• 한국대기환경학회지
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• 제32권2호
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• pp.131-157
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• 2016

A smog chamber has been an effective tool to study air quality, particularly secondary organic aerosol (SOA), which is typically formed by atmospheric oxidation of volatile organic compounds (VOCs). In controlled environments, smog chamber studies have validated atmospheric oxidation by identifying, quantifying and monitoring products with state-of-art instruments (e.g., aerosol mass spectrometer, scanning mobility particle sizer) and provided chemical insights of SOA formation by elucidating reaction mechanisms. This paper reviews types of smog chambers and the current state of smog chamber studies that have accomplished to find pathways of SOA formation, focusing on gas-particle partitioning of semivolatile products of VOC oxidation, heterogeneous reactions on aerosol surface, and aqueous chemistry in aerosol waters (e.g., cloud/fog droplets and wet aerosols). For future chamber studies, then, this paper discusses potential formation pathways of fine particles that East Asia countries (e.g., Korea and China) currently suffer from due to massive formation that gives rise to fatal health problems.

• 한국자기공명학회논문지
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• 제9권2호
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• pp.138-154
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• 2005

Vanadium-incorporated aluminophosphate molecular sieve $VO^{2+}-SAPO-5$ was studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopies to determine the vanadium structure and interaction with various adsorbate molecules. It was found that the main species at low concentration of vanadium is a monomeric vanadium units in square pyramidal or distorted octahedral coordination, both in oxidation state (IV) for the calcined hydrated material and in oxidation state (V) for the calcined material. After calcinations in $O_2$ and exposure to moisture, only species A is observed with reduced intensities. It is suggested as a $VO(H_2O)_3^{2+}$ complex coordinated to two framework oxygen bonded aluminum. When calcined, hydrated $VO^{2+}-}SAPO-5$ is dehydrated at elevated temperature, a species loses its water ligands and transforms to $VO^{2+}$ ions coordinated to two framework oxygens (species B). Species B reduces its intensity, significantly after treatment with $O_2\;at\;600^{\circ}C$ for 5 h, thus suggesting oxidation of $V^{4+}\;to\;V^{5+}$. When dehydrated $VO^{2+}-SAPO-5$ contacts with $D_2O$ at room temperature, the EPR signal of species A is observed. Thus species assumed as a $VO^{2+}(O_f)_2(D_2O)_3$, by considering two framework oxygens. Adsorption of deuterated ethanol, propanol on dehydrated $VO^{2+}_{-}SAPO-5$ result in another new vanadium species E and F, respectively, which are identified as a $VO^{2+}-(CH_3CH_2OD)_3,\;VO^{2+}-(CH_3CH_2CH_2OD)_2$ complex. When deuterated benzene is adsorbed on dehydrated $VO^{2+}-SAPO-5$, another new vanadium species G, identified as a $VO^{2+}-(C_6D_6)$ is observed. Possible coordination geometries of these various complexes are discussed.

• Journal of Nutrition and Health
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• 제44권6호
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• pp.507-517
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• 2011

The purpose of this study was to investigate the effects of gender on the thermic effect of food and substrate oxidation rate during 5 hours after a mixed meal. Twenty healthy college students (10 males and 10 females) aged 20-26 years participated in this study. The energy contents of the experimental diets were 775 kcal and 627 kcal for males and females respectively, which were 30% of individual energy requirements and were composed of 65/15/20% as the proportion of carbohydrate/protein/fat. Resting and postprandial energy expenditure and substrate oxidation rates were measured with indirect calorimetry in the fasting state and every 30 min for 5 hours after meal consumption. Thermic effects of food expressed as ${\Delta}AUC$ and TEF% were not significantly different between males and females. However, TEF% adjusted for body weight and fat-free mass in males (0.095% and 0.120%) were significantly lower than those in females (0.152% and 0.213%)(p < 0.05). The total amount of carbohydrate oxidized was significantly lower in males than that in females (58.6 vs. 86.6 mg/kcal energy intake/5 h, p < 0.05). In contrast, the total amount of fat oxidized was significantly higher in males than that in females after the meal (32.9 vs. 17.2 mg/kcal energy intake/5 h, p < 0.01). These results indicate that gender affects the thermic effects of food and the substrate oxidation rate after a meal. The results show that males use relatively less carbohydrate and more fat as an energy source after a meal than that of females.

