• Structural Monitoring and Maintenance
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• v.2 no.3
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• pp.253-267
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• 2015

Corrosion has significant adverse effects on the durability of reinforced concrete (RC) structures, especially those exposed to a marine environment and subjected to mechanical stress, such as bridges, jetties, piers and wharfs. Previous studies have been carried out to investigate the corrosion behaviour of steel rebar in various concrete structures, however, few studies have focused on the corrosion monitoring of RC structures that are subjected to both mechanical stress and environmental effects. This paper presents an exploratory study on the development of corrosion monitoring and detection techniques for RC structures under the combined effects of external loadings and corrosive media. Four RC beams were tested in 3% NaCl solutions under different levels of point loads. Corrosion processes occurring on steel bars under different loads and under alternative wetting - drying cycle conditions were monitored. Electrochemical and microscopic methods were utilised to measure corrosion potentials of steel bars; to monitor galvanic currents flowing between different steel bars in each beam; and to observe corrosion patterns, respectively. The results indicated that steel corrosion in RC beams was affected by local stress. The point load caused the increase of galvanic currents, corrosion rates and corrosion areas. Pitting corrosion was found to be the main form of corrosion on the surface of the steel bars for most of the beams, probably due to the local concentration of chloride ions. In addition, visual observation of the samples confirmed that the localities of corrosion were related to the locations of steel bars in beams. It was also demonstrated that electrochemical devices are useful for the detection of RC beam corrosion.

• Korean Chemical Engineering Research
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• v.62 no.2
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• pp.147-152
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• 2024

Most medical sensors are disposable products. In order to reduce inspection and diagnosis costs, it is more important to develop the inexpensive electrode materials. We fabricated the CuO NPs/PANI/E-PGE as an electrode material for disposable electrochemical sensors and applied it to a non-enzymatic glucose sensor. For surface activation of PGE, pretreatment was performed using chemical and electrochemical methods, respectively. Electrochemical properties according to the pretreatment method were analyzed through chronoamperometry (CA), cyclic voltammetry (CV) and electrochemical impedance (EIS). From these analytical results, the electrochemically pretreated PGE (E-PGE) was finally adopted. The non-enzymatic glucose sensor based on CuO NPs/PANI/E-PGE shows sensitivity of 239.18 mA/mM×cm² (in a linear range of 0.282~2.112 mM) and 36.99 mA/mM×cm² (3.75423~50 mM), detection limit of 17.6 μM and good selectivity. Based on the results of this study, it was confirmed that the modified PGE is a high-performance electrode material. Therefore, these electrodes can be applied to a variety of disposable sensors.

• Journal of the Korean Electrochemical Society
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• v.23 no.3
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• pp.73-80
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• 2020

Fenton oxidation method using hydrogen peroxide is an eco-friendly oxidation method used in water treatment and soil restoration. When removing pollutants by this method, it is quite important to properly regulate the concentration of hydrogen peroxide according to the concentration of the contaminants. In this study, electrochemical biosensors using HRP (horseradish peroxidase) enzymes were manufactured and studies were conducted on the activity of enzymes and the detection characteristics of hydrogen peroxide. HRP were electro deposited with chitosan and AuNP on the working electrode surface of the SPCE (Screen Printed Carbon Electrode). Then, the fixation of enzymes was confirmed using the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The activity of HRP enzymes was also identified from chronoamperometry (CA) and UV spectroscopy. After immersing the biosensor in PBS solution the current generated from electrodes by titrating hydrogen peroxide was measured from CA analysis. The generated current increased linearly for the concentration of hydrogen peroxide, and a calibration curve was derived that could predict the concentration of hydrogen peroxide from the current.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.598-607
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• 1992

The environment degradation of structural steel under high temperature is one of the key phenomena governing the availability and life of plant. This degradation resulted from the microstructural changes due to the long exposure at high temperature affect the mechanical properties such as creep strength and toughness. For instance, boiler tube materials usually tend to degrade, after long term operation, by precipitates, spherodizing, coarsening, and change in chemical composition of carbides. In this study, the material degradation under high temperature exposure was investigated by evaluating the carbide precipitation. The electrochemical polarization method was facilitated to investigate the precipitation and coarsening of carbides. It was shown by the modified electrochemical potentiokinetic reactivation (EPR) tests that the passivation of Mo-rich carbides did not occur even in the anodic peak current (Ip) which indicates the precipitation of Mo$_{6}$C was also observed. And it was assured that special electrolytic cell assembled in this research can be used for the detection of Mo$_{6}$C precipitation in the field.eld.

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.147-153
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• 2008

Improvement of the selectivity of nonenzymatic glucose based on mesoporous platinum ($H_1$-ePt) by using A.C. impedance is reported. The idea of the present work is based on the novel effect of the mesoporous electrode that the apparent exchange current due to glucose oxidation remarkably grows although the reaction kinetics on the surface is still sluggish. It is expected that the enlarged apparent exchange current on the mesoporous electrode can raise the sensitivity of admittance in A.C. impedance to glucose concentration. At a low frequency, A.C. impedance could become more powerful. The admittance at 0.01 Hz is even more sensitive to glucose than to ascorbic acid while amperometry exhibits the inverse order of sensitivity. This is the unique behavior that is neither observed by A.C. impedance on flat platinum electrode nor obtained by amperometry. The study shows how the combination of A.C. impedance and nano-structured surface can be applied to the detection of sluggish reaction such as electrochemical oxidation of glucose.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2363-2368
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• 2007

