• Korean Journal of Materials Research
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• v.31 no.9
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• pp.496-501
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• 2021

Metal halide perovskite nanocrystals, due to their high absorption coefficient, high diffusion length, and photoluminescence quantum yield, have received significant attention in the fields of optoelectronic applications such as highly efficient photovoltaic cells and narrow-line-width light emitting diodes. Their energy band structure can be controlled via chemical exchange of the halide anion or monovalent cations in the perovskite nanocrystals. Recently, it has been demonstrated that chemical exfoliation of the halide perovskite crystal structure can be achieved by addition of organic ligands such as n-octylamine during the synthetic process. In this study, we systematically investigated the quantum confinement effect of methylammonium lead bromide (CH₃NH₃PbBr₃, MAPbBr₃) nanocrystals by precise control of the crystal thickness via chemical exfoliation using n-octylammonium bromide (OABr). We found that the crystalline thickness consistently decreases with increasing amounts of OABr, which has a larger ionic radius than that of CH₃NH₃⁺ ions. In particular, a significant quantum confinement effect is observed when the amounts of OABr are higher than 60 %, which exhibited a blue-shifted PL emission (~ 100 nm) as well as an increase of energy bandgap (~ 1.53 eV).

• Journal of Plant Biology
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• v.12 no.4
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• pp.9-18
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• 1969

In the previous paper(part III), a certian relationships between the changes of chlorinity and organic acid released from organic material were seemed to be concened to each other in saline soil suspension. Such a possibility had been a cause to take this experiments and this experiment was carried out under the treatment of organic acid crystal, oxalic acid and succinic acid, to the soil suspension(soil: water=20g:40cc) directly. The amount of organic acid treated to the suspension were related to the contents of organic material, as amount of organic acid per gram of organic material(391.76mg). The saline soil suspension were grouped and treated with the acids in order of 78.35mg(Group 1), 391.76mg(Group 2) 979.4mg(Group 3), and 1958.8mg(Group 4), respectively. Treated suspension had been incubated at room temperature and extract from suspension was used for analysis. Followings are summary of this report. 1) Changes of pH in soil suspension appeared a little increase after the treatment of organic acid until 168 hours. 2) Total acidity of soil suspension showed a variation, however, the values of total acidity appeared not to be increased or decreased during the period of experiment. 3) Sugar contents of soil suspension was increased until 168 hours after treatment. These results are similar tendency to the previous paper. 4) Addition of organic acid to soil suspension was confirmed not to be effective method for desalination from saline soil. Chlorinity of group 3 and 4 which were treated with high concentration of organic acid showed a decrease comparing to control group.

• Journal of Integrative Natural Science
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• v.5 no.4
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• pp.253-256
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• 2012

The rugate porous silicons containing multiple photonic band gaps have been generated by applying a composite waveform summed three computer-generated pseudo-sinusoidal current waveforms and exhibit three sharp photonic band gaps in the optical reflectivity spectrum. Generated multiple rugate porous silicons display three rugate peaks corresponding to the each of the sine components varied from 0.42, 0.36, and 0.30 Hz, with a spacing of 0.06 Hz between each sine component. The resulting rugate PSi films have been removed from the silicon substrate by applying an lift-off current and are then made into particles by ultrasono-method in a organic solution. The sensing experiments using these particles for organic solvents such as toluene, hexane, acetone, and methanol have been achieved. Condensing of organic vapors in the pores increases the refractive indices of entire particle which results a red shift in the photonic peaks.

• Textile Coloration and Finishing
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• v.22 no.2
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• pp.123-131
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• 2010

Shape and size controlled synthesis of gold particles has been studied by using wet-chemical method. When ${AuCl_4}^-$ in aqueous $HAuCl_4$ precursor was reduced using $Na_2SO_3$ as a reducing agent, mixtures of spherical, triangular and hexagonal particles were prepared in a few minutes. It was found that the shape selective oxidative etching by ${AuCl_4}^-\;+\;Cl^-$ anions and crystal growth took place simultaneously. As the ${AuCl_4}^-$ and $Cl^-$ concentration increased, yields of large triangular and hexagonal plate type particles increased, while the spherical particles decreased in most cases. Possible etching and growth mechanisms are discussed.

