• Bulletin of the Korean Chemical Society
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• v.26 no.11
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• pp.1653-1668
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• 2005

Assembly of hybrid mesophases through the combination of amphiphilic block copolymers, acting as structuredirecting agents, and silicon sources using low acid catalyst concentration regimes is a versatile strategy to produce large quantities of high-quality ordered large-pore mesoporous silicas in a very reproducible manner. Controlling structural and textural properties is proven to be straightforward at low HCl concentrations with the adjustment of synthesis gel composition and the option of adding co-structure-directing molecules. In this account, we illustrate how various types of large-pore mesoporous silica can easily be prepared in high phase purity with tailored pore dimensions and tailored level of framework interconnectivity. Silica mesophases with two-dimensional hexagonal (p6mm) and three-dimensional cubi (Fm$\overline{3}$m, Im$\overline{3}$m and Ia$\overline{3}$d) symmetries are generated in aqueous solution by employing HCl concentrations in the range of 0.1−0.5 M and polyalkylene oxide-based triblock copolymers such as Pluronic P123 $(EO_{20}-PO_{70}-EO_{20})$ and Pluronic F127 $(EO_{106}-PO_{70}-EO_{106})$. Characterizations by powder X-ray diffraction, nitrogen physisorption, and transmission electron microscopy show that the mesoporous materials all possess high specific surface areas, high pore volumes and readily tunable pore diameters in narrow distribution of sizes ranging from 4 to 12 nm. Furthermore, we discuss our recent advances achieved in order to extend widely the phase domains in which single mesostructures are formed. Emphasis is put on the first synthetic product phase diagrams obtained in $SiO_2$-triblock copolymer-BuOH-$H_2O$ systems, with tuning amounts of butanol and silica source correspondingly. It is expected that the extended phase domains will allow designed synthesis of mesoporous silicas with targeted characteristics, offering vast prospects for future applications.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.463-472
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• 1997

A mesoporous molecular sieve, MCM-41, was synthesized and the effent of various initial pH of reaction mixtures on the synthesis and physical properties of MCM-41 was investigated. Adjustment of initial pH for reaction mixtures was made before starting hydrothermal reaction rather than during the reaction. Highly crystalline MCM-41 which shows pore diameters of $30{\AA}$ to $40{\AA}$ and specific surface areas greater than $1000m^2/g$ has been successfully prepared through a single adjustment of initial pH. Results also suggest that the initial pH adjustment has a significant effect on the formation of MCM-41 with a long-range ordered hexagonal array and an excellent thermal stability. Finally, it is speculated that the adjustment of initial pH might accelerate the dissolution of stable polymeric sodium silicate to highly reactive monomeric sodium silicate resulting in well-ordered MCM-41.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.252-256
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• 2010

The study was done to change the morphology and pore size of SBA-15 silica, and the characteristics of SBA-15 silica were investigated with TG-DSC, XRD, SEM, TEM and N2 adsorption-desorption under changing aging conditions. SBA-15 silica having a 2D-hexagonal structure was synthesized and confirmed by SEM and TEM. The structure of mesoporus silica SBA-15 showed a pore having regularly formed hexagonal structure and a passage having a cylindrical shape. This result is in good agreement with the pore forming in XRD and cylindrical shape of the structure in $N_2$ adsorption-desorption isotherm. SBA-15 silica showed a large BET surface area of $603-698\;m^2/g$, a pore volume of $0.673-0.926\;cm^3/g$, a large pore diameter of 5.62-7.42 nm, and a thick pore wall of 3.31-4.37 nm. This result shows that as the aging temperature increases, the BET surface area, pore volume, and pore diameter increase but the pore wall thickness decreases. The BET surface areas in SM-2 and SM-3 are as large as $698\;m^2/g$. However, SM-2 has a large surface area and forms a thick pore wall, when the aging temperature is $100^{\circ}C$ and is synthesized into stable mesoporous SBA-15 silica.

• Journal of the Korean Applied Science and Technology
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• v.21 no.4
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• pp.345-351
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• 2004

Highly ordered pure-silica MCM-41 materials possessing well-defined morphology have been successfully prepared with surfactant used as a template. The fabrication of mesoporous silica has received considerable attention due to the need to develop more efficient materials' for catalysis, separations, and chemical sensing. The surface modified MCM-41 was used as anadsorbent for biomolecules. Silica-supported organic groups and DNA adsorption on surface modified MCM-41 were investigated by FT-IR and UV-Vis spectrometer, respectively. The use of MCM-41 as the modification of electrode surfaces were investigated electrochemical properties of metal mediators with biomolecules. The modified ITO electrodes increased peak currents for a redox process of $[Ru(bpy)_3]^{2+}$ relative to the bare electrode. The electrochemical detection of DNA by cyclic voltammetry when the current is saturated in the presence of the mediator appeared more sensitive due to a higher catalytic current on the MCM-41 supported electrodes modified by carboxylic acid functional groups. The carboxyl or amine groups on the surface of MCM-41 interact and react with the $-NH_2$ groups of guanine and backbone, respectively. Highly ordered mesoporous materials with organic groups could find applications as DNA sensors.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.125-132
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• 2018

