Significantly Increased Solubility of Carbon Nanotubes in Superacid by Oxidation and Their Assembly into High‐Performance Fibers

This study demonstrates that small amount of oxygen incorporated into carbon nanotubes (CNTs) during the purification process greatly increases their solubility in chlorosulfonic acid (CSA). Using as‐purchased and unpurified CNT powders, the optimal purification process is established to significantly increase the solubility of CNTs in CSA, and spin CNT fibers with high mechanical strength (0.84 N tex^?1) and electrical conductivity (1.4 MS m^?1) from the CNT liquid crystal dope with high concentration of CNTs in CSA. The knowledge obtained here may guide development of a way to dissolve extremely long CNTs at high concentration and thereby to enable production of CNT fibers with ultimate properties.     

Megahertz operation of flexible low-voltage organic thin-film transistors

Bottom-gate, top-contact (inverted staggered) organic thin-film transistors with a channel length of 1 μm have been fabricated on flexible plastic substrates using the vacuum-deposited small-molecule semiconductor 2,9-didecyl-dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (C₁₀-DNTT). The transistors have an effective field-effect mobility of 1.2 cm²/V s, an on/off ratio of 10⁷, a width-normalized transconductance of 1.2 S/m (with a standard deviation of 6%), and a signal propagation delay (measured in 11-stage ring oscillators) of 420 ns per stage at a supply voltage of 3 V. To our knowledge, this is the first time that megahertz operation has been achieved in flexible organic transistors at supply voltages of less than 10 V.     

Direct reproduction of 3D microstructures using a hybrid approach; by creation of master-patterns and metallic molds for embossing

The fabrication of a three-dimensional (3D) metallic mold for multi-production of microstructures was studied to settle the problem of long processing time and efforts in 3D fabrication based on the accumulation of layer-by-layer. Even though two-photon induced polymerization (TPP) has been considered as a unique way for fabrication of precise real 3D microstructures such as 3D filters, 3D photonic crystals, microlens arrays, it required considerable effort and much processing time inevitably for these fabrications. Therefore, a simple and effective method was proposed using a metallic mold in this work. 3D micro-master patterns were prepared using TPP, and then counter-shaped Ni molds were created using an electroforming process. With this hybrid approach, 3D microstructures were much more easily and quickly reproduced by hot-forming compared to the TPP approach was used only. In this work, we report on the processing parameters used to fabricate a metallic mold and reproduce 3D microstructures using the mold.     

Synthesis of an active and stable Ptshell–Pdcore/C catalyst for the electro-oxidation of methanol

A Pt_shell–Pd_core/C catalyst is prepared via electroless deposition and galvanic displacement. The catalyst is active toward the electro-oxidation of methanol and is more stable against CO_ad-poisoning than a commercial Pt/C catalyst. The stable activity of Pt_shell–Pd_core/C is ascribed to the tuned electronic property of the Pt over-layer in the Pt_shell–Pd_core/C, which leads to weak binding with CO_ad and increases the kinetics of OH_ad formation. The weakened binding property of the surface Pt with CO_ad and the facile oxidation of CO_ad by OH_ad were confirmed by a spectroscopic analysis and in a CO_ad-stripping experiment, respectively. The electro-oxidation of CO_ad by OH_ad is the rate-determining step of methanol oxidation. Therefore, the accelerated formation of OH_ad contributes to the overall oxidation reaction, preventing CO_ad-poisoning. In addition, Pt_shell–Pd_core/C maintains its activity longer than Pt/C does during a prolonged cycle experiment.     

Wild and hatchery populations of Korean starry flounder (Platichthys stellatus) compared using microsatellite DNA markers

Starry flounder (Platichthys stellatus) is an important sport and food fish found around the margins of the North Pacific. Aquaculture production of this species in Korea has increased because of its commercial value. Microsatellite DNA markers are a useful DNA-based tool for monitoring the genetic variation of starry flounder populations. In this study, 12 polymorphic microsatellite DNA markers were identified from a partial genomic starry flounder DNA library enriched in CA repeats, and used to compare allelic variation between wild and hatchery starry flounder populations in Korea. All loci were readily amplified and demonstrated high allelic diversity, with the number of alleles ranging from 6 to 18 in the wild population and from 2 to 12 in the farmed population. A total of 136 alleles were detected at the 12 microsatellite loci in the two populations. The mean observed and expected heterozygosities were 0.62 and 0.68, respectively, in the hatchery samples and 0.67 and 0.75, respectively, in the wild samples. These results indicate lower genetic variability in the hatchery population as compared to the wild population. Significant shifts in allelic frequencies were detected at eight loci, which resulted in a small but significant genetic differences between the wild and hatchery populations (F(ST) = 0.043, P < 0.05). Further studies with additional starry flounder sample collections are needed for comprehensive determinations of the genetic varieties between the wild and hatchery populations. These microsatellite loci may be valuable for future population genetic studies, monitoring the genetic variation for successful aquaculture management and the preservation of aquatic biodiversity.     

A simple HPLC-UVD method for detection of etofenprox in green tea using sample hydration

Residue levels were estimated using HPLC-UV detection. Samples were hydrated and extracted using acetonitrile. Analytical linearity in the range of 0.02 to 2.0 mg/kg was excellent with a determination coefficient (R ²) of 1.0. Recovery at levels of 0.2 and 1.0 mg/kg ranged from 89.9 to 94.6% with a relative standard deviation <5%. Sufficient sensitivity was achieved. The limits of detection and quantification were 0.006 and 0.02 mg/kg, respectively. The method was successfully applied to analysis of field samples. This method was effective and can be used for routine analysis of etofenprox in tea samples at low concentrations.     

Characterization of MOCVD Pt electrode for ferroelectric thin films

Abstract

Platinum thin films were deposited by low pressure chemical vapor deposition (LPMOCVD) on SiO₂/Si and (Ba, Sr)TiO₃/Pt/SiO₂/Si substrates using Pt-hexafluoroacetylacetonate at various deposition temperatures. The shiny mirror-like Pt thin films of a high electrical conductivity were obtained, when the deposition temperature is between 325°C and 350°C, whereas above 375°C Pt thin films showed rough surface as well as poor adhesion property to oxide substrate. Pt thin films had a good step coverage of 90%. The results indicate that LPMOCVD Pt thin films can be applied for the top electrode of high dielectric thin film, which is thought to be one of the best candidate materials for a capacitor of ULSI DRAM.     

Fabrication of nickel micromesh sheets and evaluation of their water-repellent and water-proof abilities

Nickel micromesh sheets were designed and fabricated and their water-repellent and water-proof abilities were characterized. The network-type microstructures of the micromesh sheets functioned as micro-protrusions of lotus leaves, which allowed the sheets to superhydrophobic. The micromesh enabled the material waves, including sound and light waves, to pass through the microholes, but repelled water. Because of the effects of the micromesh and plasma polymerized fluorocarbon (PPFC) coating, the contact angle of the micromesh sheets was drastically jumped up from 63° of the non-coated nickel flat film to 140° of the PPFC-coated nickel micromesh, which modified the nickel sheet from hydrophilic to superhydrophobic. The narrower lattice width in the micromesh was more effective at enhancing the water-repellency. On the other hand, the narrow lattice width weakened the water-proof ability. Reducing the hole size and increasing the lattice width of the micromesh are necessary to improve the water-proof ability.