• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.3
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• pp.306-312
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• 2016

Gargle solution has typically been used for the prevention of oral infectious disease such as dental caries and periodontitis. However, the use of most gargle solutions is controversial in application for children because some gargle solutions have harmful side effects. Electrolyzed water is generated by passed an electric current and has antimicrobial activity. The purpose of this study was to investigate and compare the efficacy of electrolyzed water in various conditions for eliminating cariogenic bacteria. Electrolyzed water was generated by a platinum electrode in the presence of sodium chloride at various concentrations. Streptococcus mutans and Streptococcus sobrinus were cultivated into a brain heart infusion broth. After harvesting planktonic bacteria, the pellets were treated with the electrolyzed water and commercial gargle solutions and plated on a mitis-salivarius agar plate. Also, the anti-biofilm activity of the electrolyzed water and commercial gargle solutions was investigated after biofilm formation of S. mutans and S. sobrinus. The bacteria in the biofilm were plated onto a mitis-salivarius agar plate. The plates were incubated, and the colony forming unit was measured. The electrolyzed water containing sodium chloride showed significant antibacterial activity against S. mutans and S. sobrinus as well as some gargle solutions. Furthermore, the electrolyzed water had more disruptive effect on the biofilm of S. mutans and S. sobrinus and killed more bacteria in the biofilm than commercial gargle solutions. The results demonstrate that electrolyzed water may be a useful gargle solution for prevention of dental caries.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.645-652
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• 1997

Electrochemical characteristics and kinetic parameters of copper ion reduction were investigated with a platinum rotating disk electrode (RDE) in a diffusion controlled region. Reduction of Cu(II) in sulfate had one-step two-xelectron process, while the reduction of Cu(II) in chloride solution was involved two one-electron processes. The transfer coefficient of Cu(II) in sulfate solution was lowest, and the transfer coefficient of Cu(I) in halide solutions had the value of nearly one. In chloride solutions, electrodeposition rate of Cu(II) was about one hundred times faster than Cu(I). Diffusion coefficient increased in the order of Cu(II) in chloride solution, Cu(I) in the iodide, bromide, chloride solution, Cu(II) in sulfate solution. The calculated ionic radii and activation energy for diffusion decreased in the same order as above. Morphological study on the copper electrodeposition indicated that the electrode surface became rougher as both concentration and reduction potential increases, and the roughness of the surface was analyzed with UV/VIS spectrophotometer.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.6
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• pp.28-34
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• 1999

We fabricated a planar ultra-violet photodetector whose ohmic and schottky contacts were respectively formed with evaporated Al and Pt on the GaN layer. To examine the applicability of the device to the UV sensor, we investigated its electrical and optical characteristics. The GaN layer on the sapphire waver had $7.8{\times}10^{16}cm^{-3}$ of doping concentnation and the $138 cm^2/V{\cdot}s$ of electron mobility and it absorbed the spectrum of the light below 325 nm wavelength. It had the responsivity of 2.8 A/W of at 325 nm, and the signal to noise ratio(SNR) of $4{\times}10^4$, and the noise equivalent power(NEP) of $3.5{\times}10^9$W under 5 V reverse bias. These results confirmed that the GaN schottky diode had a solar blind properly when it was applied to the UV photodetector.

• Journal of the Korean Chemical Society
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• v.27 no.4
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• pp.279-286
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• 1983

An apparatus was made for the electrodeposition of alpha emitting actinide nuclides, $^{207}Bi$ and $^{210}Po$. The electrodeposition was made on a polished stainless steel plate cathode. The anode was made of platinum wire and to stir the solution. With the ammonium chloride as electrolyte initial pH = 4, chloride concentration = 0.6M and solution volume = 15ml, a current of 1.5 ampere(current density = 0.59A/$cm^2$) was flowed for 100 minutes for the quantitative recovery of electrodeposition and on average recovery of 98.3% was obtained within ${\pm}$0.7% uncertainty. Alpha spectrometry of the electrodeposited sample showed alpha peaks from $^{210}Po, ^{234}U$ and $^{239}Pu$ having energy resolution (FWHM) of 18.3, 21.8 and 36.0 keV respectively. The electrodeposition and alpha spectrometry for a natural uranium sample of domestic origin gave $^{238}U : ^{234}U = 1 : 6.1{\times}10^{-5}$ and for a neutron-irradiated uranium sample did $^{238}U : ^{239}Pu : ^{241}Am = 100 : 0.0263 : 5.20{times}10^{-5}$. The result of $^{238}U$ determination in the irradiated sample by electrodeposition-alpha spectrometry was in accord within ${\pm}1.6%$ of relative error with the results of solid fluorimetry and mass spectrometry. For $^{239}Pu$ the result of electrodeposition-alpha spectrometry was in accord within ${\pm}$4.0% of relative error with the results of anion exchange separation and the thenoyltrifluoroacetone(TTA) extraction both followed by alpha spectrometries.

