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KIST, South Korea

Yoo Y.,KAIST | Yoon I.,KAIST | Lee H.,KAIST | Ahn J.,KAIST | And 2 more authors.
ACS Nano | Year: 2010

We report that twin-free single-crystalline Pd nanowire (NW) arrays grow epitaxially in a selected pattern on a substrate. Parallel aligned Pd NWs are synthesized on a SrTiO 3 (110) substrate in a very high density. On a SrTiO 3 (001) substrate, Pd NWs grow horizontally in two perpendicular directions. Vertical Pd NWs are synthesized instead of horizontal NWs when a c-cut sapphire substrate is employed. We reveal that the atomic structure of the substrate surface determines the geometry and orientation of seeds, which in turn direct the growth patterns of the NWs. The interface energy between the NW material and the substrate is also critical in determining the NW growth pattern. Polarization-dependent localized surface plasmon resonance of as-synthesized epitaxial Pd NW arrays is investigated for application as a plasmonic platform. © 2010 American Chemical Society. Source


Shen C.,Wonkwang University | Jun H.Y.,Wonkwang University | Choi S.,Hannam University | Kim Y.,Advanced Analysis Center | And 5 more authors.
Bulletin of the Korean Chemical Society | Year: 2010

Black pine barks from the southern region of Korea were extracted using pressurized hot water and the water soluble extracts were then separated in a stepwise fashion using a variety of solvents, column chromatography (CC), thin layer chromatography (TLC), and high pressure liquid chromatography (HPLC). The antioxidant activities of each fraction and the active compounds were determined based on the radical scavenging activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH), reductive potential of ferric ion, and total phenol contents. A DPPH test showed that the half maximal effective concentration (EC50 value : 6.59 ± 0.31 μg/mL) of the ethyl acetate fraction (ca. 0.67%) was almost the same as that of the control compounds and inversely proportional to the value of the total phenol contents. The cell viability of the water extracts was confirmed by methyl thiazol-2-yl-2,5-diphenyl tetrazolium bromide (MTT) with enzyme linked immune sorbent assay (ELISA). Catechin, epicatechin, quercetin and ferulic acid were isolated from the ethyl acetate fraction as active compounds and identified by nuclear magnetic resonance. The antioxidant activity as value of DPPH of each of the separated compounds was lower than the ethyl acetate fraction, and ferulic acid was the lowest among these compounds. Source


Kim I.,Gyeongsang National University | Kim C.H.,Gyeongsang National University | Choi S.H.,Gyeongsang National University | Ahn J.-P.,Advanced Analysis Center | And 5 more authors.
Journal of Power Sources | Year: 2016

This study introduces a new flexible cathode that contains no binder, conductive additive and current collector, but instead consists solely of a sulfurized polyacrylonitrile nanofiber (SPAN) web which is prepared by a simple pyrolysis process with low cost raw materials. This not only exhibits good electrochemical properties, but also a high flexibility, rollability, and bendability to 180° without fracture. Its feasibility as a cathode for a low cost and flexible Na/S battery is subsequently evaluated on the basis that S, PAN, and Na are cheap materials. The SPAN web delivers a high first discharge capacity of 604 mAh g-1 - electrode (1473 mAh g-1 - sulfur) at 0.01 C based on sulfur content. In cycle performance at 0.1 C, a first discharge capacity of 342 mAh g-1 - electrode is obtained and remains over 266 mAh g-1 - electrode after 200 cycles along with the coulombic efficiency near 100% from the second cycle. In terms of rate capability, it is shown to be capable of delivering a capacity of as high as 71 mAh g-1 at 1 C. The reversible electrochemical reaction of the SPAN web with Na is related to a reversible bond between the C-S and S-S bonds of the SPAN web. © 2015 Elsevier B.V. All rights reserved. Source


Kim I.,Gyeongsang National University | Park J.-Y.,TAEMYUNG E and E | Kim C.H.,Gyeongsang National University | Park J.-W.,Gyeongsang National University | And 4 more authors.
Journal of Power Sources | Year: 2016

To realize a high-performance room temperature Na/S battery with an elemental sulfur cathode, it is important that sodium polysulfides stay within the cathode and that they have room enough to react freely. In this work, sodium polysulfides are confined to the cathode using a β″ alumina solid electrolyte separator and an optimal amount of tetraethylene glycol dimethyl ether (TEGDME) electrolyte. In addition, an activated carbon material, in the form of a sulfur/carbon (S/C) composite, with high surface area, porosity, and pore volume is employed in the cathode. The resulting Na/S battery shows a high first discharge capacity of 855 mAh g-1 and coulombic efficiency close to 100%, as well as stable cyclability, with a discharge capacity of 521 mAh g-1 at the 104th discharge. © 2015 Elsevier B.V. Source


Lee E.-H.,Gyeongsang National University | Seo Y.-J.,Gyeongsang National University | Ahn H.-C.,Advanced Analysis Center | Kang Y.-M.,Gyeongsang National University | And 4 more authors.
FEBS Letters | Year: 2010

The Yaba-like disease viruses (YLDV) are members of the Yatapoxvirus family and have double-stranded DNA genomes. The E3L protein, which is essential for pathogenesis in the vaccinia virus, consists of two domains: an N-terminal Z-DNA binding domain and a C-terminal RNA binding domain. The crystal structure of the E3L orthologue of YLDV (yabZαE3L) bound to Z-DNA revealed that the overall structure of yabZαE3L and its interaction with Z-DNA are very similar to those of hZαADAR1. Here we have performed NMR hydrogen exchange experiments on the complexes between yabZαE3L and d(CGCGCG)2 with a variety of protein-to-DNA molar ratios. This study revealed that yabZαE3L could efficiently change the B-form helix of the d(CGCGCG)2 to left-handed Z-DNA via the active-mono B-Z transition pathway like hZαADAR1. © 2010 Federation of European Biochemical Societies. Source

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