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Radio frequency plasma (RFP) could provide reliable, compact, cost-effective irradiation applications against insect pests of stored food and feed products. Sensitivity of red flour beetleTribolium castaneumto RFP has been investigated using an irradiation applicator system with the two types of inert gases, argon (Ar) and helium (He), at 100 W for five exposure time levels of 0, 20, 40, 60 and 90 s, respectively. We demonstrated that He RFP was more efficient againstT. castaneumthan Ar RFP. In addition, a positive correlation was observed between mortality percentages of treated insect stages and exposure times for both He and Ar RFP. The adult stage showed the highest tolerance to RFP irradiation followed by larvae and pupae; however, it was more susceptible than larvae within 24 h after He RFP treatments. The optimum exposure time was 90 s with He RFP, where a full mortality at all tested stages was accomplished, while mortalities of 71.4, 65.3 and 36.7% were recorded for pupae, larvae and adult stage, respectively, after an Ar RFP treatment of 90 s. In case of treated adults, the reproduction rate was higher than treated larvae and pupae. Our findings indicated that He RFP was an effective method for inhibitingT. castaneumdevelopment and impacting the insect life cycle and could be considered a promising tool for pest control of stored food.

(−)–Epigallocatechin gallate (EGCG) and olivetol hybrid molecules 1-4 were conveniently synthesized using dielectric barrier discharge plasma irradiation. The structures of these unprecedented hybrid molecules were determined by interpretation of spectroscopic data. The unusual hybrid 1 showed improved antiglycation potency toward the advanced formation of glycation end products than the original EGCG and olivetol. The novel hybrid 1 is an interesting new class of antiglycation candidate that requires further investigation.

Paint protects the outer surface of ships. The antifouling component of paint prevents aquatic organisms from attaching to the surface of the ship. However, marine paints deteriorate with time. Therefore, periodic repainting is required. Repainting is performed via sandblasting, in which an abrasive is sprayed onto the surface of the paint. However, in this method, the base material of the paint is damaged. According to previous studies, when a painted surface is irradiated by plasma, the paint tends to peel off easily. Herein, we hypothesize that the paint is easily peeled off because of the thermal stress induced by the plasma during irradiation. To verify this hypothesis, we experimentally investigated the effect of thermal stress due to atmospheric pressure plasma. Results show that the streamer is a factor that easily peels off the paint. In addition, the effect of thermal stress due to the crosslinking reaction was confirmed via plasma irradiation. Furthermore, the effect of chipping due to intermittent discharge was explored by observing the painted surface via SEM.

Electrocatalysis plays a decisive role in various energy-related applications. Engineering the active sites of electrocatalysts is an important aspect to promote their catalytic performance. In particular, defect engineering provides a feasible and efficient approach to improve the intrinsic activities and increase the number of active sites in electrocatalysts. In this review, recent investigations on defect engineering of a wide range of electrocatalysts such as metal-free carbon materials, transition metal oxides, transition metal dichalcogenides and metal-organic frameworks (MOFs) will be summarized. Different defect creation strategies will be outlined, for example, heteroatom doping and removal, plasma irradiation, hydrogenation, amorphization, phase transition and reduction treatment. In addition, we will overview the commonly used advanced characterization techniques that could confirm the existence and identify the detailed structures, types and concentration of defects in electrocatalysts. The defect characterization tools are beneficial for gaining an in-depth understanding of defects on electrocatalysis and thus could reveal the structure-performance relationship. Finally, the major challenges and future development directions on defect engineering of electrocatalysts will be discussed.

In our previous study, internal stress was suggested as the mechanism causing the deterioration of paint adhesion through atmospheric-pressure plasma irradiation. In this paper, this mechanism is examined in detail. According to the Japanese Industrial Standards (K-5600-5-7), we evaluate the experimental results by varying some parameters. An applied voltage of 10 kV, plasma irradiation distance of 10 mm, and plasma irradiation duration of 60 s are the parameters that resulted in the peeling of the paint at a lower peeling-off load. In addition, from the simulation results, the generation and thermal input of a plasma streamer are confirmed and considered as one of the factors causing the paint to peel more readily.

