• Journal of Electrochemical Science and Technology
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• v.6 no.3
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• pp.88-94
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• 2015

In this study we investigated the electrocatalytic oxidation of saccharose on conductive polymer- Nickel oxide modified graphite electrodes based on the ability of anionic surfactants to form micelles in aqueous media. This NiO modified electrode showed higher electrocatalytic activity than Ni rode electrode in electrocatalytic oxidation of saccharose. The anodic peak currents show linear dependency with the square root of scan rate. This behavior is the characteristic of a diffusion controlled process. Under the CA regime the reaction followed a Cottrellian behavior and the diffusion coefficient of saccharose was found in agreement with the values obtained from CV measurements.

• Journal of the Korean Chemical Society
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• v.43 no.4
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• pp.407-411
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• 1999

Studies have been carried out on the fabrication of PPy/GC and PPy/Pt electrode modified with polypyrrole film and determination of Cr(VI) by using 3-electrode system with modified electrodes. Modified electrodes were able to easily fabricated by cyclic voltammetry scanned from +1.0V to -1.0V(vs. Ag/AgCl) at 50 mV/sec. Film thickness could be controlled at same condition by the number of cycling up to 26 times. Reduction behaviour of Cr(VI) at PPy/GC electrode could be seen at wide potential ranges from +0.6V to -0.5V(vs. Ag/AgCl), and maximum reduction peak potential of the ion was observed at -0.25V(vs.Ag/AgCl). Calibration graph at its potential was linear from 0.1 ppm to 80.O ppm. Slope factor and relative coefficient were 1.75 mA/ppm and 0.998, respectively. Reduction behaviour of Cr(VI) at PPy/Pt electrode was similar to PPy/GC electrode, Calibration graph was linear from l.0 ppm to 60.0 ppm. Slope factor and relative coefficient were 0.5mA/ppm and 0.923, respectively. But PPy/GC modified electrode had about 3 times higher sensitivity than PPy/Pt modified electrode. Reduction behaviour of Cu(II), As(IlI), Pb(II), and Cd(II) couldn't be seen at PPy/GC electrode,Its metals had not lnterfered with Cr (VI) determination.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.845-849
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• 2010

A gold nanoparticles modified carbon paste electrode (GN-CPE) has been used for the determination of atenolol (ATN) in drug formulations by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronocoulometric methods. The results revealed that the modified electrode shows an electrocatalytic activity toward the anodic oxidation of atenolol by a marked enhancement in the current response in buffered solution at pH 10.0. The anodic peak potential shifts by -80.0 mV when compared with the potential using bare carbon paste electrde. A linear analytical curve was observed in the range of $1.96\;{\times}\;10^{-6}$ to $9.09\;{\times}\;10^{-4}\;mol\;L^{-1}$. The detection limit for this method is $7.3\;{\times}\;10^{-8}\;mol\;L^{-1}$. The method was then successfully applied to the determination of atenolol in tablets and human urine. The percent recoveries in urine ranged from 92.0 to 110.0%.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2685-2690
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• 2013

The activities of Au-modified Cu electrodes toward glucose oxidation are evaluated according to their fabrication conditions and physico-chemical properties. The Au-modified Cu electrodes are fabricated by the galvanic displacement of Au on a Cu substrate and the characteristics of the Au particles are controlled by adjusting the displacement time. From the glucose oxidation tests, it is found that the Au modified Cu has superior activity to the pure Au or Cu film, which is evidenced by the negative shift in the oxidation potential and enhanced current density during the electrochemical oxidation. Though the activity of the Au nanoparticles is a contributing factor, the enhanced activity of the Au-modified Cu electrode is due to the increased oxidation number of Cu through the electron transfer from Cu to more electronegative Au. The depletion of electron in Cu facilitates the oxidation of glucose. The stability of the Au-modified Cu electrode was also studied by chronoamperometry.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.6
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• pp.1102-1108
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• 2008

Wearable physiological signal monitoring systems are regarded as an important sensing unit platforms in ubiquitous/mobile healthcare application. In this paper, we suggested the modified bipolar electrodes implemented on the portable heart activity monitoring system, which minimized the distance of electrodes formed on a attachable pad. The proposed electrode configuration is useful in mobile measurement environments, but has a disadvantage of reduced amplitude of the heart action potential. In order to overcome the shortcoming of the suggested electrode configuration, we implemented the amplifying circuit to increase the signal-gain and decrease the artifacts. For evaluations, we analyzed the specificity of measured cardiography using the proposed electrodes through the comparing of heart activity monitoring system with standard clinical ECG(lead2) by pearson correlation coefficients. The result showed that the average correlation coefficient is $0.903{\pm}0.036,\;0.873{\pm}0.072$ at V3, V4 chest lead position, respectively. Thus, the modified bipolar electrode is quite suitable to monitor the electrical activity of the heart in the situation of the mobile environment, and could be considered having high similarity with standard clinical ECG.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.93-94
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• 2006

