• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.5
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• pp.432-441
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• 2006

2D fluorescence sensors produce a great deal of spectral data during fermentation processes, which can be analyzed using a variety of statistical techniques. Principal component analysis (PCA) and a self-organizing map (SOM) were used to analyze these 2D fluorescence spectra and to extract useful information from them. PCA resulted in scores and loadings that were visualized in the score-loading plots and used to monitor various fermentation processes with recombinant Escherichia coli and Saccharomyces cerevisiae. The SOM was found to be a useful and interpretative method of classifying the entire gamut of 2D fluorescence spectra and of selecting some significant combinations of excitation and emission wavelengths. The results, including the normalized weights and variances, indicated that the SOM network is capable of being used to interpret the fermentation processes monitored by a 2D fluorescence sensor.

• Bulletin of the Korean Chemical Society
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• v.25 no.6
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• pp.889-894
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• 2004

Polyaddition reactions of 1,1-diethynyl-3-triethylsilyl-1-silacyclopent-3-ene with several organoborane derivatives have afforded the oligomeric materials containing organosilacyclic group and organoboron moiety along the oligomer main chains. All of these materials are soluble in THF as well as chloroform, and their molecular weights are in the range of 1,990/1,190-21,950/7,050 ($M_w/M_n$) with the polydispersity indexes of 1.67-3.43. The prepared oligomers are characterized by several spectroscopic methods such as $^1H,\;^{13}C, \;^{29}Si,\;^{11}B$ NMR and FTIR spectra along with elemental analysis. FTIR spectra of all the oligomers show that the new strong C=C stretching frequencies appear at 1599-1712 $cm^{-1}$, in particular. The UV-vis absorption spectra of the materials in THF solution exhibit the strong absorption bands at the ${\lambda}_{max}$ of 268-275 nm. The oligomeric materials show that the strong excitation peaks appear at the ${\lambda}_{max}$ of 255-279 nm and the strong fluorescence emission bands at the ${\lambda}_{max}$ of 306-370 nm. All the spectroscopic data suggest that the obtained materials contain both the organoboron ${\pi}$-conjugation moiety of C=C-B-C=C and the organosilacyclic group of 3-triethylsilyl-1-silacyclopent-3-ene along the oligomer main chains. The oligomers are thermally stable up to 162-200 $^{\circ}C$ under nitrogen.

• Journal of the Korean institute of surface engineering
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• v.55 no.2
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• pp.96-101
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• 2022

The effects of the growth temperature on the structural, optical, and morphological properties of BaWO₄:Sm³⁺ phosphor thin films were investigated. The BaWO₄:Sm³⁺ thin films were grown on quartz substrates at several growth temperatures by radio-frequency magnetron sputtering. All the thin films crystallized in a tetragonal structure with a main BaWO₄ (112) diffraction peak. The 830 nm-thick BaWO₄:Sm³⁺ thin films grown at 300 ℃ exhibited numerous polygon-shaped particles. The excitation spectra of BaWO₄:Sm³⁺ thin films consisted of a broad excitation band in the 200-270 nm with a maximum at 236 nm due to the O^2--Sm³⁺ charge transfer and two small bands peaked at 402 and 463 nm, respectively. Under 236 nm excitation, the BaWO₄:Sm³⁺ thin films showed an intense red emission peak at 641 nm due to the ⁴G_5/2→⁶H_9/2 transition of Sm³⁺, indicating that the Sm³⁺ ions occupied sites of non-inversion symmetry in the BaWO₄ host lattice. The highest emission intensity was observed for the thin film grown at 300 ℃, with a 51.8% transmittance and 5.09 eV bandgap. The average optical transmittance in the wavelength range of 500-1100 nm was increased from 53.2% at 200 ℃ to 60.8% after growing at 400 ℃. These results suggest that 300 ℃ is the optimum temperature for growing redemitting BaWO₄:Sm³⁺ thin films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.7
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• pp.477-482
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• 2014

