Non-thermal Atmospheric Plasma Research Articles

An in vitro and in vivo study of plasma treatment effects on oral biofilms

ABSTRACTManagement of dental plaque/biofilms is critical to maintain oral health. The objective of this study is to investigate the treatment effects of non-thermal atmospheric gas plasmas on oral biofilm formation and recovery under in vitro and in vivo conditions. Streptococcus mutans biofilms, a significant contributor to tooth decay, were cultured and treated by plasma. It was found that plasma treatment not only significantly reduced the in vitro biofilms, but also increased the metabolic activity of the bacteria in the biofilms. As compared with untreated control group, the cell metabolic activity, as measured by MTT assay, increased by 273%, and the aconitase activity increased by 446% for the plasma-treated group. The increased metabolic activity of the plasma-treated biofilm bacteria enhanced their susceptibility to antibiotic and host defense. An in vivo animal model using a total of 60 female rats (19 days old) were used to evaluate the anti-caries effects on the molars by 2 min of plasma treatment. It was found that, 6 months after the plasma treatment, the decayed surfaces were reduced by 62.5% on the upper molars and by 31.6% on the lower molars as compared with the untreated upper and lower molars, respectively. These in vitro and in vivo data demonstrate that the physiological state change of the biofilm due to plasma treatment provided benefit to caries control and prevention.

Plasma-deposition of α-FeOOH particles on biochar using a gliding arc discharge in humid air: a green and sustainable route for producing oxidation catalysts.

Non-thermal atmospheric plasma of the gliding arc type was used as a tool for goethite-on-biochar hybrid material preparation. Biochars were first prepared by carbonizing raffia bamboo (the leafstalk of raffia palm) pith at 300 °C (BC3), 500 °C (BC5) and 700 °C (BC7). A suspension of each biochar in Fe2+ aqueous solution was then exposed to a plasma discharge burning in humid air. α-FeOOH particles were thus formed and spontaneously deposited on the biochar surface. In order to investigate the effect of plasma species on the support during goethite deposition, biochars were also treated with plasma in the absence of Fe2+ ions and then characterized. Results revealed a substantial hydroxylation and slight N-doping of biochar after plasma treatment. The prepared composite materials were tested in oxidative degradation of nitroresorcinol. The catalytic performances were in the order Fe-BC3 < Fe-BC7 < Fe-BC5 according to the abatement efficiency and half-time values obtained for each catalyst. This study establishes that waste biomass and atmospheric air can be simultaneously valorised for green production of heterogeneous catalysts.

Improvement in Molecular-Level Adhesive Strength of PTFE Film Treated by Atmospheric Plasma Combined Processing

Atmospheric pressure plasma graft polymerization-treated fluorocarbon plastics are bonded with a metal, to evaluate adhesiveness. In this research, the atmospheric nonthermal plasma graft polymerization technique is used in treating the surface of polytetrafluoroethylene (PTFE) in a dry process, capable of reducing environmental loading. The treated PTFE is joined with the stainless steel plate to perform a peeling test. We examine the peeling strength and the best condition for practical application using peeling strength as an optimization variable. A concrete numerical target is 2 N/mm, which is the standard adhesive strength applicable for industry uses. To conduct the graft polymerization, we use a monomer such as acrylic acid (CH2 = CHCOOH) and target material such as PTFE. Peeling strength is maximized (averaged value of 1.56 N/mm, largest value of 2.0 N/mm) when the temperature of the acrylic acid is 60 °C and the Ar main flow rate is 40 L/min. Influence of plasma torch cover on peeling strength and entrained flow near the torch are investigated to realize the stronger adhesion, and better shape of the cover is determined. Furthermore, by analyzing X-ray photoelectron spectroscopy and scanning electron microscope images, we evaluate the atmospheric pressure plasma graft polymerization process from a different perspective and search for optimal operating conditions of the processing method.

Nonthermal atmospheric plasma enhances myoblast differentiation by eliciting STAT3 phosphorylation.

