• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.264.1-264.1
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• 2013

Graphene is a two-dimensional carbon material whose structure is one-atom-thick planar sheet of sp2-bonded carbon atoms densely packed in a honeycomb crystal lattice. It has drawn significant attention with its distinguished structural and electrical properties. Extremely high mobility and a tunable band gap make graphene potentially useful for innovative approaches to electronics. Although mechanical exfoliation of graphite and decomposition of SiC surfaces upon thermal treatment have been the main method for graphene, they have some limitations in quality and scalability of as-produced graphene films. Solutionphase and solvothermal syntheses of graphene achieved a major improvement for processing, however for device fabrication, a reproducible method such as chemical vapor deposition (CVD) growth yielding high quality films of controlled thickness is required. In this research, we synthesized hexagonal graphene flakes on Cu foils by CVD method and controlled its coverage, density and the size of graphene domains by changing reaction parameters. It is important to control these parameters of graphene growth during synthesis in order to achieve tunable properties and optimized device performance.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.300-301
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• 2003

Nowadays as the concerns with global environmental issue increase, the application of TiO$_2$ to the treatment of polluted air and wastewater has become more and more widespread because of its promising photocatalytic performance. The photocatalytic activity of TiO$_2$ is greatly influenced by its crystal structure, particle size, surface area and porosity. (omitted)

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.470-475
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• 2013

Zr-benzendicarboxylate structure, UiO-66 was prepared in 1-L batch scale by using a unique sonochemical-solvothermal combined synthesis method. The produced UiO-66 showed uniform particles of ca. $0.2{\mu}m$ in size with the BET surface area of $1,375m^2/g$ in high product yield (>95%). The UiO-66 showed 198 and 84 mg/g $CO_2$ adsorption capacity at 273 K and 298 K, respectively, with excellent $CO_2$ selectivity ($CO_2:N_2=32:1$) at ambient conditions. The isosteric heat of $CO_2$ adsorption varied from 33 to 25 kJ/mol as the adsorption progressed. The UiO-66 tested for xylene isomer separation in a liquid-phase batch mode confirmed preferential adsorption of the adsorbent for o-xylene over m-, and p-xylene.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2813-2817
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• 2014

A new magnetic semiconductor material was synthesized to enable separation after a liquid-type photocatalysis process. Core@shell-structured $CuFeS_2@TiO_2$ magnetic nanoparticles were prepared by a combination of solvothermal and wet-impregnation methods for photocatalysis applications. The materials obtained were characterized using X-ray diffraction, transmission electron microscopy, ultraviolet-visible, photoluminescence spectroscopy, Brunauer-Emmett-Teller surface area measurements, and cyclic voltammetry. This study confirmed that the light absorption of $CuFeS_2$ was shifted significantly to the visible wavelength compared to pure $TiO_2$. Moreover, the resulting hydrogen production from the photo-splitting methanol/water solution after 10 hours was more than 4 times on the core@shell structured $CuFeS_2@TiO_2$ nanocatalyst than on either pure $TiO_2$ or $CuFeS_2$.

• Proceedings of the KAIS Fall Conference
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• 2011.05a
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• pp.147-150
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• 2011

A copper-based metal organic framework (MOF) named Cu-BTC, also known as HKUST-1, was successfully synthesized by using a solvothermal method. The properties of the Cu-BTC sample were characterized with Powder X-ray diffraction (XRD) for phase structure, Thermogravimetric analysis (TGA) for thermal stability, Scanning electron microscopy (SEM) for crystal structure, and Nitrogen adsorption-desorption for pore textural structure. The analysis results displayed that the Cu-BTC sample exhibited a good crystal structure with uniform size of octahedral particles. The BET data revealed a high surface area of $1457 \;m^2g^{-1}$ and a pore volume of $0.60\; cm^3g^{-1}$. The Cu-BTCs ample was also studied for $CO_2$ adsorption and exhibited a maximum $CO_2$ adsorption capacity of 170 mg/g of the sorbent (3.8 mol/kg) at $25^{\circ}C$.

• Korean Journal of Materials Research
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• v.30 no.11
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• pp.609-614
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• 2020

3 mol% yttria-doped stabilized zirconia (3YSZ) is synthesized by a solvothermal process, and its characteristics are investigated using various methods. Also, the dispersibility of synthesized 3YSZ nanoparticles is observed with the species of surface modifier. The 3YSZ nano sol prepared with an optimum condition is employed in prism coating and its properties are evaluated. The synthesized 3YSZ nanoparticles show a globular shape with about 10 to 20 nm crystallite size. The mixed phases with the nano sol show a high specific surface of 178 ㎡/g. The prism sheet coated with the 3YSZ nano sol present an excellent refractive index, transmittance, and luminance; refractive index is 1.603, transmittance is 90.2 %, and luminance of coating film is improved by 5.9 % compared to that of the film without 3YSZ nano sol. It is verified that the surface modified 3YSZ is suitable as the prism sheet for optical displays.

