• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1236_1237
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• 2009

Organic light emitting diode (OLED) is currently the focus of intense interest in the field of photonics. It is attractive for the in low-operating voltage, low power consumption, easy fabrication and low cost. A typical OLED consists of one or more organic layers sandwiched between a high work function anode, such as indium tin oxide (ITO), and a low work function cathode such as Ca, Mg:Ag, and Al. Tris-(8-hydroxy)quinolinealuminum ($Alq_3$) has taken a prominent position in the development of OLED due to its relative stability as an electron transporting and emitting material. We investigated an efficiency improvement of the OLED depending on thickness variation of $Alq_3$.

• Journal of Microbiology and Biotechnology
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• 제19권10호
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• pp.1184-1190
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• 2009

A thermostable extracellular $\beta$-mannanase from the culture supernatant of a fungus Aspergillus niger gr was purified to homogeneity. SDS-PAGE of the purified enzyme showed a single protein band of molecular mass 66 kDa. The $\beta$-mannanase exhibited optimum catalytic activity at pH 5.5 and $55^{\circ}C$. It was thermostable at $55^{\circ}C$, and retained 50% activity after 6 h at $55^{\circ}C$. The enzyme was stable at a pH range of 3.0 to 7.0. The metal ions $Hg^{2+}$, $Cu^{2+}$, and $Ag^{2+}$ inhibited complete enzyme activity. The inhibitors tested, EDTA, PMSF, and 1,10-phenanthroline, did not inhibit the enzyme activity. N-Bromosuccinimide completely inhibited enzyme activity. The relative substrate specificity of enzyme towards the various mannans is in the order of locust bean gum>guar gum>copra mannan, with $K_m$ of 0.11, 0.28, and 0.33 mg/ml, respectively. Since the enzyme is active over a wide range of pH and temperature, it could find potential use in the food-processing industry.

• Journal of Applied Biological Chemistry
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• 제42권1호
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• pp.7-11
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• 1999

An extracellular chitinase of the selected strong antifungal microorganism, Serratia sp. 3095, was purified by salting out, affinity adsorption, Sepadex G-100 gel fitration, Sepadex G-75 gel fitration and DEAE Sepadex A-50 chromatography. The molecular weight of the purified chitinase was estimated to be 62,000 dalton by SDS-PAGE. Optimal pH and temperature of the chitinase were pH 7.5 and 45, respectively. The enzyme retained more than 80% of the activity between pH 5.5 and pH 10.5, and below $50^{\circ}C$ but was unstable above $60^{\circ}C$, below pH 5.0. The activity of the chitinase was inhibited about 60% by $Sn^{2+}$, 40% by $Hg^{2+}$ and $Ag^+$, 70% by AHA, 40% by iodoacetate, 35% by thiourea and p-CMB, but stabilized by SDS. $K_m$ value of the purified chitinase was 3.68 mg/ml for colloidal chitin. The chitinase from Serratia sp. 3095 showed antifungal activity to Fusariurm solani.

• 한국응용과학기술학회지
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• 제21권1호
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• pp.24-30
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• 2004

New electroluminescent materials based on anthracene chromophore with naphthylethenyl substituent, 9,10-bis($\alpha$-naphthylethenyl)anthracene (a-BNA), as well as four kinds of its derivatives were synthesized, and luminescent properties of these materials were investigated. Electrolumineecent(EL) emission band was discussed based on their substituent structure differences. It was found that the emission band strongly depends on the molecular structure of introduced substituent. It can be tuned from 557 nm to 591 nm by changing the substituent structures. On the other hand, the anthracene chromophore with bulky substituent possessed high melting point and they gave stable films through vacuum-sublimation. The double layer EL device of ITO/TPD/emission layer/Mg:Ag was employed, and exhibited efficient orange light originating from emitting materials. EL emission with a maximum luminance was observed in the b-BNA emitting material, : maximum luminance was about 8,060 cd $m^{-2}$ at an applied voltage of 10 V and current density of 680 $mA/cm^2$. In conclusion, the electroluminescent properties also showed good difference with their substituent structure.

• Journal of Microbiology and Biotechnology
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• 제8권4호
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• pp.318-324
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• 1998

A ${\beta}$-galactosidase with high transgalactosylic activity was purified from a Bacillus species, registered as KFCC10855. The enzyme preparation showed a single protein band corresponding to a molecular mass of 150 kDa on SDS-PAGE and gave a single peak with the estimated molecular mass of 250 kDa on Sephacryl S-300 gel filtration, suggesting that the enzyme is a homodimeric protein. The amino acid and sugar analyses revealed that the enzyme is a glycoprotein, containing 19.2 weight percent of sugar moieties, and is much more abundant in hydrophilic amino acid residues than in hydrophobic residues, the mole ratio being about 2:1. The pI and optimum pH were determined to be 5.0 and 6.0, respectively. Having a temperature optimum at $70^{\circ}C$ for the hydrolysis of lactose, the enzyme showed good thermal stability. The activity of the enzyme preparation was markedly increased by the presence of exogenous Mg (II) and was decreased by the addition of EDTA. Among the metal ions examined, the most severely inhibitory effect was seen with Ag (I) and Hg (II). Further, results of protein modification by various chemical reagents implied that 1 cysteine, 1 histidine, and 2 methionine residues occur in certain critical sites of the enzyme, most likely including the active site. Enzyme kinetic parameters, measured for both hydrolysis and transgalactosylation of lactose, indicated that the enzyme has an excellent catalytic efficiency for formation of the transgalactosylic products in reaction mixtures containing high concentrations of the substrate.

