graphics processing unit (GPU) code. Besides the data streaming analysis, the system is also designed to support post-shot analysis with the entire frame data for the same shot to address frame drop issues encountered during data streaming. Radiation front control experiments with N2 gas seeding are successful results of the data streaming IRVB for its commissioning. This paper focuses on the development of the data streaming IRVB system.

TECXY simulations of the power exhaust in the multi-impurity plasma of DTT reactor

Reduction of the heat load to plasma-facing components is a crucial problem for future fusion reactors like Divertor Test Tokamak (DTT). Mitigation of the power load via increased plasma radiation with the use of puffed ions of impurities would be one way to mitigate power in the scrape-off layer. This paper presents a numerical investigation of the impact of seeded impurities on the radiation pattern and the power load to the divertor plates of the high-field DTT reactor in the single null (SN) configuration. The simulations have been done with the use of the TECXY code, which solves multi-species plasma transport equations for multiple impurity species simultaneously and all associated ionization stages in a two-dimensional poloidal geometry. TECXY represents the model of plasma transport in the scrape-off layer region by a classical set of transport equations of multi-species plasma derived by Braginskii. The paper aims to compare the mitigation capabilities of neon and argon impurities seeded in the plasma of the DTT device and to obtain a significant energy flux reduction to the target plate at the smallest possible impurity concentration. Performed investigations showed the effects of neon and argon impurities seeding separately for constant electron density at the separatrix. It has been found that the decrease in electron temperature on the divertor plates up to 3 eV at the outer and the inner divertor plates and the peak power load below 15 MW m−2 at the outer divertor plate can be achieved with argon seeding and much lower impurity concentration than that in the case of neon impurity seeding. Studies have shown the complexity of the effect of neon and argon impurities on the boundary plasma. It was found that the reduction of temperature and the power on both divertor plates was the most effective for the high upstream plasma densities. The results show also that diffusive perpendicular transport strongly affects impurity radiation and thus plasma condition at divertor plates.

Incremental effects of near-atmospheric-pressure low-temperature air plasma jet irradiation on polyphenol content in harvested onions

Abstract We present a new food processing method to increase the content of polyphenols, which are a type of health-promoting food component, in harvested onions using atmospheric-pressure low-temperature plasma technologies. Harvested onions were locally irradiated for different times with a low-temperature air plasma jet generated near atmospheric pressure and stored in the dark for various periods. The plasma-irradiated area was 7 mm2. The plasma irradiation was performed without removing the onion peel. After storage following plasma irradiation, the onion was peeled and cut into the outer, middle, and inner parts, analysing polyphenol content at each edible onion part, namely the bulb. The polyphenol content in the onions irradiated for 30 min and stored for 3 days increased over that of unirradiated onions stored for the same period. This increase occurred regardless of the bulb parts. Neither the plasma-irradiated onions without storage nor the air gas-irradiated onions without air plasma irradiation exhibited a higher polyphenol content. In particular, quercetin aglycone, quercetin 4’-O-glucoside, quercetin 3-O-glucoside, and quercetin 3,4’-O-glucoside were increased in the polyphenol content, contributing to an increase in the antioxidative activity. NO3− and NO2− were introduced into water under an onion peel by air plasma irradiation for 30 min and decreased after 3 days of storage but remained. However, no H2O2 was introduced. The plasma-introduced NO3− was distributed throughout the onion owing to the plasmodesmata serving as channels for cell-to-cell transports of molecules. These results suggest that the increased polyphenol content originates from the transcriptional factors acting in stress responses to the plasma-introduced NO3− and NO2−, not the electric field-induced electroporation, in onion cells. The present study provides valuable insights into interactions between low-temperature air plasma jets and onion cells.

Investigating the effect of gliding discharge plasma on polystyrene and Polyamide6 by positron annihilation lifetime spectroscopy

Polymers are widely used today and the changes in their properties are investigated by different methods such as plasma irradiation. One of the most important methods for modifying polymers is cold plasma, by which the surface properties of the polymers can be changed under atmospheric pressure. In this study, the effect of plasma on Polystyrene (PS) and Polyamide 6 (PA6) samples was investigated. Surface and depth changes of the PS and PA6 have been investigated by various experimental techniques such as Fourier Transform Infrared (FTIR), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Contact Angle (CA), and Positron Annihilation Lifetime Spectroscopy (PALS). The results of Attenuated Total Reflectance (ATR)-FTIR show that the chemical bonds of PA6 have been changed, and preserved in PS in the depths. The XRD results show that there are no volume changes for chemical bands. The FESEM analysis results reveal that the plasma causes digging and creates roughness on the surface. The CA measurement confirms the FESEM results and points out an increase in hydrophobicity after plasma processing. The PALS results indicate that the free volumes of the matter are changed after plasma irradiation in the depths of PS and PA6. In addition, the plasma also causes changes in the micrometer depth.

Effects of surface anisotropy on the surface morphological response of plasma-facing tungsten

Surface free energy has been hypothesized as the cause behind the experimental evidence (Parish et al., 2014) of a strong correlation between crystallographic orientation and surface morphology changes in helium ion-irradiated tungsten at the early stages of ‘fuzz’ growth in fusion plasma-facing tungsten. Here, this hypothesis is tested through self-consistent dynamical simulation based on an atomistically informed model of surface evolution in plasma-irradiated tungsten. Low-energy helium plasma irradiation of a tungsten surface, even when the ion energy is below the sputtering threshold, generates surface vacancy-adatom pairs in addition to adatoms from the flux of self-interstitial atoms to the surface resulting from the growth of high-pressure helium bubbles. Along with the stress-driven surface morphological instability as the primary driving force, preferential diffusion of these surface adatoms modulated by the associated Ehrlich–Schwoebel (ES) barriers, combined with the surface free energy anisotropy drive the anisotropic surface nanostructure growth. Simulation results for helium irradiation on W(100) show growth of pyramidal surface features, akin to experimental observations. This work confirms the hypothesis on the effect of tungsten surface crystallographic orientation on helium-ion-induced surface morphology changes, where surface mound formation is the outcome of a stress-driven surface morphological instability, while the anisotropic growth of the mounds is controlled by the ES-barrier-modulated anisotropic surface adatom diffusion and faceting of the mounds is controlled by the surface free energy anisotropy.

Detection and Visualization of Minor Irradiation-Induced Changes in Polytetrafluoroethylene (PTFE) by Raman Spectroscopy.

Exposure of polytetrafluoroethylene (PTFE) to argon plasma results in chemical modification of the polymer near the surface. Interestingly, PTFE modification can be induced by the sub-band gap ultraviolet (UV) irradiation. In the latter case, the changes in the chemical structure are very subtle, and they are practically invisible to conventional experimental techniques. Raman spectra of irradiated and raw samples show practically identical peaks. However, the baseline that is commonly considered as an unwanted spectral component contains an important information that reflects the minor structural changes. With the proper data analysis, this allows us to visualize the effects of the argon plasma and sub-band gap UV irradiation on the polymer.