• Journal of Integrative Natural Science
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• v.2 no.3
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• pp.211-214
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• 2009

A new porous silicon (PSi) microcavity sensor for the detection of volatile organic compounds (VOCs) was developed. PSi microcavity sensor exhibiting unique reflectivity was successfully obtained by an electrochemical etching of silicon wafer. When PSi was fabricated into a structure consisting of two high reflectivity muktilayer mirrors separated by an active layer, a microcavity was formed. This PSi microcavity is very sensitive structures. Reflection spectrum of PSi microcavity indicated that the full-width at half-maximum (FWHM) was of 10 nm and much narrower than that of fluorescent organic molecules or quantum dot. The detection of volatile organic compounds (VOCs) using PSi microcavity was achieved. When the vapor of VOCs condensed in the nanopores, the refractive indices of entire particle increased. When PSi microcavity was exposed to acetone, ether, and toluene, PSi microcavity in reflectivity was red shifted by 28 nm, 33 nm, and 20 nm for 2 sec, respectively.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1588-1592
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• 2009

Lithium cyanoaluminum hydride (LCAH) was prepared by the metal cation exchange reaction of sodium cyanoaluminum hydride with lithium chloride in tetrahydrofuran. The reducing characteristics of LCAH were explored systematically by the reaction with selected organic compounds containing representative functional groups under the standardized conditions (tetrahydrofuran, 0 ${^{\circ}C}$). The reducing ability of LCAH was also compared with of the sodium derivative, sodium cyanoaluminum hydride (SCAH). Generally, the reducing behavior of LCAH resembles that of SCAH closely, but the reactivity of LCAH toward representative organic functional groups appeared to be stronger than that of SCAH. Thus, the regent reduces carbonyl compounds, epoxides, amides, nitriles, disulfides, carboxylic acids and their acyl derivatives to the corresponding alcohols or amines, at a relatively faster rate than that of SCAH. The cyano substitution, a strong election-withdrawing group, diminishes the reducing power of the parent metal aluminum hydrides and hence effects the alteration of their reducing characteristics.

• Bulletin of the Korean Chemical Society
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• v.8 no.5
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• pp.418-421
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• 1987

Syntheses of cefotaxime analogs with halosubstituted phenyltetrazolthiomethyl at the $C_{3^-}$position are described. Their in vitro potency was established. The compounds exhibited a broad antibacterial spectrum. Some of these compounds showed activity against Gram-positive bacteria superior to the parent cefotaxime. Against Gram-negative bacteria, these compounds are less effective than cefotaxime.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.6
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• pp.885-891
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• 2005

The study was carried out to find the effect of freeze drying on the volatile organic components in garlic (Allium sativum L.). The volatile organic compounds from fresh and freeze dried garlic were extracted by simultaneous steam distillation and extraction (SDE) method and identified with GC/MS analysis. A total of 42 and 32 compounds were identified in fresh and freeze-dried garlic, respectively. Sulfur containing compounds in the garlic samples were detected as the major compounds, and alcohols, aldehydes and esters were detected as minor compounds. Diallyl disulfide, diallyl trisulfide, allyl methyl disulfide and ally1 methyl trisulfide were the main sulfur compounds in fresh and freeze dried garlic. The amount of sulfur containing compounds were decreased freeze-drying but methyl propyl trisulide, 3- allylthiopropionic acid, cyclopentyl ethyl sulfide etc. were increased. The others, non- sulfur containing compounds such as ethyl acetate, ethanol, 2-propenol, 2- propenal and hexanal were increased in freeze-dried garlic. Consequently, the total amount of volatile organic compounds in garlic became lower during freeze-drying from 853.42 mg/kg to 802.21 /kg, and the composition of major components were nearly same in fresh and freeze-dried garlic.

• Journal of Korea Soil Environment Society
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• v.3 no.2
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• pp.101-114
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• 1998

Soil vapor extraction (SVE) is known to be an effective process to remove the contaminants from the soils by enhancing the vaporization of organic compounds using forced vapor flows or applying vacuum through soils. Experiments are carried out to investigate the effects of the organic contaminants, types of soils, and water contents on the removal efficiency with operating time. In the study, simulated soils include the glass bead which has no micropore, sand and molecular sieve which has a large volume of micropores. As model organic pollutants, toluene, methyl ethyl ketone, and trichloroethylene are selected. Desorption experiments are conducted by flowing nitrogen gas. Under the experimental conditions, it is found that there are linear relationships between logarithm of removal efficiency and logarithm of number of pore volumes. The number of pore volumes are defined as the total amount of air flow through the soil column divided by the pore volume of soil column. For three organic compounds studied, the removal rate is slow for no water content, while the number of pore volumes for removal of organic compounds are notably reduced for water contents up to 37%. For the removal of dense organic compound, such as trichloroethylene, a large number of pore volumes are needed. Also, the effects of the characteristics of simulated soils on the removal efficiency of organic compounds are studied. After the characterization of soil surface, porosity of soil columns and types of contaminants, the results could provide a basis for the design of SVE process.

