Air Dielectric Barrier Discharge Plasma Research Articles

The Role of Gas-Liquid Interface in Controlling the Reactivity of Air Dielectric Barrier Discharge Plasma Activated Water

The Role of Gas-Liquid Interface in Controlling the Reactivity of Air Dielectric Barrier Discharge Plasma Activated Water

Investigation of the effect of mass percentage concentration of polystyrene–toluene solution on the surface properties of the plasma‐treated polystyrene thin films

AbstractPolystyrene (PS) finds diverse applications across various fields, often necessitating a hydrophilic PS surface. In this study, the PS films were prepared using PS–toluene solutions of 15, 20, and 25 mass percentage concentrations (% w/v). Here, the main focus is on the influence of concentration on the hydrophilization of the prepared PS thin films under atmospheric pressure air dielectric barrier discharge plasma treatment. The contact angle, surface energy measurements, atomic force microscopy, and Fourier‐transform infrared spectroscopy analysis were conducted to evaluate the PS surface properties. Our results demonstrate, for the first time, the significant role of concentration in altering surface properties; the lower concentration of PS films leads to the most hydrophilic surface. Fourier‐transform infrared spectroscopy analysis confirms an increase in the OH functional group on the PS surface. atomic force microscopy analysis reveals needle‐shaped surface morphology, increased roughness and an expanded effective surface area. Surface energy analysis confirms an increase in the polar sector of surface energy. Overall, the findings from this research underscore the increase in film hydrophilicity with a decrease in PS–toluene concentration.Highlights Polystyrene (PS)–toluene solutions with different concentrations were prepared. PS–toluene films were spin‐coated and were been treated with dielectric barrier discharge plasma. The contact angle, surface energy measurements, atomic force microscopy, and Fourier‐transform infrared spectroscopy analysis were conducted. PS films with lower concentration have more impact from plasma treatment. Concentration, impact the hydrophilicity and roughness of treated PS films.

The contribution of electrode spacing and operating voltage on the time-resolved optical emission spectra of atmospheric-pressure air and Ar DBD plasma

This paper reports the optical characterization of a controlled atmospheric-pressure dielectric barrier discharge (DBD) plasma source in air and Ar environments. In this study, Ar flow rate is held constant at 1 L/min while the operating voltages varied from 6.5 kV to 12.7 kV. Under these conditions, a calibrated commercial compact spectrometer covering the range from 200 to 850 nm was used to record the emission spectra of DBD plasma operating at different voltages, gap distances, and gas types. Using the Boltzmann distribution, we calculated the electron density ( n e ) and excitation temperatures in the plasma of air and Ar DBD at 2 mm gap distance . The emission spectra lines of the hydroxyl radicals (OH), N 2 , and Ar ions are acquired at different operating conditions. According to the findings, the light intensity of Ar DBD is significantly higher than that of air DBD under the same conditions of operation. The intensity of the generated plasma spectrum is also shown to rise with both an increase in the input voltage and a decrease in the gap distance. The measurements also showed that the average temperature of the excited electrons is around 1.1 eV for air DBD and 0.11 eV for Ar DBD, while n e for both is on the order of 10 16 cm − 3 . These results show that as the working voltage increases, the plasma changes from a filamentary state to a homogeneous mode. Knowing the DBD parameters increases its chance to compete with traditional methods in many fields, such as water, polymers, and biomedical treatments.