In this research, the enhancement of electron-transfer activity of hemoglobin (Hb) in dodecanoic acid film was investigated for the first time. This type of composite film was made on glassy carbon electrode by casting method. Cyclic voltammetric result of the modified electrode displays a well defined redox peaks which was attributed to the direct electrochemical response of Rb. Our results illustrate that Rb exchange electrons directly with electrode and exhibits the characteristics of peroxidase. When we apply this modified electrode as a biosensor, it gives excellent performances in the electrocatalytic reduction of hydrogen peroxide ($H_{2}O_{2}$). Through the optimal conditions, the proposed biosensor shows the linear range for H2O2 determination was from $1{\times}10^{-5}$ to $1.25{\times}10^{-4}mol/L$ with a detection limit of $1{\times}10^{-7}mol/L$. The biosensor retained more than 90% of the initial response after 14 days.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.106-110
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• 2009

An amperometric glucose biosensor has been developed using viologen derivatives as a charge transfer mediator between a glucose oxidase (GOD) and a gold electrode. A highly stable self-assembled monolayer (SAM) of thiol-based viologen was immobilized onto the gold electrode of a quartz crystal microbalance (QCM) and GOD was immobilized onto the viologen modified electrode. This biosensor response to glucose was evaluated amperometrically in the potential of -300mV. Upon immobilization of the glucose oxidase onto the viologen modified electrode, the biosensor showed rapid response towards glucose. Experimental conditions influencing the biosensor performance, such as pH potential, were optimized and assessed. This biosensor offered excellent electrochemical responses for glucose concentration below ${\mu}$ mol level with high sensitivity and selectivity and short response time. The levels of the RSDs (<5%) for the entire analyses reflected the highly reproducible sensor performance. A linear calibration range between the current and the glucose concentration was obtained up to $4.5{\times}10^{-4}M$. The detection limit was determined to be $3.0{\times}10^{-6}M$.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.86-87
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• 2007

An amperometric glucose biosensor has been developed using viologen derivatives as electron mediator of glucose oxidase (GOD) at Au electrode. Highly stable self assembled monolayer (SAM) of thiol-based viologen is immobilized onto the Au electrode followed byGOD is immobilized onto the viologen modified electrode. This biosensor response to glucose was evaluated amperometrically in the potential of -300 mV. Upon immobilization of glucose oxidase onto the viologen modified-electrode, the biosensor showed rapid response towards glucose. Experimental conditions influencing the biosensor performance such as, pH, potential were optimized and assessed. This biosensor offered an excellent electrochemical response for glucose concentration below ${\mu}mol$ level with high sensitivity and selectivity and short response time. The levels of the RSD's (< 5 %) for the entire analyses reflected the highly reproducible sensor performance. Using the optimized a linear relationship between current and glucose concentration was obtained up to $4.5{\times}10^{-4}$ M. In addition, this biosensor showed well reproducibility and stability.

• Journal of the Mineralogical Society of Korea
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• v.18 no.1
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• pp.1-9
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• 2005

The electrocatalytic reduction of O₂ was investigated with methyl viologen and methylene blue incorporated clay-modified electrodes. Clay suspensions were prepared with Na-montmorillonite, Ca-montmorillonite, and kaolinite. The methyl viologen-clay modified electrodes were made by coating clay suspensions adsorbing methyl viologen on a glassy carbon electrode. Cyclic voltammetry were performed in aqueous media to investigate the electrocatalytic property of the modified electrode in reducing O₂. A Na-montmorillonite modified electrode showed the greatest adsorption capacity for methyl viologen. The modified electrode made of Na-montmorillonite suspension of 0.87 g/10 mL and a 2.5 mM of methyl viologen solution showed the most effective electrocatalytic property, where the catalytic reduction potential was shifted by 242.6 mV toward the positive potential. The electrocatalytic ability was more significant in acidic (pH=3.7) and alkaline (pH=12.7) media than the neutral pH range (6.3∼8.3). The methyl viologen-Na-montmorillonite modified electrode had the good reproducibility and maintain the electrocatalytic property over 20 times reuse.

• Journal of the Korean Chemical Society
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• v.31 no.3
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• pp.271-279
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• 1987

A nitrate ion-selective PVC membrane electrode based on ammonia modified bakelite A-Ni$(NO_3)_2$ complex as ion exchanger was prepared. The electrode gave a linear response with a Nernstian slope of 60mV per decade within the concentration range $1{\sim}10^{-4}$ M $KNO_3$ but nonresponse to hydrogen ion and multivalent anions. The selectivity, response time and life time of the electrode were investigated and it was found that the electrode exhibited good selectivity for four univalent anions ($Cl^-,\;Br^-,\;I^-,\;{ClO_4}^-$). Analytical application to the determination of nitrate were also studied.