The use of nonthermal atmospheric plasma (NTP) in the biomedical field has recently expanded into cell death induction in cancer, infection prevention, inflammation treatment, and wound-healing enhancement. NTP has been demonstrated to enhance skin and muscle regeneration, but its effects on tissue regeneration, following deep tissue or muscle damage, remains underinvestigated. In this study, we determined the effects of NTP on muscle differentiation and the mechanisms of NTP's contribution to differentiation and regeneration. NTP treatment enhanced cell differentiation in primary normal human skeletal muscle myoblast cells and increased the relative expression of mRNA levels of MyoD which is one of the earliest markers of myogenic commitment, and myogenin, which are important transcription factors required for myogenic differentiation. Furthermore, NTP treatment induced increases in the levels of myosin heavy chain, a differentiated muscle-specific protein, and in myotube formation of myoblasts. We observed that signal transducer and activator of transcription 3 (STAT3) activation induced by NTP treatment affects the myogenic differentiation. In addition, STAT3 phosphorylation was also enhanced by NTP treatment in injured animal muscle. These findings indicate that NTP could enhance musculoskeletal differentiation by acting as an external stimulus for myoblast differentiation, suggesting its treatment potential in promoting regeneration of damaged muscle.-Park, J. K., Kim, Y. S., Kang, S. U., Lee, Y. S., Won, H.-R., Kim, C.-H. Nonthermal atmospheric plasma enhances myoblast differentiation by eliciting STAT3 phosphorylation.

Antifungal effect of non-thermal atmospheric plasma and its application for control of postharvest Fusarium oxysporum decay of paprika

Non-thermal atmospheric plasma (NTAP) has been shown to be effective for controlling postharvest fungi in vitro, but little is known regarding its mode of action, fungal response to NTAP, and the effect of its application on fresh produce. NTAP was evaluated for its in vitro and in vivo antifungal activity against Fusarium oxysporum on paprika. NTAP treatment resulted in complete inhibition of mycelial growth and spore germination of F. oxysporum, particularly at 1000 W for 90 s. To further investigate the mechanisms by which NTAP inhibits fungal growth, the membrane integrity and the expression of a membrane-related gene (SHO1) were tested, which indicated that NTAP treatment results in the loss of plasma membrane integrity and up-regulation SHO1. In vivo assays demonstrated that NTAP treatment for 90 s inhibited the growth of this fungal pathogens by approximately 50%. Color and hardness parameters had no significant changes during 14 days of storage after NTAP treatment. The mechanisms by which NTAP treatment decreased fungal growth on paprika were directly associated with the disruption of the fungal cell membrane. These findings suggest that application of NTAP as an antifungal is an effective approach for preserving paprika.

The effect of non-thermal atmospheric plasma on the production and activity of recombinant phytase enzyme

Atmospheric pressure cold plasma (ACP) is introduced as a useful tool in a variety of biological applications. Proteins are the most abundant macromolecules in living systems with a central role in all biological processes. These organic molecules are modified by ACP exposure that is responsible for many of ACP’s biological effects. This study evaluated the effect of ACP on the production of recombinant phytase in yeast Pichia pastoris (P. pastoris) as well as the structure and function of the phytase enzyme. The results indicated that yeast cells treated with ACP, directly or indirectly, produced higher amounts of recombinant phytase, which was associated with the time of ACP treatment. The exposure of commercial phytase solution with ACP caused a significant increase in the enzyme activity (125%) after 4 hours. Evaluation of the phytase solution by far- and near-UV circular dichroism (CD) and fluorescence analysis indicated that this protein maintained its secondary structure when exposed to ACP while the tertiary structure was slightly unfolded. The effects of heat and H2O2 on the phytase structure and function were compared with the effect of ACP treatment. The modification of Cys, Tyr and Trp amino acids upon reactive oxygen/nitrogen spices was simulated using a molecular dynamics approach. RMSF and RMSD analysis suggested that this structural alteration occurs owing to changes made by reactive species in accessible amino acids.

Benefits of Nonthermal Atmospheric Plasma Treatment on Dentin Adhesion.

