Low-temperature Plasma Treatment Research Articles

Sputtering-grown undoped GeSn/Ge multiple quantum wells on n-Ge for low-cost visible/shortwave infrared dual-band photodetection

Multispectral photodetectors (PDs) operating in visible (VIS) to shortwave infrared (SWIR) wavelength ranges are highly desired for various civil and military applications. Traditional vertical p-i-n SWIR PDs lack the detection ability for VIS light due to photon dissipation in the neutral regions. Herein, an i-n type PD was proposed and demonstrated with sputtering-grown undoped Ge0.92Sn0.08/Ge multiple quantum wells (MQWs) on n-Ge substrate to realize VIS/SWIR dual-band detection from 400 to 2000 nm. Three response peaks resulted from the resonate cavity effect at 430, 660 and 1530 nm, respectively, were observed. Benefiting from the defect-free coherent GeSn/Ge MQWs and low-temperature surface plasma treatment, a remarkably low bulk leakage current density of 5.9 mA/cm2 and a low surface leakage current of 37.5 μA/cm were achieved at room temperature under −1 V, resulting in an ultralow dark current density of 13.36 mA/cm2 for a 200-μm-diameter PD. Temperature-dependent electrical characterizations revealed that the dark current was ideally dominated by carrier diffusion mechanism. Eminent detectivities of 5.2 × 108, 7.1 × 108 and 5.6 × 109 Jones at 410, 660 and 1530 nm, respectively, under −1 V were achieved simultaneously at room temperature. This work provides a path way for fabricating low-cost, VIS/SWIR dual-band PDs with complementary metal–oxide–semiconductor (CMOS) compatible technology.

In-Situ FTIR and Laser Induced Fluorescence RONS Characterization of Atmospheric Pressure Nanosecond-Pulsed Surface DBD Plasma for Indirect Treatments of E. Coli

We study the bactericidal efficacy of surface dielectric barrier discharge low-temperature plasma treatments, powered by nanosecond high voltage pulses. We achieve ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim $$\\end{document}4-log reduction in Escherichia coli population, after 10 min treatments, at a distance of 1.5 cm from the plasma surface. To investigate the reactive oxygen and nitrogen species (RONS) responsible for the bactericidal effect, we employ in-situ fourier transform infrared (FTIR) spectroscopy to measure a selection of relevant species, such as O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}, NO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}, N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O and N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_5$$\\end{document}. The measurements are taken under various relative humidity conditions to replicate the bacteria treatment environment. While RONS originating from nitrogen chemistry are detected, nitric oxide (NO), a pivotal molecule in nitrate production, is absent due to the sensitivity limitations of FTIR detection. To overcome this limitation, we employ laser induced fluorescence utilizing a picosecond-pulsed laser to measure the kinetics of NO produced by the plasma. Our results show that the NO concentration is smaller than 1 ppm and primarily localized near the plasma surface, with concentrations increasing proportionally with relative humidity. Notably, at a distance of 1.5 cm from the plasma surface, at which the E. coli is treated, the concentration of NO falls below 50 ppb. Although NO is pivotal in generating secondary reactive species within the plasma, our results suggest that it does not directly contribute to the bacteria inactivation process. Instead, other molecules, such as O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}, NO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}, and N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O, which are found in higher concentrations, may be responsible for the bactericidal properties observed in indirect plasma treatments.

Effect of adsorption processes during low-temperature plasma treatment for changing of electrophysical properties of CVD coatings of carbide plates

The results of a study of the influence of adsorption processes during low-temperature plasma treatment on changes in the electrical properties of CVD coatings of replaceable multifaceted carbide inserts are presented.

Synergistic low-temperature plasma (DBD) treatment of n-hexane gas

The experiment is based on a single dielectric barrier discharge (DBD) plasma generator, using micro-discharge to produce non-equilibrium plasma synergizing with two different catalysts (TiO2, 4A molecular sieve) to decompose n-hexane gas. In the n-hexane degradation experiment, the study investigates the influence of factors such as the type of catalyst, discharge voltage, and flow rate on the degradation rate of n-hexane. The experiments revealed that in all synergistic experiments with catalysts, the degradation rate of n-hexane increased with the decrease in flow rate and with the increase in voltage. Among the four catalysts selected, the 4A molecular sieve catalyst showed the best removal effect for n-hexane gas, reaching 73.2%.

