• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1941-1944
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• 2010

The heterojunction structures of BiOCl/$Bi_3O_4Cl$, exhibiting considerable visible-light photocatalytic efficiency, were prepared by a simple wet-chemical process at ambient condition. The prepared nanocomposites were characterized by XRD, TEM, and UV-visible diffuse reflectance spectra. Under visible light (${\lambda}\geq$420 nm) irradiation, BiOCl/$Bi_3O_4Cl$ exhibited an enhanced photocatalytic activity in decomposing 2-propanol (IP) in gas phase and salicylic acid (SA) in aqueous solution, whereas the bare BiOCl and $Bi_3O_4Cl$ showed negligible activities. It is deduced that the remarkable visible-light photocatalytic activity of the BiOCl/$Bi_3O_4Cl$ originates from the hole $(h^+)$ transfer between VB of the $Bi_3O_4Cl$ and BiOCl semiconductors.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.190.1-190.1
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• 2016

One of the most serious problems faced by billions of people today is the availability of fresh water. According to statistics, 15% of the world's total output of dye products is discharged into the environment as dye wastewater, which seriously pollutes groundwater resources. For the treatment of chemically and biologically contaminated water the advanced oxidation processes (AOPs) shows the promising action. The main advantage with AOPs is the ability to degrade the organic pollutants to $CO_2$ and $H_2O$. For this degradation process the AOPs generation of powerful and non-selective radicals that may oxidize majority of the organic pollutants present in the water body. To generate the various reactive chemical species such as radicals (${\bullet}OH$, ${\bullet}H$, ${\bullet}O$, ${\bullet}HO_2$) and molecular species ($H_2O_2$, $H_2$, $O_2$) in large amount in water, we have used the atmospheric pressure plasma. Among the reactive and non-reactive species, the hydroxyl radical (${\bullet}OH$) plays important role due to its higher oxidation potential (E0: 2.8 V). Therefore, in this work we have checked the degradation of various dyes such as methyl orange, methylene blue and congo red using different type of atmospheric pressure plasma sources (Indirect jet and direct jet). To check the degradation we have used the UV-visible spectroscopy, HPLC and LC-MS spectroscopy. Further, to estimate role of ${\bullet}OH$ on the degradation of dyes we have studied the molecular dynamic simulation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.241-245
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• 2013

Granular bamboo-derived active carbons (AC) were impregnated (or coated) with $TiO_2$ nano crystalline powders. The photocatalytic activity of the $TiO_2$-impregnated active carbons ($TiO_2$/AC) were determined on the basis of the degradation rate of methylene-blue aqueous solution under UV irradiation. The active compounds of $TiO_2$ were impregnated onto the AC under moderate hydrothermal conditions (${\leq}200^{\circ}C$, pH 11). The mean size of $TiO_2$ particles calculated from BET surface area were found to be as 50 nm. The $TiO_2$ precipitates were coated on the cavities or pores on the surfaces of highly activated carbons. Since the hydrothermal process led to a lowering of the on-set temperature of the anatase-to-rutile transition of $TiO_2$ as low as $200^{\circ}C$, $TiO_2$ crystallites of a pure anatase or a mixed form with rutile were successfully coated on the AC depending on the synthesis temperatures.

• Membrane Journal
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• v.14 no.2
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• pp.149-156
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• 2004

This work focused on the degradation of natural organic matter (NOM) present in lake water using a combined pkotocatalysisimicrofiltration (MF) process. The system performances were investigated in terms of organic removal efficiency and membrane permeability. The addition of iron oxide particles (IOP) into the photocatalytic membrane reactor improved initial NOM removal by sorption, but during photocatalysis the removal efficiency was reversed, probably due to the scattering of UV light by IOP. The modification of TiO$_2$ surfaces by IOP deposition was conducted to enhance the photocatalytic NOM removal efficiency. A minimal amount of Impregnation of IOP on TiO$_2$ surfaces was required to prevent the light scattering effect as well. The coating of MF membranes with IOP helped to improve the NOM removal efficiency while sorbing NOM by IOP. Regardless of tile operating conditions and particles addition examined, no significant fouling was occurring at a flux of 15 L/$m^2$-h during entire MF operation.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.105-105
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• 2012