E. Coli inactivation by humidified air barrier discharge plasmas and the chemical stability of amino acids

In this study, we use atmospheric air dielectric barrier discharge (DBD) plasma to inactivate E. coli (E. coli) by changing the air humidity levels. In order to analyze the inactivation process of E. coli during the humidified air DBD plasma treatment, we analyze the byproducts of 12 representational amino acids and compare their chemical stability. The experimental results show that the E. coli surface density (CFU cm−2) on a steel disc decreased significantly when the air humidity was increased from 20% to 60%, and humidified air DBD plasma at 60% humidity is very effective in inactivating E. coli. A consistently potent deactivation effect on E. coli can be seen in plasma afterglow treatment experiments over a storage time of two minutes, indicating that plasma-activated long-lived reactive oxygen and nitrogen species play a crucial role in controlling the E. coli inactivation. Compared to the low humidity (20%) condition, the concentration of reactive species produced by the plasma at high humidity (60%) increased 2-fold for 2-hydroxyterephthalic acid and 5-fold for hydrogen peroxide while ozone production was halved. Amino acid experiments showed that amino acids may be oxidized, hydroxylated and nitroxylated by reactive species. The reduction of amino acids by air DBD plasma was even more pronounced at high air humidity compared to low air humidity. Our analysis indicates that the significant inactivation of E. coli by humified air DBD plasma is related to the chemical instability of amino acids.

Influence of air DBD plasma treatment on the shear and flexural strength of adhesively bonded glass fiber reinforced epoxy composite joints

In this study, air dielectric barrier discharge (DBD) plasma treatment was applied at various voltages and treatment durations to improve the bonding strength of glass fiber reinforced epoxy composites (GF/EP). In addition, single lap shear and three-point bending strengths of adhesively bonded joints were compared between untreated and surface-treated (sanding, peel ply, and plasma) samples. Surface properties of GF/EP composites were examined using contact angle, surface free energy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and Atomic Force Microscopy (AFM). Then, mechanical tests (single lap shear and three point bending) were performed and the damage modes were determined. Surface analyses revealed that wettability and polar functional groups increased on the GF/EP surface after plasma treatment. From the mechanical test results, it was observed that the plasma treatment applied to GF/EP composites increased both single lap shear and flexural strength compared to untreated, sanding and peel ply surface treatments. After both single lap shear and 3-point bending tests, adhesive, and light fiber tear failure modes were observed.

Synergistic degradation levofloxacin through dielectric barrier discharge and sodium persulfate

The release of antibiotics that are difficult to degrade by themselves into the environment have received increasing attention because they have posed great threat to natural ecosystem and human health. Sodium persulfate (PS) is used to treat organic wastewater because of its strong oxidation, but it needs to be activated. Dielectric barrier discharge (DBD) can product stable gas discharge plasma that is suitable for activating PS. The synergistic degradation process of levofloxacin (LFX) by air DBD plasma with PS were investigated. The effects on the degradation ratio and energy efficiency of LFX were studied, including input power, air flow rate, original concentration, discharge spacing, and PS dosage. The degradation kinetics and synergistic factors were calculated under different PS additions. After plasma alone treatment 45 min, the maximum degradation ratio of LFX was 58.74 % and 88.63 % via plasma alone and plasma synergistic with PS under 15 W input power and 50 mg·L−1 LFX original concentration. The energy efficiency, the first-order reaction rate constant and the synergistic factor SI was 0.1532 g·(kW·h)−1, 4.116 × 10−2 min−1 and 1.64, respectively. The change of ozone concentration in the reaction system after adding PS was measured. The effects on the synergistic degradation of LFX of two radical scavengers, methanol (MeOH), and tert-butanol (TBA), were investigated. After calculation, the contribution ratios of ·OH and SO4-· were 48.08 % and 26.97 %, respectively. The intermediate products were analyzed by LC-MS in the decomposition process of LFX, and the probable decomposition pathway of LFX was presented.

Efficient treatment of bio-contaminated wastewater using plasma technology for its reuse in sustainable agriculture

Water-related crisis represents one of the significant challenges of the rapidly growing world population. This study demonstrates an example of the novel technology of Non-Thermal Plasma (NTP) wastewater treatment for its sustainable recovery and reuse in agriculture. NTP treatment of wastewater not only causes microbial decontamination but produces Reactive Oxygen and Nitrogen Species (RONS), which can consequently improve seed germination and plant growth. We investigated the effects of the new Fountain Dielectric Barrier Discharge air plasma reactor for the treatment of bulk quantity water contaminated by Staphylococcus epidermidis or Escherichia coli bacteria. Then, employing the treated water for barley seed germination showed >20% enhancement compared to using tap water. The inactivation of bacteria in water was determined in dependence on pH, Oxidation-Reduction Potential, and correlated with chemical RONS produced in the water (hydrogen peroxide, nitrites, and especially nitrates). By utilizing the Responses Surface Methodology, we identified the optimal plasma treatment time per litre required for efficient RONS production and bactericidal effect in the wastewater treatment, which was linearly scalable with water volume. After the optimum plasma treatment time, a sharp drop in pH, and the concentrations of nitrites and hydrogen peroxide were observed, which is related to the peroxynitrite formation leading to the significant bacterial reduction up to 7-log.

