• Journal of the Korean Electrochemical Society
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• v.9 no.4
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• pp.158-169
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• 2006

The present article is concerned with the overview of the chemically/surface modified cubic spinel $LiMn_2O_4$ as a cathode electrode far lithium ion secondary batteries. Firstly, this article presented a comprehensive survey of the cubic spinel structure and its correlated electrochemical behaviour of $LiMn_2O_4$. Subsequently, the various kinds of the chemically/surface modified $LiMn_2O_4$ and their electrochemical characteristics were discussed in detail. Finally, this article reviewed our recent research works published on the mechanism of lithium transport through the chemically/surface modified $Li_{1-\delta}Mn_2O_4$ electrode from the kinetic view point by the analyses of the experimental potentiostatic current transients and ac-impedance spectra.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.415-419
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• 2012

Electrochemical characteristics of nitrite ion were investigated at a poly(methylene blue)-modified glassy carbon electrode by cyclic voltammetry and differential pulse voltammetry. The poly(methylene blue)-modified glassy carbon electrode exhibited enhanced anodic signals for nitrite. The effects of key parameters on the detection of nitrite were evaluated at the modified electrode, such as pH, accumulation time, and scan rate. Under optimum condition, the chemically modified electrode can detect nitrite in the concentration range $2.0{\times}10^{-6}$ to $5.0{\times}10^{-4}$ M with the detection limit of $2.0{\times}10^{-6}$ M and a correlation coefficient of 0.999. The detection of nitrite using the chemically modified electrode was not affected by common ions such as $Na^+$, $K^+$, $Ca^{2+}$, $Cl^-$, $HPO_4^{2-}$ and $H_2PO_4^- $. The modified electrode showed good stability and reproducibility. The practical application of the present method was successfully applied to the determination of nitrite ion in cabbage samples.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.2
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• pp.107-111
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• 2004

A comparative study was performed to evaluate the signal amplification strategies in electrochemical affinity sensing, which included the direct electron transfer and diffusible-group mediated electron transfer between label enzymes that were specifically bound to target proteins and chemically modified electrode surfaces. As a platform surface for affinity recognition reactions, a double functionalized poly(amidoamine) dendrimer monolayer that was modified with ferrocene and biotin groups was constructed on a gold surface. With the chemically modified electrode, a model affinity sensing with avidin was investigated. The advantages of adopting the diffusible-group mediated signaling strategy were demonstrated in terms of signal sensitivity and stability.

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.43-47
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• 2007

Electrochemical rectification at electrode chemically modified with redox active agents isolated at monolayer level was considered. Formulation of the rising part of linear sweep voltammogram at steady and rotating disc electrode was introduced.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.886-891
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• 1995

Electroactive monolayers based on zirconium(Ⅳ) phosphonate film were prepared on gold and tin oxide electrodes by sequential layer-by-layer depostion technique. High transfer coefficient values and surface coverages of surface bound redox molecules were obtained from the electrochemical measurements of heterogeneous electron transfer rates for monolayer modified electrodes. 1,10-Decanediylbis(phosphonic acid) (DBPA) monolayer as insulating barrier was effective in blocking electron transfer. However, these film modified oxide electrode shows voltammetric behavior of diffusion/permeation process taking place at very small exposed area of modified electrode through channels due to structural defects within film when a very fast redox couple such as Ru(NH3)63+ is hired.

• Analytical Science and Technology
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• v.9 no.3
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• pp.235-243
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• 1996

A carbon paste electrode were chemically modified using ${\alpha}$-cyclodextrin. Characteristics of chemically modified carbon paste electrodes were studied on the basis of the inclusion complex formation of ${\alpha}$-cyclodextrin and p-nitrophenol in solution. Cyclic voltammetry and differential pulse voltammetry were used to monitor the efficiency of the chemical modification. When the ${\alpha}$-cyclodextrin and carbon powder ratio of 2 : 1 in weight were used, the reduction peak current of p-nitrophenol was decreased almost completely, whereas those of o-nitrophenol and hydroquinone were not changed much. This result is due to the large difference in the inclusion complex formation constants of p-nitrophenol and the other probes with ${\alpha}$-cyclodextrin. Taking advantage of this difference, we can determine the concentration of o-nitrophenol even in the presence of p-nitrophenol.

