• Korean Journal of Medicinal Crop Science
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• v.7 no.1
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• pp.11-15
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• 1999

The uptake of germanium(Ge) by health foodstuffs was interesting because of a therapeutic effect of organic germanium. Germanium contents in different plant parts of the cultivated Korean Angelica keiskej Koidz in several growing districts were determined by square wave anodic stripping voltammetry. Experimental conditions in germanium determination from Angelica kejskej Koidz were as follows : deposition time; 20 sec, deposition potential; -0.9 volts vs Ag/AgCl, and frequency; 100 Hz in 0.1M\;HClO_4, supporting electrolyte solution at pH 2.43 containing $1.5\;{\times}\;10^5\;M$ pyrocatechol violet. Calibration curve showed a good lineality in the range of 0.4 ppb to 2.0 ppm and the detection limit was 0.08 ppb. There was a large difference in content according to growing districts ranging from 102 to 386ppm. Germanium content in leaf parts was much higher than that in stems.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.357-361
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• 1999

GOD electrochemically immobilized in PPy/GOD complex have an effect on redox properties of the complex. In the cyclicvoltammetry, GOD shows the redox reaction at the potential below -0.6Y vs. Ag/AgCI. That leads to new peaks in the cyclicvoltammograms in additional to typical PPy peaks. The pH of electrolyte solution during potential swing decreased to 4.4, and then increased to 10. That suggests the redox of GOD for the cycling. As the concentration of GOD was increased, the anodic wave of the new peaks was strong as much as increased. GOD obstructs the diffusion of electrolyte anion because of its net chain. Insulating property of GOD is cause that it made the faradic impedance of complex large in charge transfer. It suggests that increase of the concentration of GOD be against electrochemical coupling. Therefore, the concentration of GOD and electrochemical coupling should be dealt with each other. The apparent Michaelis-lenten constant ( K\`$_{M}$ ) was determined by 30.7 mmol d $m^{-3}$ fur the PPy/GOD complex. The value is of the same order of magnitude as that for soluble glucose oxidase from Aspergillus Niger.r.

• Bulletin of the Korean Chemical Society
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• v.25 no.10
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• pp.1499-1502
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• 2004

An amperometric biosensor based on carbon paste electrodes (CPEs) for the determination of urea was constructed by enzyme (urease/GL-DH)-modified method. Urea was hydrolyzed to ${NH_4}^+$ by catalyzing urease onto the enzyme-modified electrode surface in sample solution. In the presence of ${\alpha}$-ketoglutarate and reduced nicotinamide adenine dinucleotide(NADH), a liberated ${NH_4}^+$ produce to L-glutamate and $NAD^+$ by Lglutamate dehydrogenase (GL-DH). After the chemical reaction was proceeded, the electrochemical reaction was occurred that an excess of the NADH was oxidized to $NAD^+$. The oxidation current of NADH was monitored at +1.10 volt vs. Ag/AgCl. An optimum conditions of biosensor were investigated: The optimum pH range for catalyzed hydrolysis reaction of urea was pH 7.0-7.4. The linear response range and detection limit were $2.0\;{\times}\;10^{-5}{\sim}2.0\;{\times}\;10^{-4}M\;and\;5.0\;{\times}\;10^{-6}M$, respectively. Another physiological species did not interfere, except L-ascorbic acid.

• Advances in materials Research
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• v.1 no.1
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• pp.1-12
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• 2012

There have been many efforts on the generating metal nanocrystals enclosed by high-index facets for the use as highly active catalysts. This paper describes a facile synthesis of Au trisoctahedra with high-index facets. In brief, the Au trisoctahdra were prepared by reduction of $HAuCl_4$ in N,N-dimethylformamide (DMF) containing poly (vinyl pyrrolidone) (PVP) and trace amount of $AgNO_3$. The Ag ions in the reaction solution played a critical role in controlling the trisoctahedral shape of the final product by underpotential deposition (UPD) on the Au surfaces. The as-prepared Au trisoctahedra were single crystal and enclosed by high-index {441}, {773} and {331} facets.

• Membrane and Water Treatment
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• v.7 no.3
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• pp.193-207
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• 2016

Boron is one of the most problematic inorganic pollutants and is difficult to remove in water. Strict standards have been imposed for boron content in water because of their high toxicity at high concentrations. Technologies using membrane processes such as reverse osmosis (RO) and nanofiltration (NF) have increasingly been employed in many industrial sectors. In this work, removal of boron from model water solutions was investigated using polyamide reverse osmosis and nanofiltration membranes. RO-AG, RO-SG, NF-90 and NF-HL membranes were used to reduce the boron from model water at different operational conditions. To understand the boron separation properties a characterization of the four membranes was performed by determining the pure water permeability, surface charge and molecular weight cut-off. Thereafter, the effect of feed pressure, concentration, ionic strength, nature of ions in solution and pH on the rejection of boron were studied. The rejection of boron can reach up to 90% for the three membranes AG, SG and NF-90 at pH = 11. The Spiegler-Kedem model was applied to experimental results to determine the reflection coefficient of the membrane ${\sigma}$ and the solute permeability $P_s$.

