• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2523-2528
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• 2012

Green phosphors $(Zn_{1-a-b}M_aM^{\prime}_b)_xGa_yS_{x+3y/2}:Eu^{2+}$ (M, M' = alkali earth ions) with x = 2 and y = 2-5 were prepared, starting from ZnO, MgO, $SrCO_3$, $Ga_2O_3$, $Eu_2O_3$, and S with a flux $NH_4F$ using a conventional solidstate reaction. A phosphor with the composition of $(Zn_{0.6}Sr_{0.3}Mg_{0.1})_2Ga_2S_5:Eu^{2+}$ produced the strongest luminescence at a 460-nm excitation. The observed XRD patterns indicated that the optimized phosphor consisted of two components: zinc thiogallate and zinc sulfide. The characteristic green luminescence of the $ZnS:Eu^{2+}$ component on excitation at 460 nm was attributed to the donor-acceptor ($D_{ZnGa_2S_4}-A_{ZnS}$) recombination in the hybrid boundary. The optimized green phosphor converted 17.9% of the absorbed blue light into luminescence. For the fabrication of light-emitting diode (LED), the optimized phosphor was coated with MgO using magnesium nitrate to overcome their weakness against moisture. The MgO-coated green phosphor was fabricated with a blue GaN LED, and the chromaticity index of the phosphor-cast LED (pc-LED) was investigated as a function of the wt % of the optimized phosphor. White LEDs were fabricated by pasting the optimized green (G) and the red (R) phosphors, and the commercial yellow (Y) phosphor on the blue chips. The three-band pc-WLED resulted in improved color rendering index (CRI) and corrected color temperature (CCT), compared with those of the two-band pc-WLED.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.579-582
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• 2000

(R,S)-3-amino-n-butanoic acid$(DL-\;{\beta}\;-homoalanine)$ has been kinetically resolved using Alcaligenes denitrificans Y2k-2 as a biocatalyst, which was isolated from soil by enrichment culture, which was carried out with minimal media containing (R,S)-3-amino-n-butanoic acid as a sole nitrogen source. The enzyme which peformed this kinetic resolution assumed to belong to the ${\omega}-transaminase$ family, because A. denitrificans used pyruvate as amino acceptor and its transaminase activity was inhibited by gabaculine, aminooxy acetic acid and hydroxylamine. In whole cell reaction, (R,S)-3-amino-n-butanoic acid was kinetically resolved to the corresponding (R)-3-amino-n-butanoic acid with excellent E (>100) in the presence of pyruvate as an amino acceptor at $37^{\circ}C$. (S-specific) We observed the substrate inhibition for pyruvate at 100mM. In this study, characteristics of transaminase activity of Alcaligenes denitrificans Y2k-2, such as substrate specificity and thermostability, are carried out for the development of (R)-3- amino-n-butanoic acid production system.

• Microbiology and Biotechnology Letters
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• v.5 no.3
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• pp.141-151
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• 1977

Distribution of tellurite and tellurate-reducing enzymes in the cell of Nocardia sp, the purifcation and the chemical properties of enzymes were investigated. Tellurite- and tellurate-reducing enzymes were located in the cytoplasm, but T. T. C. reduction part was in the cell membrane. Purification of tellurite- and tellurate-reducing enzymes was possible with the application of ammonium sulfate precipitation method and DEAE-Cellulose or CM-Cellulose column chromatographic method from the crude soluble part of the cell. On investigating the properties of purified enzyme, one of NADP, NADPH and reductive methylene blue(leucomethylene blue) was thought to react as a hydrogen donor. Both NADH and NADPH, or either of them would be physiological hydrogen donor.) In the reaction of this enzyme, either tellurite or tellurate reacts as a hydrogen acceptor, but on the other hand either selenate or selenate also reacts as a hydrogen acceptor.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.587-596
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• 2014

A new ${\pi}$-stacked donor-acceptor (D-A) system, [Ru(1-([2,2'-bipyridine]-6-yl-methyl)-3-(2-cyclohexa-2',5'-diene-1,4-dionyl)-1H-imidazole)(2,2':6',2"-terpyridine)]$[PF_6]_2$ (ImQ_T), has been synthesized and characterized. Similar to its precedent, [Ru(6-(2-cyclohexa-2',5'-diene-1,4-dione)-2,2':6',2"-terpyridine)(2,2':6',2"-terpyridine)]$[PF_6]_2$ (TQ_T), this system has a cofacial alignment of terpyridine (tpy) ligand and quinonyl (Q) group, which facilitates an electron transfer through ${\pi}$-stacked manifold. Despite the presence of lowest-energy charge transfer transition from the Ru-based-HOMO-to-Q-based-LUMO (MQCT) predicted by theoretical calculations by using time-dependent density functional theory (TD-DFT), the experimental steady-state absorption spectrum does not exhibit such a band. The selective excitation to the Ru-based occupied orbitals-to-tpy-based virtual orbital MLCT state was thus possible, from which charge separation (CS) reaction occurred. The photo-induced CS and thermal charge recombination (CR) reactions were probed by using ultrafast visible-pump/mid-IR-probe (TrIR) spectroscopic method. Analysis of decay kinetics of Q and $Q^-$ state CO stretching modes as well as aromatic C=C stretching mode of tpy ligand gave time constants of <1 ps for CS, 1-3 ps for CR, and 10-20 ps for vibrational cooling processes. The electron transfer pathway was revealed to be Ru-tpy-Q rather than Ru-bpy-imidazol-Q.