The direct synthesis of $C_2$ chemical directly from methane was studied by employing catalysts with ordered mesopores in a dielectric barrier discharge plasma reactor. The reaction was carried out using MgO/OMA (ordered mesoporous alumina), $MgO/{\gamma}-Al_2O_3$ and $MgO/{\alpha}-Al_2O_3$ as catalysts. When MgO/OMA was applied, it showed excellent performance in the plasma reactor using pulse-type power supply and the selectivity of $C_2$ chemicals was measured as 67%. The effects of metal oxide type, textural property of support, alumina phase and power supply type on catalytic performance were investigated especially in terms of $C_2$ chemical formation. BET (Brunauer, Emmett, Teller), X-ray diffraction, transmission electron microscope and thermogravimetric analysis were used to investigate the characterization of the catalyst before and after the reaction.

• Journal of the Korean Ceramic Society
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• v.41 no.7
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• pp.528-533
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• 2004

Macroporous SiC with pore size 84∼658 nm and mesoporous SiC with pore size 15∼65 nm were respectively prepared by infiltrating low viscosity preceramic polymer solutions into the various sacrificial templates obtained by natural sedimentation or centrifuge of 20∼700 nm silica sol, which were subsequently etched off with HF after pyrolysis at 1000∼140$0^{\circ}C$ in an argon atmosphere. Three-dimensionally long range ordered macroporous SiC ceramics derived from polymethylsilane (PMS) showed surface area 584.64$m^2$g$^{-1}$ when prepared with 112nm silica sol and at 140$0^{\circ}C$, whereas mesoporous SiC from polycarbosilane (PCS) exhibited the highest surface area 619.4 $m^2$g$^{-1}$ with random pore array when prepared with 20-30 nm silica sol and at 100$0^{\circ}C$. Finally, tile pore characteristics of porous SiC on the types of silica sol, polymers and pyrolytic conditions were interpreted with the analytical results of SEM, TEM, and BET instruments.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.518-522
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• 2013

Cyclohexanone is important intermediate for the manufacture of caprolactam which is monomer of nylron. Cyclohexanone is generally produced by dehydrogenation reaction of cyclohexanol. In this study, highly mesoporous metal oxides such as meso-$WO_3$, meso-$TiO_2$, meso-$Fe_2O_3$, meso-CuO, meso-$SnO_2$ and meso-NiO were synthesized using mesoporous silica KIT-6 as a hard template via nano-replication method for dehydrogenation of cyclohexanol. The overall conversion of cyclohexanol followed a general order: meso-$WO_3$ >> meso-$Fe_2O_3$ > meso-$SnO_2$ > meso-$TiO_2$ > meso-NiO > meso-CuO. In particular, meso-$WO_3$ significantly showed higher activity than the other mesoporous metal oxides. Therefore, the meso-$WO_3$ has wide range of application possibilities for dehydrogenation of cyclohexanol.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.231-231
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• 2009

In this work, we prepared the Ni-loaded porous SBA-15 (SBA-15) by a depositionprecipitation (D-P) method, in order to enhance the hydrogen storage capacity. The structure and morphology of the Ni/SBA-15 were characterized by X-ray diffraction (XRD) and field emission transmission electron microscopy (FE-TEM). The results showed that, at the Ni loading used at the DP times in the range of 0-120 min, SBA-15 preserved the well-ordered hexagonal porous arrangement. The textural properties of the Ni/SBA-15 were analyzed using N2 adsorption isotherms at 77 K. Specific surface area and mesopore volume of the samples were determined from the Brunauer-Emmett-Teller (BET) equation and Barrett-Joiner-Halenda (BJH) method, respectively. The hydrogen storage capacity of the Ni/SBA-15 was evaluated at 298 K/10 MPa. The hydrogen storage capacity of the Ni/SBA-15 was increased in accordance with Ni content. Consequently, it was found that the presence of Ni on mesoporous SBA-15 created hydrogen-favorable sites which enhanced the hydrogen storage capacity by spillover effect.

• Elastomers and Composites
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• v.54 no.2
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• pp.149-155
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• 2019

Controlled mass transport in response to stimuli is essential for drug carriers. The complexity of the signaling system under physiological conditions has led researchers to develop precise nanocontainers that respond to stimuli in the physiological environment. Owing to several reasons, soft nanocontainers such as liposomes and micelles have been investigated for use as drug delivery systems. However, such carriers often suffer from the undesired leakage of drug molecules. In contrast, inorganic nanocontainers are robust, and their surfaces can be easily functionalized. For example, mesoporous silica nanoparticles equipped with gatekeeper molecules are increasingly being used for the controlled release of drug molecules in response to the desired stimuli. Since the development of the first hybrid nanocontainer comprising molecular machines, multiple versions of such gatekeeper systems featuring significantly improved stability and precise response to stimuli have been reported. In this study, various methods for incorporating photoresponsive nanocontainers with porous channels are developed.

• Carbon letters
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• v.20
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• pp.66-71
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• 2016