Plasma Chemistry and Plasma Processing最新文献

This work presents the experimental study of the transport of typical air plasma long-lived reactive nitrogen species (RNS: HNO₂, NO₂, and NO) into deionized water and compares them with the most typical reactive oxygen species (ROS: H₂O₂ and O₃). RONS are generated either by external sources or by a hybrid streamer-transient spark plasma discharge, in contact with bulk water or aerosol of charged electrospray (ES) or non-charged nebulized microdroplets with a large gas/plasma-water interface. It was found that NO’s contribution to NO₂¯ ion formation was negligible, NO₂ contributed to about 10%, while the dominant contributor to NO₂¯ ion formation in water was gaseous HNO₂. A higher transport efficiency of O₃, and a much higher formation efficiency of NO₂¯ from gaseous NO₂ or HNO₂ than predicted by Henry’s law was observed, compared to the transport efficiency of H₂O₂ that corresponds to the expected Henry’s law solvation. The improvement of the transport/formation efficiencies by nebulized and ES microdroplets, where the surface area is significantly enhanced compared to the bulk water, is most evident for the solvation enhancement of the weakly soluble O₃. NO₂¯ ion formation efficiency was strongly improved in ES microdroplets with respect to bulk water and even to nebulized microdroplets, which is likely due to the charge effect that enhanced the formation of aqueous nitrite NO₂¯ ions when NO₂ or HNO₂ are transported into water. Comparisons of the molar amounts of O₃, H₂O₂, and NO₂¯ formed in water by hybrid streamer-transient spark plasma discharge with those obtained with single RONS from the external sources enabled us to estimate approximate concentrations of gaseous concentrations of HNO₂, NO₂, O₃, and H₂O₂. The medium or highly soluble gaseous HNO₂ or H₂O₂, with a low concentration of < 10 ppm are sufficient to induce the measured aqueous NO₂¯ or H₂O₂ amounts in water. This study contributes to a deeper understanding of the transport mechanism of gaseous plasma RONS into water that can optimize the design of plasma–liquid interaction systems to produce efficient and selected aqueous RONS in water.

Graphene oxide sheets were irradiated with argon and hydrogen plasma in the configuration of plasma immersion ion implantation with a pulsed negative voltage of -5 kV at varying time intervals, ranging from 2 to 8 min. Their characteristics were investigated in terms of surface and structural modification, elemental compositions and bonding, and sheet resistance. The irradiation removed surface irregularities and transformed it into a smoother surface. Raman spectroscopy analysis revealed that the sp² network was restored after the radiation. Due to different energy loss mechanisms, hydrogen irradiation resulted in a smaller size of sp² domains, while argon radiation led to more structural defects. The XPS results showed that a significant amount of hydroxyl/epoxy groups were removed, and an increase in carboxyl groups was observed after the irradiation. This indicates that some surface reactions, such as hydrogenation and adsorption of molecules from the environment, occurred. Conductive graphene oxide sheets were obtained as the sheet resistance of the irradiated graphene oxide was reduced compared to that of the pristine graphene oxide. This demonstrates that PIII could be a potential technique to reduce graphene oxide.

Plasma technology for generating activated water has garnered significant interest among researchers for its antimicrobial properties post-treatment. This study aimed to produce chitosan hydrogels incorporating various types and concentrations of plasma activated water (PAW) derived from tap water and purified water. Initially, the physicochemical properties of PAW, including pH, electrical conductivity (EC), and total dissolved solids (TDS), were assessed, revealing a notable decrease in pH and an increase in EC and TDS post-activation. Chitosan hydrogels were then synthesized using PAW and subjected to Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM) analyses. Results indicated a minimal impact on the chemical structure of the hydrogels post-PAW addition. TGA and DSC results revealed differences between tap water-based hydrogels and purified water-based hydrogels, indicating the presence of impurities or minerals in tap water. SEM observations depicted morphological alterations with increased plasma exposure, potentially enhancing antimicrobial activity. In degradation and swelling tests, the hydrogels exhibited pH sensitivity, maintaining integrity in neutral and alkaline media while dissolving in acidic conditions. Hemocompatibility and antimicrobial efficacy were confirmed through hemolysis tests and antibacterial/antifungal assays, particularly in hydrogels with prolonged water activation times, attributed to reactive species in PAW. These findings underscore the potential of these hydrogels as disinfectants in the biomedical field.

