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Efficient generation of ozone by cold atmospheric plasmas is interesting for sterilisation and decontamination of thermally-sensitive surfaces. This paper presents a study of robust coplanar dielectric barrier discharge (DBD) for generating atmospheric pressure plasma in synthetic air and in oxygen. The atmospheric plasma generated by coplanar DBD in synthetic air showed considerably high ozone production of 2.41 g/h (2.25 slm, 45 W), while the production yield and energy cost were 54 g/kWh and 40.9 eV/molecule. The use of oxygen instead of synthetic air, at much lower discharge power (2.25 slm, 17 W), maintained the ozone production of 2.35 g/h, whereas the production yield significantly increased to 138 g/kWh with a corresponding energy cost of 12.9 eV/molecule. The temperature of coplanar DBD ceramics in synthetic air (45 W) and oxygen (17 W) plasma generation (continuous alternating-current operation) showed temperatures below 70 °C and 30 °C, respectively. The rotational temperatures obtained from optical emission spectroscopy indicated similar gas temperatures in the thin plasma layer close to the surface of the DBD ceramics. The low temperature of the plasma–ceramics interface evidences the applicability of coplanar DBD for the contact treatment of thermally sensitive surfaces where a high concentration of ozone is required. [ABSTRACT FROM AUTHOR]

Cold plasma (CP) has been used to accelerate seed germination. During this study, foxtail millet was exposed to low pressure air plasma at 1 kV and 2 kV for 1, 3, and 5 min, and its germination characteristics and nutrient composition were studied. Among the applied treatment conditions, 2 kV for 3 min showed a higher germination percentage of 84.00%, followed by 1 kV for 5 min with 77.33% after 48 h. In addition, a significant increase in other germination characteristics, such as germination speed, germination potential, seed length, and seed vigour indices I and II, was observed after CP exposure. Optical emission spectroscopy analysis asserted that reactive species generated during CP generation are responsible for hastening the foxtail millet germination through seed surface modification. Further, the CP exposure increased the soluble protein content of foxtail millet up to 19.00 g/100 g, γ-amino butyric acid content up to 62.27 mg/100 g, and reduced phytic acid and tannins to 1.1 mg/g and 0.8 mg/100 g, respectively, through germination. This research explores the potency of cold plasma in accelerating foxtail millet germination and enhancing its nutritional bioavailability. [ABSTRACT FROM AUTHOR]

Rice seeds (Oryza sativa L.) have been treated with cold atmospheric plasma in air both directly in a dielectric barrier discharge and indirectly by gliding arc discharge with plasma activated mist. Comparisons of impacts of the two methods on rice seeds germination and physiological parameters are presented. Plasma has been found to increase seeds hydrophilization and water uptake through decrease of liquid contact angle and increase of total surface free energy of seed's coat. Germination of treated seeds and their seedling growth parameters are enhanced by plasma application. After 20 min of seeds direct and indirect exposures respectively, germination potential increases by 36.73 and 50.4%, germination rate by 26.0 and 30.0%, and germination index by 25.92 and 36.53%. Also, total shoot length increases by 42.2 and 48.5%, and total root length by 15.93 and 22.42%. Plasma enhances physiological changes by increasing nonenzymatic antioxidants substances which in turn increase the tolerance against abiotic stresses. After 20 min for direct and indirect exposures respectively, free proline increases by 30.0 and 40.0%, total soluble carbohydrates by 49.7 and 54.6%. Also, cellular reactive oxygen species (ROS) increase by 52.0 and 60.0%, and malondialdehyde (MDA) decreases by 68.0 and 88.0%. Indirect exposure of rice seeds by plasma activated mist shows enhanced effects on germination and physiological parameters compared to direct one and could be more practical when applied to large scale seeds plasma treatment. [ABSTRACT FROM AUTHOR]

The present work is devoted to the study of DBD discharge development in Ne–Xe gas mixture for optimization of UV source efficiency in excimer lamps. This study was based on a longitudinal on-dimensional model of the dielectric barrier discharge DBD with the aim to investigate the discharge conditions for excimer lamps working and VUV emissions optimization. The results of the present description show the concentration of charged particles, photonic species, and excited atoms and molecules. The effect of operation conditions such as applied voltage, gas mixture composition, and gas pressure, as well as the secondary electron emission due to ion impact at the cathode on DBD discharge characteristics and 173 nm photon generation have been also analyzed and discussed. [ABSTRACT FROM AUTHOR]

