• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.661-667
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• 2008

In this study, cholesteric liquid crystal (CLC) was synthesized and applied as a polarizing component on the optical film of back light units (BLU) for LCDs. After mixing CLC with nematic liquid crystal, this mixture was fulfilled in the module consisting of two films and then its amplifying efficiency and polarizing ability for a planarly emitted light were examined to apply as a BLU polarizer film for increasing the brightness of light. The properties of CLC compound were tested by UV/Visible spectroscopy and polarizing optical microscopy (POM). Flexible spacer was made by linear carboxylic acid group of cholesteric derivatives between cholesterol mesogen units for one-axis orientation in each layer. The CLC containing film could be used as a module to increase the ability of polarization and to enhance brightness of BLU and to widen wavelength range by stacking the films.

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.266-273
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• 2013

Phthalocyanine (Pc), porphyrin, subphthalocyanine, and perylene compounds can be applicable to the fields of optical storage media, organic solar cell, LCD, PDP, semiconductor, and counterfeit money detection etc. In this study, phthalocyanine hybrid derivatives were synthesized by cross-linking perylene, subphthalocyanine, or porphyrin to the main frame of Pc. Absorbtion band of two different wavelengths appeared simultaneously in the phthalocyanine hybrid derivatives. Compared to phthalocyanine, the solubility was enhanced and the degree of Q-band shift was changed according to the kind of substitute compounds. The chemical and optical properties of samples were analyzed using FT-IR, $^1H-NMR$, and UV-Vis spectroscopic techniques.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.564-569
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• 2010

Highly anti-reflective optical property has been focussed in the field of thin film and display because of increasing demands to the high transparency and clearness of optical component. In this study, to obtain anti-reflective property, the formation of aluminium oxide with nanoscaled flowerlike frame structure was introduced as oxide material monolayer on the substrate by hydrothermal synthesis through sol-gel method. The properties of coating layer were measured by the means of UV-Vis spectroscopy, FT-IR spectroscopy, XRD, and FE-SEM. The morphology of coating layer in alumina-sol coated samples was controlled by hydrothermal temperature and time with aid of ultrasound. It was found that high transparency and anti-reflective optical properties were obtained the formation of flowerlike nanoframe structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.330-331
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• 2011

희토류 이온이 첨가된 형광체는 조명, 정보 디스플레이, 태양 에너지 변환 소자에 응용 가능하기 때문에 상당한 주목을 받고 있다. 특히, 결정 입자의 형상과 크기는 산업체 응용에 있어서 중요한 변수 중의 하나이다. 구형의 형광체 입자는 형광층의 광학 및 기하학적 구조를 최적화 시킬 수 있고, 결정 입자의 크기는 양질의 코팅을 위해 필요한 결정 입자의 양에 영향을 미친다. 본 연구에서는, $YVO_4$ 모체 결정에 Eu 이온의 농도를 선택적으로 주입하여 발광 효율이 높은 적색 형광체를 합성하고자 한다. 형광체 분말 시료는 활성체인 Eu의 함량을 0.00, 0.05, 0.10, 0.15, 0.20 mol로 변화시키면서 고상 반응법을 사용하여 합성하였다. 볼밀링 작업을 수행한 후에, 60$^{\circ}C$에서 20시간 건조하였고, 잘게 갈아서 체로 걸러낸 다음에 세라믹 도가니에 넣고 전기로에서 서서히 온도를 승온시켜 500$^{\circ}C$에서 10시간 동안 하소를 실시한 후에 1,100$^{\circ}C$에서 5시간 동안 소결하였다. Eu 이온의 함량비를 변화시켜 합성한 $YVO_4$ : Eu 형광체 분말 시료의 발광 세기의 변화, 결정 구조와 표면 형상을 각각 PL과 PLE, XRD, FE-SEM 장치를 사용하여 측정한 결과들을 종합해 볼 때, Eu 이온의 비가 0.15 mol일때 발광 세기가 최대값을 나타냄을 알 수 있었으며, 더욱 Eu의 함량을 증가시키자 농도 억제 현상에 의하여 발광 세기는 급격히 감소함을 보였다. SEM으로 촬영한 결정 입자의 형상의 경우에, Eu 이온의 함량비가 증가함에 따라 결정 입자들이 더욱 조밀하게 구형에 가까운 형상을 나타냄을 관측할 수 있었다(Fig. 1). 형광체 분말의 형광 스펙트럼의 경우에, 619 nm에 주 피크를 갖는 적색 형광 스펙트럼들이 관측되었으며, Eu 이온의 함량비에 따라 형광 세기는 상당한 의존성을 나타내었다(Fig. 2). Eu 함량에 따른 결정입자의 크기, 형광 세기와 회절 피크의 반치폭 사이의 상관 관계를 제시하고자 한다.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.1
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• pp.33-37
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• 2013

In this research, we investigated the effect of mole concentration of precursor on morphological, structural and optical properties of ZnO nanorods. ZnO nanorods were hydrothermally grown on c-plane sapphire substrates in aqueous solution which contains zinc nitrate hexahydrate and hexamethylenetetramine at 90oC in the precursor range of 0.01 M to 0.025 M. With the increase of mole concentration, length and diameter of ZnO nanorods increased. In all the conditions, the growth direction of rods was longitudinally c-axis direction. From the strong emission peak at 380 nm of PL spectra at room temperature, we could confirm that the crystal quality of ZnO nanorods is good to emit radiative recombination spectra.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.175-180
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• 2016

