• BMB Reports
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• v.44 no.2
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• pp.77-86
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• 2011

Over the years, nanostructures have been developed to enable to support enzyme usability to obtain highly selective and efficient biocatalysts for catalyzing processes under various conditions. This review summarizes recent developments in the nanostructures for enzyme supporters, typically those formed with various inorganic materials. To improve enzyme attachment, the surface of nanomaterials is properly modified to express specific functional groups. Various materials and nanostructures can be applied to improve both enzyme activity and stability. The merits of the incorporation of enzymes in inorganic nanomaterials and unprecedented opportunities for enhanced enzyme properties are discussed. Finally, the limitations encountered with nanomaterial-based enzyme immobilization are discussed together with the future prospects of such systems.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.217-217
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• 2011

Recently, demand for thermally stable metal nanoparticles suitable for chemical reactions at high temperatures has increased to the point to require a solution to nanoparticle coalescence. Thermal stability of metal nanoparticles can be achieved by adopting core-shell models and encapsulating supported metal nanoparticles with mesoporous oxides [1,2]. However, to understand the role of metal-support interactions on catalytic activity and for surface analysis of complex structures, we developed a novel catalyst design by coating an ultra-thin layer of titania on Pt supported silica ($SiO_2/Pt@TiO_2$). This structure provides higher metal dispersion (~52% Pt/silica), high thermal stability (~600$^{\circ}C$) and maximization of the interaction between Pt and titania. The high thermal stability of $SiO_2/Pt@TiO_2$ enabled the investigation of CO oxidation studies at high temperatures, including ignition behavior, which is otherwise not possible on bare Pt nanoparticles due to sintering [3]. It was found that this hybrid catalyst exhibited a lower activation energy for CO oxidation because of the metal-support interaction. The concept of an ultra-thin active metal oxide coating on supported nanoparticles opens-up new avenues for synthesis of various hybrid nanocatalysts with combinations of different metals and oxides to investigate important model reactions at high-temperatures and in industrial reactions.

• Journal of the Korean Chemical Society
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• v.33 no.1
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• pp.46-54
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• 1989

The extraction method and quantitative analysis for the fat-soluble vitamins present in food stuffs and vitamin products have been investigated. The simultaneous separation and analysis of the vitamins by reverse phase high performance liquid chromatographic method was conducted using an isocratic elution with methanol : water (95 : 5) eluent on a Novapak $C_{18}$ column. The detection of vitamins was achieved by a variable wavelength UV detector. To improve the detection sensitivity detection wavelengths were set at the highest absorption bands such as 330, 265, 285, and 290nm for the respective vitamins. The analysis for the fat-soluble vitamins was finished within 40 minutes. Alkaline hydrolysis and enzymatic hydrolysis were investigated for the sample preparation; and liquid-liquid extraction and liquid-solid extraction were attempted for the extraction of vitamins. Both hydrolysis methods were turned out to be appropriate for the analysis for vitamins A, D, and E, while for the analysis of vitamin K the enzymatic hydrolysis method demonstrated better results. Diethyl ether, pentane, and n-hexane were found to give higher recovery for the liquid-liquid extraction and silica cartridge for the liquid-solid extraction.

• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.43-51
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• 2004

In this study, gas permeation and separation characteristics of $CO_2$ and $N_2$ on nano-porous TPABr(Tetrapropylammoniumbromide) templating silica/alumina composite membrane were studied by using GMS (Generalized Maxwell Stefan) model. Since the transport mechanisms of meso-porous alumina support are Knudsen diffusion and viscous diffusion(or poiseulle flow), they can be identified by DGM (dusty gas model). The transport mechanism of TPABr templating silica layer, which would contribute mainly to the separation of $N_2/CO_2$ mixture, showed surface diffusion rather than pore diffusion. Therefore, the oermeationjseparation mechanisms in multi-component suface diffusion were successfully analyzed by the GMS model. In the separation of $N_2/CO_2$ mixture using the composite membrane, $CO_2$, the strongadsorbate, was permeated through the membrane more than Na due to the pore-blocking phenomena of $CO_2$ by adsorption isotherm and solace diffusion.

• Journal of the Korean Applied Science and Technology
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• v.22 no.3
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• pp.281-288
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• 2005

The silica nanoparticles were used as support of catalyst, filling material, electronic assembler, thin film material, and sensor material. And, the titania nanoparticles were used as pigment, dielectric substance, sensor and photocatalyst. In this paper, the spherical composite particles of $TiO_2/SiO_2$with narrow size distribution and phase pure were synthesized by ultrasonic spray pyrolysis method from $TiOSO_4$ and colloidal silica solution. Using ultrasonic apparatus, this starting solution was vaporized to droplets, and these droplets were induced into tube furnace by carrier gas. The resulting composite powder was characterized by scanning electron microscopy, X-ray diffraction analysis, TG-DTA, in vitro sun protection factor(SPF) and BET surface area analysis.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.103-108
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• 2003

