• Bulletin of the Korean Chemical Society
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• v.28 no.10
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• pp.1715-1719
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• 2007

New bispsoralen derivatives 5-10, 8-MOP-NHCO(CH2)nCONH-8-MOP (BPSBA-Cn, n = 0, 1, 2, 3, 4 and 5) in which 5 position of an 8-methoxypsoralen (8-MOP) is linked by various lengths of bisamide polymethylene chain to 5 position of the other 8-MOP, have been synthesized by the amidation of 5-amino-8-methoxypsoralen (12) with α,ω-alkanoyl dichloride. Photophysical properties of their derivatives including π?π stacking interaction between the two aromatic moieties were investigated by UV absorption and fluorescence emission spectra. Efficient ring-ring stacking interactions have been observed in BPSBA-C4 (9) from the percent hypochromism (%H) of the models.

• Bulletin of the Korean Chemical Society
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• v.12 no.4
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• pp.441-444
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• 1991

The intramolecular proton transfers of 2-hydroxy-4,5-naphthotropone in room temperature solutions are studied using static and time-resolved absorption and emission spectroscopy. Dual normal and tautomer fluorescence is observed in ethanol solution, while only the tautomer fluorescence is observed in cyclohexane solution. The fluorescence lifetimes and quantum yields in ethanol and cyclohexane solutions indicate that in hydrocarbon solvents, rapid intersystem crossing competes with proton transfer in the first excited singlet state. Transient absorption spectra and kinetics indicate that proton transfer also undergoes in the first triplet state with a transfer time of ∼ 3 ns. No transient absorption from the tautomer ground state indicates a rapid back proton transfer in the ground state.

• 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.

• ETRI Journal
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• v.27 no.2
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• pp.181-187
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• 2005

Alkoxy-substituted poly(spirobifluorene)s and their copolymers with a triphenylamine derivative have been synthesized by Ni(0)-mediated polymerization. The polymers were well soluble in common organic solvents. Pure blue-light emissions without the long wavelength emission of poly(fluorene)s have been observed in the fluorescence spectra of polymer thin films. The light emitting diodes with a device configuration of ITO/PEDT:PSS(30 nm)/polymer(60 nm)/LiF(1 nm)/Al(100 nm) have been fabricated. The electroluminescence spectra showed the blue emissions without the long wavelength emission as observed in the fluorescence spectra. The relatively poor electroluminescence quantum yield of the homopolymer (0.017% @ 20 $mA/cm^{2}$) with color coordinates of (0.16, 0.07) has been improved by the introduction of triphenylamine moiety, and the copolymer with derivative exhibited an electroluminescence quantum yield of 0.15 % at 20 $mA/cm^{2}$ with color coordinates of (0.16, 0.08). Moreover, the introduction of polar side chains to the spirobifluorene moiety enhanced the device performance and led to the quantum yields of 0.6 to 0.7 % at 20 $mA/cm^{2}$, although there was some expense of color purities.

• Korean Journal of Food Science and Technology
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• v.13 no.2
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• pp.114-120
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• 1981

A rapid and simple method for detecting colors was attempted on the basis of absorption and emission spectra of reflected light at $45^{\circ}$ angle from color-adsorbed filter paper illuminated by ultraviolet light through interference filter. Absorption spectra of prepared samples revealed more characteristic patterns than emission spectra. Detection of colors was readily accomplished by the investigation of wave length range, distribution pattern, the number of absorption bands and the degree of quenching.

• Bulletin of the Korean Chemical Society
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• v.13 no.1
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• pp.17-20
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• 1992

Photoionization processes of TMPD in $H_2O$ and $D_2O$ were studied, by measuring steady-state absorption, emission, fluorescence excitation spectra, and fluorescence lifetimes on picosecond time scale. The steady-state absorption spectra showed that there exists a cation-ion pair (Wurster's Blue) in $H_2O$ and in $D_2O$ in the electronic ground state. Temperature and excitation wavelength dependence were also studied and the results show that the photoionization reaction in water is an activated process and the fluorescence lifetime is independent of the vibrational excess energy in the uv excitation range of 283-310 nm.

