Fluorescence Spectroscopic and Time-Dependent Density-functional Theory Studies of Diphenylsilane

부봉현,이재광 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.3

We investigated fluorescence and fluorescence excitation of diphenylsilane (DPS) in a solution and molecular beams in combination with the aid of the DFT method. When the molecule was photoexcited at 250 nm in a cyclohexane solution, normal and excimer fluorescences were observed in the ranges of 260-320 and 330-450 nm, respectively. The fluorescence excitation spectrum indicates that the channel leading to the intramolecular excimer formation is not efficient in comparison with the normal fluorescence. Vibrationally resolved fluorescence excitation spectra were measured for the DPS molecules cooled in pulsed supersonic expansion of He in the range 262.2-271.7 nm, in which we can see several electronic excitation spectra exhibiting the electronic band origins. We found that the simulated absorption spectrum based on the time-dependent densityfunctional theory calculations accords well with the absorption spectrum.

Fluorescence Spectroscopic and Time-Dependent Density-Functional Theory Studies of Diphenylsilane

Boo, Bong-Hyun,Lee, Jae-Kwang Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.3

We investigated fluorescence and fluorescence excitation of diphenylsilane (DPS) in a solution and molecular beams in combination with the aid of the DFT method. When the molecule was photoexcited at 250 nm in a cyclohexane solution, normal and excimer fluorescences were observed in the ranges of 260-320 and 330-450 nm, respectively. The fluorescence excitation spectrum indicates that the channel leading to the intramolecular excimer formation is not efficient in comparison with the normal fluorescence. Vibrationally resolved fluorescence excitation spectra were measured for the DPS molecules cooled in pulsed supersonic expansion of He in the range 262.2-271.7 nm, in which we can see several electronic excitation spectra exhibiting the electronic band origins. We found that the simulated absorption spectrum based on the time-dependent densityfunctional theory calculations accords well with the absorption spectrum.

Excitation and Emission Properties of Adsorbed U(VI) on Amorphous Silica Surface

Jung, Euo Chang,Kim, Tae-Hyeong,Kim, Hee-Kyung,Cho, Hye-Ryun,Cha, Wansik Korean Radioactive Waste Society 2020 방사성폐기물학회지 Vol.18 No.4

In the geochemical field, the chemical speciation of hexavalent uranium (U(VI)) has been widely investigated by performing measurements to determine its luminescence properties, namely the excitation, emission, and lifetime. Of these properties, the excitation has been relatively overlooked in most time-resolved laser fluorescence spectroscopy (TRLFS) studies. In this study, TRLFS and continuous-wave excitation-emission matrix spectroscopy are adopted to characterize the excitation properties of U(VI) surface species that interact with amorphous silica. The luminescence spectra of U(VI) measured from a silica suspension and silica sediment showed very similar spectral shapes with similar lifetime values. In contrast, the excitation spectra of U(VI) measured from these samples were significantly different. The results show that distinctive excitation maxima appeared at approximately 220 and 280 nm for the silica suspension and silica sediment, respectively.

Development of sensor materials for fluorescence thermometer application using LED excitation

Toru Katsumata,Hiroaki Aizawa,Shuji Komuro 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

Phosphor materials, such as Cr doped spinel (MgAl2O4), garnet (Y3Al5O12) and sapphire (Al2O3) crystals and composites of these materials are developed for a highly sensitive thermo-sensor in fluorescence thermometer excited using LED. Temperature dependences of photoluminescence (PL) intensity from these materials are evaluated using LED excitation. PL intensity from sensor materials decreases linearly with temperature. Impurities doped sapphire, spinel, garnet crystals and their composites are found to be suitable materials as sensor materials for fluorescence thermometer using LED excitation. Yellow colored LED is found to be useful excitation light for Cr doped sensor materials. All the materials examined in this paper can be effectively excited using a yellow colored LED.

Spectroscopic Evidence for Aggregation of Stilbene Derivatives in Solution

Aguiar, M.,Akcelrud, L.,Pinto, M.R.,Atvars, T.D.Z.,Karasz, F.E.,Saltiel, Jack Korean Society of Photoscience 2003 Journal of Photosciences Vol.10 No.1

The absorption, fluorescence and fluorescence-excitation spectra of concentrated toluene solutions of selected para substituted trans-stilbene derivatives provide strong evidence for aggregation. A red-shifted fluorescence spectrum peaking at 420 nm gains in intensity as the stilbene concentration is increased. The excitation spectrum of this new emission is well to the red of the normal stilbene absorption spectrum, consistent with the appearance of a red shifted shoulder in the UV spectrum. Formation of a fluorescent ground state dimer (or higher aggregate) is proposed to account for these observations. The presence of polar substituents is crucial to the formation of this ground state complex.

정수공정에서 유기물 모니터링을 위한 Fluorescence EEM의 적용

남숙현 ( Sookhyun Nam ),이주원 ( Juwon Lee ),김은주 ( Eunju Kim ),구재욱 ( Jaewuk Koo ),황태문 ( Tae-mun Hwang ) 한국수처리학회(구 한국수처리기술연구회) 2020 한국수처리학회지 Vol.28 No.3

Natural organic matter (NOM) is a substance that affects performance in the water treatment process that is crucial to understand. NOM can have different composition according to environmental changes. In this study, we applied the fluorescence excitation emission matrices-parallel factor analysis (FEEM-PARAFAC) method for characterizing dissolved organic matter (DOM). This method provides valuable insight into the chemical composition of DOM and the effects of various treatment processes in engineered systems. This study was conducted on raw water, coagulation/sedimentation, sand filtration, and activated carbon in N water treatment. The correlation between the component and the process was derived by PARAFAC with 100 fluorescence spectra. Using this method, components correlated with the DOM removal for water process were derived. It was determined, C1 (E_x/E_m = 250(350)/450) is the main component to monitor the removal rates of DOM in the flocculation/sedimentation process, the C1/C2 fraction (E_x/E_m = 250(325)/400) is the main component in the sand filter process, and C2 (E_x/E_m = 250(325)/400) is the main component in the activated carbon process. It has been found to be a suitable tool to track the change of organic matter quantity and quality in water treatment processes.

