• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.27-28
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• 2003

Synthesis and properties of novel excited-state intramolecular proton transfer (ESIPT) materials recently developed in our group are described. Highly efficient ESIPT in polymeric system has been investigated theoretically and experimentally with a semi-rigid polyquinoline (PQH, PQDH) possessing an intramolecular tautomerizable hydrogen bond. Poly(aryl ether) dendrimers of three different generations that are cored with photo-tautomerizable quinoline (QGn, n=1,2,3) were also synthesized and characterized to investigate the effect of dendritic architecture on the ESIPT activity. Stimulated emission and amplified spontaneous emission in these organic materials system are discussed in terms of ESIPT activity.

• Proceedings of the Korean Society of Potoscience Conference
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• spring
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• pp.23-23
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• 2003

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.981-987
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• 2011

The anomalous spectroscopic properties of quercetin-3-O-rhamnoside (QCRM) and quercetin-3-O-rutinoside (QCRT) in AOT reverse micelle were studied. The excited state intramolecular proton transfer (ESIPT) occurs through the strong hydrogen bond between the -OH at position 5 and the carbonyl oxygen. Because the ESIPT can only happens in the $S_1$ state and the Franck-Condon factor involved in the $S_2\;{\rightarrow}\;S_1$ internal conversion is small, the $S_2\;{\rightarrow}\;S_o$ emission alone appears. Because the molecular planarity is improved at the interior of the micelle, the excited state intramolecular charge transfer in the $S_1$ state is extended, and the excited state is more tolerable for any quenching effects in the micelle. Therefore, an $S_1\;{\rightarrow}\;S_o$ emission was newly discovered under this micelle microenvironment. For the $S_2\;{\rightarrow}\;S_o$ emission, the quantum yields increase but the quantum yield of the $S_1\;{\rightarrow}\;S_o$ emission approximately decreases as the water concentration in the micelle increases.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.616-621
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• 1996

The transfer of excitation energy from solvent to solute in polystyrene films doped with 2-(2'-hydroxyphenyl)benzothiazole (HBT) which undergoes intramolecular proton transfer in excited electronic state has been studied by employing steady state and time-resolved fluorescence measurements. The degree of Forster overlap between donor and acceptor molecule in this system is estimated to be moderate. Energy transfer efficiency increases with solute concentration at low concentration range and levels off at high concentration. It is observed that the excimer form of polystyrene is largely involved in energy transfer process. Photostability of HBT in polystyrene to UV light is also investigated to get insight into the long wavelength absorption band of HBT which was observed upon electron radiation.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.828-832
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• 2014

The spectroscopic properties of quercetin (QCT) were studied in the AOT reverse micelle by fluorescence spectroscopy. Because the molecular structure of QCT is completely planar, excited state intramolecular proton transfer (ESIPT) occurs between the -OH at C(5) and carbonyl oxygen via intramolecular hydrogen bonding. This ESIPT happens at the $S_1$ state but not at the $S_2$ state. Because QCT is a good donor-acceptor-conjugated molecule at the excited state, this molecule can emit strong fluorescence but shows no $S_1{\rightarrow}S_o$ emission due to this ESIPT. Since the $S_2{\rightarrow}S_1$ internal conversion was very slow due to the small Franck-Condon factors, $S_2{\rightarrow}S_o$ fluorescence emission was observed. All of the experimental results indicated that the QCT resided at the bound water interface and that the position of solute did not change significantly in the micelle at various water concentrations.

• Proceedings of the Korean Society of Potoscience Conference
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• spring
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• pp.82-82
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• 1999

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.92-93
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• 2005

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.133-134
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• 2006

• Bulletin of the Korean Chemical Society
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• v.1 no.3
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• pp.113-114
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• 1980

Lumichrome (7,8-dimethylalloxazine) exhibits two fluorescence emission maxima at 440 and 540 nm in pyridine-dioxane. These emission band maxima are attributable to radiative decays from the excited states of lumichrome and its flavin tautomer, 7,8-dimethylisoalloxazine, respectively. The growth of the latter can be followed upon excitation of the former with a 2-nanosecond light pulse generated from the nitrogen plasma discharge lamp. The excited state tautomerism results from proton transfer from N-1 to N-10 position during the lifetime of the lumichrome singlet excited state. The rate depends on the concentration of general base, pyridine, and it is an order of magnitude slower than diffusion-controlled processes.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.481-481
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• 2009

For a new generation of white light sources, we present the first example of a concentration-independent ultimate white-light-emitting molecule based on excited-state intramolecular proton transfer materials. Our molecule is composed of covalently linked blue- and orange-light-emitting moieties between which energy transfer is entirely frustrated, leading to the production of reproducible, stable white photo- and electroluminescence.