• Journal of Microbiology and Biotechnology
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• 제28권6호
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• pp.957-967
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• 2018

A novel $g-C_3N_4$/ZnO/stellerite (CNZOS) hybrid photocatalyst, which was synthesized by coupled hydro thermal-thermal polymerization processing, was applied as an efficient visible-light-driven photocatalyst against Staphylococcus aureus. The optimum synthesized hybrid photocatalyst showed a sandwich structure morphology with layered $g-C_3N_4$ (doping amount: 40 wt%) deposited onto micron-sized ZnO/stellerite particles (ZnO average diameter: ~18 nm). It had a narrowing band gap (2.48 eV) and enlarged specific surface area ($23.05m^2/g$). The semiconductor heterojunction effect from ZnO to $g-C_3N_4$ leads to intensive absorption of the visible region and rapid separation of the photogenerated electron-hole pairs. In this study, CNZOS showed better photocatalytic disinfection efficiency than $g-C_3N_4/ZnO$ powders. The disinfection mechanism was systematically investigated by scavenger-quenching methods, indicating the important role of $H_2O_2$ in both systems. Furthermore, $h^+$ was demonstrated as another important radical in oxidative inactivation of the CNZOS system. In respect of the great disinfection efficiency and practicability, the CNZOS heterojunction photocatalyst may offer many disinfection applications.

• Journal of Electrochemical Science and Technology
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• 제2권4호
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• pp.187-192
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• 2011

Photoelectrochemical performances of ZnO electrodes are enhanced by coupling with cobalt-based catalyst (CoPi) in phosphate electrolyte (pH 7). For this study, hexagonal pillar-shaped ZnO nanorods are grown on ZnO electrodes through a chemical bath deposition, onto which CoPi is deposited with different photodeposition times (10-30 min). A scanning electron microscopic study indicates that CoPi deposition does not induce any change of ZnO morphology and an energy-dispersive X-ray spectroscopic analysis shows that inorganic phosphate ions (Pi) exist on ZnO surface. Bare ZnO electrodes generate the current of ca. $0.36mA/cm^2$ at a bias potential of 0.5 V vs. SCE, whereas ZnO/CoPi (deposited for 10 min) has ca. 50%-enhanced current ($0.54mW/cm^2$) under irradiation of AM 1.5G-light ($400mW/cm^2$). The excess loading of CoPi on ZnO results in decrease of photocurrents as compared to bare ZnO likely due to limited electrolyte access to ZnO and/or CoPi-mediated recombination of photogenerated charge carriers. The primary role of CoPi is speculated to trap the photogenerated holes and thereby oxidize water into molecular oxygen via an intervalency cycle among Co(II), Co(III), and Co(IV).

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권6호
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• pp.540-545
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• 2008

Since mid 20th century, dental treatments with laser have been introduced and improved a lot. Because early $CO_2$, Nd:YAG, diode, argon, and holmium lasers are used for dealing soft tissue, so it applied just limited field. But, in 1997 the lasers of erbium family that able to dealing soft and hard tissue also were introduced, laser application fields are enlarged. In today, the application fields reach on implantation treatment, so clinicians can use the laser to make holes for implantation, and flap elevation, even though treating peri-implantitis. So our class want to discover the optimal setting of Er:YAG laser when treating peri-implantitis. We observed the surface that initially treated by RBM and TPS passion and laser with varied options of exposure time and power with SEM image. For this we conclude the optimal setting range that does not alter the implant surface structure and report it.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.29.1-29.1
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• 2009

Fabrication of good quality P-type GaN remained as a challenge for many years which hindered the III-V nitrides from yielding visible light emitting devices. Firstly Amano et al succeeded in obtaining P-type GaN films using Mg doping and post Low Energy Electron Beam Irradiation (LEEBI) treatment. However only few region of the P-GaN was activated by LEEBI treatment. Later Nakamura et al succeeded in producing good quality P-GaN by thermal annealing method in which the as deposited P-GaN samples were annealed in N2 ambient at temperatures above $600^{\circ}C$. The carrier concentration of N type and P-type GaN differs by one order which have a major effect in AlGaN based deep UV-LED fabrication. So increasing the P-type GaN concentration becomes necessary. In this study we have proposed a novel method of activating P-type GaN by electrochemical potentiostatic method. Hydrogen bond in the Mg-H complexes of the P-type GaN is removed by electrochemical reaction using KOH solution as an electrolyte solution. Full structure LED sample grown by MOCVD serves as anode and platinum electrode serves as cathode. Experiments are performed by varying KOH concentration, process time and applied voltage. Secondary Ion Mass Spectroscopy (SIMS) analysis is performed to determine the hydrogen concentration in the P-GaN sample activated by annealing and electrochemical method. Results suggest that the hydrogen concentration is lesser in P-GaN sample activated by electrochemical method than conventional annealing method. The output power of the LED is also enhanced for full structure samples with electrochemical activated P-GaN. Thus we propose an efficient method for P-GaN activation by electrochemical reaction. 30% improvement in light output is obtained by electrochemical activation method.