Growth of helium bubbles near the surface of metals leads to various morphology changes when sufficient helium ions are continuously implanted on the surface. In this study, low energy (< 100 eV) helium plasma irradiations to various noble metals were conducted, and consequent surface morphology changes were analyzed. It was found that fiberform nanostructures were formed by the helium plasma irradiation on rhodium and ruthenium thin films, which were deposited by magnetron sputtering, and on platinum and iridium wires. Growth of fiberform structures were not identified on gold, silver, and palladium samples exposed to helium plasmas even though the irradiations were conducted at various surface temperatures, though pinholes were observed on palladium surface. We discussed the relation between the morphology changes and material properties., ファイル公開：2020-04-25

Recently, cold atmospheric plasma (CAP) with the unique bio-disinfection features is used in various fields of industry, medicine, and agriculture. The main objectives of this work were to design FSG plasma (a semi-automatic device) and investigate the effect of the cold plasma in the enhancement of the Pea and Zucchini seed germination. Plasma irradiation time was studied to obtain a proper condition for the germination enhancement of seeds. The growth rate was calculated by measuring length of root and stem and dry weight of plants treated by plasma. To investigate drought resistance of plants, all treated and untreated samples were kept in darkness without water for 48 h. From the experimental results, it could be confirmed both drought resistance and germination of seedlings increased after plasma was applied to seeds at 30 s, while seeds treated whiten 60 s showed a decrease in both germination rate and seedling growth.

Epitaxial growth of Si-C alloy films on Si(100) were achieved in the C fraction range up to about 5 at% by surface reaction of SiH 4 and CH 4 under low-energy Ar plasma irradiation without substrate heating in electron-cyclotron-resonance (ECR) plasma chemical-vapor deposition (CVD). Moreover, it was found that the Si-C alloy (C fraction of 1.4 at%) with an about 1%-larger vertical lattice constant than unstrained Si could be epitaxially grown on Si(100) under perfect lattice matching, which was different from the generally-reported results of tensile-strained Si-C alloy epitaxy on Si(100) at relatively higher temperatures. It was also found that deposition interruption effectively improved crystal quality of the film with an increased strain.

Non-mechanical procedures for removing caries-infected dentin are warranted in dentistry. We previously demonstrated the marked sterilization effect for direct irradiation of low-temperature plasma using dentin model infected with Streptococcus mutans. However it requires 180 s of intraoral plasma irradiation to eliminate bacteria. We alternatively investigated whether plasma-treated water (PTW), i.e., pure water exposed to plasma in an atmosphere, has a same bactericidal activity with the plasma irradiation. In the infected dentin model, the viable S. mutans counts recovered by bur at depth of 0.8-2.4 mm from the cavity floor were 104-106 CFU/round bur. After PTW application for only 10 s, the count was significantly decreased to below the detection limit (2.5 CFU/round bur) or 3.0±5.0 CFU/round bur. Since the bactericidal activity of PTW is rapidly deactivated at body temperature (37°C), PTW is likely to be biocompatible and holds significant potential for non-mechanical procedures for removing caries-infected dentin.

Previous studies have shown that paint tends to easily peel off when irradiated with plasma. In this study, we use atmospheric pressure plasma irradiation to peel off surface paint. The variable parameters were the applied voltage and the plasma irradiation time. We were able to irradiate the painted surface with atmospheric pressure plasma for 1 min and peel off more than 80% of the paint. It was hypothesized that plasma irradiation affects the internal stress in the painting.