• Analytical Science and Technology
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• v.12 no.4
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• pp.290-298
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• 1999

A study on the application of impedance phase angle for redox titration, acid-base titration, chelate titration and precipitation titration has been carried out. A constant alternating current was passed between two platinum electrodes. One of them was a polarizable micro-electrode of $0.1cm^2$ or $0.026cm^2$ surface area and the other a non-polarizable large electrode of $1cm^2$ surface area dipped in the solution to be titrated. The impedance and the phase angle of the titration cell were measured with lock-in amplifier to obtain well behaved titration curve respectively. In titration of oxalic acid vs. potassium permanganate, the end-point was obtained successfully from the phase angle titration curve. In this experiment, the concentration of 0.0005 M to 0.05 M, the current of $50{\mu}A$ and the frequency of near 50 Hz were used. In titration of phosphoric acid vs. sodium hydroxide, the first end-point was obtained successfully on the optimum experimental condition of 0.001 M concentration, $50{\mu}A$ current and 25~97 Hz frequency. However, the end-point in titration of cupric sulfate vs. disodium-EDTA couldn't be obtained clearly. The end-point was obtained with the out-of-phase impedance curve on the experimental condition of 0.01 M concentration, $100{\mu}A$ current, 5~35 Hz frequency range. In titration of sodium chloride vs. silver nitrate, the end-point was obtained successfully on the experimental condition of 0.1 M concentration, $100{\mu}A$ current and 5~47 Hz frequency range. This study showed that the impedance phase angle was applicable for the detection of the end-points in redox titration curve, acid-base titration curve, chelate titration curve and precipitation titration curve.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.143.1-143.1
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• 2010

고분자 전해질막 연료전지(Polymer Electrolyte Membrane Fuel Cell; PEMFC)는 수소를 이용하여 전기를 발생시키는 친환경적이고 이상적인 발전장치로 고효율과 높은 전류밀도를 가지며 그 응용분야가 다양하다. 저온에서 작동하는 PEM fuel cell은 전극에서 효과적인 산화환원반응을 위해 그 촉매로 활성이 우수한 Pt(Platinum)을 사용하고 있으나, Pt의 높은 가격은 연료전지의 상용화에 걸림돌이 되고 있다. 본 연구에서는 연료전지의 Pt/C 촉매 층에서 Pt의 분산성을 높여 Pt의 담지량을 줄이고 작동 중 발생하는 Pt의 응집 현상을 방지하여 Pt의 수명을 연장시킬 목적으로, Au(gold) 나노입자를 첨가한 Pt-Au/C 복합나노촉매를 제조하였다. 본 발표에서는 합성된 Pt-Au/C 복합촉매 중 Au 첨가량이 Pt 촉매의 활성에 미치는 영향을 조사하기 위하여, 복합촉매 중에 금속(Pt+Au)의 총 함량이 30 wt.%와 40 wt.% 인 Pt-Au/C 촉매에 대하여 각각 Au 첨가량을 변화시켜, cyclic voltammetry 법에 의해 Au 첨가 효과를 조사한 결과에 대하여 보고하고자 한다. Au 나노입자를 제조하기 위한 출발 물질로는 $HAuCl_4{\cdot}4H_2O$를 이용하였고 trisodium citrate와 $NaBH_4$를 환원제로 하여, 입경이 5~8 nm 인 Au 콜로이드를 제조하였다. Pt-Au/C 복합나노촉매를 제조하기 위하여 먼저 Au/C 복합분체가 제조되었다. 0.03g의 carbon이 첨가된 carbon 현탁액에 합성된 Au 콜로이드 수용액을 첨가한 후 24시간 동안 교반하여 Au/C 복합분체를 제조하였다. 이 Au/C 복합분체에 $H_2PtCl_6{\cdot}6H_2O$ 수용액을 현탁하고 methanol 을 환원제로 사용해 Pt를 환원 석출시켜 Pt-Au/C 복합촉매를 제조하였다. Pt-Au/C 복합 나노촉매에서 Pt와 Au를 다양한 비율(3:1, 2.5:1.5, 2:2)로 합성하였으며 Pt-Au/C 복합촉매 중 금속(Pt+Au) 촉매의 총 함량은 30 wt.%와 40 wt.%로 각각 제조되었다. Au 나노입자 콜로이드의 분산성은 UV-visible spectrum의 흡광도에 의해 관찰되었고, Pt-Au/C 복합 나노촉매의 형상 및 분산성 분석은 transmission electron microscopy(TEM)에 의해 이루어졌다. 또한, 촉매의 전기화학적 특성평가는 cyclic voltammetry(CV)에 의해 조사되었다.