Structure and Deformation Behavior of Polyphenylene Sulfide-Based Laminates Reinforced with Carbon Fiber Tapes Activated by Cold Atmospheric Plasma.

Low-temperature plasma treatment with atmospheric discharge with runaway electrons (DRE) was shown to be an efficient way to activate carbon fiber's (CF) surface and subsequently increase its interlayer shear strength (ILSS) values. It was demonstrated that an acceptable ILSS level was achieved after a DRE plasma treatment duration of 15 min. The treatment of CFs resulted in their surface roughness being increased and their functional groups grafting. The XPS data showed a change in the chemical composition and the formation of reactive oxygen-containing groups. SEM examinations of the PPS/CF laminates clearly demonstrated a difference in adhesive interaction at the PPS/CF interface. After the DRE plasma treatment, CFs were better wetted with the polymer, and the samples cohesively fractured predominantly through the matrix, but not along the PPS/CF interface, as was observed for the sample reinforced with the untreated CFs. The computer simulation results showed that raising the adhesive strength enhanced the ILSS values, but reduced resistance to transverse cracking under the loading pin. In general, higher flexural strength of the PPS/CF laminates was achieved with a greater interlayer adhesion level, which was consistent with the obtained experimental data.

Low-Temperature Plasmas Improving Chemical and Cellular Properties of Poly (Ether Ether Ketone) Biomaterial for Biomineralization.

Osteoblastic and chemical responses to Poly (ether ether ketone) (PEEK) material have been improved using a variety of low-temperature plasmas (LTPs). Surface chemical properties are modified, and can be used, using low-temperature plasma (LTP) treatments which change surface functional groups. These functional groups increase biomineralization, in simulated body fluid conditions, and cellular viability. PEEK scaffolds were treated, with a variety of LTPs, incubated in simulated body fluids, and then analyzed using multiple techniques. First, scanning electron microscopy (SEM) showed morphological changes in the biomineralization for all samples. Calcein staining, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) confirmed that all low-temperature plasma-treated groups showed higher levels of biomineralization than the control group. MTT cell viability assays showed LTP-treated groups had increased cell viability in comparison to non-LTP-treated controls. PEEK treated with triethyl phosphate plasma (TEP) showed higher levels of cellular viability at 82.91% ± 5.00 (n = 6) and mineralization. These were significantly different to both the methyl methacrylate (MMA) 77.38% ± 1.27, ethylene diamine (EDA) 64.75% ± 6.43 plasma-treated PEEK groups, and the control, non-plasma-treated group 58.80 ± 2.84. FTIR showed higher levels of carbonate and phosphate formation on the TEP-treated PEEK than the other samples; however, calcein staining fluorescence of MMA and TEP-treated PEEK had the highest levels of biomineralization measured by pixel intensity quantification of 101.17 ± 4.63 and 96.35 ± 3.58, respectively, while EDA and control PEEK samples were 89.53 ± 1.74 and 90.49 ± 2.33, respectively. Comparing different LTPs, we showed that modified surface chemistry has quantitatively measurable effects that are favorable to the cellular, biomineralization, and chemical properties of PEEK.

Comparative study of methods for the modernization of mesh prostheses as a matrix for the cultivation of fibroblasts

Objective: conduct a comparative study of methods for the modernization of mesh prostheses as a matrix for the cultivation of fibroblasts.
 Materials and methods: In the experiment conditions, polycaprolactone substance was applied to the surface of mesh hernioendoprostheses according to the original method proposed by V.V. Bereshchenko and a team of co-authors (2019). The polyvinylidene fluoride "Uniflex Standard" prosthesis (Lintex LLC, St. Petersburg, Russia) was chosen as the object of study. After applying the polymer, low-temperature plasma treatment was performed with the characteristics: frequency 5 kHz, pulse voltage 10 kV, power density 2 W/cm2, exposure time 5 minutes. After that, the samples were sterilized using X-ray radiation with a power of 150 kV and an exposure of 3 min. The application of cells was carried out by introducing samples into a DMEM medium with fibroblast culture for 5 days. The obtained samples were studied using scanning electron microscopy. Statistical processing was performed using the nonparametric Mann-Whitney test in the Statistica 10 program (Dell Software Company, Round Rock, Texas, United States of America).
 Results: The data obtained indicate the successful attachment of fibroblasts to the surface of modified hernioprostheses.