This study aimed to evaluate the influence of two nonthermal atmospheric plasma (NTAP) application times and two storage times on the microtensile bond strength (μTBS) to dentin. The influence of NTAP on the mechanical properties of the dentin-resin interface was studied by analyzing nanohardness (NH) and Young's modulus (YM). Water contact angles of pretreated dentin and hydroxyapatite blocks were also measured to assess possible alterations in the surface hydrophilicity upon NTAP. Forty-eight human molars were used in a split-tooth design (n=8). Midcoronal exposed dentin was flattened by a 600-grit SiC paper. One-half of each dentin surface received phosphoric acid conditioning, while the other half was covered with a metallic barrier and remained unetched. Afterward, NTAP was applied on the entire dentin surface (etched or not) for 10 or 30 seconds. The control groups did not receive NTAP treatment. Scotchbond Universal (SBU; 3M ESPE) and a resin-based composite were applied to dentin following the manufacturer's instructions. After 24 hours of water storage at 37°C, the specimens were sectioned perpendicular to the interface to obtain approximately six specimens or bonded beams (approximately 0.9 mm2 in cross-sectional area) representing the etch-and-rinse (ER) approach and another six specimens representing the self-etch (SE) approach. Half of the μTBS specimens were immediately loaded until failure, while the other half were first stored in deionized water for two years. Three other bonded teeth were selected from each group (n=3) for NH and YM evaluation. Water contact-angle analysis was conducted using a CAM200 (KSV Nima) goniometer. Droplet images of dentin and hydroxyapatite surfaces with or without 10 or 30 seconds of plasma treatment were captured at different water-deposition times (5 to 55 seconds). Two-way analysis of variance revealed significant differences in μTBS of SBU to dentin after two years of water storage in the SE approach, without differences among treatments. After two years of water aging, the ER control and ER NTAP 10-second groups showed lower μTBS means compared with the ER NTAP 30-second treated group. Nonthermal atmospheric plasma resulted in higher NH and YM for the hybrid layer. The influence of plasma treatment in hydrophilicity was more evident in the hydroxyapatite samples. Dentin hydrophilicity increased slightly after 10 seconds of NTAP, but the difference was higher when the plasma was used for 30 seconds. Dentin NTAP treatment for 30 seconds contributed to higher μTBS after two years of water storage in the ER approach, while no difference was observed among treatments in the SE evaluation. This result might be correlated to the increase in nanohardness and Young's modulus of the hybrid layer and to better adhesive infiltration, since dentin hydrophilicity was also improved. Although some effects were observed using NTAP for 10 seconds, the results suggest that 30 seconds is the most indicated treatment time.

Evaluation of ultraviolet light (UV), non-thermal atmospheric plasma (NTAP) and their combination for the control of foodborne pathogens in smoked salmon and their effect on quality attributes

Abstract The effectiveness of UV-C and Non-Thermal Atmospheric Plasma (NTAP) treatments, applied individually or in combination, for the inactivation of Listeria monocytogenes, Listeria innocua, Salmonella enterica serovar Typhimurium, Salmonella enterica serovar Enteritidis, Staphylococcus aureus, Escherichia coli O157:H7, Aeromonas hydrophila and Plesiomonas shigelloides on smoked salmon, compared to an abiotic surface (BHI agar), was evaluated. The impact of these technologies on the color, external appearance and degree of lipid oxidation of vacuum-packaged smoked salmon during refrigerated storage (4 ± 1 °C) for up to 28 days was also determined. D values (mJ/cm2) required to reduce the microbial population in 1 log cycle ranged from 3.12 (S. Enteritidis) to 1.00 mJ/cm2 (P. shigelloides) and t99% values (time of exposure to NTAP needed to inactivate the 99% of the population) ranged between 2.48 (P. shigelloides) and 0.48 (L. innocua) min. Although all microorganisms exhibited a higher resistance to UV-C and NTAP treatments on smoked salmon, the application of a a 900 mJ/cm2 UV-C or a 15 min NTAP treatment allowed the inactivation of −0.5–1.3 log CFU units of the microbial population, with no significant changes in the sensory quality properties of the treated products. The sequential application of UV-C and NTAP resulted in an additive lethal effect, except in combined treatments involving high UV-C energies (500 mJ/cm2) and long (≥4 min) NTAP exposure times, which showed an antagonistic interaction. In addition, these latter combined treatments induced lipid oxidation and adverse changes in appearance. In conclusion, UV-C and NTAP can be considered as promising surface decontamination technologies against foodborne microorganisms of concern in fishery industries, especially for their application on abiotic materials. In addition, they cause minor effects on quality properties of smoked salmon, achieving log reductions ranging from 0.1 to 1.57 when applied in combination, what evidences their potential within hurdle technology approaches aimed at maintaining smoked salmon quality and safety.