• Journal of Information Display
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• v.9 no.4
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• pp.11-14
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• 2008

A highly efficient organic light-emitting diode (OLED) with an in-cell polarizer made of an imprinted liquid crystalline polymer (LCP) layer doped with dichroic dye molecules is presented. The in-cell polarizer was found to be capable of effectively polarizing the emission light of the OLED and of significantly improving the luminance through the periodic microstructures fabricated using an imprinting method. This type of OLED with an imprinted in-cell polarizer is useful for efficient light source applications in liquid crystal displays (LCDs).

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.928-931
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• 2003

In order to realize full color display, two approaches were used. The first method is the patterning of red, green, and blue emitters using a selective deposition. Another approach is based on a white-emitting diode, from which the three primary colors could be obtained by micro-patterned color filters. White-light-emitting organic light emitting devices (OLEDs) are attracting much attention recently due to potential applications such as backlights in liquid crystal displays (LCDs) or other illumination purposes. In order for the white OLEDs to be used as backlights in LCDs, the light emission should be bright and have Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.33, 0.33). For obtaining white emission from OLEDs, different colours should be mixed with proper balances even though there are a few different methods for mixing colors. In this study, we will report a white organic electroluminescent device using exciton diffusion length concept.

• Journal of the Korean Chemical Society
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• v.59 no.1
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• pp.31-35
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• 2015

Diastereoselective reduction of 2,3-dioxo-4-carboxy-5-(substituted)pyrrolidine 1 by $NaBH_4/AcOH$ and heterogenous hydrogenation were reported. Stereochemical assignment and diastereomeric ratios of the products were determined using $^1H$ NMR and single crystal X-ray analyses. The steric factors of the C-5 substituents of the pyrrolidinone was shown to have an interesting influence on both the yield and diastereoselectivity of the reduced product.

• Elastomers and Composites
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• v.52 no.1
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• pp.9-16
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• 2017

Graphene-$BiOCl/Fe_3O_4$ nanocomposites were synthesized from $BiOCl/Fe_3O_4$ and graphene in an electric furnace operating at $700^{\circ}C$ for 12 h. The nanocomposite surface morphology and crystal structure were characterized by scanning electron microscopy and X-ray diffraction. The produced graphene-$BiOCl/Fe_3O_4$ nanocomposites acted as efficient heterogeneous photocatalysts for the degradation of organic dyes, as confirmed by UV-vis spectrophotometry.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1565-1568
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• 1996

The adsorption and desorption behavior of orgnaic gases were investigated using the resonant frequency and admittance method. Sensitive material were depositied on the quartz crystal microbalence by using Langmuir-Blodgett method. To investigate the response characteristics of organic gases, Resonant frequency-Resonant admittance (F-A) diagram was used. The quantity and quality information about organic gases can be obtained by that diagram. As a results, when the organic gases were adsorpted into sensitive material, the physical property changees of sensitive material were occured.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.31-34
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• 1996

In this paper, the rheological chances in sensitive materials was investigated by using QCA(Quartz Chemical Analyzer). Langmuir-Blodgett method was used to transfer sensitive material to the quartz crystals because of its facility to control that amount, and deposited sensitive material has uniformity to compare with other methods respectively. For the gas sensor using mass loading effect of quartz crystal microbalance, generally the Sauberary equation has been believed to represent the only mass loading effect. But when the organic gas is adsorpted into sensitive material, the rheological changes are occurred with different pattern as to the kinds of gases. Thus, much simpler method to identify the organic or hazard gas will be obtained by the consideration of resonant frequency changes and resonant admittance changes simultaneously.