• Korean Journal of Materials Research
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• v.20 no.1
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• pp.25-30
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• 2010

Si nanowire/multiwalled carbon nanotube nanocomposite arrays were synthesized. Vertically aligned Si nanowire arrays were fabricated by Ag nanodendrite-assisted wet chemical etching of n-type wafers using $HF/AgNO_3$ solution. The composite structure was synthesized by formation of a sheath of carbon multilayers on a Si nanowire template surface through a thermal CVD process under various conditions. The results of Raman spectroscopy, scanning electron microscopy, and high resolution transmission electron microcopy demonstrate that the obtained nanocomposite has a Si nanowire core/carbon nanotube shell structure. The remarkable feature of the proposed method is that the vertically aligned Si nanowire was encapsulated with a multiwalled carbon nanotube without metal catalysts, which is important for nanodevice fabrication. It can be expected that the introduction of Si nanowires into multiwalled carbon nanotubes may significantly alter their electronic and mechanical properties, and may even result in some unexpected material properties. The proposed method possesses great potential for fabricating other semiconductor/CNT nanocomposites.

• Journal of the Korean Electrochemical Society
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• v.8 no.3
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• pp.117-124
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• 2005

Electrochemical oxidation of ethanol at nickel electrodes has been studied in 1 M KOH solution containing 0.20M ethanol using electrochemical impedance spectroscopy. Equivalent circuits have been worked out by simulating the impedance data, and the results were used to model the oxidation of ethanol as well as the passivation of the electrode. The maximum rate of oxidation of $Ni(OH)_2$ to NiOOH was observed at about 0.37V vs. Ag/AgCl reference electrode, while the maximum rate of ethanol oxidation at the Ni electrode was observed at about 0.42V, The charge-transfer resistance for oxidation of the electrode itself became smaller in the presence of ethanol than in its absence. These results suggest that the $\beta-Ni(OH)_2/\beta-NiOOH$ redox couple is acting as an effective electron transfer mediator far ethanol oxidation. The kinetic parameters also were obtained by the experimental and simulated results.

• Journal of Environmental Health Sciences
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• v.26 no.4
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• pp.110-114
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• 2000

Determination of mercury(II) using Nafion-EDTA-modified glassy carbon electrodes is proposed. it is based on the chemical reactivity of an immobilized modifier, Nafion-EDTA. Differential pulse voltammetry is employed, and the oxidation of complexes, at +0.43V vs. Ag/AgCl, is observed. For a 5-min preconcentration period, a linear calibration curve is obtained for mercury(II) concentrations ranging from 1.0$\times$ 10$^{-8}$ to 1.0$\times$10$^{-6}$ M. Further, when an approximate amount of copper(II) is added to the test solution, We demonstrate that at a preconcentration time of 5 min the Nafion-EDTA-modified glassy carbon electrode has a dynamic range of 2 orders of magnitude(from 10$^{-10}$ to 10$^{-8}$ M) and the detection limit is as low as 0.5$\times$ 10$^{-10}$ M(0.01 ppb). This method is applied to the determination of mercury(II) in sea water(4.0$\times$10$^{-10}$ M, 0.08ppb). The result agrees satisfactorily with the value(below 0.1 ppb) measured by using ICP/MS.

• Restorative Dentistry and Endodontics
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• v.19 no.1
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• pp.106-113
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• 1994

Dental professions are considered high risk for contracting hepatitis infection. In Korea, many patients are hepatitis B virus carriers. HBV are most efficiently transmitted by blood. Root canal treatment, as in cases of acute pulpitis always accompanied by contaminated blood. Therefore it is absolutely necessary to use irrigation solutions having strong antiviral effect for prophylaxis both dental personnel and patients. The purpose of this study was to investigate the antiviral effect of seven root canal irrigation solutions by radioimmunometric test. The solutions were 5% sodium phyochlorite, 5% cresol, 2% glutaraldehyde, 3% hydrogen peroxide, 0.05% chlorohexidine, 10% iodine, and 70% isoprophyl alcohol. Each irrigation solutions was mixed with serum preparated from HBsAg positive patients and sera were diluted to 1:1. 1:4. 1:20 and 1:100. Percentage of radioactivity was assayed with AUK(Sorbin biomedica, Italy) and COBRA(Packwood Instrument company, USA). Sodium hypochlorite and glutaraldehyde showed most strong antivral activity against HBsAg. Isoprophyl alcohol had moderate antiviral effect and the effect and the effect was increased especially in 1:4 solution. Hydrogen peroxide exihibited very weak aintivral activity. Cresol, chlorohexidine, and iodine exhibited little antiviral activity.

• Korean Journal of Materials Research
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• v.19 no.6
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• pp.344-348
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• 2009

The electrolyte effects of the electroplating solution in Cu films grown by ElectroPlating Deposition(EPD) were investigated. The electroplated Cu films were deposited on the Cu(20 nm)/Ti (20 nm)/p-type Si(100) substrate. Potentiostatic electrodeposition was carried out using three terminal methods: 1) an Ag/AgCl reference electrode, 2) a platinum plate as a counter electrode, and 3) a seed layer as a working electrode. In this study, we changed the concentration of a plating electrolyte that was composed of $CuSO_4$, $H_2SO_4$ and HCl. The resistivity was measured with a four-point probe and the material properties were investigated by using XRD(X-ray Diffraction), an AFM(Atomic Force Microscope), a FE-SEM(Field Emission Scanning Electron Microscope) and an XPS(X-ray Photoelectron Spectroscopy). From the results, we concluded that the increase of the concentration of electrolytes led to the increase of the film density and the decrease of the electrical resistivity of the electroplated Cu film.