Cold Plasma Conditions Research Articles

The effect of variations in cold plasma conditions on the detoxification of Aflatoxin M1 and degradation products

The aim of this study was to explore the chemical reactive species of different operating gases, and their effect on the degradation of aflatoxin M1 (AFM1) by cold plasma by measuring the reactive species concentration. Helium, at 80, 90 or 95%, was used mixed with oxygen, nitrogen and air. The efficacy of cold plasma on aflatoxin M1 (AFM1) reduction was improved when decreasing the ratio of helium in the gas mixture. The ratio of the gas mixtures changed the cold plasma chemistry believed to be due to the differences in the concentrations of the reactive species. The degradation products of AFM1 after cold plasma treatment using a helium/air gas mixture and the degradation pathway were identified by LCMS. AFM1 was oxidised by reactive species in the cold plasma to produce degradant products with, theoretically, lower toxicity than AFM1.

Inactivation Effect of Germination Combined with Cold Plasma Treatment on Bacillus licheniformis Spores.

Food spoilage, primarily caused by spore-forming bacteria, has become a critical concern since it results in substantial economic losses within the food industry. Past investigations have successfully identified Bacillus licheniformis as the main bacterium responsible for spoilage in roast chicken. In this study, we screened a new sterilization combination from 16 germinants and 4 cold plasma conditions, respectively. Among them, the combination of "A"GFNa-1 (composed of 60 mmol/L L-alanine, 10 mmol/L D-glucose, 10 mmol/L D-fructose, and 1 g/L NaCl) with cold plasma treatment (packed with 100% argon at 70 kV) proved effective in deactivating B. licheniformis spores, resulting in a reduction of approximately 2.1 log CFU/mL. Furthermore, we exposed the spores to different conditions: CK (no germination, no cold plasma), MF (germination only), CP (no germination, 100% argon packed, 70 kV cold plasma treatment for 3 min), and MF + CP (germination for 5 h, 100% argon packed, 70 kV cold plasma treatment for 3 min). The results of heat inactivation and dipicolinic acid (DPA) release rate demonstrated that cold plasma treatment effectively inactivated both spores and vegetative cells without inducing germination. Additionally, the reduced survival under hyperosmotic conditions and the presence of distinct red fluorescence patterns observed through confocal laser scanning microscopy (CLSM) collectively suggest that cold plasma treatment disrupts the inner membrane structure and leads to the inactivation of B. licheniformis. Overall, our findings indicate a spore clearance rate of 99.2% and suggest that the combination of efficient germinants and cold plasma treatment holds promise as a viable approach to mitigate spore contamination in the food industry.

Optimization of the Radiofrequency Low-Pressure Cold Plasma Conditions for Decontamination of Saffrons

Optimization of the Radiofrequency Low-Pressure Cold Plasma Conditions for Decontamination of Saffrons

Low-Pressure Microwave Plasma Reduction of Iron and Copper Salt Compounds at Low Temperatures for Oxidation State Alteration and Functional Applications.

The influence of plasma-reduction treatment on iron and copper compounds at different oxidation states was investigated in this study. For this purpose, reduction experiments were carried out with artificially generated patina on metal sheets and with metal salt crystals of iron(II) sulfate (FeSO4), iron(III) chloride (FeCl3), and copper(II) chloride (CuCl2), as well as with the metal salt thin films of these compounds. All the experiments were carried out under cold low-pressure microwave plasma conditions; the main focus was on plasma reduction at a low pressure in order to evaluate an implementable process in a parylene-coating device. Usually, plasma is used within the parylene-coating process as a supporting tool for adhesion improvement and micro-cleaning efforts. This article offers another useful application for implementing plasma treatment as a reactive medium in order to apply different functionalities by an alteration in the oxidation state. The effect of microwave plasmas on metal surfaces and metal composite materials has been widely studied. In contrast, this work deals with metal salt surfaces generated from a solution and the influence of microwave plasma on metal chlorides and sulfates. While the plasma reduction of metal compounds commonly succeeds with hydrogen-containing plasmas at high temperatures, this study shows a new reduction process that reduces iron salts at temperatures between 30 and 50 °C. A novelty of this study is the alteration in the redox state of the base and noble metal materials within a parylene-coating device with the help of an implemented microwave generator. Another novelty of this study is treating metal salt thin layers for reduction purposes in order to provide the opportunity to include subsequent coating experiments to create parylene metal multilayers. Another new aspect of this study is the adapted reduction process of thin metal salt layers consisting of either noble or base metals, with an air plasma pre-treatment prior to the hydrogen-containing plasma-reduction procedure.

