• Bulletin of the Korean Chemical Society
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• v.25 no.9
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• pp.1309-1313
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• 2004

A simple and reliable method has been developed to selectively separate and concentrate trace amounts of thallium ion from real samples for the subsequent measurement by flame atomic absorption spectrometry (FAAS). Thallium ions are absorbed quantitatively during passage of aqueous real samples through an octadecyl bonded silica membrane disk modified by 4-(4-Chloro-phenylazo)-2-[(4-hydroxy-phenylamino)-methyl]-phenol. The retained $Tl^+$ ions are then stripped from the disk quantitatively with a minimal amount of thiosulfate solution as eluent. The proposed method permitted large enrichment factors of about 130 and higher. The relative standard deviation for ten replicate extraction of thallium from 1 L samples containing 5 ${\mu}g$ thallium is 1.2%. The break through volume for 5 ${\mu}g$ thallium is 1000 mL. The limit of detection of the proposed method is 11.2 ng of $Tl^+$ per 1000 mL. The effects of various cationic interferences on the recovery of thallium in binary mixtures were studied. The method was applied to the recovery of $Tl^+$ ions from natural water and human hair samples.

• Applied Science and Convergence Technology
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• v.26 no.6
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• pp.174-178
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• 2017

The reactions of thermal hydrogen atoms H(g) with the Ge(100) surface were examined with temperature-programmed desorption (TPD) mass spectrometry. Concomitant $H_2$ and $CH_4$ TPD spectra taken from the H(g)-irradiated Ge(100) surface were distinctly different for low and high H(g) doses/substrate temperatures. Reactions suggested by our data are: (1) adsorbed mono(${\beta}_1$)-/di-hydride(${\beta}_2$)-H(a) formation; (2) H(a)-by-H(g) abstraction; (3) $GeH_3$(a)-by-H(g) abstraction (Ge etching); and (4) hydrogenated amorphous germanium a-Ge:H formation. While all these reactions occur, albeit at higher temperatures, also on Si(100), H(g) absorption by Ge(100) was not detected. This is in contrast to Si(100) which absorbed H(g) readily once the surface roughened on the atomic scale. While this result is rather against expectation from its weaker and longer Ge-Ge bond as well as a larger lattice constant, we attribute the absence of direct H(g) absorption to insufficient atomic-scale surface roughening and to highly efficient subsurface hydrogenation at moderate (>300 K) and low (${\leq}300K$) temperatures, respectively.

• Journal of the Korean Solar Energy Society
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• v.31 no.4
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• pp.48-56
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• 2011

Black cobalt solar selective coatings were prepared by thermal oxidation of electroplated cobalt metal on copper and nickel substrates. The optical properties and structure of the black cobalt selective coating for solar energy utilizations were characterized by glow discharge spectrometry (GDS), ultraviolet-visible-near infrared (UV-VIS-NIR) spectrometer, atom force microscopy(AFM) and X-ray photoelectron spectroscopy(XPS). The optical properties of optimum black cobalt selective coating prepared on copper substrate were a solar absorptance of 0.82 and a thermal emittance of 0.01. From the GDS depth profile analysis of these coatings, the concentration of cobalt particles near the interface was higher than at the surface, but oxygen concentration at the surface was higher than at the interface. These results suggest that the selective absorption was dominated by this chemical composition variation in the coating. The surface of this film exhibited morphology with root-mean-square(rms) roughness of about 144.3nm. XPS measurements data showed that several phases of Co coexist($Co_3O_4$,CoO) in the film.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.273-281
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• 1992

A new sputtering chamber, as Atomsource, for atomic absorption measurements was designed and built to have maximum ground state atoms in view and minimum emission. The high velocity gas jets not only change the visual and electrical characteristics of the discharge, but also increase the amount of material atomized, as is apparent from the craters that are produced in the sample where the jets strike the surface. The use of gas jets in a sputtering cell makes this a direct sampling method practical for atomic absorption spectrometry. The factors influencing absorption sensitivity and reproducibility have been investigated for the newly developed atomizer.

• Journal of Ginseng Research
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• v.39 no.2
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• pp.183-187
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• 2015

Background: Gut microflora play a crucial role in the biotransformation of ginsenosides to compound K (CK), which may affect the pharmacological effects of ginseng. Prebiotics, such as NUTRIOSE, could enhance the formation and consequent absorption of CK through the modulation of gut microbial metabolic activities. In this study, the effect of a prebiotic fiber (NUTRIOSE) on the pharmacokinetics of ginsenoside CK, a bioactive metabolite of ginsenosides, and its mechanism of action were investigated. Methods: Male Sprague-Dawley rats were given control or NUTRIOSE-containing diets (control diet + NUTRIOSE) for 2 wk, and ginseng extract or vehicle was then orally administered. Blood samples were collected to investigate the pharmacokinetics of CK using liquid chromatography-tandem mass spectrometry. Fecal activities that metabolize ginsenoside Rb1 to CK were assayed with fecal specimens or bacteria cultures. Results: When ginseng extract was orally administered to rats fed with 2.5%, 5%, or 10% NUTRIOSE containing diets, the maximum plasma concentration ($C_{max}$) and area under the plasma concentration-time curve values of CK significantly increased in a NUTRIOSE content-dependent manner. NUTRIOSE intake increased glycosidase activity and CK formation in rat intestinal contents. The CK-forming activities of intestinal microbiota cultured in vitro were significantly induced by NUTRIOSE. Conclusion: These results show that prebiotic diets, such as NUTRIOSE, may promote the metabolic conversion of ginsenosides to CK and the subsequent absorption of CK in the gastrointestinal tract and may potentiate the pharmacological effects of ginseng.

