• Korean Journal of Materials Research
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• v.31 no.10
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• pp.582-585
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• 2021

Y₂O₃:Eu_x (x = 0.005, 0.01, 0.02, 0.03, 0.05, 0.1 mol) phosphors are synthesized with different concentrations of Eu³⁺ ions by solvothermal method. The crystal structure, surface and optical properties of the Eu doped Y₂O₃ phosphors are investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) and photoluminescence excitation (PLE) analyses. From X-ray diffraction (XRD) results, the crystal structure of the Eu doped Y₂O₃ phosphor is found to be cubic. The maximum emission spectra of the Eu doped Y₂O₃ phosphors are observed at 0.05 mol Eu³⁺ concentration. The photoluminescence of 615 nm in the Eu doped Y₂O₃ phosphors is associated with ⁵D₀ → ⁷F₂ transition of Eu³⁺ ions. The decrease in emission intensity of 0.1 mol Eu doped Y₂O₃ is interpreted by concentration quenching. The International Commission on Illumination (CIE) coordinates of 0.05 mol Eu doped Y₂O₃ phosphor are X = 0.6547, Y = 0.3374.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.5
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• pp.494-499
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• 2023

In this paper, in order to apply the CF (color filter) type of the micro light emitting device (Micro LED) display method, a study on the manufacturing process of red and green phosphor inks for the inkjet process was conducted. The blue light-emitting KSF and LuAG phosphors were respectively used to control the phosphor particle size to about 1㎛, and a phosphor ink was prepared by synthesizing with a low-viscosity solution (IPA/Eg). A chemical dispersion method was applied to selectively control the dispersion characteristics in the manufacture of phosphor inks, and in particular, phosphor inks with a dispersant applied a dispersant secured stable dispersion characteristic compared to phosphor inks without a dispersion process. Therefore, it seems possible to manufacture CF for Micro LED through an inkjet process capable of controlling the dispersion characteristics of phosphor ink.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.6
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• pp.253-257
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• 2008

To enhance the luminescence properties, the red phosphor composed of $(Y,\;Zn)_2O_3$:$Eu^{3+}$ as doping concentration of Zn ion is synthesized at $1200^{\circ}C$ for 6 hrs in air atmosphere by conventional solid reaction method. As a result of the red phosphor $(Y,\;Zn)_2O_3$:$Eu^{3+}$ is measured X-ray diffraction (XRD), The main peak is nearly corresponded to the same as JCPDS card (No. 41-1105). When the doping concentration of Zn ion is more than 5 mol%, However, the ZnO peak is showed by XRD analysis. Therefore, when the doping concentration of Zn ion is less than 5 mol%, the Zn ion is well mixed in $Y_2O_3$ structure without the impurity phases. The photoluminescence (PL) properties is shown as this phosphor is excited in 254 nm region and the highest emission spectra of $(Y,\;Zn)_2O_3$:$Eu^{3+}$ has shown in 612 nm region because of a typical energy transition ($^5D_0{\rightarrow}^7F_2$) of $Eu^{3+}$ ion. As the doping concentration of Zn ion is more than 10 mol%, the emission peak is suddenly decreased. when the highest emission peak as doping concentration of Zn ion is shown, the composition of this phosphor is $(Y_{0.95},\;Zn_{0.05})_2O_3$:$Eu^{3+}_{0.075}$ and the particle size analyzed by FE-SEM is confirmed from 0.4 to $3{\mu}m$.