• YAKHAK HOEJI
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• v.42 no.3
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• pp.257-264
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• 1998

5-Methylthebaine was obtained by treating thebaine with n-butyllithium and methylfluorosulfonate. Hetero Diels-Alder reaction of thebaine and 5-methylthebaine with trifluoroacet aldehyde afforded 14-${\beta}$-(triflu-oro-2-hydroxyethyl)codeine (2) and 14-${\beta}$-(trifluoro-2-hydroxyethyl)-5-methylcodeinone (9). 6-${\alpha}$-OH compound (4) was obtained by employing $CeCl_2$ and $NaBH_4$. After synthesized a derivative substituted for 3-OH (5), using boron tribromied, We synthesized a new derivative that make double bond in C-7, C-8 into epoxode (6), (10). Through inspecting an influence on structure-activity and analgetic action, we are going to examine which opiold acceptor has a selectivity.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.165-165
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• 2006

We prepared nonlinear optical (NLO) polymers possessing thermal and temporal stability, which were based on the polyimides appended with NLO chromophores. NLO chromophores with a terminal hydroxyl group have been synthesized by coupling between aminobenzene or julolidine donor and phenylene bridge, and then subsequent coupling between the resulting product and tricyanofuran acceptor. The chromophores were chemically bonded to the polyimides backbone through Mitsunobu reaction. The NLO polymers showed $160-170^{\circ}C$ of Tgs and were thermally stable up to $200^{\circ}C$. We obtained optical quality films by spincoating and evaluated their electro-optical properties and temporal stability.

• Korean Journal of Materials Research
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• v.12 no.6
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• pp.476-481
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• 2002

In this work, we report on the synthesis of the GaN powders from gallium oxide hydroxide (GaOOH) powders and on the structural and optical properties of them. Simple heat treatment of GaOOH in the flow of $NH_3$ gas leads to the formation of submicron hexagonal GaN powders even at the low reaction temperature of $800^{\circ}C$. XRD measurements show that the powders obtained are the single phase GaN. EDS, FTIR, and PL measurements indicate the oxygen-associated characteristics. It is shown from the low temperature PL measurement on GaN powders synthesized at $1000^{\circ}C$ that the shallow donor-acceptor recombination induced emission is more intense than the near band-edge excitonic emission.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.23-23
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• 1998

Michael Reaction을 이용하여 상업적으로 이용 가능한 APS(3-aminopropyltrime thoxysilane)과 AEAPS(N-[3-(trimethoxysilyl)propy1] ethylenediamine)을 다수의 Michael acceptor(ethyl acrylate, acrylonitrile, acrylamide, 2-cyanoethyl acrylate, 2-hydroxyethyl acrylate 그리고 3-(trimethoxysilyl)propylmethacrylate)와 반응시켜 10종류의 aminosilane ([3-｛N-2-carboethoxyethyl)aminopropyl]triethoxysilane, [3-(N-2-cyanoethyl)aminopropyl] triethoxysilane, [3-(N-di-2-carboethoxyethyl) aminopropyl]triethoxysilane, [3-(N-di-2-cyanoethyl)aminopropyl]triethoxysilane, [3-(N-2-cyanoethoxypropionyl)aminopropyl] triethoxysilane, [3-(N-di-2-cyanoethoxypropionyl)aminopropyl] triethoxysilane, [3-(N-di-2-hydroxyethoxypropionyl) aminopropyl]-triethoxysilane, [3-(N-2-amidoethyl aminopropyl]triethoxysilane, ｛3-[N-(N-di-2-cyanoethyl)ethyl]aminopropyl)triethoxysilane, ｛3-[N-(3-trimethoxy-silylpropyl)-2-methylpropionyl]aminopropyl)triethoxysilane 등을 35-70% 수율로 제조하였으며, 이들의 구조는 $^1$H-NMR과 FT-IR spectroscopy를 이용하여 확인하였다.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2369-2376
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• 2007

N2O has been found from experimental and theoretical considerations to bind on-top to the Pd(110) surface in a tilted end-on fashion via its terminal N atom. We use a frontier orbital description of the bonding interactions in the Pd-N2O system to obtain molecular insight into the catalytic mechanism of the activation of N2O by the Pd(110) surface giving rise to the formation of N2 and O on the surface. For the tilted end-on N2O binding mode, the LUMO 3π of N2O has good overlap with the Pd dσ and dπ orbitals which can serve as the electron donors. The donor-acceptor orbital overlap is favorable for electron transfer from Pd to N2O and is expected to dominate the surface reaction pathway of N2O decomposition.

• Journal of the Korean Ceramic Society
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• v.44 no.12
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• pp.683-689
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• 2007

Grain-boundary conduction in the fluorite-structure solid oxide electrolytes such as acceptor-doped zirconia and ceria were reviewed. The siliceous impurity, even several hundreds ppm, affects the ionic conduction across grain boundary to a great extent. Various approaches to improve grain-boundary conduction in fluorite-structure oxide electrolytes have been investigated, which include (1) the scavenging of siliceous phase by the reaction with second phase, (2) the gathering of intergranular siliceous phase into a discrete configuration and (3) the dewetting of intergranular liquid phase by post-sintering heat treatment.