• Journal of Ginseng Research
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• v.38 no.3
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• pp.203-207
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• 2014

Background: There is limited understanding of the effect of dietary components on the absorption of ginsenosides and their metabolites into the blood. Methods: This study investigated the pharmacokinetics of the ginseng extract and its main constituent ginsenoside Rb1 in rats with or without pretreatment with a prebiotic fiber, NUTRIOSE, by liquid chromatography tandem mass spectrometry. When ginsenoside Rb1 was incubated with rat feces, its main metabolite was ginsenoside Rd. Results: When the intestinal microbiota of rat feces were cultured in vitro, their ginsenoside Rd-forming activities were significantly induced by NUTRIOSE. When ginsenoside Rb1 was orally administered to rats, the maximum plasma concentration (Cmax) and area under the plasma drug concentratione-time curve (AUC) for the main metabolite, ginsenoside Rd, were $72.4{\pm}31.6ng/mL$ and $663.9{\pm}285.3{\mu}g{\cdot}h/mL$, respectively. When the ginseng extract (2,000 mg/kg) was orally administered, Cmax and AUC for ginsenoside Rd were $906.5{\pm}330.2ng/mL$ and $11,377.3{\pm}4,470.2{\mu}g{\cdot}h/mL$, respectively. When ginseng extract was orally administered to rats fed NUTRIOSE containing diets (2.5%, 5%, or 10%), Cmax and AUC were increased in the NUTRIOSE receiving groups in a dose-dependent manner. Conclusion: These findings reveal that intestinal microflora promote metabolic conversion of ginsenoside Rb1 and ginseng extract to ginsenoside Rd and promote its absorption into the blood in rats. Its conversion may be induced by prebiotic diets such as NUTRIOSE.

• Journal of the Korean Ceramic Society
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• v.56 no.1
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• pp.98-103
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• 2019

Optical filters to control light wavelength of displays or cameras are fabricated by multi-layer stacking process of low and high index thin films. The process of multi-layer stacking of thin films has received much attention as an optimal process for effective manufacturing in the optical filter industry. However, multi-layer processing has disadvantages of complicated thin film process, and difficulty of precise control of film morphology and material selection, all of which are critical for transmittance and coloring effect on filters. In this study, the composite $TiO_2$, which can be used to control of UV absorption, coated on nano hollow silica sol, was synthesized as a coating material for optical filters. Furthermore, systematic analysis of the process parameters during the chemical reaction, and of the structural properties of the coating solutions was performed using SEM, TEM, XRD and photo spectrometry. From the structural analysis, we found that the 85 nm nano hollow silica with 2.5 nm $TiO_2$ shell formation was successfully synthesized at proper pH control and titanium butoxide content. Photo luminescence characteristics, excited by UV irradiation, show that stable absorption of 350 nm-light, correlated with a 3.54 eV band gap, existed for the $TiO_2$ shell-nano hollow silica reacted with 8.8 mole titanium butoxide solution. Transmittance observed on substrate of the $TiO_2$ shell-nano hollow silica showed effective absorption of 200-300 nm UV light without deterioration of visible light transparency.

• Journal of Photoscience
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• v.9 no.2
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• pp.344-346
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• 2002

Eight intact bacteriochlorophyll (BChl)-d homologs and isomers were isolated from a strain of green sulfur bacterium Chlorobium vibrioforme. All the molecular structures of the BChl-d components were fully determined by a combination of mass spectrometry and $^1$H-NMR spectroscopy. The aggregation behavior of the isomerically pure BChls-d in hydrophobic organic solvents was examined with respect to the stereoisomeric configuration at the C3$^1$ position as well as the bulkiness of the C8 and C12 side-chains by using electronic- absorption spectroscopy.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.78-78
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• 2012

In this presentation I will review the expanding thermal plasma chemical vapour deposition (ETP-CVD) technology, a deposition technology capable of reaching ultrahigh deposition rates. High rate deposition of a-Si:H, ${\mu}c$-Si:H, a-SiNx:H and silicon nanocrystals will be discussed and their various applications, mainly for photovoltaic applications demonstrated. An important aspect over the years has been the fundamental investigation of the growth mechanism of these films. The various in situ (plasma) and thin film diagnostics, such as Langmuir probes, retarding field analyzer, (appearance potential) mass spectrometry and cavity ring absorption spectroscopy, spectroscopic ellipsometry to name a few, which were successfully applied to measure radical and ion density, their temperature and kinetic energy and their reactivity with the growth surface. The insights gained in the growth mechanism provided routes to novel applications of the ETP-CVD technology, such as the ultrahigh high growth rate of silicon nanorystals and surface passivation of c-Si surfaces.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.663-663
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• 2013

We prepared Cu oxides, and Ni and Pd-TiO2@SiO2 core-shellnanostructures, and tested their CO oxidation performances by temperature-programmed mass spectrometry. We found the starting temperatures of CO oxidation are around $200^{\circ}C$ and $300^{\circ}C$ for Ni and Pd-TiO2@SiO2 nanostructures, respectively. Cu oxides are cubes with 50~200 nm with, prepared with different concentrations of NaOH and ascorbic acid. For the core-shell structures, we prepared 100 nm SiO2 spheres, first coated the surface with TiO2 precursor, and then coated with Ni and Pd. Their characteristics are further examined by scanning electron microscopy, optical microscope, FT-IR, and UV-Vis absorption spectroscopy.