Modeling reactive pollutant dispersion in an urban street canyon

Baik, J.-J.,Kang, Y.-S.,Kim, J.-K. Pergamon Press ; Elsevier [distribution] 2007 Atmospheric environment Vol.41 No.5

Reactive pollutant dispersion in an urban street canyon with a street aspect ratio of one is numerically investigated using a computational fluid dynamics (CFD) model. The CFD model developed is a Reynolds-averaged Navier-Stokes equations (RANS) model with the renormalization group (RNG) k-ε turbulence model and includes transport equations for NO, NO<SUB>2</SUB>, and O<SUB>3</SUB> with simple photochemistry. An area emission source of NO and NO<SUB>2</SUB> is considered in the presence of background O<SUB>3</SUB> and street bottom heating (ΔT=5<SUP>o</SUP>C) with an ambient wind perpendicular to the along-canyon direction. A primary vortex is formed in the street canyon and the line connecting the centers of cross-sectional vortices meanders over time and in the canyon space. The cross-canyon-averaged temperature and reactive pollutant concentrations oscillate with a period of about 15min. The averaged temperature is found to be in phase with NO and NO<SUB>2</SUB> concentrations but out of phase with O<SUB>3</SUB> concentration. The photostationary state defect is small in the street canyon except for near the roof level and the upper downwind region of the canyon and its local minimum is observed near the center of the primary vortex. The budget analysis of NO (NO<SUB>2</SUB>) concentration shows that the magnitude of the advection or turbulent diffusion term is much larger (larger) than that of the chemical reaction term and that the advection term is largely balanced by the turbulent diffusion term. On the other hand, the budget analysis of O<SUB>3</SUB> concentration shows that the magnitude of the chemical reaction term is comparable to that of the advection or turbulent diffusion term. The inhomogeneous temperature distribution itself affects O<SUB>3</SUB> concentration to some extent due to the temperature-dependent photolysis rate and reaction rate constant.

상구조가 조절된 고분자 미립구에서 자외선 흡수제의 거동에 대한 연구

이종석 ( Jong-suk Lee ),김진웅 ( Jin-woong Kim ),김준오 ( Junoh Kim ),한상훈 ( Sang-hoon Han ),장이섭 ( Ih-seop Chang ) 대한화장품학회 2004 대한화장품학회지 Vol.30 No.3

본 연구는 poly(methyl methacrylate) (PMMA) 마이크로 입자 내의 상 조절을 통하여 자외선 A 흡수제인 butyl methoxydibenzoylmethane (BMDM)을 효과적으로 안정화시킨 새로운 자외선 흡수 시스템에 관한 것으로, 마이크로 입자 내의 BMDM의 광학특성을 고분자와의 상 특성에 연관하여 해석함으로써 자외선 A 흡수제의 분자거동과 광 에너지 흡수 거동을 체계적으로 이해하고자 하였다. 본 연구에서는 고분자 마이크로 입자 내에서 BMDM의 상 특성을 제어하여, BMDM의 광 및 열 안정성을 유지하면서 자외선 A를 효과적으로 차단할 수 있었다. 본 연구를 통하여 고분자 마이크로 입자 내에 자외선 흡수제의 상 특성을 조절하는 것이 자외선 흡수제를 함유하는 화장품 제형 내에서 광화학 및 광 안정도를 결정하는 중요한 인자임을 알 수 있었다. In this study, a different UV (ultra-violet) ray absorption system is presented in which butyl methoxydibenzoylmethane (BMDM, a model UV-A absorbent, 320~400 nm) is stabilized in phase-controlled poly(methyl methacrylate) (PMMA) microspheres. The photochemistry of BMDM in the microspheres was investigated considering its phase characteristics therein. The analysis of a differential scanning calorimeter and X-ray diffractometer showed that the BMDM in the microspheres was present with a non-crystalline state. The phase control of BMDM in the polymer microsphere has an excellent ability to protect UV-A with maintaining its photo- and thermal stability. The results obtained in this study illustrate well that the phase control of the UV absorbents in the polymer microspheres is another key factor that determines its photochemistry and photostability in the final formulations.

