• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.93-99
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• 2020

A colorimetric paper sensor was used to detect volatile nitrogen-containing compounds emitted from spoiled salmon filets to determine their freshness. The sensing mechanism was based on acid-base reactions between acidic pH-indicating dyes and basic volatile ammonia and amines. A sensing layer was simply fabricated by drop-casting a dye solution of bromocresol green (BCG) on a polyvinylidene fluoride substrate, and its color-change response was enhanced by optimizing the amounts of additive chemicals, such as polyethylene glycol, p-toluene sulfonic acid, and graphene oxide in the dye solution. To avoid the adverse effects of water vapor, both faces of the sensing layer were enclosed by using a polyethylene terephthalate film and a gas-permeable microporous polytetrafluoroethylene sheet, respectively. When exposed to basic gas analytes, the paper-like sensor distinctly exhibited a color change from initially yellow, then to green, and finally to blue due to the deprotonation of BCG via the Brønsted acid-base reaction. The use of ammonia analyte as a test gas confirmed that the sensing performance of the optimized sensor was reversible and excellent (detection time of < 15 min, sensitive naked-eye detection at 0.25 ppm, good selectivity to common volatile organic gases, and good stability against thermal stress). Finally, the coloration intensity of the sensor was quantified as a function of the storage time of the salmon filet at 28℃ to evaluate its usefulness in monitoring of the food freshness with the measurement of the total viable count (TVC) of microorganisms in the food. The TVC value increased from 3.2 × 10⁵ to 3.1 × 10⁹ cfu/g in 28 h and then became stable, whereas the sensor response abruptly changed in the first 8 h and slightly increased thereafter. This result suggests that the colorimetric response could be used as an indicator for evaluating the degree of decay of salmon induced by microorganisms.

• Journal of the Korean Chemical Society
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• v.55 no.2
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• pp.208-217
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• 2011

The effects of pH and temperature on the removal of two dyes (neutral red; NR and malachite green oxalates; MG) from aqueous effluents using Maghnia montmorillonite clay in a batch adsorption process were investigated. The results showed the stability of the optical properties of MG in aqueous solution and adsorbed onto clay under wide range of pH 3-9. However, the interaction of NR dye with clay is accompanied by a red shift of the main absorption bands of monomer cations under pH range of 3-5, whereas, those of neutral form remains nearly constant over the pH range of 8-12. The optimal pH for favorable adsorption of the dyes, i.e. ${\geq}$90% has been achieved in aqueous solutions at 6 and 7 for NR and VM respectively. The most suitable adsorption temperatures were 298 and 318 K with maximum adsorption capacities of 465.13mg/g for NR and 459.89 mg/g for MG. The adsorption equilibrium results for both dyes follow Langmuir, Freundlich isotherms. The numerical values of the mean free energy $E_a$ of 4.472-5.559 kj/mol and 2.000-2.886 kj/mol for NR and MG respectively indicated physical adsorption. Various thermodynamic parameters, such as ${\Delta}H^{\circ}$, ${\Delta}S^{\circ}$, ${\Delta}G^{\circ}$ and Ea have been calculated. The data showed that the adsorption process is spontaneous and endothermic. The sticking probability model was further used to assess the potential feasibility of the clay mineral as an alternative adsorbent for organic ion pollutants in aqueous solution.

• Journal of the Korean Chemical Society
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• v.31 no.4
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• pp.295-300
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• 1987

Spectroscopic studies have been carried out on the metachromatic behavior of methylene blue(MB) and acridine orange(AO) in the presence of chondroitin sulfate A(CSA) and chondroitin sulfate C(CSC). The characteristic changes of the meta-band with the changes of P/D value are discussed in terms of the stacking theory. Quantitative studies on the stacking effect are made to calculate the number of bound molecules of dye per unit molecule of the polyanion. The result shows that MB has stronger stacking effect than AO. A stacking model and the dimension of the bound dyes on the surface of the polyanion are proposed, on the basis of the dimer model of planar aromatic dyes and the most stable conformation of the CSA chain. The model is found to be reasonable in accordance with the experimental results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.440-440
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• 2009