We have developed a photoemission-assisted plasma-enhanced chemical vapor deposition (PAPE-CVD) [1,2], in which photoelectrons emitting from the substrate surface irradiated with UV light ($h{\nu}$=7.2 eV) from a Xe excimer lamp are utilized as a trigger for generating DC discharge plasma as depicted in Fig. 1. As a result, photoemission-assisted plasma can appear just above the substrate surface with a limited interval between the substrate and the electrode (~10 mm), enabling us to suppress effectively the unintended deposition of soot on the chamber walls, to increase the deposition rate, and to decrease drastically the electric power consumption. In case of the deposition of DLC gate insulator films for the top-gate graphene channel FET, plasma discharge power is reduced down to as low as 0.01W, giving rise to decrease significantly the plasma-induced damage on the graphene channel [3]. In addition, DLC thickness can be precisely controlled in an atomic scale and dielectric constant is also changed from low ${\kappa}$ for the passivation layer to high ${\kappa}$ for the gate insulator. On the other hand, negative electron affinity (NEA) of a hydrogen-terminated diamond surface is attractive and of practical importance for PAPECVD, because the diamond surface under PAPE-CVD with H2-diluted (about 1%) CH4 gas is exposed to a lot of hydrogen radicals and therefore can perform as a high-efficiency electron emitter due to NEA. In fact, we observed a large change of discharge current between with and without hydrogen termination. It is noted that photoelectrons are emitted from the SiO2 (350 nm)/Si interface with 7.2-eV UV light, making it possible to grow few-layer graphene on the thick SiO2 surface with no transition layer of amorphous carbon by means of PAPE-CVD without any metal catalyst.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.49.2-49.2
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• 2011

$PbMoO_4$ nanoparticles were successfully obtained in the presence of ethylene glycol (EG) with the assistance of a prolonged sonication process. The nanoparticles were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and adsorption-desorption $N_2$ isotherms (BET). The catalyst prepared sonochemically showed higher photocatalytic activity than $PbMoO_4$ prepared by solid-state reaction in the degradation reactions of rhodamine B (rhB), indigo carmine (IC), orange G (OG), and methyl orange (MO) under UV-Vis light radiation. In order to elucidate aspects of the degradation mechanism of the organic dyes, some experimental variables were modified such as pH, $O_2$ level in solution, and radiation source. In general, the photocatalytic activity for the degradation of organic dyes followed the sequence IC>OG>rhB>MO.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.5
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• pp.240-246
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• 2002

$TiO_2$ films on soda-lime-silica glasses were prepared by spin coating-pyrolysis process using titanium naphthenate as a starting material. As-deposited films were pyrolyzed at $500^{\circ}C$ for 10 min in air and annealed at 500, 550 and $600^{\circ}C$ for 30 min in air. Crystallinity of the film was investigated by X-ray diffraction analysis. A field emission-scanning electron microscope and an atomic force microscope were used for characterizing the surface morphology and the surface roughness of the film. After annealing at 550 and $600^{\circ}C$, the X-ray diffraction patterns consist of only anatase peak. Films annealed at 500 and $550^{\circ}C$ exhibited flat surfaces. While with the increase in annealing temperature to $600^{\circ}C$, the $TiO_2$ film showed abnormal growth of three-dimensional needle-shaped grains. For all samples, high transmittance, above 90 % at 500 nm, was obtained at visible range. To investigate photocatalytic properties, IR absorbance associated with the C-H stretching vibrations of a thin solution-cast film of stearic acid under 365 nm (2.4 mW/$\textrm{cm}^2$) UV irradiation was estimated.