영산강 수계 자연유기물질의 계절별 형광특성 연구

조재원 ( Jae Weon Cho ) 한국하천호수학회 2012 생태와 환경 Vol.45 No.1

This study investigated the characteristics of natural organic matter (NOM) with general water characteristics (pH, DO, electrical conductivity, BOD, COD, TN, TP, Chl-a, DOC, UV254, SUVA) and the 3D fluorescence excitation-emission matrix (FEEM) in the Yeongsan River basin. FEEM was used to classify protein-like and fulvic & humiclike substances with fluorescence intensity in the matrix of excitation and emission wavelength. The concentration of BOD, COD, TN, electrical conductivity and DOC in the region of Gwangju city (Gwangju sewage treatment plant: GJS, Gwangjucheon: GJC, Gwangju 2: GJ2) was relatively higher than the upper reaches and lower reaches of the Yeongsan River basin. SUVA in most sites was lower than 3 L mg--1 m--1 as the hydrophilic substances, except Damyang (DY) in the upper reaches of Yeongsan river was higher than 3 L mg--1 m--1 as the hydrophobic substances during winter and autumn. In the FEEM investigation the fulvic and humic substances were found in most sites, and in sites regarding Gwangju city (GJS, GJC, GJ2) during winter and GJC in summer, protein-like substances were found. The trend of fluorescence intensities from the upper reaches to the lower reaches in most sites corresponded to that regarding the concentration of water characteristics (BOD, COD, TN, DOC). That is why the region of Gwangju city (GJS, GJC, GJ2) was relatively higher. This results were an equivalent trend to those of fluorescence index (FI) in most sites, and the higher FIs in the sites of Gwangju city indicate more microbial-derived substances due to enormous effluent organic matters (EfOM) from huge Gwangju sewage treatment plants.

Tailoring the Excited-State Intramolecular Proton Transfer (ESIPT) Fluorescence of 2-(2'-Hydroxyphenyl)benzoxazole Derivatives

Seo, Jang-Won,Kim, Se-Hoon,Park, Sang-Hyuk,Park, Soo-Young Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.11

The excited-state intramolecular proton transfer (ESIPT) fluorescence in the 2-(2'-hydroxyphenyl)benzoxazole (HBO) derivatives with different electron donor and acceptor substituents was studied by spectroscopic and theoretical methods. Changes in the electronic transition, energy levels, and orbital diagrams of HBO analogues were investigated by the semi-empirical molecular orbital calculation and were correlated with the experimental spectral position of ESIPT keto emission. It was found that the presence of substituents, regardless of their nature, resulted in the red-shifted absorption relative to HBO. However, the spectral change of the ESIPT fluorescence was differently affected by the nature of substituent: hypsochromic shift with electron donor and bathochromic shift with electron acceptor.

Tailoring the Excited-State Intramolecular Proton Transfer (ESIPT) Fluorescence of 2-(2'-Hydroxyphenyl)benzoxazole Derivatives

박수영,Sehoon Kim,박상혁,Jangwon Seo 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.11

The excited-state intramolecular proton transfer (ESIPT) fluorescence in the 2-(2'-hydroxyphenyl)benzoxazole (HBO) derivatives with different electron donor and acceptor substituents was studied by spectroscopic and theoretical methods. Changes in the electronic transition, energy levels, and orbital diagrams of HBO analogues were investigated by the semi-empirical molecular orbital calculation and were correlated with the experimental spectral position of ESIPT keto emission. It was found that the presence of substituents, regardless of their nature, resulted in the red-shifted absorption relative to HBO. However, the spectral change of the ESIPT fluorescence was differently affected by the nature of substituent: hypsochromic shift with electron donor and bathochromic shift with electron acceptor.

Excited State Intramolecular Proton Transfer Dynamics of Oxadiazole-based Dyes

김진용,김세훈,박수영,주태하 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.3

Excited state intramolecular proton transfer (ESIPT) dynamics of two oxadiazole-based model compounds, 2,5-bis-[5-(4-tert-butyl-phenyl)-[1,3,4]oxadiazol-2-yl]-phenol (SOX) and 2,5-bis-[5-(4-tert-butyl-phenyl)-[1,3,4]oxadiazol-2-yl]-benzene-1,4-diol (DOX) have been investigated by time-resolved fluorescence. SOX and DOX have one and two intramolecular hydrogen bond moieties, respectively, where ESIPT may occur. Time-resolved fluorescence fully resolves the ESIPT dynamics and establishes the two-state conversion between the enol and keto isomers in the S1 potential energy surface. The apparent inconsistency between the ESIPT rate and the steady-state spectrum is settled by invoking the conformational inhomogeneity including the intermolecular hydrogen bonding with protic solvents. The ESIPT rates of SOX and DOX are not as fast as those of typical ESIPT molecules, which indicates a finite barrier for the reaction. For DOX, ESIPT is enabled for only one hydroxyl moiety, and the ESIIPT rate is twice as fast as that of SOX. We propose a symmetric potential energy surface along the two proton transfer coordinates, and bifurcation of the initial probability density of the enol isomer into the two potential minima representing the keto isomer.