• Journal of the Korean Ceramic Society
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• v.38 no.9
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• pp.806-810
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• 2001

$La_{2/3}TiO_3$, $La_2Ti_2O_7$ are used in various parts by dielectric properties. The purpose of the present study is to understand the photoluminescence properties of $Al^{3+}\;and\;Pr^{3+}$ doped perovskite-type $La_{2/3}TiO_3$ and pyrochlore-type $La_2Ti_2O_7$ phosphor, which characterized by the red emission $(^1D_2{\rightarrow}^3H_4)\;of\;Pr^{3+}$ of $Pr^{3+}$ ion. The explanation for the energy transfer and the corresponding critical distance were proposed on the role of Al^3+ ions as energy transfer mediates in perovskite-type $La_{2/3}TiO_3$:Pr phosphor. In order to clarify the distinction of photoluminescence propoerties between the perovskite-type $La_{2/3}TiO_3$ and the pyrochlore $La_2Ti_2O_7$, the trap-involved process and the charge transfer band have been investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.9
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• pp.577-582
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• 2017

The white light of a hybrid LED is obtained by using red and green organic fluorescent layers made of polymethylmethacrylate (PMMA) films, which function as color down-conversion layers of blue light-emitting diodes. In this research, we studied the fluorescence properties of a red organic fluorophore, employing perylene bisimide derivatives applicable to hybrid LEDs. The solubility, thermal stability, and luminous efficiency are important characteristics of organic fluorophores for use in hybrid LEDs. The perylene fluorescent compounds (1A and 1B) were prepared by the reaction of 4-bromophenol and 4-iodophenol with N,N'-bis(4-bromo-2,6-diisopropylphenyl)-1, 6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxyl diimide (1) in the presence of dimethyl formaldehyde (DMF) at $70^{\circ}C$. The synthesized derivatives were characterized by using $^1H-NMR$, FT-IR, UV/Vis absorption and PL spectra, and TGA analysis. Compounds 1A and 1B showed absorption and emission at 570 nm and 604 nm in the UV/Vis spectrum. We also documented favorable solubility and thermal stability characteristics of the perylene fluorophores in our work. Perylene fluorophore 1, with the 4-bromophenol substituent 1A, exhibited particularly good thermal stability and solubility in organic solvents.

• Polymer(Korea)
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• v.37 no.1
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• pp.94-99
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• 2013

Polydiacetylene (PDA) is made by photopolymerization of self-assembled diacetylene monomers. If diacetylene monomers are arranged systematically and close enough with distance of atoms, 1,4-addition polymerization will occur by the irradiation of 254 nm ultraviolet rays and then PDA will have alternated ene-yne polymer chains at the main structure. Aqueous solutions of diffused PDA is tinged with blue which shows ${\lambda}_{max}$ 640 nm. Visible color changes from blue to red occurs in response to a variety of environmental perturbations, such as temperature, pH, and ligand-receptor interactions. In this study, we synthesized cationic peptides - PCDA(10,12-pentacosadyinoic acid) liposome using a solid phase peptide synthesis (SPPS) method and prepared liposome solutions at various molar ratios using MPEG-PCDA. When mammalian cells were treated with the liposomes, high transfection efficiency and low toxicity were observed.

• Journal of Sensor Science and Technology
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• v.8 no.1
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• pp.10-15
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• 1999

White emission thin film electroluminescent device was fabricated using ZnS for phosphor layer and BST ferroelectric thin film for insulating layer. For fabrication conditions of BST thin film, stoichiometry of target was $Ba_{0.5}Sr_{0.5}TiO_3$, substrate temperature was $400^{\circ}C$, working pressure was 30 mTorr, and A:$O_2$ ratio was 9:1. At this time, dielectric constant was 209 at 1kHz frequency. For phosphor layer ZnS:Mn, ZnS:Tb, and ZnS:Ag were used. Mixing rates of activators were respectively 0.8, 0.8, and 1 wt%. Total thickness of phosphor tapers was 500 nm, thickness of lower insulating layer was 200 nm, and thickness of upper insulating layer was 400 nm. In this conditions, luminescence threshold voltage of thin film electroluminescent device was $95\;V_{rms}$, maximum brightness was $3,000\;cd/m^2$ at $150\;V_{rms}$. Luminescence spectrum peak was observed at region of blue(450 nm), green(550 nm), and red(600 nm).

