• Bulletin of the Korean Chemical Society
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• v.30 no.6
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• pp.1383-1384
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• 2009

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.319-319
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• 2011

Hydrolysis of sodium borohydride provides a safe and clean approach to hydrogen generation. Having the proper catalytic support for controlling this reaction is therefore a valuable technology. Here we demonstrate the capability of hydroxyapatite as a novel catalytic support material for hydrogen generation. Aside from being inexpensive and durable, we reveal that Ru ion exchange on the HAP surface provides a highly active support for sodium borohydride hydrolysis, exemplifying a high total turnover number of nearly 24,000 mol $H_2$/ mol Ru. Moreover, we observe that the RuHAP support exhibits a high catalytic lifetime of approximately one month upon repeated exposure to $NaBH_4$ solutions. In addition to examining surface area effects, we also identified the role of complex surface morphology in enhancing hydrolysis by the catalytic transition metal covered surface. Particularly, we found that a polycrystalline RuHAP catalytic support exhibits shorter induction times for the initial bubble formation as well as increased hydrogen generation rates as compared to a single crystal supports. The independent factor of a complex surface morphology is believed to provide enhanced sites for gas release during the initial stages of the reaction. By demonstrating the ability to shorten induction time and enhance catalytic activity through changes in surface morphology and Ru content, we find it feasible to further explore this catalyst support in the construction of a practical hydrogen generator.

• Journal of Integrative Natural Science
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• v.6 no.3
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• pp.170-175
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• 2013

Silicon nanowires were detached and obtained from silicon nanowire arrays on silicon substrate using a ultrasono-method. Silicon nanowire arrays on silicon substrate were prepared with an electroless metal assisted etching of p-type silicon. The etching solution was an aqueous HF solution containing silver nitrate. SEM observation shows that well-aligned nanowire arrays perpendicular to the surface of the silicon substrate were produced. After sonication of silicon nanowire array, an individual silicon nanowire was confirmed by FESEM. Optical characteristics of SiNWs were measured by FT-IR spectroscopy. The surface of SiNWs are terminated with hydrogen.

• Journal of Photoscience
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• v.12 no.3
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• pp.171-174
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• 2005

The relationship between porous surfaces and photoluminescence (PL) behavior of porous silicon carbide (PSC) in various solvents has been studied. The porous surfaces of p-type silicon carbide can be fabricated by electrochemical anodization from the 6H, 15R, 4H-${\alpha}$-SiC substrates in dark-current mode (DCM) condition. We have been investigated the dependence of the PL spectra of PSC under the medium having the different dielectric constants. It has been found that PL depends sensitively on the environment surrounding the surface. The extent of chemically stability on the surface of PSC due to the various solvents was confirmed by reflectance Fourier transform infrared (FTIR) spectroscopy. Detailed IR experiments on the PSC samples were carried out before and after various solvents immersion. These results will be offered important information on the origin of PL in porous structure.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.30-34
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• 2014

We report a novel approach for fabricating active surface-enhanced Raman scattering (SERS) substrate for sensitive detection. This approach is based on the assembling of gold nanoparticles (AuNPs) onto the electrospun polycaprolactone (PCL) nanofiber film. The hydrophobic surface of PCL nanofiber film was pretreated using UV-inducing graft polymerization with acrylic acid. Afterwards this PCL nanofiber film was incubated with the AuNP solution to promote the assembly of AuNPs onto the PCL nanofibers and the formation of SERS active substrate. 4-aminothiophenol (4-ATP) molecule was used as a test probe for SERS experiments, indicating that the substrate has high sensitivity to SERS response. Our method has great advantage in term of environment-friendly synthesis, large-scale, high stability and good reproducibility. This highly active SERS substrate can be employed to detect the drug molecule, 2-thiouracil.

• Journal of Integrative Natural Science
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• v.4 no.4
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• pp.282-288
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• 2011

We describe the synthesis and characterization of silicon nanoparticles prepared by the solution reduction of silicon tetrachloride by lithium naphthalenide and subsequently with n-butyllithium at room temperature. These reactions produce silicon nanoparticles with surfaces that are covalently terminated with butyl group. Reaction with lithium aluminium hydride instead of n-butyllithium produces hydride-terminated silicon nanoparticles. The butyl or hydride terminated silicon nanoparticles can be suspended in hexane and their optical behavior have been characterized by photoluminescence spectroscopy. Stabilization of silicon nanoparticles were investigated upon illumination, indicating that as-prepared silicon nanoparticles are very stable at room temperature for several days.

