• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.2130-2134
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• 2014

A kinetic study is reported on nucleophilic substitution reactions of 4-nitrophenyl isonicotinate (7) with a series of cyclic secondary amines in MeCN. The plots of $k_{obsd}$ vs. [amine] curve upward for the reactions with weakly basic amines (e.g., morpholine, 1-(2-hydroxyethyl)piperazine, and piperazine) but are linear for those with strongly basic amines (e.g., piperidine and 3-methylpiperidine). The curved plots for the reactions with the weakly basic amines are typical for reactions reported previously to proceed through uncatalyzed and catalyzed routes with two intermediates (e.g., a zwitterionic tetrahedral intermediate $T^{\pm}$ and its deprotonated form $T^-$). In contrast, the linear plots for the reactions with the strongly basic amines indicate that the catalytic route (i.e., the deprotonation process to yield $T^-$ from $T^{\pm}$ by a second amine molecule) is absent. The Br${\o}$nsted-type plots for $Kk_2$ and $Kk_3$ (i.e., the rate constants for the uncatalyzed and catalyzed routes, respectively) exhibit excellent linear correlations with ${\beta}_{nuc}$ = 0.99 and 0.69, respectively. The effect of amine basicity on the reaction mechanism is discussed in detail.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.318.1-318.1
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• 2014

Metal nano-crystals have been received much attentions owing to their excellent catalytic property and surface plasmon effect. In the last decade, many studies on synthesizing well-dispersive nanoparticles and on understanding their distinct physical properties have been performed. There were tremendous reports revealing the electrochemical activities and enhancement of surface plasmonic effect were dependent mainly on the size, shape, and composition. So far, most fabrication methods have been based on vacuum based deposition techniques, such as chemical vapor deposition and electron-beam evaporation, and then annealed them to transform into the nanoparticles. Recently, there were several reports regarding to the photoinduced nano-crystal synthesis as an effective way to produce the metal nanoparticles. In this study, we report synchrotron x-ray mediated synthesis of Au nanoparticles on ZnO nanowires. ZnO nanowires were fabricated by hydrothermal method, and then they were dip into a solution having Au clusters. Detailed structural evolution of Au nanoparticles was investigated using scanning electron microscopy and photoluminescence measurements. The results on formation of well-dispersive Au nanoparticles on ZnO nanowires will be presented.

• Journal of Physiology & Pathology in Korean Medicine
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• v.24 no.2
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• pp.296-301
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• 2010

The purpose of this study was to investigate the mechanism of Hexane extract of Fructus Ligustri Lucidi (HFLL)-induced regulation of melanogenesis. An apparent down-regulatory effect of tyrosinase activity was observed when B16F10 cells were incubated with HFLL. Interestingly, HFLL did not inhibit the catalytic activity of cell-free tyrosinase from B16F10 cells, whereas kojic acid directly inhibited tyrosinase activity. Regarding protein levels of melanogenic enzymes, the amounts of tyrosinase and tyrosinase-related protein 1 (TRP-1) were decreased by HFLL, while the amount of tyrosinase-related protein 2 (TRP-2) slightly was reduced after incubation with HFLL. Treatment with HFLL was found to down-regulate microphthalmia-associated transcription factor (MITF). These results suggest that HFLL is an effective inhibitor of pigmentation caused by down regulation via MITF, tyrosinase, and TRP-1 expressions.

• Textile Coloration and Finishing
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• v.5 no.4
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• pp.10-19
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• 1993

Broad, mercerized broad, mercerized twill cotton fabrics and rayon fabric were treated with cellulase for 30~480 minutes at different temperature, concentration, time, and also treating methods such as continuously-treated or repeatedly-treated, and dyed with two direct dyes before or after enzyme treatment. From the experimental result by treating under the various conditions above, it was obtained that the weight loss increased more in thin fabric than thick one. In addition, it was considered that the treatment in 5$0^{\circ}C$ for 240 minutes brought about the ideal weight loss and flexible hand of the specimens. For both broad and mercerized broad, repeated treatment showed more weight loss than continuous. Direct dye on cotton fabric apparently inhibited hydrolysis. Ionic surfactants showed the inhibition effect of the catalytic hydrolysis of enzyme, on the other hand, nonionic surfactant did not.

• Korean Journal of Food Science and Technology
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• v.17 no.6
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• pp.490-494
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• 1985

The effect of organic solvents on the stability and catalytic activity of the microbial lipase from Rhizopus arrhizus for interesterification of fats and oils has been examined. The reaction system used was nonaqueous solvent system (two phase system). The solvents examined were 5 hydrocarbons (n-hexane, n-heptane, n-octane, isooctane, and cyclohexane) and 3 ethers (diethylether, diisopropylether, di-n-butylether). The results revealed that diisopropylether and isooctane are superior to the other solvents examined for interesterification of fats and oils in two phase systems.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.3005-3012
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• 2013