Tailoring Polymorphic Heterostructures of MoS2–WS2 (1T/1T, 2H/2H) for Efficient Hydrogen Evolution Reaction

Earth-abundant and inexpensive transition metal dichalcogenides (TMDCs) with existing polymorphisms (metallic 1T phase and semiconducting 2H phase) have been proposed as alternatives to noble metals (e.g., Pt, Ir, and Ru) to achieve an efficient hydrogen evolution reaction (HER). Although the 1T phase of TMDCs (1T-TMDCs) is essential as an HER catalyst, practical application in the HER has not been realized owing to the lack of any large-scale production of the 1T-TMDC and 1T/1T-TMDC heterostructure fabrication method. Here, polymorphic TMDC–TMDC heterostructures at a 4 in. wafer scale is reported for 1T-MoS2/1T-WS2 vertical heterostructures (1T/1T-MWH) or 2H-MoS2/2H-WS2 vertical heterostructures (2H/2H-MWH) under cold plasma conditions and process temperature. Simultaneous ion-bombardment onto substrates induces a few nanosized grain boundaries with discontinuous films, resulting in exposed edges that act as catalytically active sites. The electrocatalytic performances of the prepared polymorph (1T or 2H phases of MoS2 and WS2) and polymorphic heterostructures of 1T/1T-MWH and 2H/2H-MWH are compared. 1T/1T-MWH shows the highest electrocatalytic performance owing to its metallic 1T phase and heterostructures containing alloy structures at the heterointerface. Moreover, the nanosized grains of 1T/1T-MWH preserve their original phase after 1000 HER cycles, proving their robustness and durability.

The coloration of polyester fabric with Prangos ferulacea natural dye: new approaches toward a cleaner production

PurposeNatural colorants are believed to be safe because of their nontoxic, noncarcinogenic and biodegradable nature, and also, the demand for natural dyes is steadily increasing. This study aims to investigate the dyeing of polyethylene terephthalate (PET) fabrics under cold plasma and ultraviolet (UV) radiation conditions with Prangos ferulacea.Design/methodology/approachIn the first, some PET fabrics were modified using UV radiation and some others by cold plasma (oxygen/argon), and then the dyeing of fabrics with the natural dye was done (100°C/130°C) without using metallic mordant. Dyeability (color strengths) of the treated samples, colorfastness to washing, light and rubbing, water absorption time, crease recovery angle, air permeability and mechanical behavior were investigated.FindingsThe maximum color strength (k/s = 4.87) was achieved for the fabric exposed to UV radiation for 2 h and then dyed with Prangos ferulacea at 130 °C. The results indicated that the dyed fabric showed acceptable colorfastness (very good–excellent) properties in washing and rubbing fastness except for colorfastness to light (moderate). The strength and the angle of crease recovery of treated and dyed samples have increased, while the time of water absorption and air permeability have decreased.Originality/valueThe surface modification of PET (UV radiation and plasma treatment) provides a new idea to improve the dyeability of PET with Prangos ferulacea natural dye without using metallic mordant.

Latest results of Eurofusion plasma-facing components research in the areas of power loading, material erosion and fuel retention

The interaction between the edge-plasma in a fusion reactor and the surrounding first-wall components is one of the main issues for the realisation of fusion energy power plants. The EUROfusion Work Package on plasma-facing components addresses the key areas of plasma-surface interaction in view of ITER and DEMO operation, which are mostly related to material erosion, surface damage and fuel retention. These aspects are both investigated experimentally (in tokamaks, linear plasma devices and lab experiments) and by modelling. Here, selective results regarding the main research topics are presented: in the area of tungsten (W) surface modifications, the interplay between W fuzz formation and W fuzz erosion depends strongly on the local plasma and surface conditions, as demonstrated by tokamak experiments. Complementary, experimental findings on the dependence of erosion on the surface structure in lab-scale experiments have led to the successful implementation of surface structure effects in numerical modelling. The qualification of ITER-like monoblocks at high fluences of up to 1031 D m−2 in linear plasma facilities has shown no visible damages at cold plasma conditions. However, experiments with simultaneous plasma and pulsed heat loading (edge-localized modes simulations) show that synergistic effects can lower the W damage thresholds. Additionally, fuel retention studies show that nitrogen as a plasma impurity increases the fuel retention in W, and that deuterium implanted in the surface of W is capable of stabilizing displacement damages caused by neutron damage. Finally, the implications of these results on ITER and DEMO operation are discussed and an outlook on follow-up experiments is given: the results indicate that there are possible impacts on the ITER divertor lifetime and tritium removal. Other areas like the divertor shaping and the erosion need additional investigations in the future to quantify the impact on ITER and DEMO operation.

