Effects of Dielectric Barrier on Water Activation and Phosphorus Compound Digestion in Gas-Liquid Discharges.

To generate a stable and effective air-liquid discharge in an open atmosphere, we investigated the effect of the dielectric barrier on the discharge between the pin electrode and liquid surface in an atmospheric-pressure plasma reactor. The atmospheric-pressure plasma reactor used in this study was based on a pin-plate discharge structure, and a metal wire was used as a pin-type power electrode. A plate-type ground electrode was placed above and below the vessel to compare the pin-liquid discharge and pin-liquid barrier discharge (PLBD). The results indicated that the PLBD configuration utilizing the bottom of the vessel as a dielectric barrier outperformed the pin-liquid setup in terms of the discharge stability and that the concentration of reactive species was different in the two plasma modes. PLBD can be used as a digestion technique for determining the phosphorus concentration in natural water sources. The method for decomposing phosphorus compounds by employing PLBD exhibited excellent decomposition performance, similar to the performance of thermochemical digestion-an established conventional method for phosphorus detection in water. The PLBD structure can replace the conventional chemical-agent-based digestion method for determining the total dissolved phosphorus concentration using the ascorbic acid reduction method.

Ion-Selective Electrode Based on a Novel Biomimetic Nicotinamide Compound for Phosphate Ion Sensor.

Phosphorus is not only an import nutrient to aquatic habitats, but it also acts as a growth inhibitor in aquatic ecosystems; however, it also aggravates environmental issues, such as eutrophication. There is a growing interest in rapid phosphorus detection to manage and protect water resources. Due to the large molecular structure and high hydration energy of phosphate ions, ion-selective electrodes (ISEs) remain in their infancy for real-time measurements in terms of practical application. In this study, a newly developed ionophore based on a biomimetic nicotinamide functional group was used to detect phosphate selectively, displaying efficient binding through charge interactions and hydrogen bonds. The ISE membrane containing silicone rubber demonstrated an effective detection performance over a long period of time. With a dynamic range between 10-6 and 10-2 M and a limit of detection of 0.85 × 10-6 M (26 µg/L), the newly synthesized ISE membranes demonstrated selectivity for phosphate ions over other ions, including acetate, sulfate, and chloride.

Reusable and pH-Stable Luminescent Sensors for Highly Selective Detection of Phosphate.

Phosphate sensors have been actively studied owing to their importance in water environment monitoring because phosphate is one of the nutrients that result in algal blooms. As with other nutrients, seamless monitoring of phosphate is important for understanding and evaluating eutrophication. However, field-deployable phosphate sensors have not been well developed yet due to the chemical characteristics of phosphate. In this paper, we report on a luminescent coordination polymer particle (CPP) that can respond selectively and sensitively to a phosphate ion against other ions in an aquatic ecosystem. The CPPs with an average size of 88.1 ± 12.2 nm are embedded into membranes for reusable purpose. Due to the specific binding of phosphates to europium ions, the luminescence quenching behavior of CPPs embedded into membranes shows a linear relationship with phosphate concentrations (3-500 µM) and detection limit of 1.52 µM. Consistent luminescence signals were also observed during repeated measurements in the pH range of 3-10. Moreover, the practical application was confirmed by sensing phosphate in actual environmental samples such as tap water and lake water.

Potential Application of Pin-to-Liquid Dielectric Barrier Discharge Structure in Decomposing Aqueous Phosphorus Compounds for Monitoring Water Quality.

Here, we proposed a pin-to-liquid dielectric barrier discharge (DBD) structure that used a water-containing vessel body as a dielectric barrier for the stable and effective treatment of aqueous solutions in an open atmosphere. To obtain an intense pin-to-liquid alternating current discharge using a dielectric barrier, discharge characteristics, including the area and shape of a ground-plate-type electrode, were investigated after filling the vessel with equivalent amounts of water. Consequently, as the area of the ground electrode increased, the discharge current became stronger, and its timing became faster. Moreover, we proposed that the pin-to-liquid DBD reactor could be used to decompose phosphorus compounds in water in the form of phosphate as a promising pretreatment method for monitoring total phosphorus in water. The decomposition of phosphorus compounds using the pin-to-liquid DBD reactor demonstrated excellent performance-comparable to the thermochemical pretreatment method-which could be a standard pretreatment method for decomposing phosphorus compounds in water.