• 접착 및 계면
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• 제13권1호
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• pp.24-30
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• 2012

폴리아릴레이트(polyarylate, PAR) 섬유의 산 처리와 자외선 조사 처리에 의한 섬유표면의 미세구조 변화를 SEM과 AFM을 통하여 살펴보고 RMS roughness로 분석하였으며, 접촉각 측정을 하였다. 또한, PAR 섬유의 표면개질이 폴리에틸렌 나프탈레이트(polyethylene naphthalate, PEN) 수지와의 계면접착력에 어떠한 영향을 미치는지를 섬유 풀-아웃 시험(Fiber Pull-out)을 통해 분석하였다. 산처리 농도와 자외선 조사 처리 시간이 증가함에 따라 PAR 섬유의 표면에 에칭이나 크랙이 발생하면서 표면의 거칠기가 증가하는 양상을 보였으며, 물에 대한 접촉각은 감소하는 결과를 보였다. PEN 수지와의 계면접착력을 분석한 결과, 산 처리 농도의 증가와 자외선 조사처리 시간이 경과에 따라 증가하였고 특히, 산 처리 농도 pH 3, 자외선 조사 처리시간이 24 h일 때 최대 계면접착력을 보였다. 이는 섬유표면조도의 증가에 따른 섬유 표면적의 증가로, 계면에서 상호작용할 수 있는 면적이 증가하기 때문이라고 볼 수 있다.

• 한국재료학회지
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• 제26권3호
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• pp.149-153
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• 2016

Nanosized zeolites were prepared in an autoclave using tetraethoxysilane (TEOS), tetrapropylammonium hydroxide (TPAOH), and $H_2O$, at various hydrothermal synthesis temperatures. Using transmission electron microscopy and particle size analysis, the nanopowder particulate sizes were revealed to be 10-300 nm. X-ray diffraction analysis confirmed that the synthesized nanopowder was silicalite-1 zeolite. Using atomic layer deposition, the fabricated zeolite nanopowder particles were coated with nanoscale $TiO_2$ films. The $TiO_2$ films were prepared at $300^{\circ}C$ by using $Ti[N(CH_3)_2]_4$ and $H_2O$ as precursor and reactant gas, respectively. In the TEM analysis, the growth rate was ${\sim}0.7{\AA}/cycle$. Zeta potential and sedimentation test results indicated that, owing to the electrostatic repulsion between $TiO_2$-coated layers on the surface of the zeolite nanoparticles, the dispersibility of the coated nanoparticles was higher than that of the uncoated nanoparticles. In addition, the effect of the coated nanoparticles on the photodecomposition was studied for the irradiation time of 240 min; the concentration of methylene blue was found to decrease to 48%.

• Journal of Microbiology and Biotechnology
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• 제13권4호
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• pp.544-551
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• 2003

Interactive effects of UV-B and Cd on growth, pigment, photosynthesis, and lipid peroxidation have been studied in Anabaena, Microcystis, and Nostoc; all the tested cyanobacteria showed differential sensitivity to different dosage of UV-B and Cd alone as well as in combination. Phycocyanin was severely affected by UV-B and Cd by all the strains; the degree of pigment bleaching was most pronounced in Anabaena followed by Microcystis and Nostoc. $UV-B_2+Cd_2$ produced nearly 83, 78, and 65% inhibition of phycocyanin in Anabaena, Microcystis, and Nostoc, respectively. The above treatment also significantly decreased the contents of Chl ${\alpha}$ and carotenoid. Presence of capsule in Microcystis protected the phycocyanin bleaching as compared to decapsulated cells. Laboratory-grown Microcystis revealed about 75 and 80% inhibition, following $UV-B_2+Cd_2$ treatment, respectively. in capsulated and decapsulated cells. Damage caused by Cd was more pronounced than UV-B. Inhibition of photosynthesis did occur in all the test strains, being maximum in Anabaena. PS II was the most sensitive component of the electron transport chain, showing 84, 80, and 70% inhibition in Anabaena, Microcystis, and Nostoc, respectively. As compared to control, significant lipid peroxidation (6.5-fold higher) was observed in Anabaena with $UV-B_2+Cd_2$, $^{14}C-uptake$ was more susceptible to Cd and Uv-B than oxygen-evolution. Approximately 84, 80, and 76% inhibition of $^{14}C-uptake$ was observed in Anabaena, Microcystis, and Nostoc, respectively. Similarly, $UV-B_2+Cd_2$ inhibited APT content of Anabaena by 87%. This ,study suggests that inhibition of carbon fixation was due to decreased ATP content of the test cyanobacteria by UV-B+Cd, where Anabaena was the most sensitive and Nostoc the most tolerant.