In this work we have studied the influence of argon working pressure, substrate temperature, low power plasma irradiation and partial pressure of hydrogen in the RF-magnetron sputtering of indium tin oxide (ITO) thin films on glass substrates. This work aims at identifying the best conditions to achieve good quality ITO films at low temperature for deposition on heat-sensitive substrates. Four sets of samples were prepared which were characterized by X-ray diffraction (XRD), Van der Pauw and transmittance measurements. It was found that structural, electrical and optical properties of the films depend strongly on the deposition parameters. ITO films with a thickness of ~300 nm, displaying a sheet resistance of 68 Ω/sq and average transmittance, in the visible range, of about 90% were produced performing the deposition at low pressure and at room temperature. However, further improvements in the sheet resistance up to a factor of 3 were obtained by decreasing a little more the argon working pressure or applying a low power plasma irradiation or adding a partial pressure of hydrogen to the working gas. Films produced at low working pressures are crystalline and have [222] preferential orientation. The conductivity and transmittance of these films are higher than those of films deposited at high pressures. The electrical resistivity of the ITO thin films decreased sharply either with low power plasma irradiation or the addition of a partial pressure of H2 to the working gas. All the films showed an average transmittance of over 80% in the visible range. Therefore, as a result of this work we established that the addition of a small partial pressure of H2 to the working gas during growth allowed us to achieve the main aim of depositing low resistivity ITO films at low substrate temperature suitable for the envisaged applications. At the same time, we concluded that this approach leads to a drastic reduction in the amount of target surface conditioning required every time a new target was installed because it turns the properties of the ITO films more independent of the target surface properties.

Ar/O plasma irradiation is proposed for post-treatment of vanadium dioxide (VO2) films. Oxidation and surface migration were observed in the VO2 films following irradiation. This combined effect leads to an effective stoichiometry refinement and microstructure reconstruction in the interfacial area. A notable improvement in luminous transmittance and an enhancement in phase transition performance of the treated VO2 films were achieved. Compared with that of as-deposited VO2 films, the electrical phase transition amplitude of treated films increased more than two-fold. The relative improvement in luminous transmittance (380&ndash, 780 nm) is 47.4% (from 25.1% to 37%) and the increase in solar transmittance is 66.9% (from 29.9% to 49.9%), which is comparable to or better than the previous work using anti-reflection (AR) coatings or doping methods. The interfacial boundary state proved to be crucial and Ar/O plasma irradiation offers an effective approach for further refinement of thermochromic VO2 films.

A new divertor concept REVOLVER-D2 that uses metal pebbles as a divertor target has been proposed for the LHD-type helical fusion reactor FFHR-c1. Demonstration of sufficient plasma shielding rate is one of the important issues to show the feasibility of the REVOLVER-D2. For this purpose, an experiment on the plasma irradiation to the metal pebble flow has been conducted in the sheet plasma device TPDsheet-U in Tokai University. Reduction of the ion flux and electron density in the metal pebble flow was observed and it was confirmed that the metal pebble flow can play the role of the divertor target. The measured shielding rate is consistent with the prediction by the model based on the Lambert-Beer-Bouger’s law. Achievement of the shielding rate of > 72 % is expected in the FFHR-c1 using the nozzle with the size of > 310 mm × 310 mm and the pebble flow with the diameter of 5 mm.

An effect of discharge plasma irradiation to the circulating water in hydroponic cultivation system on plant growth rate was evaluated using Brassica rapa var. perviridis as specimen. The discharge plasma produced acids in the solution, which acts as a fertilizer. The Brassica rapa var. perviridis were cultivated in period of 42 days with the hydroponic system. The experimental result indicated that the growth rate of the Brassica rapa var. perviridis is improved drastically with the discharge treatment of the solution of hydroponic system, especially content of leaf blade is significantly increased p < 0.01.

The influence of extreme heat loads, as produced by a multiple pulses of non-homogeneous fl ow of slow plasma (0.1-1 keV) and fast ions (100 keV), on double-forged tungsten (DFW) was investigated. For generation of deuterium plasma and fast deuterons, plasma-focus devices PF-12 and PF-1000 are used. Depending on devices and conditions, the power flux density of plasma varied in a range of 107-1010 W/cm2 with pulse duration of 50-100 ns. Power flux density of fast ions was 1010-1012 W/cm2 at the pulse duration of 10-50 ns. To achieve the combined effect of different kind of plasmas, the samples were later irradiated with hydrogen plasma (105 W/cm2, 0.25 ms) by a QSPA Kh-50 plasma generator. Surface modification was analysed by scanning electron microscopy (SEM) and microroughness measurements. For estimation of damages in the bulk of material, an electrical conductivity method was used. Investigations showed that irradiation of DFW with multiple plasma pulses generated a mesh of micro- and macrocracks due to high heat load. A comparison with single forged tungsten (W) and tungsten doped with 1% lanthanum-oxide (WL10) reveals the better crack-resistance of DFW. Also, sizes of cells formed between the cracks on the DFW’s surface were larger than in cases of W or WL10. Measurements of electrical conductivity indicated a layer of decreased conductivity, which reached up to 500 μm. It depended mainly on values of power flux density of fast ions, but not on the number of pulses. Thus, it may be concluded that bulk defects (weakening bonds between grains and crystals, dislocations, point-defects) were generated due to mechanical shock wave, which was generated by the fast ions flux. Damages and erosion of materials under different combined radiation conditions have also been discussed.