• Journal of Mushroom
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• v.15 no.4
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• pp.259-263
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• 2017

In this study, we investigated the morphological characteristics and antioxidant ability of mushroom cultivar Lentinula edodes 'Nongjingo' fruiting bodies after exposure to various light conditions. Color differences between mushrooms treated with mixtures of LED light revealed that mushrooms displayed lighter color shades when compared to the control group (fluorescent light treated mushrooms). Redness increased and yellowness decreased after exposure to all treatments other than the fluorescent control. Measurement of growth characteristics of 'Nongjingo' fruiting bodies showed increases after exposure to all mixed LED treatments. In addition, the uniformity of fruiting bodies was higher when using LED light compared to fluorescent light. The measurement of stem diameters did not show a significant difference between the treatments, however, diameters were slightly larger with exposure to white-green LED. Moreover, stem length was longer in the mixed LED treatments when compared to those exposed to fluorescent light. Examination of the ratio of stem diameter to stem length revealed that the diameter of the stem was greater than the length. The antioxidant activity of water extracts made from Nongjingo fruiting bodies grown under mixed LED conditions was compared to those from mushrooms grown under fluorescence light conditions. The highest antioxidant activity was observed from mushrooms treated with white LED; however, no significant difference was found between mushrooms exposed to white-green LED compared to white-blue LED. The treatment showed higher antioxidant ability than vitamin C. Our results confirm that treatment of white LED and white-blue LED affects the growth and antioxidant ability of Nongjingo mushroom fruiting bodies.

• Korean Journal of Materials Research
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• v.22 no.3
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• pp.145-149
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• 2012

Red phosphors of $Gd_{1-x}Al_3(BO_3)_4:{Eu_x}^{3+}$ were synthesized by using the solid-state reaction method. The phase structure and morphology of the phosphors were measured using X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM), respectively. The optical properties of $GdAl_3(BO_3)_4:Eu^{3+}$ phosphors with concentrations of $Eu^{3+}$ ions of 0, 0.05, 0.10, 0.15, and 0.20 mol were investigated at room temperature. The crystals were hexagonal with a rhombohedral lattice. The excitation spectra of all the phosphors, irrespective of the $Eu^{3+}$ concentrations, were composed of a broad band centered at 265 nm and a narrow band having peak at 274 nm. As for the emission spectra, the peak wavelength was 613 nm under a 274 nm ultraviolet excitation. The intensity ratio of the red emission transition ($^5D_0{\rightarrow}^7F_2$) to orange ($^5D_0{\rightarrow}^7F_1$) shows that the $Eu^{3+}$ ions occupy sites of no inversion symmetry in the host. In conclusion, the optimum doping concentration of $Eu^{3+}$ ions for preparing $GdAl_3(BO_3)_4:Eu^{3+}$ phosphors was found to be 0.15 mol.

• Journal of Powder Materials
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• v.27 no.2
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• pp.146-153
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• 2020

The co-doping effect of aliovalent metal ions such as Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, and Zn²⁺ on the photoluminescence of the Y₂O₃:Eu³⁺ red phosphor, prepared by spray pyrolysis, is analyzed. Mg²⁺ metal doping is found to be helpful for enhancing the luminescence of Y₂O₃:Eu³⁺. When comparing the luminescence intensity at the optimum doping level of each Mg²⁺ ion, the emission enhancement shows the order of Zn²⁺ ≈ Ba²⁺ > Ca²⁺ > Sr³⁺ > Mg²⁺. The highest emission occurs when doping approximately 1.3% Zn²⁺, which is approximately 127% of the luminescence intensity of pure Y₂O₃:Eu³⁺. The highest emission was about 127% of the luminescence intensity of pure Y₂O₃:Eu³⁺ when doping about 1.3% Zn²⁺. It is determined that the reason (Y, M)₂O₃:Eu³⁺ has improved luminescence compared to that of Y₂O₃:Eu³⁺ is because the crystallinity of the matrix is improved and the non-luminous defects are reduced, even though local lattice strain is formed by the doping of aliovalent metal. Further improvement of the luminescence is achieved while reducing the particle size by using Li₂CO₃ as a flux with organic additives.