A method to determine chromium(III) ion in aqueous solution by chemiluminescence method using a lucigenin entrapped silica sol-gel film has been studied. An optical probe for chromium(III) ion has been prepared by entrapping lucigenin into silica sol-gel film coated on a glass support by dip coating. The chromium(III) optical sensor is based on the catalytic effect of chromium(IIII) ion on the reaction between lucigenin and hydrogen peroxide in basic solutions. The effects of Nafion, DMF and Triton X-100 were investigated to find the optimum condition to minimize cracking and leaching from the probe. The effects of pH and concentrations of lucigenin and hydrogen peroxide on the chemiluminescence intensity were investigated. The chemiluminescence intensity was increased linearly with increasing chromium(III) concentration from $2.5{\times}10^{-4}$M to $8.0{\times}10^{-7}$M and the detection limit was $4.0{\times}10^{-7}$M.

• Bulletin of the Korean Chemical Society
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• v.18 no.10
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• pp.1085-1089
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• 1997

A new HPLC chiral stationary phase (CSP 3) has been prepared by connecting N-phenyl N-propyl amide of (S)-naproxen to silica gel through the 6-methoxy-2-naphthyl group of (S)-naproxen. The new CSP has been applied in resolving a homologous series of N-(3,5-dinitrobenzoyl)-α-amino acid esters and a homologous series of N-(3,5-dinitrobenzoyl)-α-(4-alkylphenyl)alkylamines. The separation factors, α, for resolving a homologous series of N-(3,5-dinitrobenzoyl)-α-amino esters and a homologous series of N-(3,5-dinitrobenzoyl)-α-(4-alkylphenyl)alkylamines on the new CSP have been found to remain almost constant throughout the wide range of the length of the alkyl substituent of the analytes while those on the previously reported CSPs (CSP 1 and 2) which were prepared by connecting N-phenyl N-propyl amide of (S)-naproxen to silica gel through the N-propyl group increase or decrease continuously. These results are concluded to support the chiral recognition models which utilize the intercalation of the alkyl substituent of the racemic analytes between the adjacent strands of CSP 1 or 2 to rationalize the increasing or decreasing trends of separation factors.

• Membrane Journal
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• v.22 no.6
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• pp.424-434
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• 2012

In this study, a ceramic membrane was prepared by CVD. Tube type alpha alumina support was used for substrate and added the Ga salt in intermediate layer. Synthesized method was counter diffusion CVD method at $650^{\circ}C$ with tetramethylorthosilane (TMOS). Gas permeation was measured at $600^{\circ}C$ using single-component $H_2$, $N_2$, $CO_2$ and $CH_4$. During the steam treatment, $H_2/N_2$ permselectivity of non-Ga silica membrane was decreased 926 to 829 at $600^{\circ}C$. On the other hand $H_2/N_2$ permselectivity of added Ga silica membrane was stable 910 to 904 at $600^{\circ}C$. These results show that the metal-doped membranes improved steam stability for gas separation.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.166-166
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• 2013

Mesoporous $SiO_2$-supported Ni catalysts (Ni/$SiO_2$ and Ni/$TiO_2$/$SiO_2$) were fabricated by atomic layer deposition (ALD), and their catalytic activity and stability were investigated in carbon dioxide reforming of methane (CRM) reaction at $800^{\circ}C$ The Ni/$SiO_2$ catalysts showed high stability as a result of confinement of Ni particles with a mean size of ~10 nm within the pores of $SiO_2$ support. Besides, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that the Ni nanoparticles were partially buried inside the $SiO_2$ support. The strong interaction between Ni and the $SiO_2$ support could also be advantageous for long-term stability of the catalyst. In case of the Ni/$TiO_2$/$SiO_2$ catalyst, it was found that the catalytic activity of 10 nm-sized Ni nanoparticles was not much influenced by $TiO_2$ addition.

• Tunnel and Underground Space
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• v.17 no.4
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• pp.266-284
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• 2007

Recently, many efforts have been made to construct the first unlined tunnel, without in-situ concrete lining, in Korea. However, the lack of reliability in the performance of shotcrete as permanent tunnel support prevented from its realization. Shotcrete has been regarded to have significant problems in field application and long term performance because of unsatisfactory strength level and durability compared to those of European countries. In this study, the high strength shotcrete satisfying compressive strength over 40 MPa and flexural strength over 4.5 MPa was developed from optimized mix design. The type of accelerators and the amount of silica fume were selected as the main factors in mixing process and the analyses were carried out up to the elapsed time of 2 years. In order to evaluate the short term durability of shotcrete, an array of laboratory test consisting of freeze-thaw, carbonation chloride penetration and permeability test was performed. For long-term durability tests, specimens have been put in an operated highway tunnel to expose them to the similar environment when they are actually used as an unlined tunnel support. From the strength and durability tests, it was found that only alkali-free based accelerator satisfied the target strength of this study and also, the developed shotcrete showed very high performance in its durability.