Plasma Chemistry and Plasma Processing最新文献

Plasma-activated liquids (PALs) bridge plasma chemistry and aqueous reactivity, offering a controllable platform for biomedical, agricultural, and environmental applications. Their reactivity stems from gas-phase reactive oxygen and nitrogen species dissolving into the liquid; however, the role of the choice of solution in governing this chemistry remains insufficiently investigated. Here, we systematically compare deionized water (DW), mineral water (MW), tap water (TW), phosphate‑buffered saline (PBS), and Dulbecco’s modified Eagle medium (DMEM) treated under identical conditions using a surface dielectric barrier discharge (sDBD) in a gas‑tight reactor. By coupling in situ optical absorption spectroscopy with liquid-phase analysis, we reveal a direct link between the gas-phase O₃–NO_x transition and the formation of NO₂⁻, HNO₂, and NO₃⁻ in each solution. Among the tested media, PBS exhibited the fastest transition, occurring about 82 s earlier than in DW, driven by its high ionic strength and rapid O₃ consumption. While nitrate concentrations converged across solutions, nitrite and nitrous acid were strongly modulated by initial pH, buffering capacity, and ionic composition. In particular, PBS produced significantly higher NO₂⁻ levels, reaching 0.453 mM, which is about 6.6 times higher than the lowest concentration observed in DMEM. Dilution of PBS (0.5X, 0.1X) delayed the transition and reduced buffering, favoring HNO₂ accumulation. These findings demonstrate that PAL chemistry emerges from the interplay between plasma conditions and solution properties.

Transitions between plasma modes in pulsed discharges have a strong influence on plasma properties, and thus, they impact many plasma-based applications. The streamer-to-spark transition has been extensively studied in gases; however, it is far less explored in liquids, with only few reports published in the literature. Herein, we investigate the streamer-to-spark transition in water using a liquid–liquid interface configuration, in which a pin electrode is placed at the heptane–water interface to enhance the electric field and generate 4 mm-long discharges at 20 kV with 100% occurrence probability. Using 1-ns ICCD imaging, it is revealed that the transition occurs within 14 ns, from the moment the streamer reaches the cathode to the moment the plasma channel resistivity drops. Gaussian Process analysis shows that two successive anode-directed ionization waves are issued in the residual streamer channel upon streamer contact with the cathode. The first potential wave is identified as a return streamer due to the resistive nature of the primary streamer channel, and it propagates at 1000–4000 km/s. Comparatively, the second wave is slower (150–600 km/s) and thus, is identified as a filament. This filament is induced by progressive channel heating, which eventually leads to reduced resistivity and the formation of a thermalized spark.

Red Cherry Pepper (Capsicum annuum, local cultivar ‘Akabare chili’) is one of the important cash crops grown in the eastern and western parts of Nepal as well as in Sikkim, India. In this study, potential use of a low-cost gliding arc discharge (GAD) plasma system to enhance seed germination and vigor of Red Cherry Pepper was studied. At first, electrical and optical characteristics were studied on the basis of gas flow rates and applied voltages. In addition to these, the seeds of Red Cherry Pepper were treated with plasma plume. Favorable seed treatment conditions were identified at 24 V and 14 LPM, which maximized reactive species generation while maintaining the seed temperature below ((<) (39^{,circ })C). Direct treatment of seeds with GAD plasma altered their surface properties, as confirmed by contact angle measurements, conductivity tests, FTIR, and SEM analyses. Germination test reveals that a 120 s plasma treatment increased germination from 54% (control) to 64%, improved the germination index by 56%, and reduced mean germination time by 8% compared to the control. A 180 s treatment further enhanced vigor index I by 29%, but also increased non-viable seeds, indicating a threshold for optimal exposure. These results demonstrate that low-cost GAD plasma is an effective and scalable method for improving germination performance of Red Cherry Pepper seeds when optimized at 120 s treatment time and at 24 V and 14 LPM.

The production of plasma activated water (PAW) enriched with reactive oxygen and nitrogen species (RONS) is a prerequisite for high-efficient application of PAW in chemical fields. To address the limitations of conventional single-electrode PAW systems, this study designs a PAW generator with a dual-discharge mode consisting of an upper - liquid electrode and a submerged electrode to effectively compensate for the low mass - transfer efficiency of the upper - liquid discharge mode and the instability of the products in the under - liquid discharge mode, thereby improving the discharge stability. The upper - liquid electrode adopts a four - needle T - shaped structure to adapt to the turbulent liquid surface, while the submerged electrode is covered in a quartz tube to ensure stable plasma discharge. Optimized at 171 (:text{V}) (input voltage), 0.019 mol/L NaCl, and 30 min, the system achieves nonlinear RONS generation (172.11, 5.11, 3.25 and 0.81 µmol/L for (:{NO}_{2}^{-}), (:{NO}_{3}^{-}), (:H_2O_2), and (:O_3), respectively). The total energy consumption is 145.9 J, and the energy efficiency reaches 10.74 g/(KW×h). The device performance of the PAW generator is satisfactory, with temperature fluctuations confined to 7.67–8.33 °C, a final pH of 3.07, and a production volume of 2.4 L out of a rated capacity of 3 L These results underscore the potential of this design to establish a foundation for highly effective, low-energy PAW production across industrial applications.

