Plasma Chemistry and Plasma Processing最新文献

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.

The jet stability of a DC plasma torch affects not only the service life of the torch but also processing consistency in industrial applications. To evaluate both instantaneous and longstanding jet stabilities of a plasma torch, a novel jet stability evaluation method has been developed in this study. The collected raw signals were first analyzed using the fast Fourier transform and filtered with identified characteristic frequencies. Based on the filtered signals, a 200 ms sliding window method was employed to evaluate the relative fluctuation of arc voltage in terms of both longstanding and instantaneous jet stabilities of the plasma torch. The results show that: (1) the proposed method can effectively evaluate both instantaneous and longstanding jet stability of a DC plasma torch; (2) the arc voltage and arc current signals contain a characteristic frequency, which is strongly influenced by the gas flow rate; (3) the laminar plasma torch operates stably at an arc current of 90 A, and its longstanding jet stability improves with increasing gas flow rate. The findings and proposed method provide informative guidance to those interested in the improvement of plasma jet stability and processing consistency.

The paper reports and discusses the results of a detailed investigation of transient products and mineralization extent achieved in treatments of perfluorooctanoic acid (PFOA) in a radial plasma discharge reactor. The efforts were warranted by the excellent performance of this reactor in terms of process efficiency and by the need to verify that the quality of the treated water was of matching value. Minor amounts of transient products were detected and quantified, as a function of plasma treatment time, by means of LC/MS and LC/MS/MS analyses. These products arise from sequential chain-shortening, an established route for plasma induced PFOA degradation, and defluorination via fluorine substitution by -H and -OH groups. We focussed on the latter less known type of products (“substitution products”), which are formed in small amounts, cumulatively accounting, at any treatment time, for less than 2% of the total carbon content initially present as PFOA. In our system, hydroxy-containing substitution products with 8–6 carbon atoms are remarkably less reactive than their perfluoro- and hydro-substituted homologues, an effect attributed to improved solubility into the aqueous phase and removal from the plasma/liquid reactive interface. Mineralization extent and carbon mass balance were also determined by performing experiments with PFOA at high initial concentration (1∙10^− 4 M) to afford quantification of the CO₂ released into the gas phase by means of GC-TCD analysis. Despite the low rate of PFOA decomposition entailed by these abnormally high concentrations, remarkable carbon mass balance of 75% and mineralization extent of 67% were achieved in 90 min.

Continued advances in semiconductor manufacturing depend on the 3D integration of complex materials, with nano-scaling precision patterning being a key limiting factor. This article discusses several important aspects of plasma-surface interactions to support atomic scale precision in patterning novel materials. This includes the effect of ions that control the etch anisotropy, the role of surface chemistry that dictates reaction specificity and etch selectivity, and the broader impact of the plasma applications on chemical processing sustainability. A systematic approach is discussed for developing an atomic layer etch process, which allows for independent control of surface modification and product volatilization at low temperatures. This approach starts with predicting a plausible etch product and thermodynamic screening of possible reaction mechanisms, choosing the appropriate half-cycle reactants, leveraging chemical reactivity, and counterbalancing etch and deposition as possible pathways of achieving greater selectivity. This can be followed by experimental verification of the etch rates, product formation, and etch selectivity. Finally, it discusses how these ALE processes can be leveraged to enhance the overall chemical processing sustainability.

In this study, the effect of Mg addition on the composition and aging of water samples treated with nitrogen plasma was analyzed. The study focused on the measurements of the pH of the samples and the comparison of chosen oxygen and nitrogen reactive species (RONS) concentrations formed as a result of the plasma reaction and their changes over time. The results showed that the addition of Mg increased the concentration of RONS compared to the control samples. The pH changes resulting from the reaction of magnesium with water were also observed. Stability studies of the resulting composition also showed that the addition of Mg improved the stability of H₂O₂, NO₃⁻, and NO₂⁻ ions in water samples. The results suggest that it may be useful in water purification processes, environmental decontamination, and in analytical techniques requiring accurate control of chemical components in solutions. Additionally, it can be used in medicine and agriculture, where accurate analysis and stabilization of the composition of solutions are crucial.

Graphical Abstract

Driven by the “dual-carbon” policy, arc steam plasmas provide high-temperature, low-cost, and environmentally friendly heat sources for a variety of applications. However, severe anode erosion caused by steam condensation has limited the large-scale application of arc steam plasma torches. Suppressing condensation depends on reducing heat loss from steam in the anode cold boundary layer, a process that is influenced by plasma flow field characteristics, yet the effects of these characteristics have not been systematically reported. This study investigates two representative flow fields: one generated by a trumpet-shaped anode, which forms stratified flow between the cold boundary layer and the plasma, and the other produced by a stepped anode, which enhances boundary layer turbulence. Through systematic experiments and numerical simulations, the study comparatively analyzes their electro-thermal characteristics, anode exit temperatures, anode erosion behavior, and physical properties inside the torch. The results show that plasma flow field characteristics have a significant impact on anode erosion: stratified flow fields lead to severe erosion, while turbulence-enhanced flow fields can significantly suppress it. Moreover, only under turbulence-enhanced flow fields is the electron temperature at the torch exit higher and sensitive to changes in current. These findings highlight the importance of turbulence-enhanced flow fields for extending the operational lifetime of steam plasma torches.