Ultrafast Room Temperature Synthesis of Porous Polythiophene via Atmospheric Pressure Plasma Polymerization Technique and Its Application to NO2 Gas Sensors.

New nanostructured conducting porous polythiophene (PTh) films are directly deposited on substrates at room temperature (RT) by novel atmospheric pressure plasma jets (APPJs) polymerization technique. The proposed plasma polymerization synthesis technique can grow the PTh films with a very fast deposition rate of about 7.0 µm·min-1 by improving the sufficient nucleation and fragment of the thiophene monomer. This study also compares pure and iodine (I2)-doped PTh films to demonstrate the effects of I2 doping. To check the feasibility as a sensing material, NO2-sensing properties of the I2-doped PTh films-based gas sensors are also investigated. As a result, the proposed APPJs device can produce the high density, porous and ultra-fast polymer films, and polymers-based gas sensors have high sensitivity to NO2 at RT. Our approach enabled a series of processes from synthesis of sensing materials to fabrication of gas sensors to be carried out simultaneously.

Sequential Improvement from Cosolvents Ink Formulation to Vacuum Annealing for Ink-Jet Printed Quantum-Dot Light-Emitting Diodes.

Optimization of ink-jet printing conditions of quantum-dot (QD) ink by cosolvent process and improvement of quantum-dot light-emitting diodes (QLEDs) characteristics assisted by vacuum annealing were analyzed in this research. A cosolvent process of hexane and ortho-dichlorobenzene (oDCB) was optimized at the ratio of 1:2, and ink-jetting properties were analyzed using the Ohnesorge number based on the parameters of viscosity and surface tension. However, we found that these cosolvents systems cause an increase in the boiling point and a decrease in the vapor pressure, which influence the annealing characteristics of the QD emission layer (EML). Therefore, we investigated QLEDs' performance depending on the annealing condition for ink-jet printed QD EML prepared using cosolvents systems of hexane and oDCB. We enhanced the quality of QD EML and device performance of QLEDs by a vacuum annealing process, which was used to prevent exposure to moisture and oxygen and to promote effective evaporation of solvent in QD EML. As a result, the characteristics of QLEDs formed using ink-jet printed QD EML annealed under vacuum environment increased luminescence (L), current efficiency (CE), external quantum efficiency (EQE), and lifetime (LT50) by 30.51%, 33.7%, 21.70%, and 181.97%, respectively, compared to QLEDs annealed under air environment.

Highly stretchable, mechanically stable, and weavable reduced graphene oxide yarn with high NO2 sensitivity for wearable gas sensors.

Stretchable gas sensors are important components of wearable electronic devices used for human safety and healthcare applications. However, the current low stretchability and poor stability of the materials limit their use. Here, we report a highly stretchable, stable, and sensitive NO2 gas sensor composed of reduced graphene oxide (RGO) sheets and highly elastic commercial yarns. To achieve high stretchability and good stability, the RGO sensors were fabricated using a pre-strain strategy (strain-release assembly). The fabricated stretchable RGO gas sensors showed high NO2 sensitivity (55% at 5.0 ppm) under 200% strain and outstanding mechanical stability (even up to 5000 cycles at 400% applied strain), making them ideal for wearable electronic applications. In addition, our elastic graphene gas sensors can also be woven into fabrics and clothes for the creation of smart textiles. Finally, we successfully fabricated wearable gas-sensing wrist-bands from superelastic graphene yarns and stretchable knits to demonstrate a wearable electronic device.

Atmospheric Pressure Plasma Polymerization Synthesis and Characterization of Polyaniline Films Doped with and without Iodine.