The fluorine-containing modified polyurea was synthesized using the PTPE-diol to improve the ozone-resistance. Three types (PFDIA-10C, PFDIA-20C, PFDIA-30C) of the modified polyurea containing the fluorine content from 10 wt% to 30 wt% were prepared. After ozone treatment on the prepared films, the weight loss of film was investigated and analyzed the film properties such as hardness, wear resistance, tensile stress, elongation, etc. Also, the film surfaces were observed by the optical microscopy after ozone-resistance tests at 10 ppm for 336 h. It was shown that the defects such as the cracking, the bleaching and the mass loss were reduced and the ozone-resistance of films were improved when the contents of PFPE-diol are more than 20 wt%. It was found that the intensity of O-H peak in PFDIA compounds confirmed by FT-IR was decreased as fluorine contents were increasing.

• Polymer(Korea)
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• v.34 no.4
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• pp.376-380
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• 2010

Donor-$\pi$-acceptor (D-$\pi$-A) type chromophore-based polymers were newly synthesized. These polymers exhibited absorption peak due to intramolecular charge transfer (ICT) in a visible range as well as absorption peak due to carbonyl group in both solution and film state by measuring UV visible spectra. The addition of $Eu^{3+}$ ion into the polymers induced red-shift in absorption due to ICT and the color changes from yellow to red in the solution and film were observed by naked eyes. The contents of crosslinking agent influenced the features and solubility of the polymers. In addition, the contents of crosslinking agent and the $Eu^{3+}$ ion addition improved film-forming ability.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.577-581
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• 2011

Silicon nanoparticles have attracted a great deal of scientific interests due to its intense photoluminescence in the visible spectral region and its potential applications in biological fluorescence maker, RGB (red, green, blue) display, photonics and photovoltaics etc. Practical applications making use of optical and physicochemical properties of Si nanoparticles requires an efficient synthetic method which allows easy modulation of their size, size distribution as well as surface functionalities etc. In this study, a one-pot solution reduction scheme is attempted to prepare alkyl-terminated Si nanoparticles (<10 nm) with Si precursors, (Octyl)$SiCl_3$ or mixture of (Octyl)$SiCl_3$ and $SiCl_4$, containing alkyl-groups using Na(naphthalide) as reducing agent. The surface capping of Si nanoparticles with octyl-groups as well as Si nanoparticle formation was achieved in one-pot reaction. The hexane soluble Si nanoparticles with octyl-termination were in the range of 2-10 nm by TEM and some oxide groups (Si-O-Si) was present on the surface by EDS/FTIR analyses. The optical properties of Si nanoparticles measured by UV-vis and PL evidenced that photoluminescent Si nanoparticles with alkyl-termination was successfully synthesized by solution reduction of alkyl-containing Si precursors in one-pot reaction.

• Journal of the Korean Chemical Society
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• v.47 no.4
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• pp.315-324
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• 2003

In this study, a new method is presented to produce stable hydrophobic metal alloy nanocluster in chloroform solution including surfactant NaAOT(sodium bis(2-ethylhexyl)-sulfosuccinate) via the chemical reduction of metal salt $(HAuCl_4,\AgNO_3,\Cu(NO_3)_2)$ by sodium borohydride. For the alloy nanocluster, several samples were prepared by changing the molar ratio of Au/Cu, Au/Ag alloy nanocluster, 3:1, 1:1, 1:3. The alloy nanoclusters were characterized by UV-Visible spectrophotometer, TEM(Transmission Electron Microscope), and XPS(X-ray Photoelectron Spectrometer). With the change of the mole ratio of the alloy component, the wavelengths of the surface plasmon absorption shift linearly from 520 nm of the pure Au nanocluster to 570 nm of the pure Cu nanocluster for Au/Cu alloy nanoclusters and from 405 nm to 520 nm for Au/Ag alloy nanoclusters. The chemical shifts of the Au4f, Ag3d, Cu2p XPS peaks were observed with changing the molar ratio of the alloy element. The alloy nanoclusters in chloroform solution were made uniformly in size and colloidally stable for long periods of time. These results indicate that the method here is a very effective method for synthesizing hydrophobic alloy nanoclusters with uniform or nearly uniform particle size distribution.

• Journal of the Korean Association of Geographic Information Studies
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• v.5 no.2
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• pp.16-24
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• 2002

Classification of the land cover characteristics is a major application of remote sensing. The goal of this study is to propose an optimal classification process for electro-optical camera(EOC) of Korea Multi-Purpose Satellite(KOMPSAT). The study was carried out on Landsat TM, high spectral resolution image and KOMPSAT EOC, high spatial resolution image of Miho river basin, Korea. The study was conducted in two stages: one was image fusion of TM and EOC to gain high spectral and spatial resolution image, the other was land cover classification on fused image. Four fusion techniques were applied and compared for its topographic interpretation such as IHS, HPF, CN and wavelet transform. The fused images were classified by radial basis function neural network(RBF-NN) and artificial neural network(ANN) classification model. The proposed RBF-NN was validated for the study area and the optimal model structure and parameter were respectively identified for different input band combinations. The results of the study propose an optimal classification process of KOMPSAT EOC to improve the thematic mapping and extraction of environmental information.