Study of physico-chemical and antibacterial properties of DBD plasma treated ahimsa silk coated with natural active agent

This study investigated the effect of dielectric barrier discharge (DBD) plasma on the physicochemical and antibacterial properties of ahimsa silk fabric. The fabric was pre-treated for 1–5 min with DBD plasma in ambient air. The leaf extracts of Camellia sinensis (Green Tea) and Ocimum sanctum (Tulsi) were applied to the fabric to impart an antibacterial finish. Wettability, SEM, AFM, and tensile strength analyses demonstrated increased hydrophilicity and surface roughness with a slight reduction in mechanical strength. Both ATR-FTIR and XPS indicated an increase in the concentration of polar functional groups, such as -OH, -NH, -CHO, and -COOH, on the surface of the plasma-treated fabric. Antimicrobial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was evaluated using the agar plate method and modified Hohenstein test. The results verified the efficacy of plasma-treated fabric, with an approximately 93% reduction in E. coli and a 96% reduction in S. aureus growth that persisted even after three washing cycles. This study suggests that DBD plasma at atmospheric pressure can be used as an eco-friendly technology for modifying the surface of silk fabrics to promote better adherence of plant extracts to the fabric and subsequently enhance their microbial resistance.

Non-thermal atmospheric-pressure plasma potentiates mesodermal differentiation of human induced pluripotent stem cells

Non-thermal atmospheric-pressure plasma has been used for biological applications, including sterilization and stimulation of cell growth and differentiation. Here, we demonstrate that plasma exposure influences the differentiation pattern of human induced pluripotent stem cells (hiPSCs). We treated hiPSCs with dielectric barrier-discharge air plasma and found an exposure dose that does not kill hiPSCs. Immunohistochemical staining for E-CADHERIN showed that the exposure affected cell-cell attachment and doubled the average size of the hiPSCs. Analysis of mRNAs in embryoid bodies (EBs) from plasma-treated hiPSCs revealed repression of ectoderm genes, including WNT1, and increased expression of mesoderm genes. Importantly, hiPSCs deficient in DNA repair only displayed minimal damage after plasma exposure. Collectively, our results suggest that plasma treatment can be another tool for directing the fate of pluripotent stem cells without disrupting their genomic integrity.

Detection of NO3− introduced in plasma-irradiated dry lettuce seeds using liquid chromatography-electrospray ionization quantum mass spectrometry (LC-ESI QMS)

Discharge plasma irradiates seeds with reactive oxygen and nitrogen species (RONS). However, RONS introduced in seeds by plasma irradiation have not been successfully detected thus far. This study provides experimental evidence that nitrate ion NO3− is introduced in lettuce seeds as RONS upon irradiation with atmospheric-pressure air dielectric barrier discharge plasma. Plasma irradiation for 5 min promotes seed germination. The components of the plasma-irradiated seeds were examined using electrospray ionization quantum mass spectrometry (ESI QMS), which revealed that the plasma irradiation introduced an ion with a mass of 62 m/z in detectable amounts. This ion was identified as NO3− by liquid chromatography (LC), multiple wavelength detector (MWD), and LC-ESI QMS. A one-dimensional simulation at electron temperature Te = 1 eV, electron density Ne = 1013/m3, and gas temperature Tg = 300 K indicated the introduction of NO3−, involving nitric oxide NO. NO3− is one of the most important ions that trigger signal transduction for germination when introduced in seeds. The scanning electron microscopy (SEM) images revealed that there was no change on the surface of the seeds after plasma irradiation. Plasma irradiation is an effective method of introducing NO3− in seeds in a dry process without causing damage.