$CaNb_2O_6:RE^{3+}$ (RE=Sm or Eu) phosphor powders were prepared with different contents of activator ions by using solid-state reaction method. The X-ray diffraction patterns exhibited that the phosphors synthesized with different activator ions showed an orthorhombic system with a main (131) diffraction peak. The maximum size of the grain particles, determined from the measurement of scanning electron microscopy, was observed at 0.05 mol of $Eu^{3+}$ ions and at 0.01 mol of $Sm^{3+}$. As for the $Eu^{3+}$-doped phosphor powders, the excitation spectra were composed of a broad band peaked at 278 nm and several weak bands in the range of 350~500 nm, and the highest red emission spectrum was observed at 0.15 mol of $Eu^{3+}$ ions. As for the $Sm^{3+}$-activated phosphor powders, three strong emission bands under excitation at 273 nm were observed at 570, 612, and 659 nm, respectively. The intensities of all the emission bands approached maxima for 0.05 mol of $Sm^{3+}$ ions. The optical properties show that the $Eu^{3+}$- or $Sm^{3+}$-doped $CaNb_2O_6$ powders are promising red-orange emitting phosphor powders applicable to full-color photonic devices.

• Journal of the Korean Vacuum Society
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• v.22 no.2
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• pp.79-85
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• 2013

Rare earth ions, either $Eu^{3+}$ or $Dy^{3+}$-doped $CaMoO_4$ phosphors were synthesized by using the solid-state reaction method. The crystalline structure of all the phosphor powders, irrespective of the type and concentration of activator ions, was found to be a tetragonal system with the main diffraction peak at (112) plane. For $Eu^{3+}$-doped $CaMoO_4$ phosphors, the grain particles showed an increasing tendency and the pebble-like patterns with a very homogeneous size distribution in the range of 0.01~0.10 mol of $Eu^{3+}$ ions concentration, and the excitation spectra were composed of a broad band centered at 311 nm and weak multiline peaked in the range of 360~470 nm. The dominant emission spectrum was the strong red emission centered at 618 nm due to the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$ ions. For $Dy^{3+}$-doped $CaMoO_4$ powders, excitation spectra showed a charge transfer band centered at 303 nm and relatively weak bands resulting from the transitions of $Dy^{3+}$ ions and the main yellow emission spectrum was observed at 578 nm, which was assigned to the $^4F_{9/2}{\rightarrow}^7H_{13/2}$ transition of $Dy^{3+}$ ions.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1997-2002
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• 2010

ZnSe and ZnS:Mn nanocrystals were synthesized via the thermal decomposition of their corresponding organometallic precursors in a hot coordinating solvent (TOP/TOPO) mixture. The organic surface capping agents were substituted with EDTA molecules to impart hydrophilic surface properties to the resulting nanocrystals. The optical properties of the water-dispersible nanocrystals were analyzed by UV-visible and room temperature solution photoluminescence (PL) spectroscopy. The powders were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), and confocal laser scanning microscopy (CLSM). The solution PL spectra revealed emission peaks at 390 (ZnSe-EDTA) and 597 (ZnS:Mn-EDTA) nm with PL efficiencies of 4.0 (former) and 2.4% (latter), respectively. Two-photon spectra were obtained by fixing the excitation light source wavelengths at 616 nm (ZnSe-EDTA) and 560 nm (ZnS:Mn-EDTA). The emission peaks appeared at the same positions to that of the PL spectra but with lower peak intensity. In addition, the morphology and sizes of the nanocrystals were estimated from the corresponding HR-TEM images. The measured average particle sizes were 5.4 nm (ZnSe-EDTA) with a standard deviation of 1.2 nm, and 4.7 nm (ZnS:Mn-EDTA) with a standard deviation of 0.8 nm, respectively.

• Advances in nano research
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• v.5 no.3
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• pp.193-201
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• 2017

ZnO, ZnO: Cu, Ga, and ZnO: Cu, Ga, Ag thin films were obtained by oxidization of ZnS and ZnS: Cu, Ga films deposited onto glass substrates by electron-beam evaporation from ZnS and ZnS: Cu, Ga targets and from ZnS: Cu, Ga film additionally doped with Ag by the closed space sublimation technique at atmospheric pressure. The film thickness was about $1{\mu}m$. The oxidation was carried out at $600-650^{\circ}C$ in air or in an atmosphere containing water vapor. Structural characteristics were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). Photoluminescence (PL) spectra of the films were measured at 30-300 K using the excitation wavelengths of 337, 405 and 457.9 nm. As-deposited ZnS and ZnS: Cu, Ga films had cubic structure. The oxidation of the doped films in air or in water vapors led to complete ZnO phase transition. XRD and AFM studies showed that the grain sizes of oxidized films at wet annealing were larger than of the films after dry annealing. As-deposited doped and undoped ZnS thin films did not emit PL. Shape and intensity of the PL emission depended on doping and oxidation conditions. Emission intensity of the films annealed in water vapors was higher than of the films annealed in the air. PL of ZnO: Cu, Ga films excited by 337 nm wavelength exhibits UV (380 nm) and green emission (500 nm). PL spectra at 300 and 30 K excited by 457.9 and 405 nm wavelengths consisted of two bands - the green band at 500 nm and the red band at 650 nm. Location and intensities ratio depended on the preparation conditions.

