• Journal of the Korean institute of surface engineering
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• v.56 no.3
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• pp.208-218
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• 2023

Photocatalysts are advanced materials which accelerate the photoreaction by providing ordinary reactions with other pathways. The catalysts have various advantages, such as low-cost, low operating temperature and pressure, and long-term use. They are applied to environmental and energy field, including the air and water purification, water splitting for hydrogen production, sterilization and self-cleaning surfaces. However, commercial photocatalysts only absorb ultraviolet light between 100 and 400 nm of wavelength which comprises only 5% in sunlight due to the wide band gap. In addition, rapid recombination of electron-hole pairs reduces the photocatalytic performance. Recently, studies on blackening photocatalysts by laser, thermal, and plasma treatments have been conducted to enhance the absorption of visible light and photocatalytic activity. The disordered structures could yield mid-gap states and vacancies could cause charge carrier trapping. Herein, liquid phase plasma (LPP) is adopted to synthesize Ag-doped black ZnO for the utilization of visible-light. The physical and chemical characteristics of the synthesized photocatalysts are analyzed by SEM/EDS, XRD, XPS and the optical properties of them are investigated using UV/Vis DRS and PL analyses. Lastly, the photocatalytic activity was evaluated using methylene blue as a pollutant.

• Proceedings of the Korean Vacuum Society Conference
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• 1996.06a
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• pp.40-41
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• 1996

Nitridation technique has been receiving much attention for the formation of a thin nitrided buffer layer on which high quality nitride films can be formedl. Particularly, gallium nitride (GaN) has been considered as a promising material for blue-and ultraviolet-emitting devices. It can also be used for in situ formed and stable passivation layers for selective growth of $GaAs_2$. In this work, formation of a thin nitrided layer is investigated. Nitrogen electron cyclotron resonance(ECR)-plasma is employed for the formation of thin nitrided layer. The plasma source used in this work is a compact ECR plasma gun3 which is specifically designed to enhance control, and to provide in-situ monitoring of plasma parameters during plasma-assisted processing. Microwave power of 100-200 W was used to excite the plasma which was emitted from an orifice of 25 rnm in diameter. The substrate were positioned 15 em away from the orifice of plasma source. Prior to nitridation is performed, the surface of n-type (001)GaAs was exposed to hydrogen plasma for 20 min at $300{\;}^{\circ}C$ in order to eliminate a native oxide formed on GaAs surface. Change from ring to streak in RHEED pattern can be obtained through the irradiation of hydrogen plasma, indicating a clean surface. Nitridation was carried out for 5-40 min at $RT-600{\;}^{\circ}C$ in a ECR plasma-assisted molecular beam epitaxy system. Typical chamber pressure was $7.5{\times}lO^{-4}$ Torr during the nitridations at $N_2$ flow rate of 10 seem.(omitted)mitted)

• Journal of the Korean Chemical Society
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• v.45 no.6
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• pp.520-523
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• 2001

Hydrogen $peroxide(H_2O_2)$ reacts with HCr$O^-_4$ in an acidic condition to produce $CrO(O_2)_2$ which exhibits an intense blue color. This reaction is coupled with a technique of Flow Injection Analysis(FIA) for the absorption spectrometry of $H_2O_2$ in the aqueous samples. The method could be applied for the deter-mination of $H_2O_2$ over the range of 2.00{\times}$10^{-6}$M∼0.020 M with the limit of detection of ∼1.00${\times}10^{-6}$M. The method was also used to successfully determination of the $H_2O_2$ content in the snow and rain samples.

• The Korea Journal of Herbology
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• v.25 no.1
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• pp.83-91
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• 2010