Prevention of bacterial colonization on non-thermal atmospheric plasma treated surgical sutures for control and prevention of surgical site infections.

Surgical site infections have a remarkable impact on morbidity, extended hospitalization and mortality. Sutures strongly contribute to development of surgical site infections as they are considered foreign material in the human body. Sutures serve as excellent surfaces for microbial adherence and subsequent colonization, biofilm formation and infection on the site of a surgery. Various antimicrobial sutures have been developed to prevent suture-mediated surgical site infection. However, depending on the site of surgery, antimicrobial sutures may remain ineffective, and antimicrobial agents on them might have drawbacks. Plasma, defined as the fourth state of matter, composed of ionized gas, reactive oxygen and nitrogen species, free radical and neutrals, draws attention for the control and prevention of hospital-acquired infections due to its excellent antimicrobial activities. In the present study, the efficacy of non-thermal atmospheric plasma treatment for prevention of surgical site infections was investigated. First, contaminated poly (glycolic-co-lactic acid), polyglycolic acid, polydioxanone and poly (glycolic acid-co-caprolactone) sutures were treated with non-thermal atmospheric plasma to eradicate contaminating bacteria like Staphylococcus aureus and Escherichia coli. Moreover, sutures were pre-treated with non-thermal atmospheric plasma and then exposed to S. aureus and E. coli. Our results revealed that non-thermal atmospheric plasma treatment effectively eradicates contaminating bacteria on sutures, and non-thermal atmospheric plasma pre-treatment effectively prevents bacterial colonization on sutures without altering their mechanical properties. Chemical characterization of sutures was performed with FT-IR and XPS and results showed that non-thermal atmospheric plasma treatment substantially increased the hydrophilicity of sutures which might be the primary mechanism for the prevention of bacterial colonization. In conclusion, plasma-treated sutures could be considered as novel alternative materials for the control and prevention of surgical site infections.

Quantification of the ozone and singlet delta oxygen produced in gas and liquid phases by a non-thermal atmospheric plasma with relevance for medical treatment

In the field of plasma medicine, the identification of relevant reactive species in the liquid phase is highly important. To design the plasma generated species composition for a targeted therapeutic application, the point of origin of those species needs to be known. The dominant reactive oxygen species generated by the plasma used in this study are atomic oxygen, ozone, and singlet delta oxygen. The species density changes with the distance to the active plasma zone, and, hence, the oxidizing potential of this species cocktail can be tuned by altering the treatment distance. In both phases (gas and liquid), independent techniques have been used to determine the species concentration as a function of the distance. The surrounding gas composition and ambient conditions were controlled between pure nitrogen and air-like by using a curtain gas device. In the gas phase, in contrast to the ozone density, the singlet delta oxygen density showed to be more sensitive to the distance. Additionally, by changing the surrounding gas, admixing or not molecular oxygen, the dynamics of ozone and singlet delta oxygen behave differently. Through an analysis of the reactive species development for the varied experimental parameters, the importance of several reaction pathways for the proceeding reactions was evaluated and some were eventually excluded.

Non-thermal plasma reduces periodontitis-induced alveolar bone loss in rats

Periodontitis, a chronic infectious disease induced by microbial biofilm, is one of the most common diseases worldwide. Scaling and root planning (SRP) has always been recognized as the typical treatment. However, the therapeutic efficiency is often limited due to the intraoperative bleeding and the limitations of instruments. Non-thermal atmospheric plasma (NTP) appears to be a potential tool for periodontitis due to its promising biofilm degradation and decontamination effects. In this study, we investigated the role of NTP, as an adjuvant approach for the treatment of ligature-induced periodontitis in rats. Herein we showed that SRP or SRP-NTP application attenuated the periodontitis-induced alveolar bone loss, reflected by the increased BV/TV value and the decreased CEJ-AB distance, which might be related to the lower detection rate of periodontal pathogen in SRP and SRP-NTP groups. Besides, SRP-NTP rats showed less bone loss and lower CEJ-AB distance than that of SRP group at 30d post treatment, indicating a more comprehensive and long-lasting effect of SRP-NTP. A remarkable decrease of osteoclast number and lower expression of RANKL was also detected in SRP-NTP rats. In addition, expression of inflammatory-related cytokines such as TNF-α and IL-1β decreased significantly in SRP-NTP group, while IL-10 level increased substantially. These results together illustrated that a combination of SRP and NTP treatment was an effective way to prevent periodontitis progress, which reduced alveolar bone loss and promoted periodontium restoration in ligature-induced periodontitis rats. In conclusion, non-thermal plasma treatment may be considered as a feasible and effective supplementary approach to control periodontitis.

