• Bulletin of the Korean Chemical Society
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• 제16권12호
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• pp.1180-1184
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• 1995

The precursors of Ba1-xSrxTiO3(x=0.0-0.3) were prepared by the rapid addition of aqueous solution of titanyl oxalate to the mixed aqueous solution of barium and strontium at room temperature. The optimum pH was theoretically calculated from the equilibrium constants and solubility products. The chemical formula of the precursors obtained corresponded to Ba1-xSrxTiO(C2O4)2·4H2O(x=0.0-0.3) as determined by thermal gravimetric analysis. The precursors were converted to stoichiometric Ba1-xSrxTiO3(x=0.0-0.3) with a particle size of 0.01-0.04 μm. As increasing the amount of strontium substituted to barium sites, the structure of crystal changed from the tetragonal phase to the cubic and the unit cell volume was decreased.

• Animal cells and systems
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• 제4권2호
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• pp.157-163
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• 2000

Yeast pheromone a-factor is a 13-amino acid peptide hormone that is synthesized as a part of a larger precursor, prepro-$\alpha$-factor, consisting of a signal peptide and a proregion of 64 amino acids. The carboxy-terminal half of the precursor contains four tandem copies of mature $\alpha$-factor. To investigate the molecular basis of intracellular sorting, proteolytic processing, and storage of the peptide hormone, yeast prepro-$\alpha$-factor precursors were heterologously expressed in rat pituitary $GH_3 cells. When cells harboring the precursor were metabolically labeled, a species of approximately 27 kD appeared inside the cells. Digestion with peptide: N-glycosidase F (PNG-F) shifted the molecular mass to a 19 kD, suggesting that the 27 kD protein was the glycosylated form as in yeast cells. The nascent polypeptide is efficiently targeted to the ER in the $GH_3 cells, where it undergoes cleavage of its signal peptide and core glycosylation to generate glycosylated pro-a-factor. To look at the post ER intracellular processing, the pulse-labelled cells were chased up to 2 hrs. The nascent propeptides disappeared from the cells at a half life of 30 min and only 10-25% of the newly synthesized, unprocessed precursors were stored intracellularly after the 2 h chase. However, about 20% of the pulse-labeled pro-$\alpha$-factor precursors were secreted into the medium in the pro-hormone form. With increasing chase time, the intracellular level of propeptide decreased, but the amount of secreted propeptide could not account for the disappearance of intracellular propeptide completely. This disappearance was insensitive to lysosomotropic agents, but was inhibited at $16^{circ}C or 20^{\circ}C$, suggesting that the turnover of the precursors was not occurring in the secretory pathway to trans Golgi network (TGN) or dependent on acidic compartments. From these results, it is concluded that a pan of these heterologous precursors may be processed at its paired dibasic sites by prohormone processing enzymes located in TGN/secretpry vesicles producing small peptides, and that the residual unprocessed precursors may be secreted into the medium rather than degraded intracellularly.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.373-373
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• 2012

We fabricated conductive zinc oxide (ZnO) thin film at low temperature by UV-enhanced atomic layer deposition. The atomic layer deposition relies on alternate pulsing of the precursor gases onto the substrate surface and subsequent chemisorption of the precursors. In this experiment, diethylzinc (DEZ) and $H_2O$ were used as precursors with UV light. The UV light was very effective to improve the conductivity of the ZnO thin film. The thickness, transparency and resistivity were investigated by ellisometry, UV-visible spectroscopy and Four-point probe.

• Bulletin of the Korean Chemical Society
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• 제25권7호
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• pp.1068-1070
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• 2004

• 멤브레인
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• 제7권1호
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• pp.15-21
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• 1997

Carbon molecular sieve (CMS) membranes were synthesized by the pyrolysis of polymeric precursors. The CMS materials had oxygen-nitrogen selectivities much higher than those observed for the polymeric precursors. Typically molecular sieving materials have diffusion selectivities much higher than polymeric materials. This has been identified as a result of higher entropic selectivity of the molecular sieving materials. A study of the development of molecular sieving properties as the polymeric precursor is pyrolyzed into a CMS material will offer us an insight into polymeric molecular structures needed for enhanced entropic selectivity membrane materials.

• 약학회지
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• 제13권2_3호
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• pp.67-70
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• 1969

Gall duct cannulated rats were given daphnetin, umbelliferone, 4-hydroxy-coumarin, dicoumarol, 4,7-dihydroxycoumarin, 4,7-dimethyl-5-hydroxy-coumarin, coumarin-3-carboxylic acid, cinnamic acid, ferulic acid, caffeic acid by duodenal catheter at room temperature and output of bile flow was detected. All of the subjected compounds in this experiment indicated a significant effect on the biliary elimination except cinnamic acid alone. It is suggested that a relationship exists between chemical pattern and biological activity for coumarin derivatives and their precursors, and that the choleretic activity of these compounds requires hydroxylated cinnamic acid structure as the most fundamental chemical pattern.