• Advances in materials Research
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• v.2 no.2
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• pp.77-91
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• 2013

High quality nanoparticles of neodymium barium niobium ($NdBa_2NbO_6$) perovskites have been synthesized using an auto ignition combustion technique for the first time. The nanoparticles thus obtained have been characterized by powder X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscopy. UV-Visible absorption and photoluminescence spectra of the samples are also recorded. The structural analysis shows that the nano powder is phase pure with the average particle size of 35 nm. The band gap determined for $NdBa_2NbO_6$ is 3.9 eV which corresponds to UV-radiation for optical inter band transition with a wavelength of 370nm. The nanopowder could be sintered to 96% of the theoretical density at $1325^{\circ}C$ for 2h. The ultrafine cuboidal nature of nanopowders with fewer degree of agglomeration improved the sinterability for compactness at relatively lower temperature and time. During the sintering process the wide band gap semiconducting behavior diminishes and the material turns to a high permittivity dielectric. The microstructure of the sintered surface was examined using scanning electron microscopy. The striking value of dielectric constant ${\varepsilon}_r=43$, loss factor tan ${\delta}=1.97{\times}10^{-4}$ and the observed band gap value make it suitable for many dielectric devices.

• Journal of the Korean Chemical Society
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• v.57 no.2
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• pp.246-251
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• 2013

With -$OCH_2CO$- as a linker, a non ${\beta}$-substituted cationic bisporphyrin (4a) and a ${\beta}$-substituted cationic bisporphyrin (4b) were prepared through methylation of the intermediate which was obtained from ${\beta}$-amino-5,10,15,20-tetra (4-cyanophenyl) porphyrin or 5-hydroxylphenyl-10,15,20-tris(4-cyanophenyl) reacting with 5-hydroxy-10,15,20-trispyridinylporphyrin. Their structures were confirmed by $^1H$ NMR, IR, UV-vis, MS and elemental analysis. DNA photocleavage ability and the singlet oxygen ability of those cationic bisporphyrins were investigated. DNA photocleavage activity of ${\beta}$-substituted cationic bisporphyrin was significantly weaker than that of $H_2TMPyP$, but similar to that of non ${\beta}$-substituted cationic bisporphyrin. While 4a and 4b showed substantial photocleavage activities toward DNA, with 68% and 66% observed at 10 ${\mu}M$. The assessment of indirectly measured $^1O_2$ production rates against $H_2TMPyP$ were described and the relative singlet oxygen production yields were: free cationic bisporphyrins > $H_2TMPyP$. The results showed the cationic bisporphyrins with ${\beta}$-substitution and non ${\beta}$-substitution could be developed as potential photodynamic agents.

• Korean Journal of Food Science and Technology
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• v.4 no.2
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• pp.123-133
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• 1972

Over 90 of lysine producing auxotrophs were obtained from Corynebacterium sp. S-27-12, Brevibacterium flavum ATCC 15168 and Micrococcus glutamicus ATCC 13032 by UV light, $Co^{60}$ irradiation and N-methyl-N'-nitro-N-nitrosoguanidine treatment. One of the mutant, Brev. flavum U46-N59, was identified as a leucine auxotroph and accumulated lysine during flask (500 ml) cultivation (180 strokes/min.) up to 21.6 mg per ml of broth at pH 7.5 and $28^{\circ}C$ after 4 days. The medium consisted of glucose, 100; urea, 10; corn steep liquor, 40; $KH_2PO_4,\;2;\;K_2HPO_4,\;0.5;\; MgSO_4.\;7H_2O,\;0.4;\;antifoam\;S-57,\;1g;\;Fe_2(SO_4)_3.XH-2O,\;10;\; MnCl_2,\;4H_2O,\;10mg;\;biotin,\;30;\;thiamine-HCl,\;100{\mu}g$in 1l of distilled water, and 40 U/ml of penicillin was added after 36 hrs fermentation.