Photochemical Kinetics of Maleic to Fumaric Acid on Silver Nanoparticle Surfaces

Nak Han Jang*,Dae Hong Jeong,Jung Sang Suh* 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.5

A visible photochemistry of maleic to fumaric acid adsorbed on silver nanoparticle surfaces was investigated as probed by SERS using a simple flow method. Photoisomerization of maleic to fumaric acid was consecutively observed in the condition of various flow rates, which varied the exposure time of laser beam. The sequential SERS spectra of maleic acid indicated that the photochemical isomerization and desorption took place simultaneously on silver nanoparticle surfaces as a function of laser fluency and wavelength. For 530.9 nm laser line excitation, the rate constant coefficients were obtained with a = 5.9 sec1 mW for isomerization and b = 13.9 sec1 mW for desorption, which k1 = aIn and k2 = bIm. Both reactions were one photon process (n = 1, m = 1) of a visible light and relatively fast process whose decay time was in the range of milli-second for 50 mW laser power. The rate of photochemical reaction increased on going toward the blue and photodesorption was a dominant process. A simple flow method used in this study was very useful to study a relatively fast photochemical reaction of molecules adsorbed on silver nanoparticle surfaces.

대구에 있어서의 주중과 주말의 NO₂, O₃, PM10 농도

성미애(Mi Ae Seong),김해동(Hae Dong Kim) 계명대학교 낙동강환경원 2006 環境科學論集 Vol.11 No.1

The 1980s, if NOX contribution of air decreases even if do, O₃'s contribution decreases, and if NOx's contribution increases, O₃'s contribution increases and NOx with CO, HC was known as O₃'s connection material. But, in the 1990s, though NOx's contribution of air decreases entering, increasing preferably phenomenon of O₃'s contribution was begun to observe. Because traffic discharge decreases on weekend, NOx's discharge decreases, O₃'s formation becomes seriouser on weekend than on weekday. Because is started from greater part of nitrogen inorganic compounds as well as PM10, is considered more researches about photochemistry pollution may need for greate air quality improvement in city.

Photochemical Kinetics of Maleic to Fumaric Acid on Silver Nanoparticle Surfaces

Jang, Nak-Han,Jeong, Dae-Hong,Suh, Jung-Sang Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.5

A visible photochemistry of maleic to fumaric acid adsorbed on silver nanoparticle surfaces was investigated as probed by SERS using a simple flow method. Photoisomerization of maleic to fumaric acid was consecutively observed in the condition of various flow rates, which varied the exposure time of laser beam. The sequential SERS spectra of maleic acid indicated that the photochemical isomerization and desorption took place simultaneously on silver nanoparticle surfaces as a function of laser fluency and wavelength. For 530.9nm laser line excitation, the rate constant coefficients were obtained with a = 5.9 $sec^{-1}$ mW for isomerization and b = 13.9 $sec^{-1}$ mW for desorption, which $k_1\;=\;aI^n\;and\;k_2\;=\;bI^m$. Both reactions were one photon process (n = 1, m = 1) of a visible light and relatively fast process whose decay time was in the range of milli-second for 50 mW laser power. The rate of photochemical reaction increased on going toward the blue and photodesorption was a dominant process. A simple flow method used in this study was very useful to study a relatively fast photochemical reaction of molecules adsorbed on silver nanoparticle surfaces.

Effect of an Extra Chloro Substituent on Photochemistry of o-Alkylphenacyl Chloride

박봉서,Seongjin Jeong 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

The title compound, α,α-dichloro-o-methylacetophenone, was prepared and its photochemical behavior was investigated. Addition of an extra chlorine at alpha position to the carbonyl showed many different features from photochemical reactivities of mono chloro analogue, 2,5-dimethylphenacyl chloride. In benzene, a rearrangement product with a formal 1,5-Cl shift and a reduction product were formed beside indanone. In methanol, solvolysis and cyclization of a common dienol intermediate occurred at comparable reaction rates.

Photochemistry of hybrid organic-inorganic triarylborane-o-carboranes

Kim, S.Y.,Lee, A.R.,Cho, Y.J.,Son, H.J.,Han, W.S.,Kang, S.O. Elsevier Sequoia 2015 Journal of organometallic chemistry Vol.798 No.1