• Bulletin of the Korean Chemical Society
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• 제13권3호
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• pp.290-296
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• 1992

Four plausible precursors (21, 22, 24, and 25), just prior to formation of the oxathiazepine ring in eudistomin, were synthesized by the Pictet-Spengler condensation of N-hydroxytryptamine (15) or N-hydroxytryptophan ester (19) with cysteinal derivatives (5 and 10). In the case of the parent compound (21), one of these four precursors, treatment with dihalomethane in the presence of a phase transfer catalyst gave an eudistomin analogue (26) having the oxathiazepine ring in 35-50% yield.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.254-254
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• 2016

Tin dioxide (SnO2) thin film is one of the most important n-type semiconducting materials having a high transparency and chemical stability. Due to their favorable properties, it has been widely used as a base materials in the transparent conducting substrates, gas sensors, and other various electronic applications. Up to now, SnO2 thin film has been extensively studied by a various deposition techniques such as RF magnetron sputtering, sol-gel process, a solution process, pulsed laser deposition (PLD), chemical vapor deposition (CVD), and atomic layer deposition (ALD) [1-6]. Among them, ALD or plasma-enhanced ALD (PEALD) has recently been focused in diverse applications due to its inherent capability for nanotechnologies. SnO2 thin films can be prepared by ALD or PEALD using halide precursors or using various metal-organic (MO) precursors. In the literature, there are many reports on the ALD and PEALD processes for depositing SnO2 thin films using MO precursors [7-8]. However, only ALD-SnO2 processes has been reported for halide precursors and PEALD-SnO2 process has not been reported yet. Herein, therefore, we report the first PEALD process of SnO2 thin films using SnCl4 and oxygen plasma. In this work, the growth kinetics of PEALD-SnO2 as well as their physical and chemical properties were systemically investigated. Moreover, some promising applications of this process will be shown at the end of presentation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.86.2-86.2
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• 2015

Cu2ZnSn(S,Se)4 thin film solar cells have been fabricated using sputtered Cu/Sn/Zn metallic precursors on Mo coated sodalime glass substrate without using a toxic H2Se and H2S atmosphere. Cu/Sn/Zn metallic precursors with various thicknesses were prepared using DC magnetron sputtering process at room temperature. As-deposited metallic precursors were sulfo-selenized inside a graphite box containing S and Se pellets using rapid thermal processing furnace at various sulfur to selenium (S/Se) compositional ratio. Thin film solar cells were fabricated after sulfo-selenization process using a 65 nm CdS buffer, a 40 nm intrinsic ZnO, a 400 nm Al doped ZnO, and Al/Ni top metal contact. Effects of sulfur to selenium (S/Se) compositional ratio on the microstructure, crystallinity, electrical properties, and cell efficiencies have been studied using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscope, I-V measurement system, solar simulator, quantum efficiency measurement system, and time resolved photoluminescence spectrometer. Our fabricated Cu2ZnSn(S,Se)4 thin film solar cell shows the best conversion efficiency of 9.24 % (Voc : 454.6 mV, Jsc : 32.14 mA/cm2, FF : 63.29 %, and active area : 0.433 cm2), which is the highest efficiency among Cu2ZnSn(S,Se)4 thin film solar cells prepared using sputter deposited metallic precursors and without using a toxic H2Se gas. Details about other experimental results will be discussed during the presentation.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.5.2-5.2
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• 2009

From 10 years ago, the development of nano-devices endeavored to achieve reconstruction of information technology (IT) and nano technology (NT) industry. Among the many materials for the IT and NT industry, zinc oxide (ZnO) is a very promising candidate material for the research of nano-device development. Nano-structures of ZnO-based materials were grown easily via various methods and it attracts huge attention because of their superior electrical and optical properties for optoelectronic devices. Recently, among the various growth methods, MOCVD has attracted considerable attention because it is suitable process with benefits such as large area growth, vertical alignment, and accurate doping for nano-device fabrication. However, ZnO based nanowires grown by MOCVD process were had the principal problems of 1st interfacial layers between substrate and nanowire, 2nd a broad diameter (about 100 nm), and 3rd high density, and 4th critical evaporation temperature of Zinc precursors. In particular, the growth of high performance nanowire for high efficiency nano-devices must be formed at high temperature growth, but zinc precursors were evaporated at high temperature.These problems should be repaired for materialization of ultra high performance quantum devices with quantum effect. For this reason, we firstly proposed the growth method of vertical aligned slim MgZnO nanowires (< 10 nm) without interfacial layers using self-phase separation by introduced Mg at critical evaporation temperature of Zinc precursors ($500^{\circ}C$). Here, the self-phase separation was reported that MgO-rich and the ZnO-rich phases were spontaneously formed by additionally introduced Mg precursors. In the growth of nanowires, the nanowires were only grown on the wurzite single crystal seeds as ZnO-rich phases with relatively low Mg composition (~36 at %). In this study, we investigated the microstructural behaviors of self-phase separation with increasing the Mg fluxes in the growth of MZO NWs, in order to secure drastic control engineering of density,diameter, and shape of nanowires.