The chemical oxidation method can be used to mass-produce graphene oxides (GOs) from highly oriented pyrolytic graphite. However, numerous oxygen-containing functional groups (hydroxyl, epoxy, carbonyl, etc.) exist in typical GO surfaces, resulting in serious electrical losses. Hence, GO must be processed into reduced graphene oxide (rGO) by the removal of most of the oxygen-containing functional groups. This research concentrates on the reduction efficiency of GO films that are manufactured using atmospheric-pressure and continuous plasma irradiation. Before and after sessions of plasma irradiation with various irradiation times, shelters, and working distances, the surface, physical, and electrical characteristics of homemade GO and rGO films are measured and analyzed. Experimental results showed that the sheet resistance values of rGO films with silicon or quartz shelters were markedly lower than those of GO films because the rGO films were mostly deprived of oxygen-containing functional groups. The lowest sheet resistance value and the largest carbon-to-oxygen ratio of typical rGO films were approximately 90 &Omega, /sq and 1.522, respectively. The intensity of the C&ndash, O bond peak in typical rGO films was significantly lower than that in GO films. Moreover, the intensity of the C&ndash, C bond peak in typical rGO films was considerably higher than that in GO films.

Non-thermal atmospheric pressure plasma is a novel approach for wound healing, blood coagulation, and cancer therapy. A recent discovery in the field of plasma medicine is that non-thermal atmospheric pressure plasma not only directly but also indirectly affects cells via plasma-treated liquids. This discovery has led to the use of non-thermal atmospheric pressure plasma as a novel chemotherapy. We refer to these plasma-treated liquids as plasma-activated liquids. We chose Ringer’s solutions to produce plasma-activated liquids for clinical applications. In vitro and in vivo experiments demonstrated that plasma-activated Ringer’s lactate solution has anti-tumor effects, but of the four components in Ringer’s lactate solution, only lactate exhibited anti-tumor effects through activation by non-thermal plasma. Nuclear magnetic resonance analyses indicate that plasma irradiation generates acetyl and pyruvic acid-like groups in Ringer’s lactate solution. Overall, these results suggest that plasma-activated Ringer’s lactate solution is promising for chemotherapy.

α-SiC fabricated by the sintering method was developed as an alternative to the widely used β-SiC made by chemical vapor deposition for various functional components used in the plasma process chamber. By adapting the sintering method, larger and thicker SiC components can be fabricated practically compared with the chemical vapor deposition. Two sintering additives, Y2O3-Al2O3 and B4C, were used in the sintering processes, and the etching stability of sintered SiC against fluorinated plasmas, including SF6/Ar plasma and CF4/O2/Ar plasma, was investigated. For sintered SiC with Y2O3-Al2O3 additives, the etching rate was smaller than that of the chemical-vapor-deposited SiC, mainly because nonvolatile fluoride and/or oxides of Y and Al remained on the surface and served as a protective layer. For sintered SiC, the B4C additives, the etching rate, and the surface structure after plasma irradiation were similar to the case of the chemical-vapor-deposited SiC. The results suggest that the B4C additive has little effect on the etching stability, because fluorides of B and C are volatile, and no residue is formed, contrary to the case of the Y2O3-Al2O3 additives.

Irradiation tests of tungsten surface were performed with He and He/Ar plasma generated by microwave electron cyclotron resonance. Thickness loss was used as the erosion rate of tungsten surface under the plasma irradiation. The results revealed that the thickness loss increased linearly with negative bias. SEM images proved that the addition of Ar apparently increased the plasma erosion. The thickness loss increased sharply with the Ar fraction of Ar/He mixture when it was

The concentration of helium in tungsten fuzz-like nanostructures has been measured by means of thermal desorption spectroscopy. Fuzz was formed on the W surface under intensive plasma irradiation at 1500 K. The helium content was measured first in the as-irradiated sample, and then in a similar sample with the fuzz mechanically scraped from the sample surface. The difference gave the He content in the fuzz, which was estimated to be He/ W = (13 ± 4)%.

