• Bulletin of the Korean Chemical Society
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• v.28 no.6
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• pp.921-928
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• 2007

Three different phosphonated trisbipyridine ruthenium complexes, [(4-CH3-4'-CH2PO(OH)2-2,2'-bipyridine)- (bpy)2Ru]·(PF6)2 (Ru-P1), [(4-CH3-4'-CH2PO(OH)2-2,2'-bipyridine)3Ru]·(PF6)2 (Ru-P2), and [(4,4'-CH2PO- (OH)2-2,2'-bipyridine)3Ru]·(PF6)2 (Ru-P3) were synthesized and their photochemical and electrochemical properties were studied. These ruthenium complexes were strongly adsorbed on the surface of the layered metal oxide semiconductor K4Nb6O17 that was partially acid-exchanged and sensitized up to pH 10, while the carboxylated ruthenium complex, (4,4'-COOH-2,2'-bipyridine)3Ru·Cl2 (Ru-C) that was previously studied was sensitized only below pH 4. The visible light water reduction at K4Nb6O17 that was internally platinized and sensitized by these phosphonated Ru-complexes was comparatively studied using a reversible electron donor iodide.

• Environmental Engineering Research
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• v.10 no.6
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• pp.283-293
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• 2005

Characteristics of sulfur-based autotrophic denitrification in a semi-continuous type reactor and the kinetic parameters were studied. Enriched autotrophic denitrifying culture was used for the reactor operation. Biomass growth on sulfur particles and in the liquid medium was monitored using the DAPI staining method. From the result of ion concentration changes and the biomass growth, maximum specific growth rate, ${\mu}_{max}$, and the half velocity constant, $K_M$, were estimated as $0.61\;d^{-1}$ and 3.66 mg/L, respectively. Growth yield coefficient, Y values for electron acceptor and donor were found as 0.49 gVSS/g N and 0.16 gVSS/g S. The biomass showed specific denitrification rate, ranging 0.86-1.13 gN/g VSS-d. A half-order equation was found to best simulate the denitrification process in the packed bed reactor operated in the semi-continuous mode.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2010.03a
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• pp.49-50
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• 2010

The near-infrared absorbing donor-acceptor chromophores have been investigated by varying the electron donating and accepting molecular moiety. A series of near-infrared absorbing chromophores were offered narrow and intense absorption band in a various organic solvents. The dyes synthesised were, however, strongly bathochromic shift which extended well into the near-infrared region. The functional uses of dyes are vast in number, and it is convenient to classify them in some way. In all cases, it is the $\Pi$-chromophore that plays a major role in the functional application. "Light absorption" is of course the most commonly used property of a dye chromophore, and it can be employed directly, e.g. in light filters and optical data recording, or it can be used to drive further functional processes, e.g. fluorescence, photochromism, photosensitization.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.775-778
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• 2011

TBP (tertiarybutylphosphine), a relatively new material for phosphorus, has been studied with EDMIn (ethyldimethylindium) as an indium source for the growth of InP by MOVPE (metalorganic vapor phase epitaxy). Mirror smooth and good crystalline InP layers were obtained at $500-600^{\circ}C$ with the TBP/EDMIn molar ratio as low as 21. The deposited InP layers are all n-type with the electron concentration in the range of (5-10)${\times}10^{16}\;cm^{-3}$, which is a lot higher than those from $PH_3$. This high concentration is due presumably to the high concentration of donor impurities in TBP. And it has been found that the formation of adduct occurs between EDMIn and TBP at room temperature when the partial pressure of EDMIn in the reactant mixture is above $1{\times}10^{-2}$ Torr. The high concentration of impurities in TBP and the adduct formation between EDMIn and TBP are major obstacles in replacing $PH_3$ and TMIn for the growth of device quality InP layers.