Although polymerized aniline (polyaniline, PANI) with and without iodine (I2) doping has already been extensively studied, little work has been done on the synthesis of PANI films using atmospheric pressure plasma (APP) deposition. Therefore, this study characterized pure and I2-doped PANI films synthesized using an advanced APP polymerization system. The I2 doping was conducted ex-situ and using an I2 chamber method following the APP deposition. The pure and I2-doped PANI films were structurally analyzed using field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry (ToF-SIMS) studies. When increasing the I2 doping time, the plane and cross-sectional SEM images showed a decrease in the width and thickness of the PANI nanofibers, while the AFM results showed an increase in the roughness and grain size of the PANI films. Moreover, the FT-IR, XPS, and ToF-SIMS results showed an increase in the content of oxygen-containing functional groups and C=C double bonds, yet decrease in the C-N and C-H bonds when increasing the I2 doping time due to the reduction of hydrogen in the PANI films via the I2. To check the suitability of the conductive layer for polymer display applications, the resistance variations of the PANI films grown on the interdigitated electrode substrates were also examined according to the I2 doping time.

Conductive Polymer Synthesis with Single-Crystallinity via a Novel Plasma Polymerization Technique for Gas Sensor Applications.

This study proposes a new nanostructured conductive polymer synthesis method that can grow the single-crystalline high-density plasma-polymerized nanoparticle structures by enhancing the sufficient nucleation and fragmentation of the pyrrole monomer using a novel atmospheric pressure plasma jet (APPJ) technique. Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FE-SEM) results show that the plasma-polymerized pyrrole (pPPy) nanoparticles have a fast deposition rate of 0.93 µm·min-1 under a room-temperature process and have single-crystalline characteristics with porous properties. In addition, the single-crystalline high-density pPPy nanoparticle structures were successfully synthesized on the glass, plastic, and interdigitated gas sensor electrode substrates using a novel plasma polymerization technique at room temperature. To check the suitability of the active layer for the fabrication of electrochemical toxic gas sensors, the resistance variations of the pPPy nanoparticles grown on the interdigitated gas sensor electrodes were examined by doping with iodine. As a result, the proposed APPJ device could obtain the high-density and ultra-fast single-crystalline pPPy thin films for various gas sensor applications. This work will contribute to the design of highly sensitive gas sensors adopting the novel plasma-polymerized conductive polymer as new active layer.

Facile synthesis and enhanced ultraviolet emission of ZnO nanorods prepared by vapor-confined face-to-face annealing.

In this study, we report a novel regrowth method of sol-gel-prepared ZnO films using a vapor-confined face-to-face annealing (VC-FTFA) technique in which mica was inserted between two films, followed by annealing with the FTFA method. The ZnO nanorods are regrown when zinc acetate dihydrate and zinc chloride (ZnCl2) are used as the solvent, because these generate ZnCl2 vapor. The near-band-edge emission intensity of the ZnO nanorods was enhanced through the VC-FTFA method, increasing significantly by a factor of 56 compared to that of ZnO films annealed in open air at 700 °C. Our method may provide a route toward the facile fabrication of ZnO nanorods.

Optical parameters of boron-doped ZnO nanorods grown by low-temperature hydrothermal reaction.

Sol-gel spin-coating was used to deposit ZnO seed layers onto quartz substrates, and ZnO nanorods doped with various concentrations of B (i.e., BZO nanorods) ranging from 0 to 2.0 at% were hydrothermally grown on the ZnO seed layers. The effects of B doping on the absorption coefficient, optical band gap, Urbach energy, refractive index, extinction coefficient, single-oscillator energy, dispersion energy, average oscillator strength, average oscillator wavelength, dielectric constant, and optical conductivity of the hydrothermally grown BZO nanorods were investigated. The optical band gaps were 3.255, 3.243, 3.254, 3.258, and 3.228 eV for the nanorods grwon at 0, 0.5, 1.0, 1.5 and 2.0 at% B, respectively. B doping increased the Urbach energy from 40.7 to 65.1 meV for the nanorods grown at 0 and 2.0 at% B, respectively, and significantly affected the dispersion energy, the single-oscillator energy, the average oscillator wavelength, the average oscillator strength, the refractive index, and the optical conductivity of the hydrothermally grown BZO nanorods.