Para- and meta-substituted o-carboranes with a dimesityl(phenyl)borane (dmpb) group, namely, p-1, p-2, m-1, and m-2, were prepared and their electronic natures were evaluated by steady-state photophysical methods. It was found that excited states were greatly influenced by the linking position of the dimesityl-borane group(s) at the phenyl unit of diphenyl-o-carboranes. While intramolecular charge-transfer (ICT) prevails in both para- and meta-regioisomers, para-isomers show much enhanced ICT character, as evidenced by observation of a new emission band at λ<SUB>max</SUB> ~ 570 nm in dichloromethane (DCM) solution. Furthermore, the solvatochromic shifts, Δυ<SUB>f</SUB>, from n-hexane to DCM were significantly different for para- and meta-isomers, which showed 8105, 8184, 1834, and 1895 cm<SUP>-1</SUP> for p-1, p-2, m-1, and m-2, respectively. The difference in dipole moment between ground and excited states for para- (~31.8 D) and meta-isomers (~15.0 D) by using Mataga-Lippert plot confirmed that the ICT occurs from dimesityl-borane to o-carborane in para-isomers while the ICT occurs only from dimesityl-borane to the bridged phenyl group in meta-isomers. Excited state estimation by electrochemical and DFT studies corroborated well to the ICT character, and even with engagement of the strong electron withdrawing dimesityl-borane group o-carborane unit still acts as an electron accepter as found in the para-isomers, p-1 and p-2.

Effect of an Extra Chloro Substituent on Photochemistry of o-Alkylphenacyl Chloride

Park, Bong-Ser,Jeong, Seong-Jin Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

The title compound, ${\alpha},{\alpha}$-dichloro-o-methylacetophenone, was prepared and its photochemical behavior was investigated. Addition of an extra chlorine at alpha position to the carbonyl showed many different features from photochemical reactivities of mono chloro analogue, 2,5-dimethylphenacyl chloride. In benzene, a rearrangement product with a formal 1,5-Cl shift and a reduction product were formed beside indanone. In methanol, solvolysis and cyclization of a common dienol intermediate occurred at comparable reaction rates.

The light triggered dissolution of gold wires using potassium ferrocyanide solutions enables cumulative illumination sensing

Chen, Weida D.,Kang, Seung-Kyun,Stark, Wendelin J.,Rogers, John A.,Grass, Robert N. Elsevier 2019 Sensors and actuators. B Chemical Vol.282 No.-

<P><B>Abstract</B></P> <P>Electronic systems with on-demand dissolution or destruction capabilities offer unusual opportunities in hardware-oriented security devices, advanced military spying and controlled biological treatment. Here, the dissolution chemistry of gold, generally known as inert metal, in potassium ferricyanide and potassium ferrocyanide solutions has been investigated upon light exposure. While a pure aqueous solution of potassium ferricyanide–K<SUB>3</SUB>[Fe(CN)<SUB>6</SUB>] does not dissolve gold, an aqueous solution of potassium ferrocyanide–K<SUB>4</SUB>[Fe(CN)<SUB>6</SUB>] irradiated with ambient light is able to completely dissolve a gold electrode within several minutes. Photo activation and dissolution kinetics were assessed at different initial pH values, light irradiation intensities and ferrocyanide concentrations. Addition of small amounts of the heavy metal thallium (260 ppb) also provides tunability of the dissolution kinetics. An investigation of the involved chemical and physical processes of photochemistry, cyanide diffusion and surface reaction results in an understanding of the rate limiting steps and yields an overall transformation of irradiated light energy to dissolved gold of 2.6%. A potential application of this novel gold dissolution method as a cumulative light sensor is demonstrated and discussed.</P>

N-hydroxysuccinimidyl phenyl azide와 광반응을 이용한 펩타이드의 마이크로형태 고정화

김진희,김현정,김종원,장준근,민병구,최태부 대한의용생체공학회 1998 의공학회지 Vol.19 No.5

폴리머 표면에 생체물질의 고정화 방법은 생체적합성을 자닌 재료의 개발에있어서 중요한 방법중의 하나이다. 광반응을 이용한 photolithography방법을 사용하여 재료 표면의 원하는 부위에 단백질을 고정할 수 있다. 본 연구에서는 파이브로넥틴의 세포부탁 리간드, GRGDS펩타이드를 N-hydroxysuccinimidyl phenol azide를 이용하여 미세한 선의 형태로 표면에 광반응으로써 고정하였다. 광반응 유도체가 고정된 표면은 형광물질을 사용하여 확인하였다. 또한 혈관내피 세포는 GRGDS펩타이드가 고정화된 표면에서만 부탁됨을 관찰하였다. Defined spatial localization of biomolecules on the polymer surface Is potentially powerful method to generate biocompatible surface. Photolithography and photochemistry can be used to immobilize peptides only al a given region of the surface. In this study, peptide RGDS, one of the endothelial cells recognition sites of fibronectin, was covalently immobilized on the polystyrene coated surface with micropattern. It was performed by photochemical reactivity of a synthesized N-hydroxysuccinimidyl phenyl azide. The micropatterning was confirmed by staining with fluorescent dye, aminoacetamido fluorescein. Endothelial cell adhesion was observed only on the RGDS immobilized areas.