• Journal of Soil and Groundwater Environment
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• v.17 no.6
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• pp.59-68
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• 2012

This study provided sorption properties of chlorofluorocarbons (CFCs), and elucidated potential application of CFC sorption data in hydrogeochemistry. Prior sorption studies were reviewed for hydrophobic organic compounds similar to the CFCs, because there were only few CFC sorption studies. The CFCs are regarded as relatively conservative chemicals in groundwater environments based on their moderate hydrophobicity. However, thermally altered carbonaceous matter (TACM) can significantly increase sorption capacity and nonlinearity for hydrophobic organic compounds such as CFCs, compared to general soil organic matter. CFC sorption behavior are close to the sorption for reviewed organic chemicals. Therefore, the CFC sorption data can be used for determining hydrogeochemical properties and predicting transport of organic contaminants in TACM-containing aquifer environments.

• Korean Journal of Materials Research
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• v.30 no.10
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• pp.515-521
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• 2020

Organic-inorganic hybrid perovskite nanocrystals have attracted a lot of attention owing to their excellent optical properties such as high absorption coefficient, high diffusion length, and photoluminescence quantum yield in optoelectronic applications. Despite the many advantages of optoelectronic materials, understanding on how these materials interact with their environments is still lacking. In this study, the fluorescence properties of methylammonium lead bromide (CH₃NH₃PbBr₃, MAPbBr₃) nanoparticles are investigated for the detection of volatile organic compounds (VOCs) and aliphatic amines (monoethylamine, diethylamine, and trimethylamine). In particular, colloidal MAPbBr₃ nanoparticles demonstrate a high selectivity in response to diethylamine, in which a significant photoluminescence (PL) quenching (~ 100 %) is observed at a concentration of 100 ppm. This selectivity to the aliphatic amines may originate from the relative size of the amine molecules that must be accommodated in the perovskite crystals structure with a narrow range of tolerance factor. Sensitive PL response of MAPbBr₃ nanocrystals suggests a simple and effective strategy for colorimetric and fluorescence sensing of aliphatic amines in organic solution phase.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.11a
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• pp.281-285
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• 2000

The effect of the presence of dissolved organic matters(DOM) on the binding of phenanthrene to cetylpyridinium chloride(CPC) coated sand was investigated. The distribution coefficient of phenanthrene increased with increase of sufactant coverage, and decreased with the presence of dissolved organic matters except for the 1.600mg/g coverage case. Both Aldrich humic acid and extracted dissolved organic matter showed the similar tendency. For the quantification of the overall distribution coefficient, this study presented mass distribution model and estimated the sorption equilibrium coefficients of hydrophobic organic compounds(HOCs) in multi system. The suggested model combined a series of sorption equilibrium relationships including the adsorption of DOMs on sorbents, the binding between HOCs and DOMs, and the sorption of HOCs on sorbents with or without DOMs.

• Journal of Life Science
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• v.24 no.8
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• pp.887-894
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• 2014

The screening of the microorganisms degrading chlorinated organic compounds such as PCP (pentachlorophenol) and TCE (trichloroethylene) was conducted with soil and industrial wastewater contaminated with various chlorinated organic compounds. Isolates (GP5, GP19) capable of degrading PCP and isolates (GA6, GA15) capable of degrading TCE were identified as Acetobactor sp., Pseudomonas sp., Arthrobacer sp., Xanthomonas sp. and named Acetobacter sp. GP5, Pseudomonas sp. GP19, Arthrobacer sp. GA6 and Xanthomoas sp. GA15, respectively. The microbial augmentation, OC17 formulated with the mixture of bacteria including isolates (4 strains) degrading chlorinated organic compounds and isolates (Acinetobacter sp. KN11, Neisseria sp. GN13) degrading aromatic hydrocarbons. Characteristics of microbial augmentation OC-17 showed cell mass of $2.8{\times}10^9CFU/g$, bulk density of $0.299g/cm^3$ and water content of 26.8%. In the experiment with an artificial wastewater containing PCP (500 mg/l), degradation efficiency of the microbial augmentation OC17 was 87% during incubation of 65 hours. The degradation efficiency of TCE (300 uM) by microbial augmentation OC17 was 90% during incubation of 50 hours. In a continuous culture experiment, analysis of the biodegradation of organic compounds by microbial augmentation OC17 in industry wastewater containing chlorinated hydrocarbons showed that the removal rate of COD was 91% during incubation of 10 days. These results indicate that it is possible to apply the microbial augmentation OC17 to industrial wastewaters containing chlorinated organic compounds.

• Journal of Environmental Science International
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• v.22 no.9
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• pp.1153-1160
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• 2013

While a range of natural organic matter (NOM) types can generate high levels of disinfection by-products (DBPs) after chlorination, there is little understanding of which specific compounds act as precursors. Use of eight model compounds allows linking of explicit properties to treatability and DBP formation potential (DBPFP). The removal of model compounds by various treatment processes and their haloacetic acid formation potential (HAAFP) before and after treatment were recorded. The model compounds comprised a range of hydrophobic (HPO) and hydrophilic (HPI) neutral and anionic compounds. On the treatment processes, an ozone oxidation process was moderate for control of model compounds, while the HPO-neutral compound was most treatable with activated carbon process. Biodegradation was successful in removing amino acids, while coagulation and ion exchange process had little effect on neutral molecules. Although compared with the HPO compounds the HPI compounds had low HAAFP the ozone oxidation and biodegradation were capable of increasing their HAAFP. In situations where neutral or HPI molecules have high DBPFP additional treatments may be required to remove recalcitrant NOM and control DBPs.