Thickness of the Modified Polymer Layer Formed by Low-Temperature Plasma Treatment

Thickness of the Modified Polymer Layer Formed by Low-Temperature Plasma Treatment

Thickness of the Modified Polymer Layer Formed by Low-Temperature Plasma Treatment

Experimental data presented in the literature on the depth of processing of polymer films using low-temperature plasma are considered. Changes in the chemical composition and structure along the depth of the samples have been studied using the modern experimental techniques of X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and transmission electron microscopy; precision etching was carriedout with an Ar+2500 cluster beam; and the pit depth was measured by profilometry. It has been found that the thickness of the modified layer is ≤50 nm and depends relatively little on the polymer nature.

Tuning the Pt-N coordination in Pt/MOFs nanosheets under N2 plasma for enhanced oxygen reduction reaction

Regulation of the local coordination of metal sites can tune the electronic structure of catalysts, thereby improving electrocatalytic activity and reaction selectivity. This study proposes a strategy for designing highly active catalysts by regulating Pt-N coordination through N2 plasma treatment. Zn-BDC (1,4-benzenedicarboxylic acid) nanosheets embedded with Pt nanoparticles (Pt/Zn-BDC) were successfully fabricated. Subsequently, radio frequency (RF) discharge N2 plasma was applied to tune the Pt sites of Pt/Zn-BDC at room temperature. The plasma-treated Pt/Zn-BDC showed enhanced catalytic activity for the oxygen reduction reaction (ORR) with a high half-wave potential (0.835 V), superior to those of pristine Pt/Zn-BDC and 20 wt% Pt/C. Notably, rechargeable Zn-air batteries based on plasma-treated catalysts were demonstrated to exhibit high efficiency and stability. The enhanced catalytic performance originated from the optimized coordination environment and electronic structure of the Pt sites under N2 plasma treatment. This study provides a facile, green method of regulating promising ORR electrocatalysts via low-temperature plasma treatment.

Effect of Nitrogen Arc Discharge Plasma Treatment on Physicochemical Properties and Biocompatibility of PLA-Based Scaffolds.

The effect of low-temperature arc discharge plasma treatment in a nitrogen atmosphere on the modification of the physicochemical properties of PLA-based scaffolds was studied. In addition, the cellular-mediated immune response when macrophages of three donors interact with the modified surfaces of PLA-based scaffolds was investigated. PLA surface carbonization, accompanied by a carbon atomic concentration increase, was revealed to occur because of plasma treatment. Nitrogen plasma significantly influenced the PLA wettability characteristics, namely, the hydrophilicity and lipophilicity were improved, as well as the surface energy being raised. The viability of cells in the presence of the plasma-modified PLA scaffolds was evaluated to be higher than that of the initial cells.

Application of low-temperature plasma treatment for rapid and efficient polydopamine coating on 3D-printed polymer scaffolds

Application of low-temperature plasma treatment for rapid and efficient polydopamine coating on 3D-printed polymer scaffolds

Evaluating hydrophobic recovery of N2 and H2O(g) plasma modified silk fibroin films aged at ambient and elevated temperatures.

Silk fibroin is a naturally derived polymer with great potential for biomedical use due to its strength, lack of immune response, and ability to biodegrade. The relatively hydrophobic nature of silk, however, can cause challenges with cell adhesion in vivo. Therefore, modification must be performed to improve the surface hydrophilicity, enhancing silk utility in the biomedical space. Low-temperature plasma (LTP) treatment is an established method for polymer modification and has the benefits of being a solvent-free, adaptable process. N2 and H2O(g) LTP treatments are both well-documented as strategies to enhance polar functional groups on a polymer's surface. However, many polymers tend to revert to their original hydrophobic state upon aging, reversing the effects of LTP modification. The hydrophobic recovery of N2 and H2O(g) LTP-modified silk has not been previously studied but has important implications for the uses and longevity of silk substrates in biomedical contexts. The goal of this study was to systematically evaluate the hydrophobic recovery of N2 and H2O(g) LTP-treated silk films. Films were LTP-modified using optimized plasma parameters (applied power, pressure, treatment time) and aged under both ambient and elevated temperature conditions up to 6 weeks after the initial treatment. Silk film surface properties were evaluated immediately after treatment and throughout the aging process using both water contact angle goniometry and x-ray photoelectron spectroscopy. LTP-treated silk films demonstrated a significant decrease in hydrophobicity compared to the untreated controls. Remarkably, both N2 and H2O(g) LTP modifications resulted in surfaces that retained hydrophilic properties over the 6 week aging period. Our findings represent a departure from what has been previously demonstrated in most LTP-modified synthetic polymers, suggesting that the secondary structure of silk fibroin plays a critical role in resisting hydrophobic recovery.