Semiconductor nanowires offer exciting possibilities as components of solar cells and have already found applications as active elements in organic, dye-sensitized, quantum-dot sensitized, liquid-junction, and inorganic solid-state devices. Among many semiconductors, silicon is by far the dominant material used for worldwide photovoltaic energy conversion and solar cell manufacture. For silicon wire to be used for solar device, well aligned wire arrays need to be fabricated vertically or horizontally. Macroscopic silicon wire arrays suitable for photovoltaic applications have been commonly grown by the vapor-liquid-solid (VLS) process using metal catalysts such as Au, Ni, Pt, Cu. In the case, the impurity issues inside wire originated from metal catalyst are inevitable, leading to lowering the efficiency of solar cell. To escape from the problem, the wires of purity of wafer are the best for high efficiency of photovoltaic device. The fabrication of wire arrays by the electrochemical etching of silicon wafer with photolithography can solve the contamination of metal catalyst. In this presentation, we introduce silicon wire arrays by electrochemical etching method and then fabrication methods of radial p-n junction wire array solar cell and the various merits compared with conventional silicon solar cells.

• The Plant Pathology Journal
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• v.28 no.3
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• pp.270-281
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• 2012

The bacteria B1-9 that was isolated from the rhizosphere of the green onion could promote growth of pepper, cucumber, tomato, and melon plants. In particular, pepper yield after B1-9 treatment on the seedling was increased about 3 times higher than that of control plants in a field experiment. Partial 16S rDNA sequences revealed that B1-9 belongs to the genus Pantoea ananatis. Pathogenecity tests showed non-pathogenic on kimchi cabbage, carrot, and onion. The functional characterization study demonstrated B1-9's ability to function in phosphate solubilization, sulfur oxidation, nitrogen fixation, and indole-3-acetic acid production. To trace colonization patterns of B1-9 in pepper plant tissues, we used $DRAQ5^{TM}$ fluorescent dye, which stains the DNAs of bacteria and plant cells. A large number of B1-9 cells were found on the surfaces of roots and stems as well as in guard cells. Furthermore, several colonized B1-9 cells resided in inner cortical plant cells. Treatment of rhizosphere regions with strain B1-9 can result in efficient colonization of plants and promote plant growth from the seedling to mature plant stage. In summary, strain B1-9 can be successfully applied in the pepper plantation because of its high colonization capacity in plant tissues, as well as properties that promote efficient plant growth.

• Environmental Analysis Health and Toxicology
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• v.22 no.1 s.56
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• pp.27-36
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• 2007

Cyanides and dichlorophenols were important pollutants in industrial effluents of steel, petroleum, plastics, pesticides, synthetic dye and/or fiber manufacturing. The toxic effects of cyanide and 3, 5-dichlorophenol in the unary and binary solutions to Vibrio fischeri were determined using the newly developed $N-tox^{(R)}$ bioassay system. This bioassay system relies upon the attenuation of light intensity emitted by Vibrio fischeri exposed to various pollutants including metals and organic compounds. Most of studies dealing with toxicity of pollutants concerned single chemical species, while the organisms were typically exposed to pollutant mixtures. The present study showed that the toxicity of some binary combinations of cyanide and 3, 5-dichlorophenol significantly was lower than the predicted toxicity from the addicted model. This antagonistic interaction was well explained by chemical interaction model presented in this study.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11a
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• pp.134-142
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• 2005

The experimental setups for flow visualization and processes identification in laboratory scale (so cal led Flow Lab.) has developed to get ideas and answer fundamental questions of flow and migration in geologic media. The setup was made of a granite block of $50{\times}50cm$ scale and a transparent acrylate plate. The tracers used in this experiments were tritiated water, anions, and sorbing cations as well as an organic dye, eosine, to visualize migration paths. The migration plumes were taken with a digital camera as a function of time and stored as digital images. A migration model was also developed to describe and identify the transport processes. Computer simulation was carried out not only for the hydraulic behavior such as distributions of pressure and flow vectors in the fracture but also for the migration plume and the elution curves.