Robust Potassium Isotopic Analysis of Geological and Biological Samples via Multicollector ICP-Mass Spectrometry Using the "Extra-High Resolution Mode".

Potassium isotopic analysis is arousing increasing interest, not only in geochemistry, but also in biomedicine. However, real-life applications are still hindered by the lack of robustness of the methods used. In this work, a novel and robust method for high-precision K isotopic analysis of geological and biological samples was developed, based on the use of a multicollector ICP-mass spectrometer providing a mass resolving power of 15,000 (extra-high resolution mode, XHR). After evaluation of different measurement conditions, i.e., hot vs cold plasma conditions, standard-type vs jet-type sampling cone, and high resolution (HR) vs XHR, a combination of hot plasma conditions, use of the high-transmission jet-type sampling cone, and the XHR mode allowed for high-precision and interference-free K isotopic analysis. Potassium signal monitoring was performed in the ArH+ interference-free 0.006-0.007 amu wide peak shoulder using the XHR mode. The within-run, short-term external, and long-term external precisions for the δ41K value were 0.02‰ (2se, N = 50), 0.03‰ (2SD, N = 7), and 0.06‰ (2SD, N = 163), respectively. A two-stage chromatographic procedure was developed for the isolation of K from both geological and biological samples, and potential matrix effects affecting the K isotope ratio were systematically evaluated. The method was first applied to geological reference materials (RMs) for validation purposes, and the K isotope ratio results were in good agreement with those previously reported. Subsequently, a series of biological RMs, including serum, whole blood, cerebrospinal fluid, bovine muscle, and lobster hepatopancreas, were characterized for their K isotopic composition.

Chemical Treatment of Lignosulfonates Under DBD Plasma Conditions. I. Spectral Characterization

A new method for chemical modification of lignin product under dielectric barrier discharge (DBD) plasma at atmospheric pressure is proposed. The motivation of this study is to obtain from ammonium lignosulfonate powder (ALS) and carboxylic acids (oleic acid, OA and lactic acid, LA) and butyrolactone (BL), new products with improved functionalities (ALS-LA, ALS-OA and ALS-BL), which may be used in manufacturing of biocomposite materials. The chemical transformations on the surface of ALS were evaluated by elemental analysis, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), near-infrared (NIR) spectroscopy and near-infrared chemical imaging (NIR-CI), as well as nuclear magnetic resonance (1H-NMR and 13C-NMR), UV–VIS and fluorescence spectroscopies. The attachment of the monomeric chains to the macromolecular network of ALS was proved by the values of atomic ratios (C/H, C/O and O/C), calculated from elemental analysis, reveal. The spectral results confirmed that the grafting reaction of ammonium lignosulfonate took place under cold plasma conditions and various compounds with special structures and functionalities have been obtained. Moreover, the recorded NIR-CI images (RGB and PCA components) provide information about ALS product homogeneity.

Elemental bioimaging of Na distribution in roots ofArabidopsis thalianausing laser ablation-ICP-MS under cold plasma conditions

LA-ICP-MS under cold plasma conditions is used for imaging analysis of the sodium content in plant roots.

Estimation of Hydroxyl Free Radicals Produced by Atmospheric Air Cold Plasma with Salicylic Acid Trapping

Salicylic acid is used as a scavenger to quantify free hydroxyl radicals (•OH) produced from a cold plasma process. High-performance liquid chromatography revealed that salicylic acid was decomposed to 2,3-dihydroxybenzoic acid (2,3-DHB) and 2,5-dihydroxybenzoic acid (2,5-DHB). The concentrations of 2,3-DHB and 2,5-DHB were the highest when the concentration of salicylic acid was > 8,000 mg/L. Quantifying 2,3-DHB and 2,5-DHB concentrations revealed the association between the •OH concentration and the reaction time by using the following first-order equation: [•OH] = 0.01713t + 0.0311. Additionally, the rate of •OH formation in relation to different cold plasma conditions was also determined.

