• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.129-129
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• 2013

Nanometal alloy catalysts have been found to significantly increase catalytic efficiency, compared to the monometallic counterparts. This enhancement can be attributed to various alloying effects: i) the existence of uniquemixed-metal surface sites [the so called ensemble (geometric) effect]; ii) electronic state changes due to metal-metal interactions [the so called ligand (electronic) effect]; and iii) strain caused by lattice mismatch between the alloy components [the socalled strain effect]. In addition, the presence of low-coordination surface atoms and preferential exposure of specific facets [(111), (100), (110)] in association with the size and shape of nanoparticle catalysts [the so called shape-size-facet effect] can be another important factor for modifying the catalytic activity. However, mechanisms underlying the alloying effect still remain unclear owing to the difficulty of direct characterization. Computational approaches, particularly the prediction using first-principles density functional theory (DFT), can be a powerful and flexible alternative for unraveling the role of alloying effects in catalysis since those can give us quantitative insights into the catalytic systems. In this talk, I will present the underlying principles (such as atomic arrangement, facet, local strain, ligand interaction, and effective atomic coordination number at the surface) that govern catalytic reactions occurring on Pd-based alloys using the first-principles calculations. This work highlights the importance of knowing how to properly tailor the surface reactivity of alloy catalysts for achieving high catalytic performance.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.473-478
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• 2008

In this experimental, selective catalytic reduction (SCR) of NO with NH3 over manganese sulfates and manganese sulfates was investigated with catalytic activity, kinetics, temperature programmed reduction (TPR) and TGA. Manganese oxides showed high catalytic activity for SCR at temperature below $200^{\circ}C$. In case of manganese sulfates, the temperature at which SCR of nitric oxide appears shifted to high temperature with sulfation degree, and the maximum catalytic efficiency decreased. The temperature of the onset of reduction for manganese oxides and manganese sulfates is about $160^{\circ}C$ and over $280^{\circ}C$, respectively. We suggest that the onset of reduction in TPR correlates with the onset of SCR activity. Because the pre-exponential factor of manganese sulfates is lower as 1/1000 times than that of other catalysts, catalytic activity of manganese sulfates for NO showed low. The reduction temperature of natural manganese ore which consists of various metal oxides showed lower than that of pure manganese oxides.

• Microbiology and Biotechnology Letters
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• v.23 no.3
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• pp.311-315
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• 1995

Assay conditions for screening of $\beta$-1,3-glucan synthase inhibitor were evaluated. Cells in the beginning of mid-log phase showed the highest activity of the $\beta$-1,3-glucan synthase. Cells permeabilized with 1% digitonin treatment could be used as a good crude enzyme source for convenient screening of the $\beta$-1,3-glucan synthase inhibitors. Calcofluor white (0.125% in final) and papulacandin B (25 $\mu$g/ml) inhibit 90% and more than 50% of the $\beta$-1,3-glucan synthase activity, respectively. Cells grown at 37$\circ$C showed higher enzyme activity than those of 25$\circ$C. Catalytic factor of the $\beta$-1,3-glucan synthase was solubilized from particulated membrane preparations, holoenzyme, by extracting with 0.00938% CHAPS.

• Journal of the Korean Chemical Society
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• v.13 no.4
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• pp.241-247
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• 1969

The catalytic reaction between carbon monoxide and oxygen was investigated with the various nickel oxide catalysts at different partial pressures of carbon monoxide and oxygen and at reaction temperatures in the region of 120$^{circ}$to 250$^{circ}C$. The reaction has the highest rate with the nickel oxide catalyst which is sintered at low temperature. A reaction mechanism to explain the data is derived. From the Arrhenius equation, the activation energies in the region of experimental temperatures are found to be from 5.49 to 9.15 kcal/mole. The concentration of excess oxygen in the nickel oxide seems to vary according to the sintering temperatures and periods and is the controlling factor in determining the type of kinetics followed by the catalytic reaction.

• Bulletin of the Korean Chemical Society
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• v.21 no.12
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• pp.1233-1238
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• 2000

$Mo/{\gamma}-Al_2O_3catalysts$ modified with Fe, Co, and Ni were prepared by impregnation method and catalytic activity for water gas shift reaction was examined. The optimum amount of Mo loaded for the reaction was 10 wt% $MoO_3$ to ${\gamma}-Al_2O_3.$ The catalytic activity of $MoO_3/{\gamma}-Al_2O_3was$ increased by modifying with Fe, Co, and Ni in the order of Co${\thickapprox}$ Ni > Fe. The optimum amounts of Co and Ni added were 3 wt% based on CoO and NiO to 10 wt% $MoO_3/{\gamma}-Al_2O_3$, restectively. The TPR (temperature-programmed reduction) analysis revealed that the addition of Co and Ni enganced the reducibility of the catalysts. The results of both catalytic activity and TPR experiments strongly suggest that the redox property of the catalyst is an important factor in water gas shift reaction on the sulfided Mo catalysts, which could be an evidence of oxy-sulfide redox mechanism.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1018-1022
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• 1998