• Journal of Microbiology and Biotechnology
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• v.12 no.6
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• pp.901-908
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• 2002

The relationship between the layered structure of granules in UASB reactors and microbial resistance to toxicity was investigated using disintegrated granules. When no toxic materials were added to the media, the intact and disintegrated granules exhibited almost the same ability to decrease COD and to produce methane. However, when metal ions and organic toxic chemicals were added to a synthetic wastewater, he intact granules were found to be more resistant to toxicity than the disintegrated granules, as determined by the methane production. The difference in resistance between the intact and disintegrated granules was maximal, with toxicant concentrations ranging from 0.5 mM to 2 mM for trichloroethylene with toluene and 5 mM to 20 mM for metal ions (copper, nickel, zinc. chromium, and cadmium ions). The augmented COD removal rate by granulation compared to disintegrated granules was also measured in the treatment of synthetic and real wastewaters; synthetic wastewater, $-2.6\%$; municipal wastewater, $2.8\%$; swine wastewater, $6.4\%$; food wastewater, $25.0\%$; dye works wastewater, $42.9\%$; and landfill leachate, $61.8\%$. Continuous reactor operation also demonstrated that the granules in the UASB reactor were helpful in treating toxic wastewater, such as landfill leachate.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2765-2770
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• 2011

Organic dye-doped glasses, viz., ruthenium (II) tris(4,7'-diphenyl-1,10'-phenanthroline) $[Ru(dpp)_3]^{2+}$ incorporated into thin silica xerogel films produced by the sol-gel method, were prepared and their $O_2$ quenching properties investigated as a function of the $[Ru(dpp)_3]^{2+}$ concentration (3-400 ${\mu}M$) within the xerogel. The ratio of the luminescence from the $[Ru(dpp)_3]^{2+}$-doped films in the presence of $N_2$ and $O_2$ ($I_{N2}/I_{O2}$) was used to describe the film sensitivity to $O_2$ quenching. ($I_{N2}/I_{O2}$ changed three-fold over the $[Ru(dpp)_3]^{2+}$ concentration range. Time-resolved intensity decay studies showed that there are two discrete $[Ru(dpp)_3]^{2+}$ populations within the xerogels (${\tau}_1$ ~ 300 ns; ${\tau}_2$ ~ 3000 ns) whose relative fraction changes as the $[Ru(dpp)_3]^{2+}$ concentration changes. The increased $O_2$ sensitivity that is observed at the higher $[Ru(dpp)_3]^{2+}$ concentrations is a manifestation of a greater fraction of the 3000 ns $[Ru(dpp)_3]^{2+}$ species (more susceptible to $O_2$ quenching). A model is presented to describe the observed response characteristics resulting from $[Ru(dpp)_3]^{2+}$ distribution within the xerogel.

• Journal of the Semiconductor & Display Technology
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• v.8 no.4
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• pp.15-19
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• 2009

A high efficient organic red light emitting device with structure of DNTPD/TAPC/$Bebq_2$ :[$(pq)_2Ir(acac)$, SFC-411]/SFC-137 was fabricated on the plastic substrate, which can be applied in the fields of flexible display and illumination. In the device structure, N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolylamino)-phenyl]-biphenyl-4,4'-diamine[DNTPD] as a hole injection layer and 1,1-bis-(di-4-tolylaminophenyl) cyclohexane [TAPC] as a hole transport were used. Bis(10-hydroxybenzo[h]quinolinato) beryllium complex [$Bebq_2$] was used as a light emitting host material. The host material, $Bebq_2$ was doubly doped with volume ratio of 7% iridium(III)bis-(2-phenylquinoline)acetylacetonate[$(pq)_2$Ir(acac)] and 3% SFC-411[red phosphor dye coded by the proprietary company]. And then, SFC-137 was used as an electron transport layer. The luminous intensity and current efficiency of the fabricated device were $22,780\;cd/m^2$ at 9V and 17.3 cd/A under $10,000\;cd/m^2$, respectively. The maximum current efficiency of the device was 22.4cd/A under $580\;cd/m^2$.