Objectives : In this study, we compared the anti-oxidant and anti-inflammatory activities of Curcumae longae Radix (CLRa) and Curcumae longae Rhizoma (CLRh). Methods : We performed 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) cation scavenging assays, and determined total polyphenolic content to examine the anti-oxidant effects of CLRa and CLRh. We also evaluated the anti-oxidant effects of CLRa and CLRh against hydrogen peroxide ($H_2O_2$)-induced toxicity in PC12 cells using thiazolyl blue tetrazolium bromide (MTT) and reactive oxygen species (ROS) assays. Next, to compare the anti-inflammatory effects of CLRa and CLRh against lipopolysaccharide (LPS)-induced inflammation in microglia BV2 cells, we measured nitric oxide (NO) assay and inducible nitrite synthase (iNOS) using Western blotting analysis. Results : CLRa showed higher activity in DPPH and ABTS assays and lower total polyphenolic contents compared with CLRh. In PC12 cells, CLRa and CLRh showed no difference in H2O2-induced cell toxicity and ROS overproduction. In BV2 cells, CLRa showed higher effect than CLRh in NO and iNOS production induced by LPS. Conclusions : These results demonstrate that CLRa has higher radical scavenging activities and anti-inflammatory effect in BV2 cells comparing CLRh. However, CLRa and CLRh have no effect and no difference in $H_2O_2$-induced toxicity.

• Journal of Korean Medicine for Obesity Research
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• v.15 no.2
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• pp.93-103
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• 2015

Objectives: It was investigated the cytoprotective efficacies of isorhamnetin, a flavonoid originally derived from Hippophae rhamnoides L., against oxidative stress-induced apoptosis in C2C12 myoblasts. Methods: The effects of isorhamnetin on cell growth, apoptosis and reactive oxygen species (ROS) generation were evaluated by trypan blue dye exclusion assay, 4',6-diamidino-2-phenylindole staining and flow cytometry. The levels of apoptosis-regulatory and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway-related proteins, and caspase activities (caspase-3 and -9) were determined by Western blot analysis and colorimetric assay, respectively. Results: Our results revealed that treatment with isorhamnetin prior to hydrogen peroxide ($H_2O_2$) exposure significantly increased the C2C12 cell viability and, indicating that the exposure of C2C12 cells to isorhamnetin conferred a protective effect against oxidative stress. Isorhamnetin also effectively attenuated $H_2O_2$-induced apoptosis and ROS generation, which was associated with the restoration of the upregulation of Bax and downregulation of Bcl-2 induced by $H_2O_2$. In addition, $H_2O_2$ enhanced the activation of caspase-9 and -3, and degradation of poly (ADP-ribose)-polymerase, a typical substrate protein of activated caspase-3; however, these events were almost totally reversed by pretreatment with isorhamnetin. Moreover, isorhamnetin increased the levels of heme oxygenase-1, a potent antioxidant enzyme, associated with the induction of Nrf2. Conclusions: Our data indicated that isorhamnetin may potentially serve as an agent for the treatment and prevention of muscle disorders caused by oxidative stress.

• Microbiology and Biotechnology Letters
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• v.42 no.2
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• pp.170-176
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• 2014

In this study, the anti-oxidative and anti-inflammatory activities of Euptelea pleiosperma ethanol extract (EPEE) were evaluated using in vitro assays and cell culture model systems. EPEE possessed a more potent scavenging activity against 1,1-diphenyl-2-picryl hydrazyl than the ascorbic acid used as a positive control. EPEE effectively suppressed lipopolysaccharide (LPS), in addition to hydrogen peroxide induced reactive oxygen species on RAW 264.7 cells. Furthermore, EPEE induced the expression of the anti-oxidative enzyme heme oxygenase 1 (HO-1) and its upstream transcription factor, nuclear factor-E2-related factor 2 (Nrf2), dose and time dependently. The modulation of HO-1 and Nrf2 expression might be regulated by mitogen-activated protein kinases and phosphatidyl inositol 3 kinase/Akt as their upstream signaling pathways. On the other hand, EPEE inhibited LPS induced nitric oxide (NO) formation without cytotoxicity. Suppression of NO formation was the result of the down regulation of inducible NO synthase (iNOS) by EPEE. Suppression of NO and iNOS by EPEE may be modulated by their upstream transcription factor, nuclear factor ${\kappa}B$, and AP-1 pathways. Taken together, these results provide important new insights into E. pleiosperma, namely that it possesses anti-oxidative and anti-inflammatory activities, indicating that it could be utilized as a promising material in the field of nutraceuticals.