Changes of quality characteristics during storage of Chinese cabbage by atmospheric non-thermal plasma treatment

Chinese cabbage (Brassica rapa L. ssp. pekinensis) is widely used in Korea and the main ingredient of kimchi. To retain the freshness of two different cultivars of Chinese cabbage harvested at spring or summer season, plasma treatment was applied for 2 h a day during storage at 2°C. Changes in weight loss, softening, decay rate, freshness and yellowing score were investigated during storage. The measured ozone concentration by plasma treatment was stabilized after 10 min and occurred on average 0.5 to 1 ppm during operation. Chinese cabbage treated with plasma had significantly lower decay rate during storage compared to the control, and higher freshness until the last storage day compared to the control. However, severe shriveling and slightly higher weight loss during storage time were shown. The yellowing score of Chinese cabbage treated with plasma had significantly low discoloration. These results indicate that plasma treatment seemed to be effective in controlling the softening, freshness, discoloration and decay rate.

Effects of non-thermal atmospheric plasma treatment on dentin wetting and surface free energy for application of universal adhesives

The study aims to evaluate the effects of non-thermal atmospheric plasma (NTAP) treatments on dentin wetting and surface free energy (SFE) and compare the effects of NTAP treatment, etch-and-rinse, and self-etch protocols for application of universal adhesives. Mid-coronal dentin of intact third molars was used to measure contact angles of distilled water, ethylene-glycol, and diiodomethane and calculate SFE following different NTAP preset treatments (feeding gas consisting of pure He, He + 1% O2, He + 1.5% O2), power input (1 or 3W), and tip-to-surface distance (2, 4, or 8mm). Contact angles of reference liquids and SFE of dentin following He + 1.5% O2 at 3-W and 4-mm treatment was compared to phosphoric acid etching. Contact angles of Single Bond Universal (SBU; 3M ESPE) and Clearfil Universal Bond (CUB; Kuraray Noritake) were measured following NTAP, etch-and-rinse, and self-etch protocols. NTAP significantly reduced contact angles of reference liquids and increased dentin SFE compared to untreated dentin (p< 0.05). O2 intensified the effect of He NTAP (p< 0.05). NTAP and phosphoric acid increased dentin polarity and Lewis base surface characteristics. Phosphoric acid increased contact angles of adhesives compared to the self-etch protocol (p< 0.05). NTAP resulted in lower adhesive contact angles than phosphoric acid, the difference being statistically significant for CUB (p< 0.05). Compared to the self-etch protocol, NTAP slightly reduced CUB contact angle but not that of SBU (p> 0.05). He NTAP with and without O2 increased dentin wetting and SFE, surpassing the effect of phosphoric acid and lowering adhesive contact angles. NTAP produced no apparent micro-morphological changes on dentin surface comparable to acid etching. NTAP treatment of dentin prior to adhesive application increases dentin wetting and surface free energy facilitating better adhesive distribution on dentin surface compared to phosphoric acid etching and similar to the "self-etch" application protocol.