We construct a kind of structure of silver oxide capped silver nanoparticles (AgNPs) by cost-efficient air plasma irradiation, and study its visible-light driven photocatalytic activity (PA). By controlling the oxidization time, the relationship between the intensity of the localized surface plasmon resonance (LSPR) and the PA is well established. The PA reaches the maximum when the LSPR of AgNPs is nearly completely damped (according to absorption spectra); however, under this condition, the LSPR still works, confirmed with the high efficient selective transformation of p-Aminothiophenol (PATP) to p, p′-dimercaptoazobenzene (DMAB) under visible light. The mechanism of the LSPR damping induced PA improvement is discussed. We not only provide a cost-efficient approach to construct a LSPR strong damping structure but also promote the understanding of LSPR strong damping and its relationship with photocatalysis.

The transportation of reactive oxygen species (ROSs) in a tissue phantom after plasma irradiation was studied using a two-layered target consisting of a KI-starch gel reagent and an agarose tissue phantom. The two-layered target can visualize the two-dimensional concentration distribution of ROSs after passing through the tissue phantom. ROSs were accumulated in the tissue phantom by the plasma irradiation, and they continued to be transported in the depth direction with the standing time after the plasma irradiation. The amount of ROS after passing through the tissue phantom increased in proportion to both plasma irradiation time and standing time. In this case, the ROS distribution patterns did not depend on these times. The ROS transportation speed after plasma irradiation was 0.05 mm/min in the tissue phantom. The ROS penetration rate depended on the standing time, not on the plasma irradiation time, and it was less than 1%.

The degradation of the perpendicular magnetic anisotropy (PMA) of a Ta cap/MgO/CoFeB stack film after H2 plasma irradiation was investigated to clarify the magnetic damage induced during the hydrogen-containing plasma etching (e.g., CO/NH3 or CH3OH plasma etching). When the CoFeB layer thickness was 1.2 nm, the out-of-plane coercivity decreased from 1.0 to 0.15 mT after H2 plasma irradiation, and the perpendicular anisotropy field also decreased, from 220 to 90 mT. The dependence of the reduction in the PMA on the CoFeB thickness revealed that the interfacial anisotropy energy was reduced from 0.98 to 0.79 mJ/cm2 after H2 plasma irradiation. These results clearly indicate that hydrogen-containing plasma etching has the potential to degrade the PMA during MgO/CoFeB film patterning.

The expression of RNAs in mouse NIH3T3 cells was altered by low-temperature atmospheric-pressure plasma irradiation. Cell culture liquid media were removed before plasma irradiation so that direct plasma effects can be assessed. After 5 s irradiation, the cells were cultured in media for 1 or 3 h and RNA expression was analyzed using a microarray. When analyzed 1 and 3 h after plasma irradiation, the upregulation of hypothetical transmembrane proteins and U3 small nucleolar RNAs was detected at both time points. Our results provide a basic principle for understanding the molecular mechanisms of plasma effects on mammalian cells.

We present a photoresponse study on a lateral defect/pristine graphene junction device fabricated by a simple plasma irradiation method. The junction between pristine graphene and plasma-modified graphene was created by controlling the location of Ar+ plasma treatment. We found that a distinct photocurrent was generated at the junction by photocurrent line scanning measurements, and further analysis reveals that the photo-thermoelectric (PTE) effect, instead of the photovoltaic (PV) effect, dominates the photocurrent generation at the interface. Additionally, the obtained results suggest that tuning the defect density could be effective in modulating the optoelectronic performance of junctions in our device.

We have studied the effects of air nonthermal plasma irradiation of seeds of Arabidopsis thaliana (L.) on their growth from the beginning of cultivation to their harvest. Three minute plasma irradiation of dry seeds resulted in growth acceleration in all the growth stages. Compared with the control, the plasma irradiation led to an 11% shorter harvest period, a 56% increase in total seed weight, a 12% increase in each seed weight, and a 39% increase in seed number.