Photoluminescence properties of defect emissions in Al-doped ZnO nanorod array thin films.

The power- and temperature-dependent photoluminescence properties of Al-doped ZnO nanorod array thin films grown by the hydrothermal method were investigated. The intensities of both the near-band-edge emission (NBE) and deep-level emission (DLE) as well as the overall spectral line shape were strongly affected by the excitation power. At low excitation power, the blue emission was found to show the highest intensity among the different emission lights. A low-temperature photoluminescence analysis revealed the bound-exciton-related luminescence peak at 3.362 eV. The dependence of peak energy with the excitation power indicates that these DLE processes are generated by DAP transitions. The overall intensity of DLE was found to decrease as the temperature increases. With regard to the blue emission (around 2.52 eV), it showed a well-pronounced shoulder at 200 K. The activation energy for this blue emission was 51.93 meV, which corresponds to the thermal dissociation energy required for the donor-acceptor pair transitions.

Structural and optical properties of ZnO nanorods on Mg0.2Zn0.8O seed layers grown by hydrothermal method.

ZnO nanorods were grown on the Mg0.2Zn0.8O seed layers with different thickness by hydrothermal method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out to investigate the effects of the Mg0.2Zn0.8O seed layer thickness on the structural and the optical properties of the ZnO nanorods. The residual stress in the Mg0.2Zn0.8O seed layers was depended on the thickness while the texture coefficient of the Mg0.2Zn0.8O seed layers was not affected significantly. The smaller full width at half maximum (FWHM) of the ZnO (002) diffraction and near-band-edge emission (NBE) peak and the larger average grain size were observed from the ZnO nanorods grown on the Mg0.2Zn0.8O seed layers with 5 layers (thickness of 350 nm), which indicate the enhancement the structural and the optical properties of the ZnO nanorods.

Low-temperature growth of multiple-stack high-density ZnO nanoflowers/nanorods on plastic substrates.

Reported here is the low-temperature growth of multiple-stack high-density ZnO nanoflower/nanorod structures on polyethylene naphthalate (PEN) substrates derived from the surface modification of ZnO seed layers using an atmospheric-pressure plasma jet (APPJ) treatment. The plasma treatment could provide several advantages to the growth of multiple-stack ZnO nanoflower/nanorod structures: (i) the surface wettability of the seed layers changes from hydrophobic to hydrophilic, resulting in higher surface energies for the growth of high-density ZnO nanoflowers, (ii) the nucleation sites increase due to the increased surface roughness caused by the plasma etching, and (iii) there is no thermal damage to the plastic substrate from the plasma treatment due to its low-temperature weakly ionized discharge. It was also confirmed that multiple stacks of ZnO nanoflowers were obtained without degradation of the crystal quality or modification to the crystal shape or phase. The ZnO nanoflower/nanorod structures grew by lengths up to 4 µm due to an increased surface roughness of 10% and surface energy 5.5 times that of the seed layers. As shown, the APPJ is a very good method to obtain high-density ZnO nanostructures on plastic substrates below 150 °C, as is critical for flexible electronics.

Magnesium content ratio effects of MgxZn1-xO seed layers on structural and optical properties of ZnO nanorods.

ZnO nanorods were grown on MgxZn1-xO seed layers with different content ratio ranging from 0 to 0.3 by hydrothermal method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out to investigate the effects of Mg content ratio for the MgxZn1-xO seed layers on the structural and optical properties of the ZnO nanorods. The surface morphology and structural properties of the MgxZn1-xO seed layers were changed by the Mg incorporation. However, the appearance, such as density, diameter, and shape, of the ZnO nanorods grown on the MgxZn1-xO seed layers was not changed significantly. The highest intensity ratio of the near-band-edge emission (NBE) to deep-level emission (DLE) and the narrowest full width at half maximum (FWHM) of the NBE peaks, indicating improvement in the crystallinity and luminescent properties of the ZnO crystals, were observed in the ZnO nanorods grown on the MgxZn1_xO seed layers with the content ratio of the 0.05.