Characteristics and catalytic activities of 12-molybdophosphoricacid catalysts modified by ring opening polymerization of tetrahydrofuran (THF) were studied in this work. 12-Molybdophosphoricacid catalysts modified by THF showed higher conversions and product yields than the mother acid in the vapor-phase ethanol conversion. It was believed that the enhanced catalytic activities of modified 12-molybdophosphoricacids were due to structural flexibility of heteropolyanions and weakened hydrogen bond around heteropolyanions. THF interacted with protons and crystalline water molecules of heteropolyacids. The interaction between THF and heteropolyanoins, which crystalline water molecules act as intermediary, was the dominant factor deciding the catalytic activities of modified 12-molybophosphoricacids.

• Applied Microscopy
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• v.46 no.2
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• pp.105-109
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• 2016

Palladium has been used as a catalyst not only in Suzuki and Heck cross coupling reaction in organic chemistry, but also in automobile industry for the reduction of vehicle exhausts. The catalytic activity of Pd nanoparticles depends strongly on their size and exposed crystalline facets. In this study, the single crystalline palladium nanocubes/nanorods were prepared in the presence of polyvinyl pyrrolidone (PVP) and potassium bromide (KBr) using the polyol method. Selected area diffraction pattern and high-resolution transmission electron microscopy (TEM) were performed by TEM. The result shows that the ratio of KBr/PVP is the key factor to determine whether the product is cubes or rods. The as-prepared Pd nanocubes were highly uniform in both size and shape. The ordered packing structures including monolayer and multilayer can be fabricated via the rate-controlled evaporation of solution solvent. The catalytic activity of these Pd nanocubes towards heck reaction of iodobenzene with acrylate or acrylic acid was found to be higher than that of Pd nanorods. We suspect it is caused by the difference of energy state while Pd nanocubes is {100} plane and nanorods is {111} plane.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.878-883
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• 2011

Effect of flow uniformity on the reaction characteristics of a catalytic combustor for high temperature fuel cell system has been experimentally investigated in the present study. One of the most important factor in designing catalytic combustion is to avoid hot spot in catalysts. In this regard, it is very important to secure flow uniformity of combustor inlet. A couple of perforated plates were applied at the front of catalyst region as flow uniformity device with minimal pressure drop. Results show that the velocity and temperature profile became more uniform when applying the flow uniformity device. CO and $CH_4$ emissions at the combustor exit were decreased and the average exit temperature was slightly increased with the flow uniformity device.

• Journal of Microbiology and Biotechnology
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• v.25 no.8
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• pp.1227-1233
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• 2015

Vascular endothelial growth factor (VEGF) plays a key role in angiogenesis through binding to its specific receptors, which mainly occurs to VEGF receptor 2 (VEGFR-2), a kinase insert domain-containing receptor. Therefore, the disruption of VEGFR-2 signaling provides a promising therapeutic approach for the treatment of cancer by inhibiting abnormal or tumorinduced angiogenesis. To explore this potential, we expressed the catalytic domain of VEGFR-2 (VEGFR-2-CD) as a soluble active kinase in Escherichia coli. The recombinant protein was purified and the VEGFR-2-CD activity was investigated. The obtained VEGFR-2-CD showed autophosphorylation activity and phosphate transfer activity comparable to the commercial enzyme. Furthermore, the IC₅₀ value of known VEGFR-2 inhibitor was determined using the purified VEGFR-2-CD. These results indicated a possibility for functional and economical VEGFR-2-CD expression in E. coli to use for inhibitor screening.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.164-164
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• 2013

Among multicomponent nanostructures, hybrid nanocatalysts consisting of metal nanoparticle-semiconductor junctions offer an interesting platform to study the role of metal-oxide interfaces and hot electron flows in heterogeneous catalysis. In this study, we report that hot carriers generated upon photon absorption significantly impact the catalytic activity of CO oxidation. We found that Pt-CdSe-Pt nanodumbbells exhibited a higher turnover frequency by a factor of two during irradiation by light with energy higher than the bandgap of CdSe, while the turnover rate on bare Pt nanoparticles didn't depend on light irradiation. We also found that Pt nanoparticles deposited on a GaN substrate under light irradiation exhibit changes in catalytic activity of CO oxidation that depends on the type of doping of the GaN. We suppose that hot electrons are generated upon the absorption of photons by the semiconducting nanorods or substrates, whereafter the hot electrons are injected into the Pt nanoparticles, resulting in the change in catalytic activity. We discuss the possible mechanism for how hot carrier flows generated during light irradiation affect the catalytic activity of CO oxidation.