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

• Applied Chemistry for Engineering
• /
• v.9 no.5
• /
• pp.719-725
• /
• 1998

Tridentate Schiff base ligands were prepared by the reactions of salicylaldehyde and 2-hydroxy-1-naphthaldehyde with 2-aminophenol and 2-amino-p-cresol. And then Cu(II) complexes of those ligands were synthesized. The structures and properties of ligands and their complexes were studied by elemental analysis, $^1H$-NMR, IR, UV-visible spectra, and thermogravimetric analysis. The mole ratio of Schiff base to the metal of complexes was found to be 1:1. Cu(II) complexes were contemplated to be four-coordinated square planar configuration containing one water molecule. The redox process of ligands and complexes in DMSO solution containing 0.1 M TBAP as a supporting electrolyte was investigated by cyclic voltammetry and differential pulse voltammetry with glassy carbon electrode. The redox process of the tridentate Schiff base ligands was totally irreversible. The redox process of Cu(II) complexes was quasi-reversible and diffusion-controlled as one electron by one step process Cu(II)/Cu(I). The reduction potentials of the Cu(II) complexes shifted in the positive direction in the order of [Cu(II)(HNIPC)($H_2O$)]>[Cu(II)(HNIP)($H_2O$)]>[Cu(II)(SIP)($H_2O$)]>[Cu(II)(SIPC)($H_2O$)].

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.2
• /
• pp.185-190
• /
• 2021

Cement has been used as a main material in the modern construction industry. However, it has been pointed out as a main cause of global warming due to carbon dioxide generated during manufactured. Recently, research that replacing cement substitute to industrial by-products such as Blast Furnace Slag which is by-producted in steelworks. When Blast Furnace Slag is used as a cement substitute, it shows a problem of lower initial strength, which is caused by glassy membrane on the particle surface. In this study, we used Electrolysis Alkaline Aqueous to improve the usability and problem of lower initial strength. As a result of the experiment, cement matrix using Blast Furnace Slag and Alkaline Aqueous showed initial strength and hydrate product were developed than that using general mixing water. Also, as a result of porosity analysis, It was confirmed that cement matrix using Alkaline Aqueous and Blast Furnace Slag has a tighter structure in internal porosity and porosity distribution than using general mixing water.

• Journal of the East Asian Society of Dietary Life
• /
• v.21 no.5
• /
• pp.731-738
• /
• 2011

Cholesterol is the precursor of various steroid hormones, bile acid, and vitamin D with functions related to regulation of membrane permeability and fluidity. However, the presence of excess blood cholesterol may lead to arteriosclerosis and hypertension. Moreover, dietary cholesterol may affect blood cholesterol levels. Generally, cholesterol determination is performed by spectrophotometric or chromatographic methods, but these methods are very time consuming and costly, and require complicated pretreatment. Thus, the development of a rapid and simple analysis method for measuring cholesterol concentration in food is needed. Multi-walled carbon nanotube (MWCNT) was functionalized to MWCNT-$NH_2$ via MWCNT-COOH to have high sensitivity to $H_2O_2$. The fabricated MWCNT-$NH_2$ was attached to a glassy carbon electrode (GCE), after which Prussian blue (PB) was coated onto MWCNT-$NH_2$/GCE. MWCNT-$NH_2$/PB/GCE was used as a working electrode. An Ag/AgCl electrode and Pt wire were used as a reference electrode and counter electrode, respectively. The sensitivity of the modified working electrode was determined based on the amount of current according to the concentration of $H_2O_2$. The response increased with an increase of $H_2O_2$ concentration in the range of 0.5~500 ${\mu}M$ ($r^2$=0.96) with a detection limit of 0.1 ${\mu}M$. Cholesterol oxidase was immobilized to aminopropyl glass beads, CNBr-activated sepharose, Na-alginate, and toyopearl beads. The immobilized enzyme reactors with aminopropyl glass beads and CNBr-activated sepharose showed linearity in the range of 1~100 ${\mu}M$ cholesterol. Na-alginate and toyopearl beads showed linearity in the range of 5~50 and 1~50 ${\mu}M$ cholesterol, respectively. The detection limit of all immobilized enzyme reactors was 1 ${\mu}M$. These enzyme reactors showed high sensitivity; especially, the enzyme reactors with CNBr-activated sepharose and Na-alginate indicated high coupling efficiency and sensitivity. Therefore, both of the enzyme reactors are more suitable for a cholesterol biosensor system.

• Journal of the Korean Chemical Society
• /
• v.36 no.2
• /
• pp.261-272
• /
• 1992

Tetradentate Schiff base Cobalt(II)(3MeOSED)$(H_2O)_2$ complexe was synthesized and allowed to react with dry oxygen to form oxygen adducts of Cobalt(III) complexes such as ${\mu}$-peroxo type [Co(III)(3MeOSED)(DMF)]$_2O_2$ and [Co(III)(3MeOSED)(DMSO)]$_2O_2$in DMF and DMSO or superoxo type [Co(III)(3MeOSED)(Py)]$O_2$ in pyridine. The oxygen adducted complex was investigated by cyclic voltammetry and DPP method with glassy carbon electrode in 0.1M TEAP-DMF (-DMSO,-Py) as supporting electrolyte solution. As a result the reduction reaction process occurred to four steps including prewave Of $O_2^-$in 1 : 1 oxygen adducted superoxo type [Co(III)(3MeOSED)(Py)]$O_2$complex and three steps not including prewave of $O_2^-$ in 1 : 2 oxygen adducted ${\mu}$-peroxo type [Co(III)-(3MeOSED)(DMF)]$_2O_2$ and [Co(III)(3MeOSED)(DMSO)]$_2O_2$. A superoxo type [Co(III)(3MeOSED)(L)]$O_2\;(L: CH_3OH)$ was generated with oxygen in methanol. Selectively oxidized hydrazobenzene $(H_2AB)$ to trans-azobenzene(t-AB) and the rate constant k for oxidation reaction of the following equation is $(2.96 {\pm} 0.2)$${\times}$ $10^{-1}$M/sec. $H_2AB$ + Co (II)(3MeOSED)$(L_2)+O_2\;{\rightleftarrow^K}$ [Co(III)(3MeOSED)(L)]$O_2{\cdot}H_2AB{\longrightarrow^K}$ Co(II(3MeOSED)$(L)_2$+t-AB+$H_2O_2 $.