Traditional disinfection methods against pathogens have numerous shortcomings, and inventive methods like cold plasma are required for virus inactivation. Here, an atmospheric pressure 13.56 MHz radio-frequency hollow cathode (RF–HC) cold plasma device has been used to build a cold plasma sterilization device, and its virucidal activity is assessed against P2 bacteriophage, a model surrogate for pathogenic viruses. The heart of this device contains a three-layered sterilization chamber which is a rectangular parallelopiped of 42 × 32 × 30 cm3. Optimization experiments were performed to make each corner of this chamber completely virus free after cold plasma treatment. This two-pronged study was conducted to establish the requirement of minimum vol. % H2O2 in minimum time for the complete elimination of phages inside this sterilization chamber even when plasma is not in the direct line of sight. In initial experiments, the effect of the direct plasma line of sight was seen as the top and bottom layers showing less phage killing as compared to the middle of the sterilization chamber. Complete sterilization of bacteriophage, in all the three layers inside the sterilization chamber, was achieved by plasma treatment with 6% H2O2 for 10 min in 80 watts of plasma operating power. It was also seen that 6% H2O2 mist alone is not sufficient to provide a high degree of sterilization, and normal water mist combined with cold plasma can provide a higher level of sterilization at each corner of the chamber. [ABSTRACT FROM AUTHOR]

In the last decades, there have been numerous reports about the separate interactions of a magnetic field and cold atmospheric plasma (CAP) with the biological systems. We have investigated the combined effect of CAP with the static magnetic field (SMF) as an effective method for cancer cells treatment. MDA-MB-231 breast cancer cells were cultured and treated with CAP with different input power and exposure times in the presence and absence of the SMF. Vitamin C was also used in medium, and cell viability was investigated in the presence and absence of this antioxidant compound. The MTT assay was employed to measure cell survival, and a T-test or one-way ANOVA was used to assess the significance level of quantitative data. In order to determine the migration rate of cancer cells, wound healing assay was carried out. Results show that the presence of the SMF and vitamin C as well as increasing the input power significantly decrease the survival and migration rate of the cells. The results of the present investigation will greatly contribute to improve the CAP efficiency in cancer therapy by using the SMF and vitamin C as a complement to conventional CAP therapies. [ABSTRACT FROM AUTHOR]

This research explored the capability of seed priming with the non-thermal plasma to modify reactions of Melissa officinalis, an important medicinal plant, to zinc oxide (nZnO) or selenium (nSe) nanoparticles. The germinating seeds were primed with the plasma (0.84Wcm−2 surface power densities) under different durations (0, 50, 90, and 120 s); after that the primed seeds were cultured in petri dish containing Hoagland nutrient solution manipulated with various concentrations of nSe (0, 2, 5, 10, and 20 mgl−1) or nZnO (0, 50, and 250 mgl−1). The plasma treatments not only improved growth-related characteristics (stem length, root length, and leaf wide) and biomass accumulation but also toxicity signs of nSe (5, 10, and 20 mgl−1) were partly mitigated by the plasma priming. Interestingly, the plasma treatments induced peroxidase activity about 46%. Similarly, inductions in the activity of phenylalanine ammonia lyase were recorded in the plasma-primed seedlings. The correlations between the evaluated traits were found to be significant. Taken collectively, it could be exploited for delivering a novel tool regarding seed priming, biofortification, and seed/seedling-derived foods. [ABSTRACT FROM AUTHOR]

The antimicrobial effects of the cold plasma for the dental pathogenic microorganism propose a promising approach to the Denture Stomatitis (DS) treatment. However, it is crucial to understand that the complexity of the biofilm microenvironment may compromise the efficiency of the therapy. As one of the major issue for DS, Candida albicans biofilms (ATCC10231) formed on denture base resins were treated by cold Ar/O (2 %) plasma jet. Spatial viability of the biofilms was investigated with confocal scanning laser microscopy through evaluating their inside cross-section properties. Results showed Candida albicans biofilms with thickness of ~100 µm was completely inactivated by 8 min plasma treatment. Morphology change of the fungi was also observed by the scanning electron microscopy. Drug susceptibilities, the sessile minimum inhibitory concentration (SMIC50) of the biofilm for amphotericin B and fluconazole were decreased from >32 and >256 µg/mL to 8 and 64 µg/mL after 1 min's plasma treatment, respectively. The reactive species produced from plasma were monitored by optical emission spectroscopy. The successfully inactivation of Candida albicans biofilms and the significant enhancement of its drug susceptibilities induced by the plasma released reactive species propose a promising strategy for the treatment of DS caused by drug-resistant Candida albicans biofilms. [ABSTRACT FROM AUTHOR]