• Journal of the Korean institute of surface engineering
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• v.20 no.4
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• pp.135-143
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• 1987

Various complexing agents were investigated to see the effects on the normal orientation of HCP structure of Co-alloy to the film plane in ammoniacal electroless plating bath. To obtain the optimum condition, several complexing agents were investigated to compare the C-axis perpendicular orientation. Results were that succinate - citrate, malonate - succinate, malonate bath were useful for that purpose. Among these complexing agents, succinate - citrate system was obtained as the best one. X-ray diffraction patterns were used to compare the film properties with C-axis perpendicular orientation.

• Korean Journal of Materials Research
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• v.34 no.7
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• pp.341-354
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• 2024

Today, the principles of green chemistry are being fundamentally applied in the chemical industry, such as the nitrobenzene industry, which is an essential intermediate for various commercial products. Research on the application of response surface methodology (RSM) to optimize nitrobenzene synthesis was conducted using a sulfated silica (SO₄/SiO₂) catalyst and batch microwave reactor. The nitrobenzene synthesis process was carried out according to RSM using a central composite design (CCD) design for three independent variables, consisting of sulfuric acid concentration on the silica (%), stirring time (min), and reaction temperature (℃), and the response variable of nitrobenzene yield (%). The results showed that a three-factorial design using the response surface method could determine the optimum conditions for obtaining nitrobenzene products in a batch microwave reactor. The optimum condition for a nitrobenzene yield of 63.38 % can be obtained at a sulfuric acid concentration on the silica of 91.20 %, stirring time of 140.45 min, and reaction temperature of 58.14 ℃. From the 20 experiments conducted, the SO₄/SiO₂ catalyst showed a selectivity of 100 %, which means that this solid acid catalyst can potentially work well in converting benzene to nitrobenzene.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2546-2552
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• 2012

A novel biguanide-functionalized $Fe_3O_4/SiO_2$ magnetite nanoparticle with a core-shell structure was developed for utilization as a heterogeneous organosuperbase in chemical transformations. The structural, surface, and magnetic characteristics of the nanosized catalyst were investigated by various techniques such as transmission electron microscopy (TEM), powder X-ray diffraction (XRD), vibrating sample magnetometry (VSM), elemental analyzer (EA), thermogravimetric analysis (TGA), $N_2$ adsorption-desorption (BET and BJH) and FT-IR. The biguanide-functionalized $Fe_3O_4/SiO_2$ nanoparticles showed a superpara-magnetic property with a saturation magnetization value of 46.7 emu/g, indicating great potential for application in magnetically separation technologies. In application point of view, the prepared catalyst was found to act as an efficient recoverable nanocatalyst in nitroaldol and domino Knoevenagel condensation/Michael addition/cyclization reactions in aqueous media under mild condition. Additionally, the catalyst was reused six times without significant degradation in catalytic activity and performance.

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.361-367
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• 2020

Recently, layered nickel-rich cathode materials (NCM) have attracted considerable attention as advanced alternative cathode materials for use in lithium-ion batteries (LIBs). However, their inferior surface stability that gives rise to rapid fading of cycling performance is a significant drawback. This paper proposes a simple and convenient coating method that improves the surface stability of NCM using sulfate-based solvents that create artificial cathode-electrolyte interphases (CEI) on the NCM surface. SO_x-based artificial CEI layer is successfully coated on the surface of the NCM through a wet-coating process that uses dimethyl sulfone (DMS) and dimethyl sulfoxide (DMSO) as liquid precursors. It is found that the SO_x-based artificial CEI layer is well developed on the surface of NCM with a thickness of a few nanometers, and it does not degrade the layered structure of NCM. In cycling performance tests, cells with DMS- or DMSO-modified NCM811 cathodes exhibited improved specific capacity retention at room temperature as well as at high temperature (DMS-NCM811: 99.4%, DMSO-NCM811: 88.6%, and NCM811: 78.4%), as the SO_x-based artificial CEI layer effectively suppresses undesired surface reactions such as electrolyte decomposition.