• BMB Reports
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• 제32권4호
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• pp.370-378
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• 1999

The effects of carnosine and related compounds (CRC) including anserine, homocarnosine, histidine, and ${\beta}$-alanine, found in most mammalian tissues, were investigated on in vitro glucose oxidation and glycation of human serum albumin (HSA). Carnosin and anserine were more reactive with D-glucose than with L-lysine. In the presence of $10\;{\mu}M$ Cu (II), although carnosine and anserine at low concentrations effectively inhibited formation of ${\alpha}$-ketoaldehyde from D-glucose, they increased generation of $H_2O_2$ in a dose-dependent manner. Carnosine, homocarnosine, anserine, and histidine effectively inhibited hydroxylation of salicylate and deoxyribose degradation in the presence of glucose and $10\;{\mu}M$ Cu (II). In the presence of 25 mM D-glucose, copper and ascorbic acid stimulated carbonyl formation from HSA. Except for ${\beta}$-alanine, CRC effectively inhibited the copper-catalyzed carbonyl formation from HSA. The addition of 25 mM D-glucose and/or $10\;{\mu}M$ Cu (II) to low density lipoprotein (LDL) increased formation of conjugated dienes. CRC effectively inhibited the glucose and/or copper-catalyzed LDL oxidation. CRC also inhibited glycation of HSA as determined by hydroxymethyl furfural and lysine with free ${\varepsilon}$-amino group. These results suggest that CRC may play an important role in protecting against diabetic complications by reacting with sugars, chelating copper, and scavenging free radicals.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.264-264
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• 2013

Strong metal-support interaction effect is an important issue in determining the catalytic ac-tivity for heterogeneous catalysis. In this study, we investigated the support effect and the role of organic capping layers of two-dimensional Pt nanocatalysts on reducible metal oxide supports under the CO oxidation. Several reducible metal oxide supports including CeO2, Nb2O5, and TiO2 thin films were prepared via sol-gel techniques. The structure, chemical state and optical property were characterized using XRD, XPS, TEM, SEM, and UV-VIS spectrometer. We found that the reducible metal oxide supports have a homogeneous thin thickness and crystalline structure after annealing at high temperature showing the different optical band gap energy. Langmuir-Blodgett technique and arc plasma deposition process were employed to ob-tain Pt nanoparticle arrays with capping and without capping layers, respectively on the oxide support to assess the role of the supports and capping layers on the catalytic activity of Pt catalysts under the CO oxidation. The catalytic performance of CO oxidation over Pt supported on metal oxide thin films under oxidizing reaction conditions (40 Torr CO and 100 Torr O2) was tested. The results show that the catalytic activity significantly depends on the metal oxide support and organic capping layers of Pt nanoparticles, revealing the strong metal-support interaction on these nanocatalysts systems.

• 한국진공학회지
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• 제21권5호
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• pp.242-248
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• 2012

방사광 가속기에서 얻은 x-선을 이용하여 초고진공에서 열처리를 통하여 얻어진 $TiO_2$ (001) 단결정 표면의 원자가 전자대에 대한 광전자 분광연구를 수행하였다. 이 연구를 통하여 특히 페르미 준위 0.9 eV 근처에 있는 결함에 기인한 전자 상태의 변화로 부터 $Ti^{3+}$ 결함의 산화 또는 열확산 과정에 대한 반응 속도론적 특성을 연구하였다. 본 연구의 결과는 (001)면에서의 $Ti^{3+}$ 결함의 열역학적 특성이 $TiO_2$ (110) 단결정면에서의 그것과 어떻게 다른지를 규명하는데 큰 의미가 있다. 연구 결과, (001)과 (110) 결정면에서의 $Ti^{3+}$ 결함의 거동은 산화 반응성과 결정 내에서의 열적 확산 특성에서 매우 유사하다는 것을 알게 되었다. 이와 같은 결과를 얻게 된 주된 이유 중의 하나는 관여하는 $Ti^{3+}$ 결함이 주로 표면 근처에 분포되어 있다는데서 찾을 수 있다.

• 한국자동차공학회논문집
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• 제20권5호
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• pp.71-80
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• 2012

To improve the $NO_X$ conversion over a SCR (selective catalytic reduction) catalyst, the DOC (diesel oxidation catalyst) is usually placed upstream of the SCR catalyst to enhance the fast SCR reaction ($4NH_3+2NO+2NO_2{\rightarrow}4N_2+6H_2O$) using equimolar amounts of NO and $NO_2$. Here, a ratio of $NO_2/NO_X$ above 50% should be avoided, because the reaction with $NO_2$ only ($4NH_3+4NO+O_2{\rightarrow}4N_2+6H_2O$) is slower than the standard SCR reaction ($4NH_3+4NO+O_2{\rightarrow}4N_2+6H_2O$). In order to accurately predict the performance characteristics of SCR catalysts, it is therefore desired to develop a more simple and reliable mathematical and kinetic models on the oxidation kinetics of nitric oxide over a DOC. In the present work, the prediction accuracy and limit of three different chemical reaction kinetics models are presented to describe the chemicophysical characteristics and conversion performance of DOCs. Steady-state experiments with DOCs mounted on a light-duty four-cylinder 2.0-L turbocharged diesel engine then are performed, using an engine-dynamometer system to calibrate the kinetic parameters such as activation energies and preexponential factors of heterogeneous reactions. The reaction kinetics for NO oxidation over Pt-based catalysts is determined in conjunction with a transient one-dimensional (1D) heterogeneous plug flow reactor (PFR) model with diesel exhaust gas temperatures in the range of 115~$525^{\circ}C$ and space velocities in the range of $(0.4{\sim}6.5){\times}10^5\;h^{-1}$.