• Food Science and Biotechnology
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• v.15 no.4
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• pp.564-571
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• 2006

In order to improve the quality and preservation of nabakkimchi, omija was added as an ingredient to determine its effect on the physicochemical characteristics of kimchi during fermentation, as well as the optimum level of omija extract. Omija extract was prepared from omija seeds by extraction with water for 9 hr at room temperature in concentrations (w/v) of 0.5, 1.0, 1.5, and 2.0% for use as an ingredient in nabakkimchi. The physicochemical characteristics of nabakkimchi containing omija extract were analyzed during fermentation of the product for up to 25 days. Delayed fermentation was observed, particularly in the early stage of fermentation, and was dependent on the concentration of the omija extract, as shown by stabilization of pH decreases and increases in the total acidity. An increased concentration of omija extract also raised the initial total vitamin C content and the reducing sugar content, which both then stabilized thereafter. Delayed development of turbidity within the optimum fermentation period of 16 days, increased redness and total color difference, and an electron-donor effect were also promoted by the omija extract. However, the omija extract also triggered extra tannin production, which leads to an astringent taste, especially at the 1.5 and 2.0% treatment levels.

• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.939-945
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• 1997

Several types of 4-substituted-quinoline-2-carboxylic acid derivatives possessing different substituents at C4-position such as sulfonyl, phosphonyl, carbonyl groups, or a flexible alkyl chain have been synthesized and evaluated for their in vitro antagonistic activity at the glycine site on the N-methyl-D-aspartate (NMDA) receptor. Of them, 5,7-dichloro-4-(tolylsulfonylamino)-quinoline-2-carboxylic acid 9 was found to have the best in vitro binding affinity with IC50 of 0.57 μM. On the other hand, in compounds 21 and 22 the introduction of flexible alkyl chains on C4 of the quinoline mother nuclei caused a significant decrease of the in vitro binding affinity. In addition, replacement of polar carboxylic acid group on C2 by neutral bioisosteres in compounds 23a-d also seems to be disadvantageous to in vitro activity. In the structure-activity relationship (SAR) study of the 4-substituted quinoline-2-carboxylic acid acid derivatives, it was realized that the substitution pattern on C4 significantly influences on the binding affinity for the glycine site of NMDA receptor and the binding affinity might be increased by the introduction of a suitable electron rich substituent at C4 which has the ability of H-bonding donor.

• Bulletin of the Korean Chemical Society
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• v.18 no.10
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• pp.1090-1093
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• 1997

The solvent effects on the isotropic NMR shifts in conformationally rigid ligands such as quinuclidine, pyridine, and 4-aminopyridine coordinated to the paramagnetic polyoxometalate, [SiW11CoⅡO39]6- (SiW11Co), are reported. For these complexes the ligand exchange is slow on the NMR time scale and pure 1H NMR signals have been observed at room temperature. The signals for the SiW11Co complexes are shifted upfield whe dimethyl sulfoxide-d6 (DMSO) is added to a D2O solution. The isotropic shifts are separated into contact and pseudocontact contributions by assuming that the contact shifts are proportional to the isotropic shifts of the same ligands coordinated to [SiW11NiⅡO39]6-. It is shown that both the contact and pseudocontact shifts decrease (the absolute values of the pseudocontact shifts increase), when D2O is replaced by DMSO. It is suggested that D2O, a strong hydrogen bond donor, withdraws electron density from [SiW11CoⅡO39]6-, increasing the acidity of the cobalt ion toward the axial ligand. When D2O is replaced by DMSO, the acidity of the cobalt ion in SiW11Co decreases, weakening the Co-N bond. Then both the contact and pseudocontact shifts are expected to decrease in agreement with the observed solvent effects.

• Journal of Surface Science and Engineering
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• v.56 no.4
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• pp.265-272
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• 2023

Photoelectrochemical (PEC) water splitting is one of the promising methods for hydrogen production by solar energy. Iron oxide has been effectively investigated as a photoelectrode material for PEC water splitting due to its intrinsic property such as short minority carrier diffusion length. However, iron oxide has a low PEC efficiency owing to a high recombination rate between photoexcited electrons and holes. In this study, we synthesized nanoporous structured iron oxide by anodization to overcome the drawbacks and to increase surface area. The anodized iron oxide was annealed in Ar atmosphere with different purging times. In conclusion, the highest current density of 0.032 mA/cm² at 1.23 V vs. RHE was obtained with 60 s of pursing for iron oxide(Fe-60), which was 3 times higher in photocurrent density compared to iron oxide annealed with 600 s of pursing(Fe-600). The resistances and donor densities were also evaluated for all the anodized iron oxide by electrochemical impedance spectra and Mott-Schottky plot analysis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.197-206
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• 1999