Evaluation of the effect of cold atmospheric plasma on oxygenases’ activities for application in water treatment technologies

ABSTRACT Plasma-based technologies take an increasing place in the new conceptions of wastewater management as a promising tool for the treatment of persistent organic pollutants with low biodegradability. Plasma major advantage is the synergy of diverse active components with high oxidative action and additional benefits as disinfection of treated water. But the bactericidal effect of plasma can influence the treatment effectiveness when this technology is used in combination with biological methods for the removal of pollutants. The aim of this paper is to study the effect of non-thermal atmospheric plasma torch on key enzymes from phenol biodegradation pathways in Pseudomonas aureofaciens (chlororaphis) AP-9. The strain was isolated from contaminated soils and had a high potential for biodegradation of aromatic compounds. The used plasma source is surface-wave-sustained discharge operating at 2.45 GHz in argon produced by an electromagnetic wave launcher surfatron type. The enzyme activities of phenol 2-monooxygenase (P2MO), catechol 1,2-dioxygenase (C12DO), catechol 2,3-dioxygenase (C23DO), protocatechuate 3,4-dioxygenase (P34DO) and succinate dehydrogenase (SDH) were measured in control and after plasma treatment of 10, 30 and 60 s. At short-time treatment, the activities of intradiol dioxygenases increased with 26% and 59% for C12DO and P34DO, respectively. Other oxygenases and SDH were inhibited with 35% even at 10 s treatment. Longer treatment times had a clear negative effect but SDH kept the higher activity at 60 s treatment compared to the oxygenases. Our data suggest that plasma-based technologies are a useful approach for post-treatment of aryl-containing wastewater in order to increase the effectiveness of biological removal.

Abstract 2832: Novel therapy for oral squamous cell carcinoma using non-thermal atmospheric pressure biocompatible plasma activated water

Abstract Non-thermal atmospheric pressure biocompatible plasma (NBP) has been reported that was possible to induce apoptosis on various cancer cells including lung, ovary, brain, liver, breast, and pancreas cancer. We developed NBP device, which has been reported to have cytotoxicity on cancer cells induce DNA damage and apoptosis. In particular,reactive oxygen and/or nitrogen species (RONS) were generated by plasma device to give oxidative stress and depolarization of mitochondria membrane in cancer cells. Now we developed a microwave plasma jet system, which could generate nitric oxide (NO) and NO-plasma activated water (NO-PAW). Previously, we found that NO-PAW could induce apoptosis and accumulate ROS in human cervical cancer cells (1). In this study we investigated the efficacy of NO-PAW on oral squamous cancer cells (OSCC), a common malignant tumor of the head and neck (2, 3). We observed that cytotoxicity and apoptotic stimulation by NO-PAW were significantly increased. Also, expression level of caspase and PARP in OSCC was increased after treatment by NO-PAW. However, the apoptosis effect was not observed in human gingival fibroblasts (as normal human cells). Additionally, we found that NO-PAW inhibited cancer progression in vivo. In conclusion, NO-PAW could suppress the progress of OSCC by inducing cell apoptosis. This indicated NO-PAW as a novel tool for OSCC therapy, and probably will be also effective for other oral cancer. Acknowledgments: This work was supported by the Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF- 2016K1A4A3914113) funded by the Ministry of Science, ICT, and Future Planning (MSIP) of the Korean Government for EH. Choi, I. Han. The Korea government, and the Basic Science Research Program through the NRF of Korea, funded by the Ministry of Education (NRF-2015R1C1A2A01054137) for I. Han.

Antimicrobial Effect of Non-Thermal Atmospheric Plasma on Streptococcus Mutans -The Key Cariogenic Microorganism in Plaque Biofilm

Background: To evaluate the antimicrobial effect of non-thermal atmospheric plasma on mutans biofilms. Materials: A 100 µl culture of Streptococcus mutans poured into two 120 well flat base microtiter plates, allowed to adhere and incubated overnight using brain heart infusion (BHI). These 120 wells were grouped into four groups, group A-helium treated, group B-plasma treated, group C- chlorohexidine treated and group D-control group (untreated group) with a group size of 30 wells per group. Triphenyl tetrazolium chloride (TTC) essay & Colony Forming Units (CFU) counting was done to check the viability & survival of streptococcus mutans biofilms. Results: The results showed that there was a significant difference in the mean optical density (OD) among the four groups (p<0.001). Post-hoc analysis revealed that untreated samples and Helium had significantly higher mean OD than plasma and chlorhexidine groups. A similar result was also seen using the survival essay by CFU counting. Conclusion: Plasma utilizes the air from the atmosphere, thus rendering plasma a better reach in the oral cavity. This property of plasma can be efficiently used to neutralize Streptococcus mutans biofilms in the oral cavity.