A glassy carbon electrode (GCE) modified with phytic acid (PA) and single-walled carbon nanotubes (SWNTs) were investigated by voltammetric methods in buffer solution. The PA-SWNTs/GCE-modified electrode demonstrated substantial enhancements in electrochemical sensitivity and selectivity towards dopamine (DA) in the presence of L-ascorbic acid (AA). The PA-SWNTs films promoted the electron transfer reaction of DA, while the PA film, acting as a negatively charged linker, combined with the positively charged DA to induced DA accumulation in the film at pH under 7.4. However, the PA film restrained the electrochemical response of the negatively charged AA due to the electrostatic repulsion. The anodic peak potentials of DA and AA could be separated by electrochemical techniques, and the interferences from AA were effectively eliminated in the DA determination. Linear calibration plots were obtained in the DA concentration range of 0.1-10 μM and the detection limit of the DA oxidation current was determined to be 0.06 μM at a signal-to-noise ratio of 3. The results indicated that the modified electrode is used to determine DA without interference from AA.

• 한국전기화학회:학술대회논문집
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• 2003.11a
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• pp.141-151
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• 2003

The electrochemical activity of the olivine type $LiMPO_4$ (M=transition metals) cathodes strongly depends on various factors, e.g., the transition metal element M, perturbative doping of the supervalent cations into Li site, composite formation with conductive additives, state of charge/discharge, and particle size and its geometries, etc. This is, therefore, an important issue of interdisciplinary between electrochemistry and solid state science towards practical applications. In order to shed light on this interesting but complicated issue with the transport properties and crystallographic aspects, systematic discussion will be made with the review of our recent publications; (1) first principle derivation of the electronic structures, (2) crystallographic mapping of the selected solid solutions, (3) quantitative elucidation of the electron-lattice interaction, (4) spectroscopic detection of the local environment with Mossbauer and EXAFS, (5) synthetic optimization of the electrode composite, and (6) electrochemical evaluation of the reaction kinetics, particularly on M = Fe, Mn.

• Journal of Electrochemical Science and Technology
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• v.9 no.2
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• pp.109-117
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• 2018

A novel carbon paste electrode modified with $Cu-TiO_2$ nanocomposite, 2-(ferrocenylethynyl)fluoren-9-one (2FF) and ionic liquid (IL) (2FF/$Cu-TiO_2$/IL/CPE) was fabricated and employed to study the electrocatalytic oxidation of droxidopa, using cyclic voltammetry (CV), chronoamperometry (CHA) and differential pulse voltammetry (DPV) as diagnostic techniques. It has been found that the oxidation of droxidopa at the surface of modified electrode occurs at a potential of about 295 mV less positive than that of an unmodified CPE. DPV exhibits a linear dynamic range from $5.0{\times}10^{-8}$ to $4.0{\times}10^{-4}M$ and a detection limit of 30.0 nM for droxidopa. Finally this modified electrode was used for simultaneous determination of droxidopa and tryptophan. Also the 2FF/$Cu-TiO_2$/IL/CPE shows excellent ability to determination of droxidopa and tryptophan in real samples.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3103-3108
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• 2010

Conducting polymers (CPs) are widely used as matrixes for the entrapment of enzymes in analytical chemistry and biosensing devices. However, enzyme-catalyzed polymerization of CPs is rarely used for immunosensing due to the difficulties involved in the quantitative analysis of colloidal CPs in solution phase. In this study, an enzyme-amplified electrocatalytic immunosensor employing a CP as a redox marker has been developed. A polyanionic polymer matrix, $\alpha$-amino-$\omega$-thiol terminated poly(acrylic acid), was employed for precipitation of CP. The acrylic acid group acts as a polyanionic template. The thiol terminus of the polymer was used to produce self-assembled monolayers (SAMs) on Au electrodes and the amine terminus was employed for immobilization of biomolecules. In an enzymeamplified sandwich type immunosensor, the polyaniline (PANI) produced enzymatically is attracted by the electrostatic force of the matrix polymer. The precipitated PANI was characterized by electrochemical methods.

• Bulletin of the Korean Chemical Society
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• v.29 no.7
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• pp.1323-1325
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• 2008

The acetylene black (AB) was dispersed into water in the presence of dihexadecyl hydrogen phosphate (DHP) via ultrasonication, resulting in a stable and well-distributed AB/DHP suspension. After evaporation of water, an AB/DHP composite film-modified electrode was prepared. The electrochemical responses of $K_3$[Fe$(CN)_6$] at the unmodified electrode, DHP film-modified electrode and AB/DHP film-modified electrode were investigated. It is found that the AB/DHP film-modified electrode possesses larger surface area and electron transfer rate constant. Furthermore, the electrochemical behaviors of 1-naphthylacetic acid (NAA) were examined. At the AB/DHP film-modified electrode, the oxidation peak current of NAA remarkably increases. Based on this, a sensitive and convenient electrochemical method was proposed for the determination of NAA. The linear range is in the range from $4.0 {\times} 10^{-8}\;to\;5.0 {\times} 10^{-6}$ mol $L^{-1}$, and the detection limit is $1.0 {\times} 10^{-8}$ mol $L^{-1}$. Finally, this new sensing method was employed to determine NAA in several soil samples.