A process of CO₂ decomposition in dielectric barrier discharge reactor using mesoporous CeO₂-NiO catalysts was studied. Mesoporous materials of MCM-41, SBA-15 and MCF types were used in this study to investigate the influence of the material structure on CO₂ decomposition efficiency. The obtained catalysts were characterized by physico-chemical methods: low temperature N₂ adsorption, X-Ray diffraction and X-Ray photoelectron spectroscopy. CO₂ conversion, CO yield and CO selectivity as well as energy efficiency and specific energy input were calculated. The comparison of process efficiency was conducted with that in the absence of any catalyst (plasma-only reactor). It was shown that in the presence of Ce-based catalysts, the conversion of CO₂ (from 11 to 19%) and CO yield rise significantly, while CeNi samples show minor performance in CO₂ plasma-catalytic dissociation. Porous characteristics affected the performance of CO₂ decomposition. Using wide-porous MCF-type material as a support, it was possible to achieve the highest conversion due to enhanced CO₂ adsorption in pores and subsequent plasma-catalytic decomposition. The combination of mesoporous silica material as a support and a CeO₂ as an active component is promising for the plasma-catalytic CO₂ splitting.

Sustainable agriculture requires the exploration and development of eco-friendly technologies to increase crop production. From the last few decades, nonthermal atmospheric pressure plasma (NTAPP) based technology appears as an encouraging frontier in this quest. NTAPP with low temperature and energetic gas-phase chemistry offers potential applications to promote seed germination rate and plant growth. It initiates a cascade of biological responses at molecular levels inside the seed as well as in plants, greater nutrient uptake, elevated antioxidant activity, and pathogen control to ensure improved germination, seedling growth, plant growth, and increased harvesting. NTAPP technology has become more popular and convenient in agriculture due to its potential to produce plasma-activated water (PAW), which harnesses useful reactive species with PAW irrigation to promote plant growth. Recent advancements in NTAPP technology and its applications to promote seed germination, seedling growth, plant growth, and metabolite synthesis were summarized in this review. We delve deeper to examine the possible mechanisms that underlie the involvement of reactive species from NTAPP, surface interactions, and gene expression regulation. We also have discussed the applications of NTAPP in seed priming, pre-planting treatments, and disease control for food preservation. For sustainable agriculture, NTAPP stands out as an eco-friendly technology with the potential to revolutionize crop production of the modern age. Many researchers proved that NTAPP reduces the need for agrochemicals and presents a viable path toward sustainable agriculture. This review will provide recent progress by outlining major challenges and shaping future directions for harnessing the potential of NTAPP in agriculture.

The study investigates the efficacy of plasma-activated water (PAW) in preserving green chillies (jalapeño and pusa jwala) and compared it with various household fruits and vegetables cleaners’ solutions. PAW was prepared using a pencil plasma jet with air as the plasma forming gas. The results of visual analysis revealed that PAW-treated chillies maintain their fresh appearance even after 21 days, exhibiting significantly lower spoilage compared to control (ultrapure milli-Q water) and fruits and vegetables cleaners’ solutions. PAW demonstrated antimicrobial properties, effectively reducing microbial growth and spoilage on chillies over the storage period. Physical attributes, such as weight loss and firmness, are evaluated. It has been observed that PAW-treated chillies exhibit lower weight loss and higher firmness, indicating better membrane integrity and moisture retention. Microbial resistance was notably higher in PAW-treated chillies compared to control and when cleaning solutions were used. CIELAB color analysis revealed that PAW-treated chillies retain greenness, and color, freshness, outperforming control and cleaners. Sensory evaluation, including visual inspection, smell, taste, and touch, consistently favored PAW-treated chillies, emphasizing their superiority in terms of enhancement in shelf-life. Biochemical analysis revealed that PAW-treated chillies either maintain or show enhancement in nutritional attributes such as soluble sugar, protein, and ascorbic acid concentrations. Phenol concentration (antioxidant activity) remained stable across treatments. Overall, the study underscores the positive impact of PAW treatment on preserving the membrane integrity, antimicrobial resistance, sensory quality, and nutritional attributes of green chillies, making PAW an alternative for extending their shelf life.