The stochiometric mixture of evaporating materials for the $AgInSe_2$single crystal thin films were prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the $AgInSe_2$polycrystal, it was found tetragonal structure whose lattice constant $a_0$ and $C_0$ were 6.092 $\AA$ and 11.688 $\AA$, respectively. To obtain the single crystal thin films of AgInSe$_2$, the mixed crystal was deposited on thoroughly etched semi-insulator GaAs(100) substrate by HWE system. The source and substrate temperature were fixed to $610^{\circ}C$ and $450^{\circ}C$ respectively, and the thickness of the single thin films was obtained to 3.8 $\mu\textrm{m}$. The crystallization of single crystal thin films was investigated by the photoluminescence (PL) and double crystal X-ray dirrfaction (DCXD). The Hall effect was measured by the method of van der Pauw and carrier density and mobility dependence on temperature were studied. The carrier density and mobility of $AgInSe_2$single crystal thin films deduced from Hall data are $9.58{\times}10^{22} electron/m^3,\; 3.42{\times}10^{-2}m^2/V{\cdot}s$ at 293 K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $AgInSe_2$single crystal thin film, the spin orbit coupling $\Delta$So and the crystal field splitting $\Delta$Cr were obtained to 0.29 eV and 0.12 eV at 20 K respectively. From PL peaks measured at 20 K, 881.1 nm (1.4071 eV) and 882.4 nm (1.4051 eV) mean $E_x^U$ the upper polariton and $E_x^L$ the lower polariton of the free exciton $(E_x)$, also 884.1 nm (1.402 eV) express $I_2 peak of donor-bound exciton emission and 885.9 nm (1.3995 Ev) emerges $I_1$ peak of acceptor-bound exciton emission. In addition, the peak observed at 887.5 nm (1.3970 eV) was analyzed to be PL peak due to DAP.

• Journal of the Mineralogical Society of Korea
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• v.15 no.3
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• pp.231-240
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• 2002

Microbial metal reduction influences the biogeochemical cycles of carbon and metals as well as plays an important role in the bioremediation of metals, radionuclides, and organic contaminants. The use of bacteria to facilitate the production of magnetite nanoparticles and the formation of carbonate minerals may provide new biotechnological processes for material synthesis and carbon sequestration. Metal-reducing bacteria were isolated from a variety of extreme environments, such as deep terrestrial subsurface, deep marine sediments, water near Hydrothemal vents, and alkaline ponds. Metal-reducing bacteria isolated from diverse extreme environments were able to reduce Fe(III), Mn(IV), Cr(VI), Co(III), and U(VI) using short chain fatty acids and/or hydrogen as the electron donors. These bacteria exhibited diverse mineral precipitation capabilities including the formation of magnetite ($Fe_3$$O_4$), siderite ($FeCO_3$), calcite ($CaCO_3$), rhodochrosite ($MnCO_3$), vivianite [$Fe_3$($PO_4$)$_2$ .$8H_2$O], and uraninite ($UO_2$). Geochemical and environmental factors such as atmospheres, chemical milieu, and species of bacteria affected the extent of Fe(III)-reduction as well as the mineralogy and morphology of the crystalline iron mineral phases. Thermophilic bacteria use amorphous Fe(III)-oxyhydroxide plus metals (Co, Cr, Ni) as an electron acceptor and organic carbon as an electron donor to synthesize metal-substituted magnetite. Metal reducing bacteria were capable of $CO_2$conversion Into sparingly soluble carbonate minerals, such as siderite and calcite using amorphous Fe(III)-oxyhydroxide or metal-rich fly ash. These results indicate that microbial Fe(III)-reduction may not only play important roles in iron and carbon biogeochemistry in natural environments, but also be potentially useful f3r the synthesis of submicron-sized ferromagnetic materials.