• Microbiology and Biotechnology Letters
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• v.42 no.3
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• pp.275-284
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• 2014

This study was orchestrated with the purpose of uncovering new nutraceutical resources possessing biological activities in the plant kingdom. To fulfill our objective, we analyzed several Chinese plants and selected three possessing powerful anti-oxidative activities. The anti-oxidative and anti-inflammatory effects these three Chinese plants, Malus hupehensis, Ophiorrhiza cantonensis, and Psychotria rubra ethanol extracts were then evaluated. First of all, they possessed potent scavenging activity against 1,1-diphenyl-2-picryl hydrazyl, similar with that of ascorbic acid, used as a positive control. Moreover, they inhibited lipopolysaccharide (LPS)- and hydrogen peroxide-induced reactive oxygen species, in a dose-dependent manner, in RAW 264.7 cells. Also, they induced the expression of an anti-oxidative enzyme, heme oxygenase 1, and its upstream transcription factor, nuclear factor-E2-related factor 2. Furthermore, they suppressed LPS-induced nitric oxide (NO) formation, without cytotoxicity. The inhibition of NO formation was the result of the down regulation of inducible NO synthase (iNOS). The suppression of NO and iNOS by the three extracts might be the result of modulation by the upstream transcription factors, nuclear factor ${\kappa}B$ and activator protein-1. Taken together, these results indicate that these three Chinese plants possess potent anti-oxidative and anti-inflammatory activities. Therefore, they might be utilized as promising materials in the field of nutraceuticals.

• Korean Journal of Weed Science
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• v.8 no.1
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• pp.15-22
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• 1988

In this experiment, interactions between light and other factors such as chilling, alternating temperature, moisture, content, oxygen, and seed coat which affect germination of Oenothera lamarckiana Ser. seed were investigated to study the physiological effects of light on the germination. Light induced the initial stage of seed germination before radical protrusion by affecting embryo rather than seed coat even under anaerobic condition or low water potential (-18 bars). This light effect on germinability of seed was suppressed by blue light irradiation and the effect was increased with increment of blue light intensity and irradiation time. However, the blue light effect was reversible. Chilling, alternating temperature, softening of seed coat and light showed promotive interaction in the induction of seed germination. Irradiation of filtered light (monochrome), however, reduced chilling effect on germination. Hydrogen-ion concentration and gibberellic acid treatment had no effect on light or dark germination.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.424-429
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• 2014

YAG:$Ce^{3+}$ phosphor powders were synthesized using $Al(OH)_3$ seeds by means of a PVA-polymer-solution route. Various types of PVA with different molecular weights (different polymerization) were used. All dried precursor gels were calcined at $500^{\circ}C$ and then heated at $1500^{\circ}C$ in a mix of nitrogen and hydrogen gases. The final powders were characterized via XRD, SEM, PSA, PL, and PKG analyses. The phosphor properties and morphologies of the synthesized powders were dependent on the PVA type. As the molecular weight of the PVA was increased, the particle size gradually decreased with agglomeration, and the luminous intensity of the phosphor increased. However, the phosphor powder prepared from the PVA exhibiting very high molecular weight, showed a 531 nm (blue) shift from the 541 nm (yellow) wavelength of the YAG:$Ce^{3+}$ phosphor. Finally, the synthesized YAG:$Ce^{3+}$ phosphor powder prepared from the PVA with 89,000 - 98,000 molecular weight showed phosphor properties similar to those of a commercial phosphor powder, but without a post-treatment process.

• Textile Coloration and Finishing
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• v.23 no.3
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• pp.155-162
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• 2011

para-Aramid has limited dyeability because of its highly crystalline structure and compactness. To improve the dyeability of the para-aramid to reactive dyes of bright color in deep shade, the fabrics were photografted under continuous UV irradiation with dimethylaminopropyl methacrylamide and 4-benzoyl benzoic acid as a monomer and a hydrogen -abstractable photoinitiator respectively. A UV energy of 35J/$cm^2$ and a photoinitiator concentration of ten percent or more with respect to the monomer in the formulation was required for optimal photografting. Grafting yield increased with higher monomer application level. Surface analysis indicated significant alterations in the atomic composition of the photografted fabric surface and the fabric surface was covered with the grafted polymers. While the pristine para-aramid fabrics showed no appreciable dyeability to the ${\alpha}$-bromoacrylamide reactive dyes, the grafted para-aramid fabrics enhanced the dyeability to the reactive dyes substantially. In case of C.I. Reactive Blue 50, a K/S value of 8.7 can be obtained with the grafted para-aramid fabrics with a grafting yield of 2.3 %. Also the color fastness properties of the dyed fabrics was excellent in the conditions of washing, rubbing and light irradiation.