• Journal of Microbiology and Biotechnology
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• 제24권4호
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• pp.534-544
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• 2014

The effects of microbial iron reduction and oxidation on the immobilization and mobilization of copper were investigated in a high concentration of sulfate with synthesized Fe(III) minerals and red earth soils rich in amorphous Fe (hydr)oxides. Batch microcosm experiments showed that red earth soil inoculated with subsurface sediments had a faster Fe(III) bioreduction rate than pure amorphous Fe(III) minerals and resulted in quicker immobilization of Cu in the aqueous fraction. Coinciding with the decrease of aqueous Cu, $SO_4{^{2-}}$ in the inoculated red earth soil decreased acutely after incubation. The shift in the microbial community composite in the inoculated soil was analyzed through denaturing gradient gel electrophoresis. Results revealed the potential cooperative effect of microbial Fe(III) reduction and sulfate reduction on copper immobilization. After exposure to air for 144 h, more than 50% of the immobilized Cu was remobilized from the anaerobic matrices; aqueous sulfate increased significantly. Sequential extraction analysis demonstrated that the organic matter/sulfide-bound Cu increased by 52% after anaerobic incubation relative to the abiotic treatment but decreased by 32% after oxidation, indicating the generation and oxidation of Cu-sulfide coprecipitates in the inoculated red earth soil. These findings suggest that the immobilization of copper could be enhanced by mediating microbial Fe(III) reduction with sulfate reduction under anaerobic conditions. The findings have an important implication for bioremediation in Cu-contaminated and Fe-rich soils, especially in acid-mine-drainage-affected sites.

• Korean Chemical Engineering Research
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• 제44권2호
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• pp.193-199
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• 2006

${\gamma}-Al_2O_3$에 담지한 Cu-Mn 산화물 촉매에서 톨루엔 완전산화 반응을 $160{\sim}280^{\circ}C$의 온도 범위에서 고정층 반응기로 조사하였다. BET, SEM, TPR, TPO, XPS 및 XRD를 이용하여 촉매 특성분석을 하였다. 톨루엔의 완전산화 반응은 $280^{\circ}C$ 이하에서 이루어졌으며, 적절한 Cu-Mn 담지량은 15.0 wt％Cu-10.0 wt％Mn인 것으로 나타났다. TPR/TPO 및 XPS 분석 결과, 15 Cu-10 Mn 촉매의 산화환원 봉우리가 낮은 온도로 이동하였으며 결합에너지가 높은 값으로 이동하였다. XRD 결과, 고분산된 Mn 산화물과 CuO 보다 $Cu_{1.5}Mn_{1.5}O_4$의 촉매활성 인자로서의 역할이 더욱 우수한 것으로 추측되며, 촉매의 활성은 촉매의 산화환원 능력과 촉매의 높은 산화 상태에 기인하는 것으로 사료된다.

• 분석과학
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• 제19권5호
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• pp.422-432
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• 2006

VOC는 대기오염의 주원인으로서 인식되어왔다. 촉매산화는 저온에서 높은 효율을 나타내기 때문에 VOCs 제거를 위한 가장 중요한 처리기술중 하나이다. 이 연구에서는 ${\gamma}-Al_2O_3$ 담체에 Pt, Pt-Ru 그리고 Pt-Ir을 담시지켜 촉매를 제조하였다. 반응물로서 Xylene, toluene 그리고 MEK를 사용하였다. 단일 또는 두 가지 이상의 촉매들은 함침법에 의해 준비하였고, XRD, XPS, TEM, BET 분석을 통하여 특성화하였다. 그 결과 Pt-Ru, Pt-Ir 촉매는 Pt 촉매에 비해 더 높은 전환율을 나타내었다. ${\gamma}-Al_2O_3$ 담체상에서 Pt-Ir 촉매가 가장 높은 전환율을 보인다. VOCs산화에서, Pt-Ru, Pt-Ir 촉매는 다양한 활성점을 나타내었고 그것은 Pt의 metal 영역를 강화시켰다. 따라서 두 가지 금속으로 이루어진 촉매가 단일 금속으로 이루어진 촉매에 비해 VOCs 전환율이 더 높았다. 이 연구에서 Pt에 소량의 Ru, Ir 첨가는 VOCs의 산화반응을 증진시켰다.