• Journal of Hydrogen and New Energy
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• v.24 no.2
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• pp.107-112
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• 2013

The ZnO is able to produce hydrogen from water however it can only absorb ultraviolet region due to its 3.37eV of wide band gap. Therefore efficiency of solar hydrogen production is low. In this work we report investigation results of improved visible light photo-catalytic properties of CdSe quantum dots(QDs) sensitized ZnO nanorod heterostructures. Hydrothermally vertically grown ZnO nanorod arrays on FTO glass were sensitized with CdSe by using SILAR(successive ionic layer adsorption and reaction) method. Morphology of grown ZnO and CdSe sensitized ZnO nanorods had been investigated by FE-SEM that shows length of $2.0{\mu}m$, diameter of 120~150nm nanorod respectively. Photocatalytic measurements revealed that heterostructured samples show improved photocurrent density under the visible light illumination. Improved visible light performance of the heterostructures is resulting from narrow band gap of the CdSe and its favorable conduction band positions relative to potentials of ZnO band and water redox reaction.

• Journal of the Korean Applied Science and Technology
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• v.6 no.1
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• pp.1-7
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• 1989

To developed new process for obtaining maximum molecular weight of anionic acrylamide and acrylic acid copolymer by inverse emulsion polymerization. Concentration of initiator, reducing agent, surfactant and mole ratio of acrylamide-acrylic acid were studied for the process. Semi-batch processes with method of redox, control of reaction temperature, feeding method of monomer and reaction time, was suitable for maximum molecular weight of P(AMAC) from this process obtained $3.09\;{\time}\;10^6({\bar{M}}n.)$ and $4.41\;{\time}\;10^6({\bar{M}}w.)$ in molecular weight measured by the intrinsic viscosity method. inverse emulsion polymerization mechanism of P(AMAC) does not followed the Smith-Ewart and Medvedev theory, but selected for concentration of initiator, reducing agent, surfactant, water solubility of monomer.

• Journal of the Korean Applied Science and Technology
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• v.18 no.4
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• pp.254-260
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• 2001

The Mo(V) $di-{\mu}-oxo$ type [$Mo_{2}O_{4}(H_{2}O)_{2}L_{2}$] $SO_{4}$ complexes(L: 2,2'-dipyridyl,4,4'-ethylenedianlline) have been prepared by the reaction of $[Mo_{2}O_{4}(H_{2}O)_{6}]SO_{4}$ with a series of chelate ligands. These complexes are completed by two terminal oxygens arranged trans to one another and each ligand forms a chelate types. In $Mo_{2}O_{4}(H_{2}O)_{2}L_{2}$, two $H_{2}O$ coordinated at trans site of terminal oxygens. The prepared complexes have been characterized by elemental analysis, infrared spectra, $^{1}H$ nuclear magnetic resonance spectra, and thermal analysis(TG-DTA). In the potential range -0.00V to -1.00V at a scan rate of $50mVs^{-1}$, a cathodic peak at -0.81V ${\sim}$ -0.87V (vs SCE) and an anodic peak at -0.61V ${\sim}$ -0.63V (vs SCE) have been observed in aquous solution. We infer these redox are irreversible reaction.

• Bulletin of the Korean Chemical Society
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• v.24 no.12
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• pp.1751-1756
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• 2003

An electrochemical study related to the electroreduction of 4-amino-6-methyl-3-thio-1,2,4-triazin-5-one(I), 6-methyl-3-thio-1,2,4-triazin-5-one(II), and 2,4-dimetoxy-6-methyl-1,3,5-triazine(III) in dimethylformamide at glassy carbon electrode has been performed. A variety of electrochemical techniques, such as differential pulse voltammetry (DPV), cyclic voltammetry (CV), chronoamperometry, and coulometry were employed to clarify the mechanism of the electrode process. The compounds I and II with thiol group exhibited similar redox behavior. Both displayed two cathodic peaks, whereas the third compound, III, without thiol group showed only one cathodic peak in the same potential range of the second peak of I and II. The results of this study suggest that in the first step the one electron reduction of thiol produced a disulfide derivative and in the second reduction step the azomethane in the triazine ring was reduced in two electron processes. A reduction mechanism for all three compounds is proposed on this basis. In addition, some numerical constants, such as diffusion constant, transfer coefficient, and rate constant of coupled chemical reaction in the first reduction peak were also reported.

• Journal of Electrochemical Science and Technology
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• v.1 no.2
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• pp.75-80
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• 2010

We report Co-tetramethoxyphenylporphyrin on carbon particles (Co-TMPP/C) as a non-Pt catalyst for tri-iodide reduction in dye-sensitized solar cells (DSSCs). The presence of well-dispersed carbon and cobalt source in the catalyst surface is confirmed by transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray analysis. In the C 1s, Co 2p, and N 1s peaks measured by X-ray photoelectron spectroscopy, the C-N, Co-$N_4$, and N-C are assigned to the component at 285.7, 781.8, and 401 eV, respectively. Especially, the Co-TMPP/C shows improved current density, diffusion coefficient, and charge-transfer resistance in the ${I_3}^-/I^-$ redox reaction compared to conventional catalysts. Furthermore, in the DSSCs performance, the Co-TMPP/C shows increased short circuit current density, higher open circuit voltage, and improved cell efficieny in comparison with Pt/C.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1290-1296
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• 2012

Fenton reaction and iron autoxidation have been debated for the major process in ROS mediated DNA cleavage. We compared both processes on iron oxidation, DNA cleavage, and cyclic voltammetric experiment at different pHs. Both oxidation reactions were preferred at basic pH condition, unlike DNA cleavage. This indicates that iron oxidation and the following steps probably occur separately. The ROS generated from autoxidation seems to be superoxide radical since sod exerted the best inhibition on DNA cleavage when $H_2O_2$ was absent. In comparison of cyclic voltammograms of $Fe^{2+}$ in NaCl solution and phosphate buffer, DNA addition to phosphate buffer induced significant change in the redox cycle of iron, indicating that iron may bind DNA as a complex with phosphate. Different pulse voltammogram in the presence of ctDNA suggest that iron ions are recyclable at acidic pH, whereas they may form an electrically stable complex with DNA at high pH condition.