• Macromolecular Research
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• v.11 no.5
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• pp.297-302
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• 2003

The imidization and cure reaction of a thermosetting phenylethynyl-terminated amic acid (LaRC PETI-5) in film form have been monitored as a function of temperature by means of a steady-state fluorescence technique using a front-face illumination method. The variation of the fluorescence emission spectra of LaRC PETI-5 can be divided into four temperature regions; Region I: below 15$0^{\circ}C$, Region II: 150-25$0^{\circ}C$, Region III: 250-35$0^{\circ}C$, and Region IV: above 35$0^{\circ}C$. The fluorescence spectra in Region I are largely influenced by residual N-methyl-2pyrrolidinone in the polymer and also slightly by partial imidization of the polymer. There is a combined effect of imidization and solvent removal on the fluorescence behavior in Region II. The spectra in Regions III and IV are due significantly to the cure reaction of LaRC PETI-5 and to a post-cure effect of the polyimide, respectively. This spectroscopic evidence indicating the transformation of the amic acid imide oligomer into the corresponding polyimide via imidization and cure, agrees well with thermal analysis results obtained previously. The intermediate stage of cure in the range of 250-30$0^{\circ}C$ predominantly influences the change of the fluorescence intensity. The later stage above 30$0^{\circ}C$ significantly influences the position of the spectrum. This fluorescence study also supports the mechanism proposed in earlier work that the crosslinking reaction takes place at the reaction sites in the conjugated polyene and the phenylethynyl end group in the polyimide chain.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1567-1572
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• 2009

Conformational change of ubiquitin variant with valine to alanine mutation at sequence position 26 was studied by varying solvent pH. Fluorescence emission spectra indicated that this variant ubiquitin has some residual structures in acidic and basic solution as compared to denaturant-induced unfolded state. Far-UV circular dichroic spectra indicated that the base-denatured state had more secondary structure than the acid-denatured state. Near-UV circular dichroic spectra indicated that the aromatic side-chains were in the relatively more rigid environment in the base-denatured state than those in the acid-denatured state. Although it appears that the more tertiary structure present in the base-denatured state, refolding reactions measured by stopped-flow fluorescence device suggest that both the acid- and base-denatured states occur before the major folding transition state. The acid- and base-denatured states are considered to reflect the early event of protein folding process.

• Journal of Photoscience
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• v.3 no.3
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• pp.153-158
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• 1996

The effects of $\alpha$- and $\beta$-cyclodextrins (CD) on the twisted intramolecular charge transfer (TICT) behavior of p-N,N'-dimethylaminobenzoic acid (DMABA) in buffered aqueous solution have been investigated by examining formation and decay behaviors of the TICT-typical dual fluorescence. The ratio of the TICT emission to the normal emission (I$_a$/I$_b$) increases linearly $\alpha$-CD concentration increases, while in the presence of $\beta$-CD it shows nonlinear dependences on the CD concentration. The analysis of the CD-dependent changes of the I$_a$/I$_b$ and absorption spectra demonstrates formation of 1:1 inclusion complexes between DMABA and CDs. The decay time of the normal emission (ca. 700 ps) is little affected by the formation of $\alpha$-CD inclusion complex, whereas it increases upto ca. 1.6 ns upon formation of $\beta$-CD inclusion complex. The TICT emission for the $\beta$-CD inclusion complex exhibits two decay components while it shows a single component for the $\alpha$-CD inclusion complex, indicating formation of one or two types of inclusion complex in the presence of $\alpha$-CD or $\beta$-CD, respectively. These results are attributed to the CD cavity size dependence on patterns of complexation between CDs and DMABA. The CD size dependences of the TICT fluorescence properties with the orientation of the guest molecule demonstrate that the specific hydrogen bonding between the carboxylic acid group and water plays an important role in the excited-state TICT.

• Rapid Communication in Photoscience
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• v.3 no.4
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• pp.76-78
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• 2014

Fluorescent nucleic acids were prepared utilizing the polymerase extension (PEX) reaction to incorporate fluorescent molecules. 2'-Deoxyuridine triphosphate (dUTP) derivatives possessing pyrene molecules as fluorophores were synthesized using the aqueous-phase Sonogashira coupling between 5-Iodo-dUTP and acetylene-linked pyrene molecules. The incorporation of the pyrene (Py)-labeled deoxyuridine triphosphates (PyU) into DNA by polymerase was evaluated by polyacrylamide gel electrophoresis, demonstrating that the PyU can work as a good substrate for the PEX reaction. The fluorescent properties of the functionalized DNA prepared by the PEX reaction were characterized by steady-state fluorescence measurements. The Py-conjugated DNA showed typical emission spectra of the pyrene, and the DNA with two pyrene molecules connected to each other by a diethylene glycol linker exhibited a broadened emission attributed to the electronic interaction between the Py molecules.