Titanium and its alloys are currently considered as successful biocompatible materials because titanium made implants become easily, structurally and functionally, connected to biological systems. As far as biological systems is concerned, antibacterial activity for medical implants are worth of interest to prevent inflammation at implant site. In this study RF cold plasma is employed as potential technology to prevent or reduce bacterial activity on Ti samples. Several plasma parameters are investigated for finding the best antibacterial process conditions against Escherichia coli 32. Main results of this investigation show that high antibacterial activity is exhibited by Ti samples in several experimental set-ups. In addition, the antibacterial activity detected at same level of previous, 16 days after the treatment suggests the effectiveness of the plasma surface modification. Finally, an attempt is made to correlate antibacterial effect with plasma treated titanium surface energy and plasma parameters. [ABSTRACT FROM AUTHOR]

The delamination of polyurethane (PU) laminated glass usually occurs at the interface between PU and inorganic glass. To prevent interlaminar delamination of PU and inorganic glass, PU was treated with cold plasma. The transparency of PU improved after cold plasma treatment. The cold plasma-treated PU showed 2 to 6 % higher transmittance than untreated PU. The adhesive strength of PU laminated glass increased by at least 96 % after cold plasma treatment. The adhesive strength of untreated PU samples rapidly decreased with increased hygrothermal aging time, whereas treated PU maintained almost 93 % of the original adhesive value even after hygrothermal aging for 30 days. FTIR analysis shows that -CO-O-C-, -C=O, and -CO-N groups appeared on the surface of cold plasma-treated PU, which resulted in the formation of hydrogen bonds at the interface between PU and silicate glass. After cold plasma treatment, the contact angle of PU changed from 105° to 79°, and the surface roughness of PU membranes changed from an average value of 19.74 to 57.16 nm. [ABSTRACT FROM AUTHOR]

A continuous plug flow reactor supported by a dielectric barrier discharge (DBD) is used to study the conversion of methane, carbon dioxide, and oxygen at different compositions. The three studied gases were diluted with helium to 3 % with an overall flow rate of 200 sccm. The 13.56 MHz plasma was ignited at atmospheric pressure. The product stream and the inlet flow were analyzed by a FTIR spectrometer equipped with a White-cell and by a quadrupole mass spectrometer. The DBD reactor generates hydrogen, carbon monoxide, ethane, ethene, acetylene, formaldehyde, and methanol. Additional oxygen in the feed has positive effects on the yield of methanol, formaldehyde and carbon monoxide and reduces the total consumed energy. The hydrogen yield reaches its maximum at medium amounts of oxygen in the inlet flow. The conversion of methane increases to a limiting value of about 35 %. Methane rich feeds increase the yield of hydrogen, ethane and methanol. On the other hand, additional oxygen has a negative influence on the produced amount of C2 hydrocarbons. The conversion of methane and carbon dioxide as well as the yield of synthesis gas components and C2 hydrocarbons increases by changing the plasma power to higher values. [ABSTRACT FROM AUTHOR]

The influence of water on the plasma assisted conversion of methane and carbon dioxide in a dielectric barrier discharge (DBD) plug flow reactor was studied. The plasma at atmospheric pressure was ignited by a power supply at a frequency of 13.56 MHz. Product formation was studied at a power range between 35 and 70 W. The concentrations of the three gases were altered and diluted with helium to 3 %. FTIR spectroscopy and mass spectroscopy were applied to analyze the inlet and the product streams. The main product of this process are hydrogen, carbon monoxide and ethane. Ethene, ethine, methanol and formaldehyde are generated beside the main products in this DBD in lower concentrations. The conversion of methane, the ratio of the synthesis gas components (n(H):n(CO)), and the yield of oxygenated hydrocarbons and hydrogen increases by adding water. The total consumed energy reaches lower values for small amounts of water. Additional water does not influence the generated amount of C2 hydrocarbons and of CO, but decreases the carbon dioxide conversion. [ABSTRACT FROM AUTHOR]

The main compounds of non-thermal plasmas generated by a discharge in humid air at atmospheric pressure are re-examined to explain the twin chemical properties of discharges over aqueous waste solutions, i.e. the acid and oxidizing effects. The acid effects are attributed to transient nitrous and peroxynitrous acids and to stable nitric acid. The matching oxidizing power of the discharge species onto solutes is due to water soluble HO provided by the dimer formation of °OH and also to peroxynitrous acid ONOOH and its salt which are involved in the oxidation process of nitrous to nitric acid. [ABSTRACT FROM AUTHOR]