Inactivation of E. coli, S. aureus, and Bacteriophages in Biofilms by Humidified Air Plasma.

In this study, humidified air dielectric barrier discharge (DBD) plasma was used to inactivate Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and bacteriophages in biofilms containing DNA, NaCl, carbohydrates, and proteins. The humidified DBD plasma was very effective in the inactivation of microbes in the (≤1.0 μm) biofilms. The number of surviving E. coli, S. aureus, and bacteriophages in the biofilms was strongly dependent on the constituent and thickness of the biofilms and was greatly reduced when the plasma treatment time increased from 5 s to 150 s. Our analysis shows that the UV irradiation was not responsible for the inactivation of microbes in biofilms. The short-lived RONS generated in the humidified air DBD plasma were not directly involved in the inactivation process; however, they recombined or reacted with other species to generate the long-lived RONS. Long-lived RONS diffused into the biofilms to generate very active species, such as ONOOH and OH. This study indicates that the geminated NO2 and OH pair formed due to the homolysis of ONOOH can cause the synergistic oxidation of various organic molecules in the aqueous solution. Proteins in the biofilm were highly resistant to the inactivation of microbes in biofilms, which is presumably due to the existence of the unstable functional groups in the proteins. The unsaturated fatty acids, cysteine-rich proteins, and sulfur–methyl thioether groups in the proteins were easily oxidized by the geminated NO2 and OH pair.

Statistical optimization of open air dielectric barrier discharge plasma effect on self-cleaning activity of ultrasonically Cu2O/TiO2-coated cotton fabric

Statistical optimization of open air dielectric barrier discharge plasma effect on self-cleaning activity of ultrasonically Cu2O/TiO2-coated cotton fabric

Tetracycline degradation using combined system of dielectric barrier discharge air plasma and zeolites synthesized at different Na2O/SiO2 ratios

In this work, a combination of synthesized zeolite with a Dielectric Barrier Discharge (DBD) air plasma reactor was applied for the removal of tetracycline (TC) from effluents. The zeolites with different Na2O/SiO2 ratios were synthesized and inserted in a DBD reactor. The as-prepared zeolites were characterized by FTIR, SEM, BET, EDX, XRD, and TEM. The XRD results showed that the P-type zeolite turned to Y-type zeolite with an increasing Na2/SiO2 ratio from 0.5 to 1.5 and 2.5. The TC degradation experiments indicated that 79.1% of the initial TC was removed from the solution by the hybrid plasma- zeolite (Na2O/SiO2 ratio of 0.5) system after 45 min. The plasma in synergy with zeolite caused the changing amount of long-life oxidants in the system and converted it to higher reactive species. The combined system could reduce around 17 and 10% of the total organic carbon (TOC) and chemical oxygen demand (COD) more than the sole DBD system, respectively. Losing just 8% of the initial efficiency of the hybrid system after four successive runs revealed the stability of the proposed system. The radical trapping experiment method indicated that the role of •OH in the TC degradation was more critical than that of O2•−.

Influence of non-thermal plasma systems and two favorable surface treatments on the shear bond strength of PAEKs to composite resin

This study aimed to investigate the effect of non-thermal plasma systems with and without two favorable surface treatment techniques on the surface roughness (Ra) and shear bond strength (SBS) of polyaryletherketone (PAEK) polymers to veneering composite resin material. A total of 288 (n = 144 for each polymer) Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK) samples (7 73mm) were divided into the surface treatment methods (n = 16): untreated (CNT); dielectric barrier discharge air plasma treatment (DBD); atmospheric pressure plasma treatment with a plasma brush (APB); 98% sulfuric acid etching (SA); SA_DBD; SA_APB; tribochemical silica coating (TBC); TBC_DBD; TBC_APB. The Ra (n = 5) and scanning electron microscope (SEM) analyses (n = 1) were performed. A bonding agent was applied to the remaining samples (n = 10) and veneered with a composite resin. After storing in distilled water for 24 h at 37 °C, the SBS test was applied with a universal test machine, and the failure modes were examined with an optical microscope. The SBS and Ra data were statistically analyzed with Kruskal Wallis, two-way analysis of variance (ANOVA), and compared with Mann-Whitney_U and Tamhane tests (α = 0.05). The highest SBS value was observed in Groups SA (22.67 ± 1.48 MPa) for PEEK, Group TBC (18.91 ± 1.09 MPa) for PEKK polymer groups. The highest Ra values were determined in Group TBC_DBD for both polymers. While the TBC may enhance the SBS values of both polymers, the SA application is more effective for PEEK polymer regarding the SBS value. In contrast to the effect of DBD, APB application is beneficial for improving the bonding capacity of PAEKs.