Great Variety of Man-Made Porous Diamond Structures: Pulsed Microwave Cold Plasma System with a Linear Antenna Arrangement.

Synthetic diamond films are routinely grown using chemical vapor deposition (CVD) techniques. Due to their extraordinary combination of intrinsic properties, they are used as the functional layers in various bio-optoelectronic devices. It is a challenge to grow the dimensional layers or porous structures that are required. This study reviews the fabrication of various porous diamond-based structures using linear antenna microwave plasma (LAMWP) chemical vapor deposition (CVD), a low-cost technology for growing diamond films over a large area (>1 m2) at low pressure (<100 Pa) and at low temperature (even at 350 °C). From a technological point of view, two different approaches, i.e., templated diamond growth using three different prestructured (macro-, micro-, and nanosized) porous substrates and direct bottom-up growth of ultra-nanoporous diamond (block-stone and dendritelike) films, are successfully employed to form diamond-based structures with controlled porosity and an enhanced surface area. As a bottom-up strategy, the LAMWP CVD system allows diamond growth at as high as 80% CO2 in the CH4/CO2/H2 gas mixture. In summary, the low-pressure and cold plasma conditions in the LAMWP system facilitate the growth on three-dimensionally prestructured substrates of various materials that naturally form porous self-standing diamond structures.

Processing chocolate milk drink by low-pressure cold plasma technology

This study aimed to evaluate the effect of the process time (5, 10, and 15 min) and flow rate (10, 20, and 30 mL/min) of cold plasma technology on physio-chemical characteristics (pH), bioactive compounds (DPPD, Total Phenolic Compounds, ACE-inhibitory activity values), fatty acid composition, and volatile compounds profile of chocolate milk drink. The mild (lower flow rate and process time) and more severe (higher flow rate and process time) conditions led to a reduction of the bioactive compounds (total phenolic compounds and ACE-inhibitory activity), changes in fatty acid composition (increased saturated fatty acid and decreased monounsaturated fatty acid and polyunsaturated fatty acid), less favorable health indices (higher atherogenic, thrombogenic and hypercholesterolemic saturated fatty acids and lower desired fatty acids), and lower number of volatile compounds. In contrast, in intermediate cold plasma conditions, an adequate concentration of bioactive compounds, fatty acid composition, and health indices, and increased number of volatile compounds (ketones, esters, and lactones) were observed. Overall, cold plasma technology has proven to be an interesting alternative to chocolate milk drinks, being of paramount importance the study of the cold plasma process parameters.

Guava flavored whey-beverage processed by cold plasma: Physical characteristics, thermal behavior and microstructure

The present study aimed to compare the physicochemical (pH), physical (rheology parameters and particle size), microstructure (optical microscopy) and thermal properties (differential scanning calorimetry) of guava flavored whey-beverages submitted to cold plama technology in different processing time (5, 10, and 15 min) and gas flow (10, 20, and 30 mL min−1) conditions with a conventional pasteurized product. Whey beverages treated by cold plasma presented higher pH values, lower consistency and lower viscosity, and a flow behavior index similar to Newtonian fluids. Milder cold plasma conditions resulted in whey beverages with higher pH, lower viscosity and consistency, and similar particle distribution and microstructure compared to the pasteurized product. In contrast, more severe processing conditions resulted in a higher particle surface area ([D 3,2]) and smaller particles (~10 μM), due to the decrease in the number of larger particles (1000 μM), cell rupture, the formation of cell fragments, and higher viscosity and consistency. The treatments did not affect the thermal properties (enthalpy and bound water) of any sample.

Reverse weathering in marine sediments and the geochemical cycle of potassium in seawater: Insights from the K isotopic composition (41K/39K) of deep-sea pore-fluids

