• Bulletin of the Korean Chemical Society
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• v.19 no.9
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• pp.973-980
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• 1998

The fluorescence spectroscopic properties of both trans and cis forms of 9-anthryiethylene derivatives such as 9-AnthCH=$CHCO_2CH_3$ [Ⅰ] and 9-AnthCH=CHCN [Ⅱ] as well as 9-AnthCH=>TEX>$CHCH_2O_2CCH_3$ [Ⅲ] and 9-AnthCH=$CHCH_2OH$ [Ⅳ] have been measured in various solvents. In nonpolar solvent, the trans-I and trans-Ⅱ show dual emission spectral bands at 340 nm and 460 nm when exciting with 270 nm while the other trans derivatives show single emission band at 430 or 460 nm. The dual emissions exhibit different excitation spectra, indicating that two emissive states are different from each other. It is interesting to note that the 340 nm emission of both trans-Ⅰ and trans-Ⅱ is enhanced at the expense of the drastic quenching of the 460 nm emission as the solvent polarity increases. The dual emissions are also observed for both cis-Ⅰ and cis-Ⅱ. The solvent dependence of the fluorescence decay times and quantum yields can be correlated with the solvent and excitation wavelength dependences of the trans→cis photoisomerization quantum yields. These results indicate that the 340 nm emission is originated from the $S_2$ state of the cis-form, and the $S_1$ state is the only singlet excited state presenting a large CT (charge transfer) character to facilitate the photoisomerization.

• Bulletin of the Korean Chemical Society
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• v.23 no.9
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• pp.1315-1327
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• 2002

The model compounds, 8-methoxypsoralen-CH2O(CH2)n-adenine (MOPCH2OCnAd, n=2, 3, 5, 6, 8, and 10) in which 5 position of 8-methoxypsoralen (8-MOP) is linked by various lengths of polymethylene bridge to N9 of adenine. UV absorption spectra are identical with the sum of MOPCH2OC3 and adenine absorption spectra. Solvent effects on the UV absorption and fluorescence emission spectra indicate that the lowest excited singlet state is the $(\pi${\rightarrow}$\pi*)$ state. The spectral characteristics of the fluorescence of MOPCH2OCnAd are strongly dependent upon the nature of the solvents. The fluorescence emission spectra in aprotic solvents are broad and structureless due to the excimer formation through the folded conformation accelerated by hydrophobic ${\pi}-{\pi}$ stacking interaction. Increasing polarity of the protic solvents leads to higher population of unfolded conformation stabilized through favorable solvation and H-bonding, and consequently to an increase in the fluorescence intensity, fluorescence lifetime, and a shift of fluorescence maximum to longer wavelengths. The decay characteristics of the fluorescence in polar protic solvents shows two exponential decays with the lifetimes of 0.6-0.8 and 1.6-1.9 ns in 5% ethanol/water, while MOPCH2OC3 shows 0.5 and 1.7 ns fluorescence lifetimes. The long-lived component of fluorescence can be attributed to the relaxed species (i.e., the species for which the solvent reorientation (or relaxation) has occurred), while the short-lived components can be associated with the unrelaxed, or only partially relaxed, species.

• Bulletin of the Korean Chemical Society
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• v.20 no.12
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• pp.1441-1446
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• 1999

Laser-induced fluorescence (LIF) spectroscopy has been applied to study the supersonic jet of radicals of nitric oxide (NO) and atomic iodine produced in the flash pyrolysis of precursors n-butylnitrite (CH₃(CH₂)₃ONO) and allyl iodide (C₃$H_5$I), respectively. The systematic population analysis with spectral simulations demonstrates that the precursors are efficiently pyrolyzed and that radical beams show a substantial supersonic cooling. In addition, absence of local equilibrium was observed in the distributions of two electronic spin-orbit states ²Π$_{1/2}$ and ²Π$_{3/2}$ of NO products and can be rationalized in terms of the efficiency of collision-induced energy transfer rates.

• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.13-22
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• 2010

The photophysical properties of 7-diethylaminocoumarin (DEAC) laser dye have been measured in different solvents. The emission spectrum of DEAC has also been measured in cationic (CTAC) and anionic (SDS) micelles. The laser parameters have been calculated in different solvents namely acetone, dioxane, ethanol and dimethylforamide(DMF). The photoreactivity of DEAC has been studied in $CCl_4$ solvent using 366 nm light. The values of photochemical yield (${\Phi}_c$) and rate constant (k) are determined. The interaction of organic acceptors such as picric acid (PA), tetracyanoethylene (TCNE) and 7,7,8,8-tetracynoquinonedimethane (TCNQ) with DEAC are also studied using fluorescence measurements in acetonitrile ($CH_3CN$). The electrochemical investigation of (DEAC) has been carried out using cyclic voltammetry and convolutive voltammetry combined with digital simulation technique at a platinum electrode in 0.1 mol $L^{-1}$ tetrabutyl ammonium perchlorate (TBAP) in $CH_3CN$ solvent. The electrochemical parameters of the investigated compound were determined using cyclic and convolutive voltammetry. The extracted electrochemical parameters were verified and confirmed via digital simulation method.

• Journal of Photoscience
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• v.9 no.2
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• pp.385-387
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• 2002

Direct EPR evidence of the photo-generation of superoxide radicals ( $O_2$$^{-.}$) was obtained by using spin trapping techniques in spinach photosystem II (PSII) membranes. $O_2$$^{-.}$ was detected by following the formation of 5-diethoxyphosphoryl-5-methyl-1 -pyrroline-N-oxide (DEPMPO) superoxide adducts, DEPMPO-OOH. The significant increase of the EPR signal amplitude of DEPMPO-OOH in N$H_2O$H-, CaC $l_2$- and NaCl-treated PSII membranes showed that the oxygen-evolving system has a close relation to the $O_2$$^{-.}$ production. PSII membranes with inactivated donor side could not prevent the $O_2$$^{-.}$ production efficiently. Treatments on PSII donor side also influence the maximum level and the kinetics of Chlorophyll (Chi) a fluorescence. Results suggested that manganese cluster and extrinsic proteins might affect Chi a fluorescence in ways different from that happens at the acceptor side of PSII.SII.SII.

• Journal of Photoscience
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• v.9 no.2
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• pp.521-523
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• 2002

5-aminolevulinic acid (ALA) has been used to stimulate endogenous protoporphyrin IX (PpIX) in tumor and then initiate PDT. Recently, ALA-Hexyl ester (He-ALA) was found much effective than ALA on producing PpIX in cancer cells. To clarify the transportation mechanism of ALA and He-ALA, the detection of them is the important step. ALA and its derivatives all don't emit fluorescence, so the Raman spectroscopy was used here for the direct detection of ALA and He-ALA. The results showed that ALA and He-ALA have the common strong Raman peaks at 2930, 2950 CM$\^$-1/, due to the CH$_2$ vibration. The peak 3050 CM$\^$-1/ appeared in ALA spectrum can be attributed to OH vibration, while the peaks of 2860, 2900 CM$\^$-1/ in He-ALA spectrum were assigned as the modes of CH$_3$. This Raman spectral characteristic is consistence with the structure difference of He-ALA and ALA. Thus, Raman spectroscopy provides a new way to detect and distinguish ALA and He-ALA, and could be explored further in biology system.