The Effect of DBD Plasma Activation Time on the Dyeability of Woven Polyester Fabric with Disperse Dye.

This study consists of two parts. In the first, the woven polyester fabric, after washing to remove lubricant oils, was treated with the dielectric barrier discharge (DBD) plasma at the short plasma exposure time (from 15 to 90 s). The effect of the plasma exposure time on the activation of the polyester fabric was assessed by the wicking height of the samples. The results show that the wicking height in the warp direction of the plasma-treated samples improved but was virtually unchanged in the weft direction. Meanwhile, although the tensile strength in the warp direction of the fabric was virtually unaffected despite the plasma treatment time up to 90 s, in the weft direction it increased slightly with the plasma treatment time. Scanning Electron Microscope (SEM) images and the X-ray Photoelectron Spectroscopy (XPS) spectra of the samples before and after the plasma treatment were used to explain the nature of these phenomena. Based on the results of the first part, in the second part, two levels of the plasma treatment time (30 and 60 s) were selected to study their effect on the polyester fabric dyeability with disperse dyes. The color strength (K/S) values of the dyed samples were used to evaluate the dyeability of the fabric. The SEM images of the dyed samples also showed the difference in the dyeability between the plasma-treated and untreated samples. A new feature of this study is the DBD plasma treatment condition for polyester fabrics. The first is the use of DBD plasma in air (no addition of gas). Second is the very short plasma treatment time (only 15 to 90 s); this condition will be very favorable for the deployment on an industrial scale.

Generation and characterization of atmospheric pressure dielectric barrier discharge air plasma and its antifungal potential: a case study on Alternaria alternata

The present research evaluates the generation and characterization of 26 kHz-atmospheric pressure dielectric barrier discharge (DBD) air plasma (DBD-AP) and the possible antifungal action against the pathogenic fungus Alternaria alternata. The DBD-AP visual and emission spectra intensities increased with increasing the applied voltage. The generated plasma was mainly inhomogeneous due to the presence of streamers in the discharge gap and it showed diffuse with less gap distance or with increasing the applied voltage. The measured consumed power was 26.52 W for 10.3 kV and 17.4 mA at 3 mm gap. The emission spectra showed the presence of NO and N2 bands which were enhanced due to the increase of the applied voltage. Significant reduction in A. alternata growth accompanied by loss of fungal cells structure was observed with increasing the DBD-AP exposure time. The present article confirms the potential of DBD-AP to efficiently control the plant-pathogenic fungus A. alternata.

Investigation of Antimicrobial Activity of DBD Air Plasma-Treated Banana Fabric Coated with Natural Leaf Extracts.

This paper focuses on the investigation of the antimicrobial activity of banana fabric treated with dielectric barrier discharge (DBD) plasma. The fabric was exposed to air plasma for varying treatment times of 1–5 min followed by coating with green tea (Camellia sinensis) and tulsi (Ocimum sanctum) leaf extracts at five different concentrations. The treated fabric was evaluated in terms of surface wettability by a range of tests like wet-out time analysis, hydrophilicity test, and contact angle measurements. The functional groups formed on the treated fabric were analyzed by attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy. The surface morphology was studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM), and the surface chemistry was studied using X-ray photoelectron spectroscopy (XPS). The FTIR and XPS analysis results indicate that the plasma-treated fabric was found to have a higher concentration of polar groups (−COOH, −OH, −C=O) that has improved surface hydrophilicity and functionality. The antimicrobial activity of the treated fabric surface was determined both qualitatively and quantitatively by the agar plate method and modified Hoenstein test, against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. An improvement in the antimicrobial property was observed in plasma-treated banana fabric coated with natural extracts even after four washing cycles. This study suggests that air DBD plasma treatment followed by the absorption of tea/tulsi leaf extracts can serve as a better tool for developing natural antimicrobial textiles, which could serve the purpose in medical and healthcare sectors concerning recent times. It has eventually led to better absorption of plant extracts, thereby increasing their antimicrobial activity.