• Analytical Science and Technology
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• v.27 no.6
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• pp.314-320
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• 2014

$La_{2-x}(MoO_4)_3:Er^{3+}/Yb^{3+}$ particles with doping concentrations of $Er^{3+}$ and $Yb^{3+}$ ($x=Er^{3+}+Yb^{3+}$, $Er^{3+}$=0.05, 0.1, 0.2 and $Yb^{3+}$ = 0.2, 0.45) were successfully prepared by the microwave-modified sol-gel method, and the upconversion photoluminescence properties were investigated. Well-crystallized particles, formed after heat-treatment at $900^{\circ}C$ for 16 h, showed a fine and homogeneous morphology with particle sizes of $2-5{\mu}m$. Under excitation at 980 nm, $La_{1.7}(MoO_4)_3:Er_{0.1}Yb_{0.2}$ and $La_{1.5}(MoO_4)_3:Er_{0.05}Yb_{0.45}$ particles exhibited a strong 525 nm emission band, a weak 550 nm emission band in the green region, and a very weak 655 nm emission band in the red region. The Raman spectra of the doped particles indicated the presence of strong peaks at higher frequencies of 752, 846, 922, 1358 and $1435cm^{-1}$ and lower frequency of $314cm^{-1}$ induced by the disorder of the $[MoO_4]^{2-}$ groups with the incorporation of the $Er^{3+}$ and $Yb^{3+}$ elements into the crystal lattice or by a new phase formation.

• Journal of Sensor Science and Technology
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• v.6 no.1
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• pp.16-23
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• 1997

Bismuth germanate crystals well known as scintillator were grown by Czochralski method. In order to understand a mechanism of radiation resistance in Eu-doped BGO, we measured radiation induced-absorption spectra, excitation spectra, emission spectra and luminescence lifetimes of BGO crystals. We found that the charge transfer state of $Eu^{3+}$ ion is to play a key role to enhance the radiation resistance in BGO crystal. The $^{5}D_{0}$ emission of $Eu^{3+}$ ions that is not suitable for the radiation detectors due to a long decay time was found to be increased with increasing europium concentration. In the BGO crystal doped with 0.1 mole%, the density of radiation induced color centers was reduced about twenty times and the light output of $^{5}D_{0}$ was negligible by comparing to that of BGO.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.643-643
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• 2013

Recently, synthesis of low-dimensional nanostructures is gaining more importance due to their structural properties and growing potential applications. On the other hand, luminescent materials doped with rare earth ions have drawn immense attention. The commercial phosphors are based on many host materials. Among them, tungstates are being currently investigated by many research groups owing to a wide range of applications. Tungstates are formed by different metal cations (e.g., SrWO4, Na2WO4, NiWO4, Cr2WO6, and ZrW2O8) and their structure depends on the size of the metal cation. Tungstates with large bivalent cations (${\gg}0.1\;nm$) have the scheelite structure and the wolframite structure with smaller ions (＜0.1 nm). Strontium tungstate has the scheelite structure which is tetragonal with space group I41/a. The luminescent properties of the tungstate have been extensively explored in application fields such as sensors, detectors, lasers, photoluminiscent devices, photo catalysts, etc. In this work, we synthesized SrWO4 phosphors with different Eu3+ concentrations by using a facile route. The morphology was analyzed by using a field-emission scanning electron microscope, which exhibits the spherical shape. Transmission electron microscope image revealed the spheres composed of nanoparticles. X-ray diffraction patterns confirmed their tetragonal shape. The photoluminescence excitation and emission spectra were analyzed by varying the Eu3+ concentration, which shows a dominant red emission.