The effect of Mn-promotion on high surface area Al-pillared montmorillonite (AlMMT) supported Co nanoparticles prepared by hydrothermal method have been investigated. A series of different weight% Mn-promoted Co nanoparticles were prepared and characterized by XRD, TPR, TGA, BET and SEM techniques. An increase in the surface area of MMT is observed with Al-pillaring. Fischer-Tropsch catalytic activity of the as prepared catalysts was studied in a fixed bed micro reactor at $225^{\circ}C$, $H_2/CO$ = 2 and at 1 atm pressure. The data showed that by the addition of Mn the selectivity of $C_1$ dropped drastically while that of $C_2-C_{12}$ hydrocarbons increased significantly over all the Mn-promoted Co/AlMMT catalysts. The $C_{13}-C_{20}$ hydrocarbons remained almost same for all the catalysts while the selectivity of $C_{21+}$ long chain hydrocarbons decreased considerably with the addition of Mn. The catalyst with 3.5%Mn showed lowest $C_{21+}$ and highest $C_2-C_{12}$ hydrocarbons selectivity due to cracking of long chain hydrocarbons over acidic sites of MMT.

• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3660-3665
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• 2011

CO-tolerant PtMo/C alloy electrocatalyst was prepared by a colloidal method, and its electrocatalytic activity toward CO oxidation was investigated. Electrochemical study revealed that the alloy catalyst significantly enhanced catalytic activity toward the electro-oxidation of CO compared to Pt/C counterpart. Cyclic voltammetry suggested that Mo plays an important role in promoting CO electro-oxidation by facilitating the formation of active oxygen species. The effect of Mo on the electronic structure of Pt was investigated using X-ray absorption spectroscopy to elucidate the synergetic effect of alloying. Our in-depth spectroscopic analysis revealed that CO is less strongly adsorbed on PtMo/C catalyst than on Pt/C catalyst due to the modulation of the electronic structure of Pt d-band. Our investigation shows that the enhanced CO electrooxidation in PtMo alloy electrocatalyst is originated from two factors; one comes from the facile formation of active oxygen species, and the other from the weak interaction between Pt and CO.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.211-217
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• 2008

A $ZrO_2$ coating solution containing $ZrO_2$ photo-catalysis, which is transparent in visible light, was prepared by the hydrolysis of alkoxide, and thin films on the $SiO_2$ glass substrate were formed in a dipcoating method. These thin films were heat-treated at temperatures ranging from $250^{\circ}C-800^{\circ}C$ and their characteristics were subjected to thermal analysis, XRD, spectrometry, SEM, EDS, contact angle measurement, and AFM. Tetragonal $ZrO_2$ phase was found in the thin film heat treated at $450^{\circ}C$, and anatase $TiO_2$ phase was detected in the thin film heat-treated at $600^{\circ}C$ and above. The thickness of the films was approximately 300 nm, and the roughness was 0.66 nm. Thus, the film properties are excellent. The films are super hydrophilic with a contact angle of $4.0^{\circ}$; moreover, they have self-cleaning effect due to the photo catalytic property of anatase $TiO_2$.

• Korean Journal of Materials Research
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• v.25 no.10
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• pp.543-546
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• 2015

$TiO_2$ nanowires were grown by thermal oxidation of TiO powder in an oxygen and nitrogen gas environment at $1000^{\circ}C$. The ratio of $O_2$ to $N_2$ in an ambient gas was changed to investigate the effect of the gas ratio on the growth of $TiO_2$nanowires. The oxidation process was carried out at different $O_2$/$N_2$ ratios of 0/100, 25/75, 50/50 and 100/0. No nanowires were formed at $O_2$/$N_2$ ratios of less than 25/75. When the $O_2$/$N_2$ ratio was 50/50, nanowires started to form. As the gas ratio increased to 100/0, the diameter and length of the nanowires increased. The X-ray diffraction pattern showed that the nanowires were $TiO_2$ with a rutile crystallographic structure. In the XRD pattern, no peaks from the anatase and brookite structures of $TiO_2$were observed. The diameter of the nanowires decreased along the growth direction, and no catalytic particles were detected at the tips of the nanowires which suggests that the nanowires were grown with a vapor-solid growth mechanism.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1070-1077
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• 1998

Effect of current collecting layer on the cathode was characterized by AC impedance spectroscopy at 800$^{\circ}C$ under flowing air. LSM-YSZ composite cathode showed lower polarization resistance due to the in-crease of triple phase (LSM/YSZ/Pore) boundary length by incorporation of YSZ. Ohmic resistance {{{{ {R }_{1 } }} of LSM-YSZ was higher than that of pure LSM however because in-plane resistance of the cathode was fair-ly high due to its high specific resistivity. To reduce the in-plane resistance of LSM-YSZ cathode cathode side current collecting layer was required. Ohmic resistance {{{{ {R }_{1 } }} was reduced after forming LSM current col-lecting layer on the LSM-YSZ cathode. In case of pure LSM cathode the formation of Pt, or LSCO current collecting layer reduced polarization resistance {{{{ {R }_{p } }} but ohmic resistance {{{{ {R }_{1 } }} was relatively constant. After annealing of LSM cathode with Pt current collector at higher temperature polarization resistance {{{{ {R }_{p } }} was in-creased but ohmic resistance {{{{ {R }_{1 } }} was constant. These phenomena indicate that Pt or LSCo current col-lecting layers act as a catalytic layer for oxygen reduction of pure LSM cathode. LSCO current collector was effective in reducing the ohmic and polarization resistance of LSM-YSZ cathode.