• Bulletin of the Korean Chemical Society
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• v.25 no.9
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• pp.1392-1396
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• 2004

The micellization of dodecylpyridinum chloride (DPC) assembled on aqueous gold nanoparticles has been studied as a function of concentration using Surface-Enhanced Raman Scattering (SERS). At the low concentration, the strong SERS band of the benzene ring moiety was observed at 1025 $cm^{-1}$, and assigned to “trigonal ring breathing”. According to high concentration of DPC, a new strong band was also appeared at 1012 $cm^{-1}$, which was assigned to “totally symmetry ring breathing”. The difference of two spectra seems to ascribe to the geometry of polar head group, i.e., pyridinium cation. These geometry exist flat-down at low concentration, whereas standing-up or tilted geometry at high concentration. The critical micelle concentration (CMC) was first obtained from the ratio of intensities of the two bands related to the benzene ring moiety by vibrational spectroscopy, and was about 28 mM. After the CMC, the benzene ring moiety in the micelle state was more restricted than in monomer state because there is no more change of intensities at 1012 $cm^{-1}$. In addition, the size of gold-assembled micelle was estimated using light scattering and it was about 328.3 nm.

• Journal of Korean Vacuum Science & Technology
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• v.3 no.2
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• pp.116-120
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• 1999

Possible role of hydrogen atoms on the formation of microcrystalline silicon films was schematically investigated using a plasma enhanced chemical vapor deposition system. A layer-by-layer technique that can alternate deposition of ${\alpha}$-Si thin film and then exposure of H2 plasma was used for this end. The experimental process was extensively carried out under different hydrogen plasma times (t2) at a fixed number of 20 cycles in the deposition. structural properties, such as crystalline volume fractions and grain shapes were analyzed by using a Raman spectroscopy and a scanning electron microscopy. Electrical transports were characterized by the temperature dependence of the dark conductivity that gives rise to the calculation of activation energy (Ea). Optical absorption was measured using an ultra violet spectrophotometer, resulting in the optical energy gap (Eopt). Our experimental results indicate that both of the hydrogen etching and the structural relaxation effects on the film surface seem to be responsible for the growth mechanism of the crystallites in the ${\mu}$c-si films.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.384-388
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• 2015

We prepared blocking layers by adding 0.0 ~ 0.6 wt% nano diamond blends (DBs) to $TiO_2$ blocking layers to improve the energy conversion efficiencies (ECEs) of dye sensitized solar cells (DSSCs). TEM and micro-Raman spectroscopy were used to characterize the microstructure and phases of DBs, respectively. Optical microscopy and FE-SEM were used to analyze the microstructure of the $TiO_2$ blocking layer with DBs. UV-VIS-NIR spectroscopy was used to determine the absorbance of the working electrodes. A solar simulator and a potentiostat were used to determine the photovoltaic properties and the impedance of the DSSCs with DBs. From the results of the DBs analysis, we determined a 6.97 nm combination of nano diamonds and graphite. We confirmed that ECE increased from 5.64 to 6.48 % when the added DBs increased from 0.0 to 0.2 wt%. This indicates that the effective surface area and electron mobility increased when DBs were added to the $TiO_2$ blocking layer. Our results indicate that the ECE of DSSCs can be enhanced by adding an appropriate amount of DBs to the $TiO_2$ blocking layers.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.2
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• pp.83-89
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• 2010

Diamond-like carbon (DLC) coating was studied to be a good tribological problem-solver due to its low friction characteristics and high hardness. However, generally hydrogenated DLC film has shown a weak thermal stability above $300^{\circ}C$. However, the silicon doping DLC process by DC pulse plasma enhanced chemical vapor deposition (PECVD) for the new DLC coating which has a good characterization with thermal stability at high temperature itself has been observed. And we were discussed a process for optimizing silicon content to promote a good thermal stability using various tetramethylsilane (TMS) and methane gas at high-temperature. The chemical compositions of silicon-containing DLC film was analyzed using X-ray photoelectron spectroscopy (XPS) before and after heat treatment. Raman spectrum analysis showed the changed structure on the surface after the high-temperature exposure testing. In particular, the hardness of silicon-containing DLC film showed different values before and after the annealing treatment.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.387-392
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• 2018

Various technical approaches and concepts have been proposed to develop conductive super-hydrophobic (SH) surfaces. However, most of these approaches are not usable in practical applications because of insufficient adhesion and cost issues. Additionally, durability and uniformity issues are still in need of improvement. The goal of this research is to produce a large-area conductive SH surface with improved adhesion performance and uniformity. To this end, carbon nanotubes (CNT) with a high aspect ratio and elastomeric polymer were utilized as a conductive filler and matrix, respectively, to form a coating layer. Additionally, nanoscale silica particles were utilized for stable implementation of the conductive SH surface. To improve the adhesion properties between the SH coating layer and substrate, pretreatment of the substrate was conducted by utilizing both wet and dry etching processes to create specific organic functional groups on the substrate. Following pretreatment of the surface, a zirco-aluminate coupling agent was utilized to enhance adhesion properties between the substrate and the SH coating layer. Raman spectroscopy revealed that adhesion was greatly improved by the formation of a chemical bond between the substrate and the SH coating layer at an optimal coupling agent concentration. The developed conductive SH coating attained a high electromagnetic interference (EMI) shielding effectiveness, which is advantageous in self-cleaning EMI shielding applications.

• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1798-1804
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• 2009

In this study, we have studied on improved performance of carbon nanotubes/titanium (CNT/TiO2) structure electrode for methylene blue (MB). The composite electrodes consisting of CNTs and a titanium oxide matrix with phenol resin binder was fabricated with a mixture method. The chemical and morphological structure of CNT/Ti$O_2$ composites were characterized by means of BET surface area, X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis absorption technique, Raman spectroscopy and energy dispersive X-ray (EDX). The electrode showed a remarkably enhanced performance for MB oxidation under UV illumination with or without electro-chemical reaction (ECR). Such a remarkably improved performance of the CNT/Ti$O_2$ structure electrode might be due to the enhanced MB oxidation by electro- and photo-generated electrons and holes in the CNTs and Ti$O_2$ under UV illumination with or without ECR.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.8
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• pp.3597-3601
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• 2013

In this study, a wet cleaning process, P II, using aqua-regia and sulfuric acid mixture with oxidant agent ($K_2S_2O_8$, $P_2O_5$, $KMnO_4$, $H_2O_2$ etc) is proposed to remove the metastable phase of graphite such as graphene and DLC for high quality synthetic diamonds. The process employed the conventional acid cleaning process (P I) as well as P I+P II to remove the graphite related impurities from the 200um-diamond powders synthesized at 7GPa-$1500^{\circ}C$-5minutes. The degree of cleaning after P I and P I+P II has been observed by naked-eye, optical microscopy, micro-Raman spectroscopy, and TGA-DTA. After P I+P II, the color of diamond became more vividly yellow with enhanced saturation with naked eye and optical microscopy analysis. Moreover, the disappearance of diamond-like-carbon (DLC) peak ($1440cm^{-1}$) observed by Raman spectroscopy confirmed the decrease in amount of remaining impurities. TGA-DTA results showed that the graphite impurities first started to dissolve at $770.91^{\circ}C$ after PI process. However, the pyrolysis started at $892.18^{\circ}C$ after P I+P II process because of the dissolution of pure diamonds. This result proved the effective dissolution of the metastable phase of graphite. We expect that the proposed P II process may enhance the quality of diamonds through effective removal of surface impurities.

• Journal of the Korean institute of surface engineering
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• v.42 no.4
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• pp.179-185
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• 2009

Diamond-like carbon(DLC) films were deposited by linear ion source(LIS)-physical vapor deposition method changing the anode voltages from 800 V to 1800 V, and characteristics of the films were investigated using residual stress tester, nano-indentation, micro raman spectroscopy, scratch tester and Field Emission Scanning Electron Microscope(FE-SEM). The results showed that the residual stress and hardness increased with increasing the ion energy up to anode voltage of 1400 V. It was also found that the content of $SP^3$ carbon increased with increasing the anode voltage $SP^3/SP^2$ ratio through investigation of $SP^3/SP^2$ ratio by the micro-raman analysis. From these results, it can be concluded that the physical properties of DLC films such as residual stress and hardness are increased with increasing the anode voltage. These results can be explained that 3-dimensional cross-links between carbon atoms and Dangling bond are enhanced and the internal compressive stress also increased with increasing the anode voltage. The optimal anode voltage is considered to be around 1400 V in these experimental conditions.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2795-2799
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• 2013

Irradiation of gold nanorods (GNRs) with laser light corresponding to the longitudinal surface plasmon oscillation results in rapid conversion of electromagnetic energy into heat, a phenomenon commonly known as the photothermal effect of GNRs. Herein, we propose a facile strategy for increasing the photothermal conversion efficiency of GNRs by integration to form graphene oxide (GO) nanocomposites. Moreover, conjugation of iron oxide (IO) with the GO-GNR nanohybrid allowed magnetic enrichment at a specific target site and the separated GO-IO-GNR assembly was rapidly heated by laser irradiation. The present GO-IO-GNR nanocomposites hold great promise for application in various biomedical fields, including surface enhanced Raman spectroscopy imaging, photoacoustic tomography imaging, magnetic resonance imaging, and photothermal cancer therapy.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.117-118
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• 2011

초경합금 위에 RF Magnetron Sputter를 이용하여 Ti 중간층을 증착 후 MPECVD(Microwave Plasma Enhanced Chemical Vapor Deposition) 시스템을 이용하여 나노결정 다이아몬드 박막을 증착 하였다. 공정압력, 마이크로웨이브 전력, Ar/$CH_4$ 조성비, 기판온도를 일정하게 놓고 직류 bias의 인가 여부를 변수로 하고 증착시간을 0.5, 1, 2시간으로 변화시켜 박막을 제작하였다. 제작된 시편은 FE-SEM과 AFM을 이용하여 다이아몬드 박막의 표면과 다이아몬드 박막의 표면 거칠기 등을 측정하였고, Raman spectroscopy와 XRD를 이용하여 다이아몬드 결정성을 확인하였다. Automatic Scratch �岵謙�ter를 이용하여 복합박막의 층별 접합력을 측정하였다. 바이어스를 인가하지 않고 다이아몬드 박막을 증착할 경우 증착 시간이 증가할수록 다이아몬드 입자의 평균 크기가 증가하며 입자들이 차지하는 면적이 증가하는 것을 확인하였다. 그러나 1시간이 경과해도 아직 완전한 박막은 형성되지 못하고 2시간 이상 증착 시 완전한 박막을 이루는 것이 확인되었다. 이에 비해서 바이어스 전압을 인가할 경우 1시간 내에 완전한 박막을 이루었다. 표면 거칠기는 바이어스를 인가한 경우가 그렇지 않은 경우에 비해서 조금 높은 것으로 나타났다. 이러한 바이어스 효과는 표면에서의 핵생성 밀도 증가와 재핵생성 속도 증가에 기인하는 것으로 해석된다.