Plasma-activated water (PAW) offers a promising biostimulant alternative in sustainable agriculture, yet its integration with endogenous signaling molecules such as salicylic acid (SA) remains underexplored. Here, we investigate the synergistic potential of PAW and SA in modulating early developmental and physiological processes in tomato seedlings. PAW was generated using an underwater capillary discharge system under varying nitrogen gas flow rates. The optimized PAW (600 sccm) displayed elevated levels of reactive oxygen and nitrogen species (H₂O₂, NO_x), along with increased ORP and electrical conductivity. Physiological assays revealed that intermediate concentrations, SA (0.25 mM) and PAW (30 min), were deliberately selected for combination studies, enabling the detection of synergistic responses without saturation effects. The combined treatment (SA + PAW) significantly enhanced seed germination (up to 99.5%), water uptake, and biomass accumulation compared to individual treatments. Antioxidant enzyme activities (SOD, CAT) and osmoprotectant levels (proline, soluble proteins) were markedly elevated. Molecular analysis confirmed upregulation of GA biosynthetic genes (GA20OX1/2/3), nitrate assimilation (NR1), and Ca²⁺-signaling regulator (GLR1), while downregulating growth repressor DELLA. Collectively, the SA + PAW co-treatment reprograms physiological and transcriptional networks, offering a robust, residue-free approach to enhance seedling vigor. This study pioneers a strategy that bridges redox, hormonal, and nutrient pathways through plasma–phytohormone synergy, revealing significant implications for plasma-integrated crop priming technologies.

Atmospheric inductively coupled plasma (ICP) etching has emerged as a critical technology for optical fabrication due to its damage-free etching, high removal efficiency, and adaptability to curved surfaces. However, the existing ICP torch design often struggles to achieve the high reactive gas ionization and low-temperature jet characteristics essential for etching applications. In this paper, a low-temperature ICP conical torch enabling stable plasma generation at reduced power inputs (250 ~ 600 W) was proposed. Through multi-physical coupling simulations, we analyzed the torch’s internal electromagnetic, temperature, and flow fields, which revealed the formation of the skin layer zone, the distribution of the core high-temperature zone, and the influences of the swirl, development, and blockage zones. On this basis, key structural parameters of the torch were optimized, including the taper of the variable-diameter section, the coil axial position and the nozzle throat geometry. Subsequently, etching experiments of fused silica were conducted to verify the removal efficiency and stability of the low-temperature ICP jet. It could achieve a peak removal rate of 11.19 μm/min and a volume removal rate of 0.69 mm³/min. The jet exhibited the relatively long-term stability, both axial and radial fluctuations of which were maintained below 5% over 60 min at 300 W. The root-mean-square (RMS) error of the fused silica surface converged from 445.12 nm to 223.88 nm after processing for 18 min at 400 W, with no visible signs of deposition. These results demonstrate the torch’s capability to mitigate the thermal effect, thus showing its promise for high-precision optical fabrication.

Lung cancer characterized by its high prevalence and aggressive nature, poses a considerable threat to global health. Recognizing the pressing need for innovative therapeutic strategies, we investigated the synergistic effect and potential mechanisms of nitric oxide-enriched plasma-treated water (NO-PTW) and curcumin in lung cancer treatment. NO-PTW was prepared using a multi-electrode cylindrical dielectric barrier discharge (MC-DBD) plasma system with air-flowing gas. Fibroblasts (MRC-5) and cancerous cells (A549 and H460) were exposed to NO-PTW and curcumin alone and in combination, followed by various analyses. Cytotoxicity assay indicated that curcumin and NO-PTW co-treatment markedly suppressed A549 and H460 cells growth without adversely affecting normal cells. Additionally, there was a marked decline in intracellular adenosine triphosphate levels and a significant increase in dead cells following the combined therapy. Moreover, curcumin and NO-PTW co-treatment increased cell death, membrane permeability, and reactive oxygen and nitrogen species generation. Immunofluorescence staining showed increased γ-H2AX protein expression following the co-therapy, indicating DNA double-strand break in cancer cells. Curcumin and NO-PTW co-treatment significantly upregulated the mRNA expression of key genes associated with DNA damage (ATR, ATM, Chk1, Chk2, and p53) and apoptosis (caspase-3, Bax, PARP, and caspase-8). Mechanistically, curcumin and NO-PTW co-treatment influences cellular processes by stimulating the ATR/ATM/p53 pathway, as evidenced by significant changes in phosphorylation levels. Conclusively, these findings suggest that curcumin and NO-PTW co-treatment induces apoptosis in lung cancer cells, presenting a possible strategy to expanding cancer treatments.

Methane pyrolysis by thermal plasma has been investigated for more than three decades as a promising route to produce CO₂-free hydrogen together with valuable carbon materials. This article is based on the plenary lecture delivered at the 26th International Symposium on Plasma Chemistry (ISPC-26, June 2023, Minneapolis) and distills the key scientific and technological advances achieved since the early 1990s. Topics include fundamentals of arc physics and thermodynamics, diagnostics and modeling of plasma–molecule interactions, and reactor engineering from laboratory to pilot scale. The extreme temperatures and rapid quench achievable in thermal plasmas enable fast CH₄ conversion and reveal radical-driven pathways for aromatic growth, particle nucleation, and carbon morphology control. Progress in arc stabilization, energy coupling, and residence-time management has improved conversion, selectivity, and carbon quality, while offering clearer scale-up criteria. Recent demonstrations indicate the onset of an industrial transition, targeting low-carbon hydrogen and engineered carbon (e.g. carbon black, nanotubes, nanofibers, graphene flakes…). We outline remaining challenges - plasma source efficiency, reliability, electrode lifetime, transport and mixing at scale, and standardized product characterization - and identify opportunities for process intensification and integration with renewables. By bridging fundamental plasma chemistry with applied reactor design, thermal-plasma methane pyrolysis emerges as a credible pathway to decarbonize hydrogen production and to manufacture high-value carbon materials.