• Textile Coloration and Finishing
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• v.11 no.3
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• pp.15-22
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• 1999

This study investigated the mordanting effect of natural mordants such as camellia ash, bean chaff ash and pyrolignite of iron(Iron(II) Acetate) on silk fabrics dyed with green tea extracts. Experimental variables include the conditions of extraction and dyeing, and types of natural mordants. Inorganic ion contents In natural mordants were analysed by Induced Coupled Plasma Atomic Emission Spectrometer. In the ash Al, Fe, Si and Mn were in % unit, Cr and Ni were detected in ppm unit, and in the aqueous extracts of the ash all the metal ions were in ppm unit. On the other hand, fairly high content of Al(2.13% ) in camellia ash extract and Fe(7.91% ) in the aqueous extracts of pyrolignite iron were detected. The absorbance intensity of green tea extracts in UV-Visible spectrum increased with the temperature and time of extraction. The maximum absorption wavelength of the extracts appeared at 272.5nm and 210.5nm. The US values of silk fabrics dyed with green tea extracts were increased with temperature and time of dyeing. Surface color of silk fabric dyed with green tea extracts was 9.1YR, but it was changed from 7.9YR to 7.5YR by camellia ash extract and 7.4YR to 6.4YR by bean chaff ash extract with increase in mordant concentration. Pre-mordanted and post-mordanted fabrics with pyrolignite of iron were changed from 1.4YR to 1.1R and 7.2P to 4.2P, respectively.

• Journal of the Korean institute of surface engineering
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• v.48 no.5
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• pp.211-217
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• 2015

To fabricate white LED having a high color rendering index value, red color phosphor mixed with the green color phosphor together in the blue chip, namely the blue chips with RG phosphors packaging is most favorable for high power white LEDs. In our previous papers, we reported on successful syntheses of $Sr_{2-}$ $Si_5N_8:Eu^{2+}$ and $CaAlSiN_3$ phosphors for red phosphor. In this work, for high power green phosphor, greenemitting ternary nitride $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphor was synthesized in a high frequency induction furnace under $N_2$ gas atmosphere at temperatures up to $1400^{\circ}C$ using $EuF_3$ as a raw material for $Eu^{2+}$ dopant. The effects of molar ratio of component and experimental conditions on luminescence property of prepared phosphors have been investigated. The structure and luminescence properties of prepared $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphors were investigated by XRD and photoluminescence spectroscopy. The excitation spectra of $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphors indicated broad excitation wavelength range of 250 - 500 nm, namely from UV to blue region with distinct enhanced emission spectrum peaking at ${\approx}530nm$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.167-170
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• 2004

The stochiometric mix of evaporating materials for the $CuGaT_2$ single crystal thin films was prepared from horizontal furnance. Using extrapolation method of X-ray diffraction patterns for the $CuGaTe_2$ polycrystal, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were 6.025 ${\AA}$ and 11.931 ${\AA}$, respectively. To obtain the single crystal thin films, $CuGaTe_2$ mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $670^{\circ}C$ and $410^{\circ}C$ respectively, and the thickness of the single crystal thin films is $2.1{\mu}m$. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the $CuGaTe_2$ single crystal thin film, we have found that the values of spin orbit coupling ${\Delta}s.o$ and the crystal field splitting ${\Delta}cr$ were $0.079\underline{1}eV$ and $0.246\underline{3}eV$ at 10 K, respectively. From the PL spectra at 10K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be $0.047\underline{0}eV$ and the dissipation energy of the donor-bound exciton and acceptor-bound exciton to be $0.049\underline{0}eV$, $0.055\underline{8}eV$, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.71-74
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• 2019

In this study, we fabricated two standard and inverted quantum dot light emitting diodes (QLEDs) using $TiO_2$ nanoparticles (NPs) with lower electron mobility than ZnO NPs as inorganic electron transport layer to suppress electron injection into the emitting layer. Current density was much higher for the inverted QLEDs than the standard ones. The inverted QLEDs were brighter, but showed low current efficiency due to the high current density. In addition, as the current density was higher, the driving voltage was higher, and the red shift was confirmed in the emission wavelength spectrum. The low current density in the standard structured devices showed that the possibility that $TiO_2$ NPs could suppress the electron injection in the QLEDs.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.39-45
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• 2013

Basically, in order to apply solid propellant as ignition source to high energy metal particle combustion system, we analyzed combustion characteristics of the HTPB/AP/Al, HTPE/AP/Al propellants by using a strand burner. The propellants were tested in a high-pressure windowed strand burner, which was pressurized up to 300 psia with pure argon gas. Strand burner was visualized with two quartz windows and ignition was accomplished by a 10 W $CO_2$ laser. The burning rate of propellant was measured with high-speed camera method for frame analysis and photodiode method for combustion time analysis. Emission spectrum was measured with spectrometer at 300 nm ~ 800 nm and 1500 nm ~ 5000 nm and then we analyzed species during propellant combustion.