In situ Al-silicate formation, also known as “reverse weathering,” is an important sink of many of the major and minor cations in seawater (e.g. Mg, K, and Li). However, the importance of this sink in global geochemical cycles and isotopic budgets of these elements remains poorly constrained. Here, we report on the potassium isotopic composition (41K/39K) of deep-sea sediment pore-fluids from four (Integrated) Ocean Drilling Program sites (1052, U1378, U1395 and U1403) to characterize potassium isotopic fractionation associated with the formation of authigenic Al-silicate minerals in marine sediments and its role in elevating the 41K/39K of seawater relative to bulk silicate Earth. Isotopic ratios are obtained by high-resolution multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in cold plasma conditions with a long-term external reproducibility of ca. 0.17‰. We find that, although all sites are characterized by pore-fluid K concentrations that decline with increasing depth, their K isotopic profiles vary systematically from site-to-site; at sites characterized by rapid sedimentation rates, pore-fluid profiles of 41K/39K are relatively invariant whereas at sites characterized by slow sedimentation rates, 41K/39K declines with depth by up to 1.8‰. Results from 1-D diffusion-advection-reaction models suggest that these differences may result from a complex interplay between sedimentation rate and fractionation of K isotopes during diffusion, Al-silicate authigenesis, and ion exchange. Model simulations suggest fractionation factors between 0.9980 and 1.0000 for reverse weathering reactions in deep-sea sediments. Although deep-sea sites do not constitute major sinks of K in seawater, some of the processes responsible for K isotopic fractionation at these sites (diffusion and Al-silicate authigenesis) likely play a role in determining the 41K/39K of seawater.

Cold Plasma: Effective Control of Argon Emission Line Interferences on the Measurement of Rubidium by Axial-view ICP-OES

Inductively coupled plasma optical emission spectrometry (ICP-OES) operated in axial-view mode and cold plasma conditions was investigated as a strategy for the measurement of rubidium to suppress ...

Evaluation of the use of cold plasma conditions for Fe isotopic analysis via multi-collector ICP-mass spectrometry: effect on spectral interferences and instrumental mass discrimination

The application of cold plasma conditions for isotopic analysis of Fe via MC-ICP-MS was evaluated in combination with the standard and the ‘jet’ interface and with dry and wet plasma conditions.

Polarization of obliquely propagating whistler mode waves based on linear dispersion theory

We discuss the variation of whistler mode wave electric and magnetic field polarizations as a function of propagation angle θkB0 with respect to the background magnetic field B0 using linear kinetic dispersion theory. The circular polarization of the whistler mode wave magnetic field at all propagation angles [Verkhoglyadova et al. J. Geophys. Res. 115, A00F19 (2010); P. M. Bellan, Phys. Plasmas 20, 082113 (2013)] is found to be valid only for cold plasma or low plasma beta conditions. The wave magnetic fields, on a plane orthogonal to the wave vector k, tend to become elliptically polarized with an increase in propagation angles for high beta plasma background conditions (βe≥0.1). The electric field polarization plane may not be orthogonal to wave vector k, especially for oblique propagations, and is found to be circularly polarized only at parallel propagation direction as reported by Verkhoglyadova et al. [J. Geophys. Res. 115, A00F19 (2010)] and Bellan [Phys. Plasmas 20, 082113 (2013)]. They become elliptically polarized with an increase in propagation angles. This is valid for arbitrary plasma beta conditions. The results are also analysed and compared for an inner magnetospheric plasma model with three electron species. The two major angles, Gendrin and resonance cone angles, are also discussed.

Steam reforming of glycerol for syngas generation under cold plasma conditions: A DFT study

ABSTRACTDensity functional theory (DFT) has been used to investigate the reaction pathways with steam reforming of glycerol under cold plasma conditions. Total energies, energy barriers, and reaction enthalpies at 298.15 K have been calculated at the GGA/PW91/DNP level. The calculation shows that, with the presence of steam, the energy barrier of glycerol conversion is reduced and the conversion from glycerol to H2 and CO is promoted under cold plasma conditions. The formation of syngas was through a multi-step pathway via the conversion of OHCH2CHOH, CH2OH, CH2O, HCO,·and CH3, while the recombination of H generated extra H2. The synthesis of hydrocarbons are from the recombination of·CH3,·CH2, and·CH, which could be primarily generated through glycerol dissociation. The structure of glycerol anion was also studied in this work, and it was less stable than the neutral molecule. The route for the formation of OHCH2CHOH·and CH2OH·from glycerol anion is thermodynamically favorable.

Theoretical study of ethanol partial oxidation for syngas production under cold plasma conditions

In this work, pathways of partial oxidation of ethanol under cold plasma conditions have been studied by density functional theory (DFT) method. The calculation results show that the energy barrier of ethanol conversion is reduced and the conversion from ethanol to H2 and CO is promoted with the presence of O2 under cold plasma conditions. The formation of syngas is through a multi-step pathway via the methoxy radical conversion and dissociation of formaldehyde, while the recombination of H generated extra H2. The present DFT study also demonstrates that the plasma synthesis will normally lead to a formation of a mixture of syngas, hydrocarbons, and oxygenates.