• Journal of the Korean Applied Science and Technology
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• v.25 no.2
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• pp.168-174
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• 2008

This study is focused on the antimicrobial activity of cyanobacteria Microcystis aeruginosa by the reduction and oxidation reaction of copper and zinc alloy metal fiber filter. Cu/Zn ion is easily makes radicals with molecular hydroperoxide. Especially, hydroperoxide radical shows strong toxicity to the strains. Plasma membrane causes conformational change when hydroperoxide radical binds to plasma membrane. Elution of copper ion from copper and zinc alloy metal fiber is detected in the cyanobacteria solution as 0.5 ppm, and that of zinc ion is 0 ppm respectively. Zinc ion is figured to form a hydroxide in the cyanobacteria solution and precipitated to form a sludge. The concentration of chlorophyll-a in the cyanobacteria solution was proved to be the index of antimicrobial level of Microcystis aeruginosa.

• Journal of Soil and Groundwater Environment
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• v.26 no.4
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• pp.1-7
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• 2021

The removal of PCBs (Polychlorinated biphenyls) in aqueous phase was investigated in the ultraviolet (UV) process, ultrasonics (US) process and ultraviolet/ultrasonic (UV/US) process using PCB No.7 and Aroclor 1260. For PCB No.7 relatively high removal efficiency over 90% was obtained during 20 min in the UV process and UV/US process. On the other hand, lower removal efficiency of 50 - 70% was achieved for it consisted of individual congeners of PCBs containing 3~8 of chlorine atom. It was found that the dechlorination reaction (the photolytic cleavage of C-Cl bond) was considered as a main removal mechanism in the UV process while PCBs were removed by cavitation-induced radical reaction in the US process. No significant dechlorination occurred in the US process. Consequently, it was suggested that the UV process or UV/US process was applicable for the removal of PCBs in aqueous phase in terms of the removal efficiency and operation time. In addition, the application of saturating gas such as Ar and Air could be considered to control redox condition and enhance the severity of acoustic cavitation for the removal of PCBs.

• Membrane and Water Treatment
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• v.14 no.4
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• pp.181-189
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• 2023

The Covid-19 pandemic has increased demand for chlorine-based sanitizing solutions, most of which contain hypochlorous acid (HOCl) as an active agent. Free chlorine (HOCl) in these sanitizers is crucial for their efficacy. Disposable test strips are affordable and convenient tools for determining various qualitative and quantitative parameters. In this study, disposable opto-chemical test strips were developed by physically immobilizing 3,3',5,5'-tetramethylbenzidine (TMB) and o-dianisidine (o-D) reagents on chromatography and filter paper-based test strips for the visualization and detection of free chlorine in the form of HOCl. The reagents undergo a rapid color change upon reaction with chlorine through a redox reaction. The paper-based test strips showed rapid color change within a minute and a low sample volume requirement (1 ml). This portable, disposable paper-based test strip is a simple and cost-effective way to rapidly detect the presence of HOCl sanitizers for home and field applications. Both TMB and o-D successfully detected chlorine. Chromatography paper proved to be the more efficient option among the two papers used as substrates for the reagents (TMB and o-D). It exhibited high retention capacity and high performance in terms of color transformation when reacting with HOCl, even after two months of storage.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.509-517
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• 2019

The birnessite (7Å manganate, δ-MnO₂) which is a manganese oxide and comprises manganese nodules, is a major manganese mineral on the earth surface and a precursor in the synthesis of todorokite. In this study birnessite was synthesized by three different methods: Feng et al. (2004) and Luo et al. (1998) based on redox reaction and Ma et al. (1999) based on reduction reaction. 12 birnessite samples were synthesized by different combinations of Na⁺ and K⁺ cations based on the base (OH^-) and permanganate (MnO₄^-) reagents in the synthesis. The mineral compositions of synthesized birnessite were identified by XRD, and the two cation ratio in the mineral was measured by ICP. The products obtained after hydrothermal treatment of Mg-buserite, by the precursor of birnessite, was examined by XRD, and then phase transition to todorokite and their characteristics were compared. Our results show that the byproducts and the characteristics of phase transition by each synthetic method have different trends. Hausmannite (γ-Mn₃O₄) and feitknechtite (β-MnOOH) were formed by both methods in the redox reaction mechanism. By Feng et al. (2004)'s method, manganite (γ-MnOOH) phase only appeared when cation was predominantly Na⁺. Two birnessite samples synthesized by redox reaction mechanism showed phase transition to todorokite (10Å manganate, OMS-1) when both NaOH and KMnO₄ were used together. However, single-phase birnessite was formed by Ma et al. (1999)'s method, and phase transition was confirmed only for the sample when the cation was only composed of Na⁺.