Plasma-Polymerized Phlorotannins and Their Enhanced Biological Activities

Here, we investigated the effect of cold plasma (CP) on the biological activities of phloroglucinol. Phloroglucinol (7.92 and 15.84 mM in methanol) was treated with air dielectric barrier discharge plasma at 250 W. In vitro 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and Ferrous reducing antioxidant power (FRAP) values of phloroglucinol increased in a plasma treatment time-dependent manner. CP treatment of phloroglucinol decreased the lipid oxidation of oil emulsion during storage and increased the antimicrobial activity against Bacillus cereus, Escherichia coli O157:H7, and Staphylococcus aureus. Angiotensin-converting enzyme (ACE) inhibitory activity of phloroglucinol increased and total phenolic content decreased based on CP treatment. CP-induced polymerization of phloroglocinol to phlorotannin derivatives was identified using high performance liquid chromatography with UV detector and electrospray ionization/mass spectrometry (HPLC-UV-ESI/MS) method. Consequently, the polymer structure of phloroglucinol was found in CP-treated phloroglucinol. In addition, CP enhances the biological activity of phloroglucinol and could be applied to bioactive materials in food and related industries.

Effects of DBD air plasma treatment on the enhancement of black gram (Vigna mungo l.) seed germination and growth

Effects of black gram (vigna mungo L.cv. Barimash 3) seed treatments with 400 torr dielectric barrier discharge (DBD) air plasma on seed surface morphology, seed germination, seedling growth and antioxidant enzyme activities in the roots, shoots and leaves were investigated. The plasma discharge voltage, frequency, electrode spacing, gas temperature and power were 5kV, 4.5kHz, 60mm, 310K and 45W, respectively. The seeds were treated for the duration ranging from 20 to 180 s. Seed germination rate, seedling growth, total chlorophyll content, total soluble protein and sugar concentrations in the seedlings grown from the treated seeds were found to increase 13.67%, 37.13%, 37.26%,53.60% and 51.71%, respectively, with respect to control. This study reveals that the DBD air plasma was involved in the enhancement of nitrogen complex in the seed coat of black gram which upregulated the protein through nitrogen conversion that was ultimately responsible for the increased seed germination and seedling growth of black gram.

Investigating the Effects of Atmospheric Pressure Air DBD Plasma on Physio-Chemical and Microbial Parameters of Groundwater

Cold atmospheric pressure plasma generated at atmospheric air produces high energetic electrons, ions, UV radiations, reactive oxygen, and nitrogen species (RONS) which has a wide range of applications in biomedicine, agriculture, textiles, water treatment, etc. Recently, many researches have been carried out on ozonation through DBD (Dielectric barrier discharge) plasma in water treatment. However, direct plasma treatment on water hasn’t been extensively studied yet. In this study, we examined the change in physical, chemical and biological parameters of groundwater by the means of direct DBD plasma activation. The significant reduction in the concentration of biological parameters such as total coliform and E. coli with increasing treatment time was found. Besides that, DBD plasma also lowered down the concentration of physical parameters such as pH, turbidity, total suspended solids, total dissolved solids, and increased electrical conductivity and dissolved oxygen. In addition, the significant drop in the concentration of chemical parameters such as sodium, phosphorus, and calcium was found along with the reduction in heavy metals concentration such as iron, cadmium, lead, chromium, manganese, and zinc. However, the concentration of nitrite, nitrate, and sulfur augmented gradually. Our results revealed the great ability of direct plasma in water treatment.