• Journal of Yeungnam Medical Science
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• 제12권1호
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• pp.75-83
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• 1995

광선치료는 신생아 황달의 효과적인 치료방법이나 광선에 의한 망막손상을 예방하기 위해 양안에 적절한 차폐를 실시하여야 한다. 광선치료후 급성기의 망막 손상정도와 차폐의 역할을 조사하기 위하여, 저자들은 토끼를 이용하여 광선치료시간, 조사방법, 차폐 유무 등을 변화 시키면서 광선치료를 실시하고 즉시, 간접검안경을 이용한 안저검사와 전자현미경 검사를 실시하여 광선치료후 수시간에서 수일후에 검사한 보고들과 비교 하였다. 모든 실험 토끼에서 안저검사상 정상소견을 나타 내었으나, 전자 현미경 검사상 12시간 이상 조사한 모든 실험군에서 광수용체 부종 및 망막내층의 부종 및 팽윤이 있었으나 광선치료후 수일이 경과한 후 검사하였던 경우에서 볼 수 있었던 광수용체 배열의 변화, 광수용체 내외절의 파괴, microvilli의 확장및 유착 등의 소견은 볼 수 없었고, 노출시간이 증가 할수록 손상의 정도가 심해졌으며, 광선 조사량이 같은 경우 간헐적인 방법으로 조사를 실시한 경우에서 망막손상이 심한 것으로 나타났다. 산동시킨 경우에서, 손상의 정도는 산동시키지 않은 경우와 비슷 하였으나 손상의 범위가 더 넓게 관찰 되었으며 차폐를 실시한 경우 망막손상을 예방할 수 있었다.

• Advances in environmental research
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• 제3권3호
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• pp.185-197
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• 2014

Efficient defluorination of perfluorooctanoic acid (PFOA) was achieved by integrating UV irradiation and $Fe^{2+}$ activation of persulfate ($S_2O{_8}^{2-}$). It was found that the UV-$Fe^{2+}$, $Fe^{2+}-S_2O{_8}^{2-}$, and UV-$S_2O{_8}^{2-}$ processes caused defluorination efficiency of 6.4%, 1.6% and 23.2% for PFOA at pH 5.0 within 5 h, respectively, but a combined system of UV-$Fe^{2+}-S_2O{_8}^{2-}$ dramatically promoted the defluorination efficiency up to 63.3%. The beneficial synergistic behavior between $Fe^{2+}-S_2O{_8}^{2-}$ and UV-$S_2O{_8}^{2-}$ was demonstrated to be dependent on $Fe^{2+}$ dosage, initial $S_2O{_8}^{2-}$ concentration, and solution pH. The decomposition of PFOA resulted in generation of shorter-chain perfluorinated carboxylic acids (PFCAs), formic acid and fluoride ions. The generated PFCAs intermediates could be further defluorinated by adding supplementary $Fe^{2+}$ and, $S_2O{_8}^{2-}$ and re-adjusting solution pH in later reaction stage. The much enhanced PFOA defluorination in the UV-$Fe^{2+}-S_2O{_8}^{2-}$ system was attributed to the fact that the simultaneous employment of UV light and $Fe^{2+}$ not only greatly enhanced the activation of $S_2O{_8}^{2-}$ to form strong oxidizing sulfate radicals ($SO{_4}^{\cdot-}$), but also provided an additional decarboxylation pathway caused by electron transfer from PFOA to in situ generated $Fe^{3+}$.

• Nano
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• 제13권12호
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• pp.1850147.1-1850147.14
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• 2018

In this work, water-soluble and blue-emitting carbon nanodots (CDs) were synthesized from apple peels for the first time via one-step hydrothermal method. The synthetic route is facile, green, economical and viable. The as-prepared CDs were characterized thoroughly by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, Fourier transform infrared (FT-IR), X-ray photoelectron (XPS), fluorescence and UV-Vis absorption spectroscopy in terms of their morphology, surface functional groups and optical properties. The results show that these CDs possessed ultrasmall size, good dispersivity, and high tolerance to pH, ionic strength and continuous UV irradiation. Significantly, the CDs had fast and reversible response towards temperature, and the accurate linear relationship between fluorescence intensity and temperature was used to design a novel nanothermometer in a broad temperature range from 5 to $65^{\circ}C$ facilely. In addition, the fluorescence intensity of CDs was observed to be quenched immediately by Cr(VI) ions based on the inner filter effect. A low-cost Cr(VI) ions sensor was proposed employing CDs as fluorescent probe, and it displayed a wide linear range from 0.5 to $200{\mu}M$ with a detection limit of $0.73{\mu}M$. The practicability of the developed Cr(VI) sensor for real water sample assay was also validated with satisfactory recoveries.