Experimental degradation of atrazine in soil by dielectric barrier discharge and optimization

In this study, a self-made rotating double-media barrier reactor was used for remediation of atrazine contaminated soil, aiming to provide a reference for industrial application of low-temperature plasma treatment of organic contaminated soil. The effects of applied voltage and reactor state on the reactor discharge performance were investigated. When the applied voltage was increased, the energy efficiency of low-temperature plasma increased; the effect of reactor state was not significant. The effects of input voltage, reactor rotational speed and soil water content on the degradation efficiency of atrazine were investigated, and the results showed that the degradation rate of atrazine increased when the input voltage was 35 kV and the treatment time was 25 min, and the degradation rate of atrazine was 71.12%; when the reactor rotational speed and soil water content were 18.7 r/min and 0.8%, the degradation rates were 73.25% and 65.41%. The response surface method was applied to optimize the selection. The results showed that the significance degree of each factor was input voltage > soil water content > rotating motor speed, and the optimal conditions were 0.6% soil water content, 37 kV input voltage, 18 r/min reactor speed, and 51.93% atrazine degradation rate.

Improving catalytic performance and reusability of flower-like Co-B-P amorphous alloy nanobelts for the selective hydrogenation of furfural in water

Herein, active, low-cost, stable, and sustainable amorphous alloy Co-B-P nanobelts (NBs) are synthesized for the selective hydrogenation of furfural (FFR) to furfuryl alcohol (FFA) in H2O. The Co-B-P NBs are flower-like bundles of ultrathin nanosheets obtained by reducing Co ions in a layered liquid crystal using double-reducing agents at room temperature. The specific surface area, hydrogen adsorption capacity, surface states, and FFR selective hydrogenation performance of the Co-B-P NB catalyst can be modified via low-temperature plasma treatment. The treatment does not change the amorphous structure of Co-B-P NBs. In H2O, Co-B-P NBs treated with plasma at an appropriate power and time exhibit 100% FFR conversion and 95.8% FFA selectivity within 80 min at 80 °C and 1.2 MPa H2 pressure. Moreover, plasma treatment can be used to regenerate Co-B-P NB catalysts. The catalytic activity of Co-B-P NB catalysts can be restored using plasma treatment when it decreases because of their oxidation after several hydrogenation cycles.

Low-Temperature Atmospheric Pressure Plasma Treatment in the Polymer and Textile Industry

Plasma treatment is a popular technique for modifying the surface properties of a wide range of materials (plastics, glass, metals, and wood) prior to gluing, bonding, and painting. Physical and chemical properties are altered to improve or confer specific characteristics of materials in an environmentally friendly manner. Low-temperature atmospheric pressure plasma (LTAPP) is an innovative technology offering surface modification of heat-sensitive materials using an easy one-step procedure. LTAPP treatment is routinely employed for the surface modification of polymer-based materials to enhance their adhesion, printability, and surface sterility. This article demonstrates that LTAPP plasma treatment also opens up new opportunities for the textile industry. It has a positive effect on fabric wettability, liquid repellency, dyeability, UV protection factor, shrink resistance, flame retardancy, and so on. This article describes selected applications of LTAPP in polymer science and the textile industry, highlighting current research trends in material science.

Сушка яблочных чипсов с применением интеллектуальной обработки низкотемпературной атмосферной плазмой

The food industry needs more effective drying procedures that would maintain the quality of the original fruit or vegetable. Infrared drying combined with advanced electrophysical technologies may be a perfect solution. The present research objective was to study the effect of low-temperature atmospheric gas plasma treatment on the drying efficiency of apple slices.
 The research featured apples of the Idared variety (Russia) sliced into pieces of 5, 7, and 10 mm. The experiment involved the parameters of drying kinetics and moisture diffusion. The quality of the apple slices was assessed by the total content of phenols and flavonoids, generalized antiradical activity, color characteristics, and the Fourier transform infrared (FT-IR) spectrum.
 The electropores induced by the cold atmospheric gas plasma processing had a tree-like structure. The pre-treatment reduced the drying time by 18.0, 13.0 and 10.5% for the samples with a thickness of 5, 7, and 10 mm, respectively. The specific energy consumption decreased by 15–18%, depending on the slice thickness. The pre-treatment also increased the total content of phenols, flavonoids, and antiradical activity by 2.5–14.3, 19.1–25.9, and 8.3–35.4%, respectively.
 Therefore, the pre-treatment with cold atmospheric gas plasma reduced the drying time and preserved the original biologically active compounds in dried apple slices.