• Journal of the Optical Society of Korea
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• v.18 no.3
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• pp.256-260
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• 2014

Columnar-structured cesium iodide (CsI) scintillators doped with thallium (Tl) are frequently used as x-ray converters in medical and industrial imaging. In this study we investigated the imaging characteristics of CsI:Tl films with various reflective layers-aluminum (Al), chromium (Cr), and titanium dioxide ($TiO_2$) powder-coated on glass substrates. We used two effusion-cell sources in a thermal evaporator system to fabricate CsI:Tl films on substrates. The scintillators were observed via scanning electron microscopy (SEM), and scintillation characteristics were evaluated on the basis of the emission spectrum, light output, light response to x-ray dose, modulation transfer function (MTF), and x-ray images. Compared to control films without a reflective layer, CsI:Tl films with reflective layers showed better sensitivity and light collection efficiency, and the film with a $TiO_2$ reflective layer showed the best properties.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.1
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• pp.86-92
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• 2019

Although perylene bisimide derivatives have advantages such as excellent thermal stability and high luminance efficiency, they have poor solubility characteristics in organic solvents. In this research, in order to improve the solubility characteristics, we prepared perylene bisimide derivatives (1C) and (2C) with swallow-tail substituted imide, which is known to lead to excellent solubility. The structures and properties of swallow-tail perylene bisimide (1C) and (2C) were analyzed by $^1H-NMR$, FT-IR, UV/Vis spectroscopy, and thermogravimetric analysis (TGA). The maximum absorption wavelengths of (1C) and (2C) in the UV/Vis spectrum were 558 nm and 556 nm, respectively, and the maximum emission wavelengths were 602 nm and 600 nm, respectively. In the TGA, (1C) demonstrated good thermal stability with less than 5 wt% weight loss up to $242^{\circ}C$. In the solubility test, (1C) and (2C) exhibited solubilities of more than 5 wt% in chloroform, ethyl acetate, and dimethylformamide, but not in methanol. When the compounds (1C) and (2C) were mixed with PMMA (polymethyl methacrylate), thin films showed peaks at 679 nm and 677 nm, respectively, in the photoluminescence spectra. (1C) was found to be a possible candidate as red organic phosphor for hybrid LEDs.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.585-590
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• 2020

Successful early diagnosis of cancer diseases such as lung, prostate, liver and adrenocortical carcinoma is a key step in determining the cost of treatment, survival rate, and cure rate. Most of current cancer diagnosis systems including biopsy, computed tomography (CT), positron emission tomography (PET)-CT, magnetic resonance imaging (MRI), ultrasonography, etc., require expensive and complicated equipment with highly trained human resources. Global medical and scientific communities have thus made numerous efforts on developing effective but rapid disease management system via introducing a wide spectrum of point-of-care medical diagnosis devices. Among them, a lateral flow immunoassay strip technique has gained a great attention due to many advantages such as cost-effectiveness, short inspection time, and user friendly accessibility. In this mini-review, we will highlight recent research trend on the development of colorimetry based LFIA strips for cancer diagnosis and discuss the future research direction and potential applications.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.17-17
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• 1998

Synchrotron radiation is produced when charged particles moving with relativistic velocities a are accelerated - for example, deflected by the bending magnets which guide the electron or p positrons in circular accelerators or storage rings. By using special focusing magnetic lattices i in the particle accelerators it is possible to make the dimensions of the particle beam very small with a hi맹 charge density which results in a light source with high b디lIiance. Synchrotron light h has important properties which make it ideal for a wide range of investigations in surface s science. The fact that the spectrum of electromagnetic radiation emitted in a bending magnet e extends in a continuum from the 얹r infra red region to hard x-rays means that it is id않I for a v variety of spectroscopic studies. Since there are no convenient lasers, or other really bright l light sources, in the vacuum ultraviolet and soft x-ray re.밍ons the development of synchrotron r radiation has enabled enormous advances to be made in this di펌C비t spectr따 re밍on. P Polarization-dependent measurements, for ex없nple ellipsometry or circular dichroism studies a are possible because the radiation has a well-defined polarization - linear in the plane of orbit w with additional right-circular, or left-circular, components for emission an생es above, or below, t the horizontal, respectively. Since the synchrotron light is emitted from a bunch of charge c circulating in a ring the light is emitted with a well-defined time structure with a short flash of l light every time a bunch passes an exit port. The time structure depends on the size of the ring a and the number and sequence of filling of the bunches. A pulsed light source enables time¬r resolved studies to be performed which provide direct information on the lifetimes and decay m modes of excited states and in addition opens up the possibility of using time of flight t techniques for spectroscopic studies. The fact that synchrotron radiation is produced in a clean u ultrahi야 vacuum environment is of gr않t importance for surce science studies. The current t비rd generation synchrotron light sources provide exceptionally high baliance and stability a and open up possibilities for experiments which would have been inconceivable only a short time ago.

• Korean Journal of Materials Research
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• v.32 no.2
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• pp.57-65
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• 2022

Herein a rich, Se-nanoparticle modified Mo-W₁₈O₄₉ nanocomposite as efficient hydrogen evolution reaction catalyst is reported via hydrothermal synthesized process. In this work, Na₂SeSO₃ solution and selenium powder are used as Se precursor material. The structure and composition of the nanocomposites are characterized by X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), EDX spectrum analysis and the corresponding element mapping. The improved electrochemical properties are studied by current density, and EIS analysis. The as-prepared Se modified Mo-W₁₈O₄₉ synthesized via Na₂SeSO₃ is investigated by FE-SEM analysis and found to exhibit spherical particles combined with nanosheets. This special morphology effectively improves the charge separation and transfer efficiency, resulting in enhanced photoelectric behavior compared with that of pure Mo-W₁₈O₄₉. The nanomaterial obtained via Na₂SeSO₃ solution demonstrates a high HER activity and low overpotential of -0.34 V, allowing it to deliver a current density of 10 mA cm^-2.