• Journal of Marine Bioscience and Biotechnology
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• v.10 no.2
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• pp.34-43
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• 2018

Silicon has become of increasing importance as the basic element of many high-technology products. Its synthesis is very difficult requiring high temperature solid-state reactions (> $1000^{\circ}C$) or lower temperature methods ($100-200^{\circ}C$) involving hydrothermal and solvothermal reactions under extreme pH conditions. In nature, on the other hand, a wide range of living organisms have collectively evolved the means of biosilicification at the astounding rate of gigatons/year. This is impressive because biosilicification in these organisms occurs under mild physiological conditions. Marine sponges possess the ability to sequester soluble silicon sources from their environments and assemble them into intricate 3D architecture. The advent of molecular biology has recently made it possible to glean molecular information about biosilicification from these systems and it turned out that enzyme silicatein is the core of biosilicification. In this review, biosilicification regulated by silicatein and its mechanism are described. Also, production of silicatein through recombinant technology and several applications of recombinant silicatein are described including immobilization of silicatein, formation of Au or Ag nanoparticles on nanowires, nanolithography approaches, core-shell materials, encapsulation, bone replacement materials, and microstructured optical fibers.

• Journal of Sensor Science and Technology
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• v.28 no.4
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• pp.225-230
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• 2019

$Au@TiO_2$ core-shell decorated rGO nanocomposite (NC) was prepared using a simple solvothermal method followed by heat treatment for gas sensor application. The crystal structure and morphology of the composites were characterized by X-ray powder diffraction and transmission electron microscopy, respectively. The $NO_2$ sensing response of the $Au@TiO_2/rGO$ NC was tested at operating temperatures from $250^{\circ}C$ to $500^{\circ}C$, and was compared with those of the bare rGO and $Au@TiO_2$ core-shell NPs. The $Au@TiO_2/rGO$ NC-based sensor showed a far higher response than the rGO or $Au@TiO_2$ core-shell based sensors, with the maximum response detected when the operating temperature was $400^{\circ}C$. This improved response was due to the high rGO gas absorption capability for $NO_2$ gas and the catalytic effect of $Au@TiO_2$ core-shell NPs in oxidizing $NO_2$ to $NO_3$.

• Korean Journal of Materials Research
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• v.31 no.10
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• pp.582-585
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• 2021

Y₂O₃:Eu_x (x = 0.005, 0.01, 0.02, 0.03, 0.05, 0.1 mol) phosphors are synthesized with different concentrations of Eu³⁺ ions by solvothermal method. The crystal structure, surface and optical properties of the Eu doped Y₂O₃ phosphors are investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) and photoluminescence excitation (PLE) analyses. From X-ray diffraction (XRD) results, the crystal structure of the Eu doped Y₂O₃ phosphor is found to be cubic. The maximum emission spectra of the Eu doped Y₂O₃ phosphors are observed at 0.05 mol Eu³⁺ concentration. The photoluminescence of 615 nm in the Eu doped Y₂O₃ phosphors is associated with ⁵D₀ → ⁷F₂ transition of Eu³⁺ ions. The decrease in emission intensity of 0.1 mol Eu doped Y₂O₃ is interpreted by concentration quenching. The International Commission on Illumination (CIE) coordinates of 0.05 mol Eu doped Y₂O₃ phosphor are X = 0.6547, Y = 0.3374.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.641-649
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• 2020

A facile microwave assisted solvothermal process is designed for fabricating SnS nanoparticles decorated on graphene nanosheet, which used as visible light driven photocatalyst. Some typical characterization techniques such as XRD, FT-IR, SEM with EDX analysis, and TEM and BET analysis are used to analyse the physical characteristics of as-prepared samples. Spherical SnS nanoparticles are uniformly dispersed on the surface of graphene nanosheet due to ammonia, which can prevent the aggregation of graphene oxide. Meanwhile, microwave radiation provides fast energy that promotes the formation of spherical SnS nanoparticles within a short time. The visible light photocatalytic activity of as-prepared SnS-GR nanocomposites is analysed through photodegradation efficiency of methylene blue with high concentration. According to the higher photocatalytic property, the as-prepared SnS-GR nanocomposites can be expected to be an efficient visible light driven photocatalyst. After five cycles for decolorization, the rate decreases from 87 % to 78 % (about 9 %). It is obvious that the photocatalytic activity of SnS-GR nanocomposite has good repeatability.