Pretreatment of Bituminous Coal By-Products for the Hydrometallurgical Extraction of Rare Earth Elements

Low-temperature plasma (LTP) oxidation has been widely used to study the mineralogy of the mineral matter existing in coal sources. The current study investigated the potential of LTP oxidation as a pre-treatment method to improve rare earth element (REE) leachability from coal and its by-products. Representative density-fractionated samples of Baker and Fire Clay coarse refuse seam materials were ground to a top size of 180 µm and subjected to low-temperature plasma oxidation. Subsequently, the treated samples were leached at 1% w/v solids concentration and 75 °C for 5 h using (i) de-ionized (DI) water, (ii) 0.1 mol/L of ammonium sulfate, and (iii) 1.2 mol/L of sulfuric acid. It was determined that LTP treatment improved REE leaching characteristics, especially the leaching of heavy REEs (HREE), existing in the lighter density fractions of the Baker seam coarse refuse material. For instance, the HREE recovery for the 1.6 specific gravity (SG) float fraction increased from 8% to 33% using 0.1 mol/L of ammonium sulfate solution after 32 h of LTP treatment. This finding indicated that HREEs associated with the organic matter were released by the LTP treatment and adsorbed onto the surfaces of highly negative charged mineral matter and was exchanged with ammonium to allow their recovery. Similarly, when using 1.2 mol/L of sulfuric acid, the HREE recovery increased from 23% to 53% for the 1.6 SG float fraction. Interestingly, LTP oxidation did not provide significant improvement in REE recovery from the 2.2 sink density fractions, which was likely due to its lower organic content. No significant benefits were observed when treating the Fire Clay coarse refuse material, which was likely due to the lack of organic affinity and the difficult-to-leach REE minerals associated with the coal source such as monazite, xenotime, and zircon. Conversely, high-temperature oxidation within a temperature range of 600–750 °C significantly improved REE leaching characteristics for both coal sources. Improvement in REE recovery was due to decarbonization of the material, clay dehydroxylation and subsequent conversion of liberated REE-bearing minerals into a more leachable form. However, increasing the temperature above 800 °C decreased REE recovery due to the conversion of meta-kaolinite into mullite, which is chemically stable.

A green process for producing xylooligosaccharides via autohydrolysis of plasma-treated sugarcane bagasse

Due to alarming energy consumption and population growth, the transition to a circular economy is being pursued by searching for alternative resources to produce chemicals and energy. In this regard, lignocellulosic biomass, as the most abundantly accessible plant material, is a suitable alternative for satisfying this high demand. Sustainable lignocellulose biorefineries could convert cellulose, hemicellulose, and lignin into high-value products. Most available approaches prioritize cellulose and lignin over hemicellulose. In this work, autohydrolysis treatment of sugarcane bagasse is developed to produce xylooligosaccharides (XOS) with a variable degree of polymerization (2−6) using low-temperature atmospheric-pressure plasma and ball-mill treatment on raw bagasse. The reactive oxygen, ozone, hydronium ions (H3O+), and nitrogen species generated by plasma increase hemicellulose conversion. XOS hydrolysate obtained from plasma pre-treated samples (41.1%) was quantified for xylobiose (12.1%), xylotriose (10.1%), xylotetrose (6.9%), xylopentaose (7.1%), and xylohexaose (4.9%) (6 h of autohydrolysis at 135 °C). Xylan hydrolysate was also yielded 21.2% xylose, and 2.2% furfural, respectively. The entire process (plasma and autohydrolysis) was conducted in water without using any other chemicals. These results suggest the potential role of plasma pre-treatment prior to hydrothermal treatments to selectively produce XOS.

Low-Temperature Plasma Treatment of Aluminum for Improved Surface Bonding

Low-Temperature Plasma Treatment of Aluminum for Improved Surface Bonding