• 한국미생물·생명공학회지
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• 제22권1호
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• pp.73-79
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• 1994

The optimum cultural temperature and time for the pullulanase production by Bacillus cereus subsp. mycoides were 35$\circ $C and 48 hrs, respectively. The addition of egg albumin and casein to the basal medium increased the enzyme production. The enzyme was purified by ammonium sulfate fractionation and DEAE-cellulose column chromatography. specific activity of the purified enzyme was 82.37 U/mg protein and yield of theenzyume activity was 62.1%. The purified enzuyme showed a single band on ployacrylamide disc gel electrophoresis and its molecular weight was estimated to be 66.,000 by SDS-polyacrylamide disc gel electrophoresis. The isoelcular point for the purified enzyme was pH 5.0. The optimum temperature and pH were 50$\circ $C and pH 6.5, respectively. The purified enzyme was stable below 40$\circ $C and in the pH range of 6.5~10.0 The pullulanase activity was greatly inhited by Ag$^{+}$, Hg$^{2+}$ and EDTA, and its heat stability was increased by the addition of Ca$^{2+}$. The tydrolysis product with the enzyme on pullulan was maltotriose.

• 한국한의학연구원논문집
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• 제6권1호
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• pp.117-122
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• 2000

The purpose of this study is to compare the contents of heavy metals of boiled ssangwhatang with those of herbal ingredients which are composed of ssangwhatang. Ssangwhatang is used for antifatigue, tonic and so on. With industrial development, our environment has been very polluted. Herbal medicines also are seriously contaminated by heavy metals and pesticides. The herbal medicines of ssangwhatang were bought at 10 defferent markets. The contents of 14 heavy metals(Ag, As, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Sn, Zn) were analysed using ICP. It was found out that 7 heavy metals(Pb, As, Ba, Cd, Hg, Sb, Sn) were not detected at all in boiled ssangwhatangs. But they were detectable in all ssangwhatangingredients before boiling. For example, the content of Pb in one pack of ssangwhatang before boiling was $0.039^{\circ}{\pm}0.005mg$ and Pb in boiled one was not detected. Herbal medicine itself is seriously contaminated by heavy metals. These results suggest that boiled ssangwhatang which we take is safe from the contamination of heavy metals.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.373-378
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• 2006

We report on plasma damage free-sputtering technologies for organic light emitting diodes (OLEDs), organic thin film transistor (OTFT) and flexible displays by using a box cathode sputtering (BCS) method. Specially designed BCS system has two facing targets generating high magnetic fields ideally entering and leaving the targets, perpendicularly. This target geometry allows the formation of high-density plasma between targets and enables us to realize plasma damage free sputtering on organic layer without protection layer against plasma. The OLED with Al cathode prepared by BCS shows electrical and optical characteristics comparable to OLED with thermally evaporated Mg-Ag cathode. It was found that OLED with Al cathode layer prepared by BCS has much lower leakage current density ($1{\times}10^{-5}\;mA/cm^2$ at -6 V) than that $(1{\times}10^{-2}{\sim}-10^0\;mA/cm^2)$ of OLED prepared by conventional DC sputtering system. This indicates that BCS technique is a promising electrode deposition method for substituting conventional thermal evaporation and DC/RF sputtering in fabrication process of organic based optoelectronics.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.153-153
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• 2008

최근 투명전극물질이 LCD, 박막태양전지, smart window, 유기발광소자 등에 폭넓게 이용됨에 따라 그 수요가 급격이 늘어나고 있다. 이러한 투명전극 물질로는 Al : ZnO, Ga : ZnO, $MgIn_2O_4$, $AgSbO_3$, $InGaZnO_4$, ITO, Zn:ITO 등이 있으며 이중 ITO 계 산화물은 우수한 전기적 특성을 바탕으로 이미 상용화 되어있는 상태이다. 그러나 ITO 계 산화물은 indium 의 희소성과 높은 가격 때문에 폭 넓은 분야의 상용화가 어려운 실정이며, 수소 플라즈마 분위기에 화학적으로 불안정한 특성은 Si 박막태양전지 응용에 큰 문제가 되고 있다. 이에 본 연구는 박막태양전지용 ITO 계 투명전극의 indium양을 줄이면서 화학적으로 안정하고, 전기적 특성이 향상된 박막을 제조하기 위해 combinatorial sputter를 이용하여 Zn의 도핑량을 연속적으로 변화시킨 ITO 박막을 제조하였다. 또한 광학적 전기적 특성의 향상을 위해 vacuum, $H_2$, $O_2$ 분위기에서 열처리 후 각 박막의 특성 변화를 관찰하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.53-54
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• 2005

We report on plasma damage free-sputtering technologies for organic light emitting diodes (OLEDs), organic thin rim transistor (OTFT) and flexible displays by using a box cathode sputtering (BCS) method. Specially designed BCS system has two facing targets generating high magnetic fields ideally entering and leaving the targets, perpendicularly. This target geometry allows the formation of high-density plasma between targets and enables us to realize plasma damage free sputtering on organic layer without protection layer against plasma. The OLED with top cathode prepared by BCS shows electrical and optical characteristics comparable to OLED with thermally evaporated Mg-Ag cathode. It was found that TOLED with ITO or IZO top cathode layer prepared by BCS has much lower leakage current density ($1\times10^{-5}$ mA/cm2 at -6V) than that ($1\times10^{-1}\sim10^{\circ}mA/cm^2$)of OLED prepared by conventional DC sputtering system. This indicates that BCS technique is a promising electrode deposition method for substituting conventional thermal evaporation and dc/rf sputtering in fabrication process of organic based optoelectronics.