The combination of plasma technology with microfluidics has gained significant attention in recent years. The unique characteristics of microfluidic chips, such as high surface-to-volume ratio and efficient mass transfer, coupled with plasma’s ability to provide the necessary green energy for the degradation of complex molecules, make this combination promising for water and wastewater treatment applications. A gas/liquid biphasic dielectric barrier discharge (DBD) plasma microreactor powered by a nano-pulsed excitation source, at atmospheric pressure, was used to study the degradation of p-benzoquinone and caffeine in water, chosen as model molecules for water pollution. Based on High Performance Liquid Chromatography (HPLC) analyses, the argon plasma was able to completely degrade both molecules at concentrations 10^− 5, 10^− 4 and 10^− 3 mol/L. At higher concentration (10^− 2 mol/L), the plasma promotes the synthesis of hydroquinone from p-benzoquinone. A 50% mineralization is achieved after plasma for the caffeine in aqueous solution at 10^− 5 M.

Plasma-catalysis has attracted significant interest in recent years as an alternative for the direct upgrading of methane into higher-value products. Plasma-catalysis systems can enable the electrification of chemical processes; however, they are highly complex with many previous studies even reporting negative impacts on methane conversion. The present work focuses on the non-oxidative plasma-catalysis of pure methane in a Dielectric Barrier Discharge (DBD) reactor at atmospheric pressure and with no external heating. A range of transition and noble metals (Ni, Fe, Rh, Pt, Pd) supported on γ-Al₂O₃ are studied, complemented by plasma-only and support-only experiments. All reactor packings are investigated either with pure methane or co-feeding of helium or argon to assess the role of noble gases in enhancing methane activation via energy transfer mechanisms. Electrical diagnostics and charge characteristics from Lissajous plots, and electron temperature and collision rates calculations via BOLSIG+ are used to support the findings with the aim of elucidating the impact of both active metal and noble gas on the reaction pathways and activity. The optimal combination of Pd catalyst and Ar co-feeding achieves a substantial improvement over non-catalytic pure methane results, with C₂₊ yield rising from 30% to almost 45% at a concurrent reduction of energy cost from 2.4 to 1.7 (:text{M}text{J}:{text{m}text{o}text{l}}_{text{C}{text{H}}_{4}}^{-1}) and from 9 to 4.7 (:text{M}text{J}:text{m}text{o}{text{l}}_{{text{C}}_{2+}}^{-1}). Pd, along with Pt, further displayed the lowest coke deposition rates among all packings with overall stable product composition during testing.

Plasma activated water (PAW) has been prepared using atmospheric pressure air dielectric barrier discharge with the bubbling method. This study aims to elucidate the crucial role of gas-liquid interface in determining the physicochemical properties and biological reactivity of PAW, as well as describe the process of mass transfer for reactive oxygen and nitrogen species (RONS) during the PAW generation. Gas-liquid interfacial area is regulated by varying the airflow rate. When the airflow rate increases from 0.5 to 16.0 SLM, the concentrations of (:text{N}{text{O}}_{text{2}}^{text{-}}), (:text{N}{text{O}}_{text{3}}^{text{-}}), (:{text{O}}_{text{3}}) and activated oxygen in PAW increase significantly, and the water-activated time for complete E. coli inactivation can be shortened from more than 320 s to 40 s. The numerical simulation result shows that when the airflow rate increases from 0.5 to 16.0 SLM, the gas-liquid interfacial area increases from 0.014 to 0.3 m²/600 mL. The analysis shows that the dependence of the chemical reactivity and the biological reactivity on the interface area is mainly attributed to the change of the mass flux with the interface area.

Nonthermal plasma (NTP) is an efficient treatment technology for cooking fumes (CFs). However, its practical implementation is hindered due to the low mineralization rate of CFs and high generation of by-products. In this study, a hybrid system coupling NTP and Mn/HZSM-5 catalysts was developed for the deep oxidation of CFs. These catalysts exhibited a remarkable synergistic effect together with NTP in improving the efficiency of CFs removal. When the specific energy density was 282 J·L^− 1, the hybrid system had stable reactivity, and the CFs removal efficiency and CO₂ yield were 100% and 78.4%, respectively, which were 10% and 61% higher than the values achieved with the NTP system alone. The Mn/HZSM-5 catalysts were also discovered to inhibit the production of O₃ and NO₂ to a large extent and to achieve a removal efficiency level at > 80%. The Mn/HZSM-5 catalysts’ high Mn⁴⁺/Mn ratio and the relatively large amount of chemisorbed oxygen on the catalyst surface engendered their remarkable performance. On the basis of the detected active species and organic products, the reaction mechanism governing the destruction of CFs by the NTP-Mn/HZSM-5 catalyst system was also discussed.