Effects of input power, gas flow rate and hydrogen concentration on Cu film deposition by a radio frequency driven non-thermal atmospheric pressure plasma jet

A radio frequency driven non-thermal atmospheric plasma jet with a copper wire used as precursor is applied for Cu film deposition. The effects of input power, hydrogen concentration (CH2) and gas flow rate on the discharge parameters, and eventually on film deposition rate and its properties are investigated. The results show that, besides the plasma gas temperature (Tg), the discharge current flowing through the copper wire (Ifc) is also a key parameter for Cu film deposition. With increasing input power, both Tg and Ifc increase, which both facilitate the increase of film deposition rate, surface roughness and particle size on the film. Higher gas flow rate leads to lower Tg, and results in the decrease of the deposition rate, surface roughness and particle size. The influences of CH2 in plasma forming gas on Cu film deposition have dual characters, due to the increase in the Tg and decease in the Ifc with CH2 increase. When the CH2 is below1.6‰, increasing CH2 has promotion role on the film deposition rate increase and particle size enlargement on the film, and the results reverse as the CH2 is above 1.6‰.

Effects of Non-Thermal Argon Plasma Produced at Atmospheric Pressure on the Optical Properties of CdO Thin Films

In this paper the effect of nonthermal atmospheric argon plasma on the optical properties of the cadmium oxide CdO thin films prepared by chemical spray pyrolysis was studied. The prepared films were exposed to different time intervals (0, 5, 10, 15, 20) min. For every sample, the transmittance, Absorbance, absorption coefficient, energy gap, extinction coefficient and dielectric constant were studied. It is found that the transmittance and the energy gap increased with exposure time, and absorption. Absorption coefficient, extinction coefficient, dielectric constant decreased with time of exposure to the argon plasma

Degradation of Low Concentrated Perfluorinated Compounds (PFCs) from Water Samples Using Non-Thermal Atmospheric Plasma (NTAP)

Perfluorinated compounds (PFCs) are manmade chemicals, containing the covalent C-F bond, which is among the strongest chemical bonds known to organic chemistry. Abundant use of these chemicals contaminates air, water, and soil around the world. Despite recent initiatives and legal regulations set to reduce their omnipresence, conventional water purification processes are either inefficient or very expensive, especially for low PFC contamination levels. This research is focused on the non-thermal atmospheric plasma (NTAP) decomposition of very low concentrations (&lt;1 µg/L) of PFCs (especially perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS)), present in the wastewater produced during the process of PFCs removal from contaminated soil. The efficiency of the decomposition process was investigated for air, oxygen, and nitrogen plasma, with exposure times of 1–10 min and different plasma nozzle- and reactor sizes. Experiments demonstrated that the NTAP treatment is an efficient alternative method for degradation of more than 50% of the initial PFC concentration in the water samples, in less than 200 s. The final concentration of PFC showed strong dependency on the tested parameters. The treatment effect showed to be strongly non-linear with time, followed by the reduction of the pH-value of the treated sample, which might present a limiting factor for further PFC decomposition.

Microcorona Discharge-Mediated Nonthermal Atmospheric Plasma for Seed Surface Modification

By exploiting the physical effect of a highly nonuniform localized electric field and electron-initiated impact ionization on space charge, we generated homogeneous nonthermal plasma under ambient atmosphere. We evaluated the physical characteristics and evolution of microcorona discharge-induced nonthermal atmospheric plasma (NAP) based on a point-to-plane electrode in open air with two distinct configurations. High-voltage pulses were employed as the primary power source of corona discharge generation to reveal the fundamental mechanism, polarity effect and feasibility of using NAP for organic surface modification. Consequently, we employed NAP to modify the surface of rice (Oryza sativa L.) seeds to improve their wettability. The surface modification of the rice seeds was investigated via water apparent contact angle (ACA) and water imbibition (WI) measurements. The ACA and WI measurements revealed not only the improvement in the wetting properties but also the mutual relationships between and limitations of ACA and WI analysis. We found that the WI time reached saturation after a certain treatment time, called the threshold treatment time. Because vacuum conditions are not required, well-established NAP technology will garner interest in many fields, ranging from the life, environmental, and biomedical sciences to solid-state electronics applications.