• Bulletin of the Korean Chemical Society
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• v.11 no.3
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• pp.200-205
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• 1990

Chemically modified electrodes(CMEs), based on 2-imino-1-cyclopentane-dithiocarboxylic acid (icdc) containing carbon paste, have been characterized using cyclic voltammetric techniques. Ag(I) was chemically deposited on the CMEs, and voltammograms were obtained with the electrode in a separate buffer solution. The CME surface can be regenerated with exposure to acid and reused for deposition. In 10 deposition/measurement/regenerate cycles, the linear response have been reproduced up to $1{\times}10^{-6}$ M in linear sweep voltammetry and 1${\times}$10-8 M in differential pulse voltammetry with relative standard deviation of 5.2% and 12.4%, respectiveiy. The sensitivity increased with deposition time and scanning rate, and detection limit was $1{\times}10^{-7}M\;and\;1{\times}10^{-9}M$ at 20 minutes deposition in the linear sweep voltammetry and differential pulse voltammetry, respectively. The presence of some metal ions does not influence the silver ion response. Satisfactory results were obtained for the analysis of the silver ion for a variety of reference materials without interference of Hg ion at the condition of pH = 5-6.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.988-992
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• 2008

A poly(methyl red) film-modified glassy carbon electrode (PMRE) was fabricated for determination of norfloxacin (NFX). The electrochemical behavior of NFX was investigated and a well-defined oxidation peak with high sensitivity was observed at the film electrode. PMRE greatly enhanced the oxidation peak current of NFX owing to the extraordinary properties of poly(methyl red) film. Based on this, a sensitive and simple voltammetric method was developed for measurement of NFX. A sensitive linear voltammetric response for NFX was obtained in the concentration range of $1\;{\times}\;10^{-6}\;-\;1\;{\times}\;10^{-4}$ mol/L and the detection limit was $1\;{\times}\;10^{-7}$ mol/L using linear sweep voltammetry (LSV). The proposed method possessed advantages such as low detection limit, fast response, low cost and simplicity. The practical application of this new analytical method was demonstrated with NFX pharmaceuticals.

• Analytical Science and Technology
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• v.8 no.4
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• pp.611-615
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• 1995

The design of appropriate chemically modified electrodes should allow development of new voltammetric measurement schemes with enhanced selectivity and sensitivity. Microorganism like algae has high ability to trap toxic and heavy metal ions and different affinities for metal ions. A copper(II) ion-selective carbon paste electrode was constructed by incorporating alga Anabaena into a conventional carbon paste mixture, and then the film of 10% Nafion was coated to avoid the swelling of the electrode surface. Copper ion could be deposited at the 25% algamodified electrode for 15 min without the applied potential while stirring the solution by only immersing the electrode in a buffer (pH 4.0) cot1taining copper(II). Temperature was controlled at $35^{\circ}C$. After preconcentration was carried out the electrode was transferred to a 0.1 M potassium chloride solution and was reduced at -0.6 volt at $25^{\circ}C$. The differential pulse anodic stripping voltammetry was employed. A well-defined oxidation peak could be obtained at -0.1 volt (vs SCE). In five deposition / measurement / regeneration cycles, the responses were reproducible and relative standard deviations were 3.3% for $8.0{\times}10^{-4}M$ copper(II). Calibration curve for copper was linear over the range from $2.0{\times}10^{-4}M$ to $1.0{\times}10^{-3}M$. The detection limit was $7.5{\times}10^{-5}M$. Studies of the effect of diverse ions showed that the coexisting metal ions had little or no effect for the determination of copper. But anions such as cyanide. oxalate and EDTA seriously interfered.

• Bulletin of the Korean Chemical Society
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• v.17 no.4
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• pp.342-347
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• 1996

Voltammetric determination of phenol derivatives, such as phenol, o-, m-, and p-cresols was studied with a β-Cyclodextrin (β-CD) modified-carbon paste electrode composing of the graphite powder and Nujol oil. Phenol derivatives were chemically deposited via the complex formation with β-CD by immersing the CME into a sample solution. The resulting surfaces were characterized with cyclic and differential pulse voltammetry. Treating the CME with 1 M nitric acid for five sec after a measurement could regenerate the electrode surface. Linear sweep and differential pulse voltammograms were recorded for the above system to optimize the experimental parameters for analysing the phenol derivatives. In this case, the detection limit for phenols was 5.0×10-7M for 25 min of the deposition time with differential pulse voltammetry. The relative standard deviation was ±5.2% of 3.0×10-6M (four repetitions). The interference effect of the following organic compounds was also investigated; Bezoic acid, hippuric acid, o-, m-, and p-methylhippuric acid. Adding the organic compounds into the sample solution reduces the peak current of the phenols to about 25%.