Temperature dependence of indigo light emission from mesoporous ZnO/porous silicon nanocomposites.

Nanocomposites of mesoporous zinc oxide (ZnO) and porous silicon (PS) were prepared through a hydrothermal method. Room-temperature (RT) and temperature-dependent photoluminescence (PL) were performed to investigate the optical properties and temperature dependence of the indigo emission peak from the ZnO/PS nanocomposites. An indigo emission peak from the nanocomposites and a red emission peak from the PS were observed in the case of the mesoporous ZnO/PS nanocomposites. At 10 K, the nanocomposites exhibited four emission peaks at 3.108, 2.929, 2.730, and 2.248 eV, which correspond to the DX, AX, DX-1LO, and DX-2LO phonon replicas, respectively. With an increase in temperature from 10 to 275 K, the curves in the intensities of the emission peaks formed an inverted "S" shape while their energies remained nearly constant. At 300 K, however, only the AX emission peak was observed; the DX and LO phonon replicas disappeared. The intensities of the DX and AX emission peaks exhibited anomalous behaviors.

Post-growth annealing effects of Mg doped GaAs epitaxial layers on microstructural and optical properties.

The post-growth thermal annealing effects of Mg doped GaAs epitaxial layers on the microstructural and optical properties grown by molecular beam epitaxy (MBE) have been investigated. The properties of Mg doped GaAs are estimated after the process of rapid thermal annealing (RTA) in the temperature range of 600 approximately 750 degrees C. The photoluminescence (PL) peak position of as-grown sample blueshifted from 1.473 to 1.485 eV as well as the pronounced enhancement in PL intensity by annealing at 600 degrees C. In the sample grown at the temperature of T(s) = 475 degrees C, the full-width at half maximum (FWHM) of double crystal X-ray diffraction (DCXRD) decreased form 27 to 8 arcsec with increasing of annealing temperature (600 approximately 700 degrees C). The crystalline quality variation of Mg doped GaAs layers by RTA is greatly dependent upon the doping level.

Molecular cloning of the DNA gyrase genes from Methylovorus sp. strain SS1 and the mechanism of intrinsic quinolone resistance in methylotrophic bacteria.

The genes encoding the DNA gyrase A (GyrA) and B subunits (GyrB) of Methylovorus sp. strain SS1 were cloned and sequenced. gyrA and gyrB coded for proteins of 846 and 799 amino acids with calculated molecular weights of 94,328 and 88,714, respectively, and complemented Escherichia coli gyrA and gyrB temperature sensitive (ts) mutants. To analyze the role of type II topoisomerases in the intrinsic quinolone resistance of methylotrophic bacteria, the sequences of the quinolone resistance-determining regions (QRDRs) in the A subunit of DNA gyrase and the C subunit (ParC) of topoisomerase IV (Topo IV) of Methylovorus sp. strain SS1, Methylobacterium extorquens AM1 NCIB 9133, Methylobacillus sp, strain SK1 DSM 8269, and Methylophilus methylotrophus NCIB 10515 were determined. The deduced amino acid sequences of the QRDRs of the ParCs in the four methylotrophic bacteria were identical to that of E. coli ParC. The sequences of the QRDR in GyrA were also identical to those in E. coli GyrA except for the amino acids at positions 83, 87, or 95. The Ser83 to Thr substitution in Methylovorus sp. strain SS1, and the Ser83 to Leu and Asp87 to Asn substitutions in the three other methylotrophs, agreed well with the minimal inhibitory concentrations of quinolones in the four bacteria, suggesting that these residues play a role in the intrinsic susceptibility of methylotrophic bacteria to quinolones.