• KSBB Journal
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• v.21 no.5
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• pp.325-330
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• 2006

This study presents the characterization of an integrated portable microfluidic electrical detection system for fast and low volume immunoassay using polystyrene microbead, which are used as immobilization surfaces. In our chip, a filtration method using the microbead was adopted for sample immobilization and immunogold silver staining(IGSS) was used to increase the electrical signal. The chip is composed of an inexpensive and biocompatible Polydimethylsiloxane(PDMS) layer and Pyrex glass substrate. Platinum microelectrodes for electric signal detection were fabricated on the substrate and microchannel and pillar-type microfilters were formed in the PDMS layer. With a fabricated chip, we reacted antigen and antibody according to the procedures. Then, silver enhancer was injected to increase the size of nanogold particles tagged with the second antibody. As a result, microbeads were connected to each other and formed an electrical bridge between microelectrodes. Resistance measured through the electrodes showed a difference of two orders of magnitude between specific and nonspecific immuno-reactions. The detection limit was 10 ng/ml. The developed immunoassay chip reduced the total analysis time from 3 hours to 50 min. Fast and low-volume biochemical analysis has been successfully achieved with the developed microfilter and immuno-sensor chip, which is integrated to the microfluidic system.

• Journal of the Korean Institute of Gas
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• v.11 no.1 s.34
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• pp.29-33
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• 2007

This study investigates the use of $TiO_{2},\;Pd,\;Pt$, and In which greatly improves a sensitivity to trimethylamine gas. The metal-$SnO_{2}$ thick films were prepared by screen-printing method onto $Al_{2}O_{3}$ substrates with platinum electrode. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a test box as a function of detecting gas concentration. This was then used to detect trimethylamine, dimethylamine, and ammonia vapours within the concentration range of 100-1000ppm. The gas sensing properties of metal-$SnO_{2}$ mixed thick films depended on the content and variety of metal. It was found that sensitivity and selectivity of the films dopped with 1 wt% Pd and 10 wt% $TiO_{2}$ for trimethylamin gas showed the best result at $250^{\circ}C$.

• Journal of Yeungnam Medical Science
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• v.11 no.2
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• pp.314-322
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• 1994

This study aimed to investigate the existence of GABA receptor and the mechanisms of action of GABA and diazepam on the trachealis muscle isolated from dog. Horizontal muscle strips of $2mm{\times}15mm$ were prepared from canine trachea, and isometric myography in isolated muscle chamber bubbled with 95/5%-$O_2/CO_2$at $36^{\circ}C$, at the pH of 7.4 was performed. Muscle strips contracted responding to the electrical field stimulation (ESP) by 2~20 Hz, 20 msec, monophasic square wave of 60 VDC GABA and diazepam suppressed the EFS-induced contractions to the similar extent, significantly. (p<0.05) Bicuculline, a $GABA_A$ receptor antagonist blocked both GABA- and diazepam- inhibitions; but DAVA, a $GABA_B$ receptor antagonist did not affect either of them. These results suggest that in the canine trachealis muscle, there may be only $GABA_A$ receptor, and GABA and diazepam inhibit the contractility via $GABA_A$A receptor.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.4
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• pp.33-37
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• 2009

Purpose: To examine the coloring condition of titanium spectacle frames with various colors by using anodization method. Methods: We made an anodization coater. Platinum plate with $3{\times}3cm^2$ was used for a cathode and titanium spectacle frame specimens was mounted on an anode in an electrolyte. An electric source device were designed to supply steady state current. The color of the coated spectacle frame specimens were measured by a spectrophotometer equipped with an integrating sphere. We use CIE $L^*a^*b$ color system as chromaticity coordinates. Results: The thickness of $TiO_2$ of titanium spectacle frame specimens was varied as controlling current flow time for electrodes. The specimens with various kinds of color as a walnut, a yellow brown, a navy blue, a blue, a light blue, a mung bean, a yellowish green, a light purple, a purple, a flower pink, a bluish green, an emerald, and a green color etc. were obtained. The values of CIE $L^*a^*b^*$ for these specimens were measured and analyzed to be changed clockwise in chromaticity coordinates as the thickness of $TiO_2$ increases. Conclusions: We identified the coloring mechanism by anodization method in titanium spectacle frame specimens.