Daejeon, South Korea
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Nam H.-S.,Hanwha Chemical Randnter | Nam H.-S.,KAIST | Jang K.-S.,Korea Research Institute of Chemical Technology | Ko J.M.,Hanbat National University | And 2 more authors.
Electrochimica Acta | Year: 2011

The nanoporous RuO2·3.38H2O was synthesized with a surfactant template using sodium dodecyl sulfate. The surface area of the material amounted to 220 m2 g-1 while the maximum specific capacitance obtained was 870 Fg-1 at a scan rate of 10 mV s-1. The specific capacitance of nanoporous RuO2·3. 38H2O electrode exhibits enhancement, compared with other porous RuO2 materials synthesized by different methods. The nanoporous RuO2·3.38H2O is a very promising material for high performance capacitance. © 2011 Elsevier Ltd. All rights reserved.

Nam H.-S.,Hanwha Chemical Randnter | Nam H.-S.,Korea Advanced Institute of Science and Technology | Kwon J.S.,Hanbat National University | Kim K.M.,Electronics and Telecommunications Research Institute | And 2 more authors.
Electrochimica Acta | Year: 2010

Nanowire-structured MnO2 active materials were prepared by a chemical precipitation method and their supercapacitive properties for use in the electrodes of supercapacitors were investigated by means of cyclic voltammetry in an aqueous gel electrolytes consisting of 1 M Na 2SO4 and fumed silica (SiO2). The MnO 2 electrode showed a maximum specific capacitance of 151 F g -1 after 1000 cycles at 100 mV s-1 when using the gel electrolyte containing 3 wt.% of SiO2, which is higher than 121 F g-1 obtained when using the 1 M Na2SO4 liquid electrolyte alone. © 2010 Elsevier Ltd. All rights reserved.

Kim J.-G.,Hanwha Chemical Randnter | Jang D.O.,Yonsei University
Synlett | Year: 2010

Various carboxylic acids were converted into acyl fluorides in excellent yields by treatment with trichloroacetonitrile, triphenylphosphine, and TBAF(t-BuOH)4 at room temperature. The reaction was applicable to the preparation of acid-sensitive amino acid fluorides without deprotection or rearrangement © 2010 Georg Thieme Verlag Stuttgart New York.

Hwang J.,Seoul National University | Park C.,Seoul National University | Choi K.,Seoul National University | Cha M.-H.,Seoul National University | And 8 more authors.
Nano | Year: 2012

We investigate the hydrogen storage capacity of the light transition metal (TM)-decorated metal organic frameworks (MOFs) by performing ab initio density functional theory calculations. We find that among all the light TM elements, divalent Ti and Fe are suitable for decorating MOFs to enhance the hydrogen uptake, considering the H2 binding energy on the TM atom and the reversibly usable number of H2 molecules attached to the metal site. In general, the magnetization of metal atoms undergoes a high-spin to low-spin state transition when H2 molecules are adsorbed, which helps to stabilize the system energetically. By analyzing the projected density of states on each TM atom, it is shown that the d-level shift induced by the ligand field of the adsorbed H2 molecules contributes substantially to the H 2 binding strength. We also study the stability of selected TM-decorated nanostructures against the attack of foreign molecules by examining the energetics of those contaminating molecules around the metal sites. © 2012 World Scientific Publishing Company.

Kim J.-G.,Hanwha Chemical Randnter | Jang D.O.,Yonsei University
Synlett | Year: 2010

We have developed a simple, mild method for N-formylation of a wide variety of amines in the presence of indium metal as a catalyst under solvent-free conditions. This reaction is applicable to the chemoselective N-formylation of amino groups and -amino acid esters without epimerization. © Georg Thieme Verlag Stuttgart.

Yu H.-C.,Yonsei University | Vijay Kumar S.,Yonsei University | Cho S.-Y.,Yonsei University | Kudo K.,University of Tokyo | And 5 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2011

Fully aliphatic polyimides (APIs) were prepared from rel-(1′R, 3S5′S)-spiro[furan-3(2H),6′-[3]oxabicyclo[3.2.1]octane]-2,2′, 4′,5(4H)-tv e etrone (D An) as unsymmetrical spiro dianhydride, and either cis-trans-1,4-diaminocyclohexane (mix-DACH) or trans-1,4-diaminocyclohexane (trans-DACH) as diamine. Structure of all prepared monomers and polymers was confirmed via 1H-NMR and FT-IR. The solubility, optical transparency, and thermal properties of the full APIs were investigated. The solubility and decomposition temperature of the full APIs were found to be correlated with their intermolecular regularity confirmed via wide-angle X-ray diffraction (WAXD). Triblock copoly-imides were synthesized through the incorporation of a thermally labile polymer, poly(propylene glycol) (PPG), into the full APIs, and their thermal properties were studied via thermogravimet-ric analysis (TGA). Nanoporous thin films of the full APIs were prepared via thermolysis of the labile block in the copolyimide films. Phase separation and nanopore formation in the copolymer films were confirmed via atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. Nanoporous pores were successfully prepared inside the films. Copyright © 2011 American Scientific Publishers All rights reserved.

Kim J.-G.,Hanwha Chemical Randnter | Mishra M.K.,Yonsei University | Jang D.O.,Yonsei University
Tetrahedron Letters | Year: 2012

A mild and efficient method to synthesize sterically hindered ketones from aldehydes via O-silyl oximes was developed. Treatment of O-triphenylsilylated oximes with alkyl iodides in the presence of triethyl borane afforded the corresponding ketones. © 2012 Elsevier Ltd. All rights reserved.

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