Degummed Bombyx mori ( B. mori) silk fabrics modified by cold oxygen plasma (COP) and/or titania sols (TSs) were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, field emission scan electronic microscopy (FE-SEM), thermo-gravimetric and differential thermal analysis, and ultraviolet (UV) transmittance methods in this study. FT-IR analysis demonstrated that titania particles were associated with B. mori silk fibers by forming organic-inorganic hybrid blends. Processing sequences of COP and TSs, and curing conditions showed significant impacts on the crystalline, thermal, micro-morphological, and UV resistant characteristics of silk fabrics. Crystallinity index by both area and height methods, and crystallite sizes of silk fabrics were calculated as well. Results showed that crystallinity index of finished samples approximate to that of degummed silk fabric could be obtained by applying TSs and curing at 160 °C for 2 min prior to COP treatment, or vice versa with lower temperature of 140 °C for 3 min, whereas the crystallite sizes of treated samples increased slightly. The initial decomposition temperatures of finished samples were elevated by 23-35 °C with increased char residues at 600 °C, while the transmittance of UVA and UVB of finished samples decreased by 11.7, 17.7%, respectively. FE-SEM analysis revealed that titania particles were associated on the fiber surfaces with different smoothness. [ABSTRACT FROM AUTHOR]

The catalytic conversion of methane and carbon dioxide was studied in a fluidized bed reactor supported by a 13.56 Hz driven coaxial DBD-reactor. Palladium or cupper catalyst which are covered on AlO particles were used. The goal was to test whether biogas can be used for the production of synthesis gas. The influences of discharge power, catalysts and temperature of the catalyst bed on the product yield were studied. The starting material and product stream was analyzed by quadrupole mass spectrometry and infrared spectroscopy. H/CO ratios can be adjusted in a range between 0.65 (without a catalyst) and 1.75 (using a copper catalyst). The process is highly selective for hydrogen production (up to 83%, using a Palladium catalyst). A copper catalyst increases the H/CO ratio can from 1.04 to 1.16 and the palladium catalyst from 1.11 to 1.43 by heating the catalyst to a temperature of 250°C. [ABSTRACT FROM AUTHOR]

Low temperature conversion of CH4 and CO2 was investigated in a coaxial dielectric barrier discharge reactor at ambient pressure. Main parameters, including the input power, the residence time, the discharge gap, the molar ratio of the feed gases and the multi-stage ionization design were evaluated to understand the ways to improve the conversion of greenhouse gases and reduce the output of by-products. At certain input power, the conversion of CH4 and CO2 can reach 0.797 and 0.527, respectively, when the molar ratio of CH4/CO2 is one. When this ratio was low to 1:5, the conversion of CH4 was promoted to 0.843 and the selectivity to CO and H2 was almost 100%. The multi-stage ionization favored the conversion of CO2, which would also be an efficient design to promote the selectivity to the main products such as CO and H2 and suppress the selectivity to the by-products. [ABSTRACT FROM AUTHOR]

Many types of carbon films are being investigated for use in many different applications for their electrical, mechanical, and optical properties. Organic based plasmas are beginning to be used for the production of a wide variety of novel film stacks. The use of these stacks can range from sensor to dielectrics for flexible electronics to biocompatible surfaces. Knowledge of how these films actually grow is largely unknown. In light of this, we have performed Fourier transform infrared (FTIR) spectroscopy to the study of hexane plasmas. We use this diagnostic to identify different plasma-produced daughter species produced from n-hexane. For example, we observe the creation of methane, ethylene, and acetylene. From this we develop a likely dissociation model for the parent gas. [ABSTRACT FROM AUTHOR]

Plasma processing of metallic cobalt was experimentally investigated with three fluorine-containing gases, CF4–O2, SF6–O2, and NF3 to determine the surface decontamination rate and to examine the reaction mechanism. Results show that the maximum etching rate reaches 17.12 μm/min with NF3 gas at 420°C, while the rates are 2.56 μm/min and 1.14 μm/min with CF4–O2 and SF6–O2 gas, respectively, at the same temperature. AES analysis identified the constituent elements of the reaction products to be oxygen, fluorine, and cobalt, and XPS analysis reveals that the reaction product with all three plasma gases is very likely to be CoF2. [ABSTRACT FROM AUTHOR]

The conversion of CO2 and (CH4+ CO2 ) mixtures to CO, at room temperature and atmospheric pressure conditions, in pulsed corona discharges, was investigated. Conversion of pure CO2 was 16.8% at 10 cm3 -min−1 flow rate, which corresponds to 75 μmol-min−1 rate of conversion. The CO2 conversion was improved to 38% (85 μmol-min−1 by feeding the reactor with CH4+ CO2 gas mixture (1:1 ratio), simultaneously with CH4 conversion of 46% (∼102.7 μmol-min−1 ) at 10 cm3 -min−1 flow rate of feed gases and 9 W power conditions. Rate of CO production is increased from ∼110 to ∼180 μmol-min−1 with the variation of feed gas (CH4+ CO2 mixture, 1:1 ratio) flow rate from 10 to 40 cm3 -min−1 at 9W, which corresponds to energy efficiency of 2.5 to 4.1%. Highest energy yield of 25 g/kWh for CH4 conversion, 29 g/kWh for CO2 conversion, and 33 g/kWh for CO production were achieved. [ABSTRACT FROM AUTHOR]