• Polymer(Korea)
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• v.35 no.4
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• pp.350-355
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• 2011

A soluble polyamide containing photosensitive l,4-phenylenediacrylic acid (PDA) in main chain with biphenyl moiety was synthesized. The chemical structure of synthesized polyamide was investigated by means of $^1H$ NMR spectroscopy. The polymer was stable up to $280^{\circ}C$ and soluble in organic solvents, giving a good quality of thin films. The photoreaction of unpolarized LTV irradiated films was investigated by means of UV-vis absorption spectroscopy and FTlR spectroscopy, and liquid crystals (LCs) alignment property was examined by exposing to linearly polarized UV light (LPUVL) of 260~380 nm. The polyamide in film has excellent photoreactivity to unpolarized UV light. Direction selective photoreaction of PDA moiety in Lhe film was found to further induce nematic liquid -crystals to align along a perpendicular direction with respect to the electric vector of LPUVL, regardless of exposure energy of LPUVL. In addition, pretilt angle was measured by means of crystal rotation method. LPUVL-exposed polymer film induced the alignment of liquid-crystals (LC) with a pretilt angle of 0.2~$0.5^{\circ}$.

• Journal of the Korean Chemical Society
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• v.41 no.12
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• pp.666-671
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• 1997

Photoreactions of pseudosaccharin pyridinemethyl ethers have been investigated. Pseudosaccharin 2-pyridinemethyl ether, pseudosaccharin 4-pyridinemethyl ether and pseudosaccharin 3-pyridinemethyl ether all undergo a facile photoreaction via reaction pathways involving homolysis of the bond between pseudosaccharyl oxygen and pyridinemethyl carbon, and excited nucleophilic substitution of pyridinemethoxy group by solvent, methanol which are not quenched by oxygen present in the reaction. Product yield demonstrates that the homolysis pathway predominates over the nucleophilic substitution.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.35-40
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• 2002

Photoreaction of guest organic anions in layered organic-inorganic hybrid materials was investigated. The layered hybrids were synthesized by an anion-exchange reaction of $[LiAl_2(OH)_6]Cl{\cdot}yH_2O$ layered double hydroxide with aqueous (Z,Z)- and (E,E)-muconates under inert atmospheric condition, to give new organicinorganic hybrids of $[LiAl_2(OH)_6]_2[(Z,Z)-C_6H_4O_4]{\cdot}zH_2O$ and $[LiAl_2(OH)_6]_2[(E,E)-C_6H_4O_4]{\cdot}H_2O$, respectively. The basal spacings calculated by XRPD of intercalates indicate that muconate anions have almost vertical arrangements against the host $[LiAl_2(OH)_6]^+$ lattices in the interlayer of organic-inorganic hybrid materials. When UV light was irradiated on the suspension of $[LiAl_2(OH)_6]_2[(Z,Z)-C_6H_4O_4]{\cdot}zH_2O$, the (Z,Z)-muconate anions of the gallery space of hybrids were polymerized in the aqueous media while it was isomerized into more stable (E,E)-muconate in the methanollic suspension in the presence of catalytic amount of molecular iodine. All the products were characterized using elemental analysis, TGA, XRPD, FT-IR, $^1H$ NMR and $^{13}C$ CP-MAS NMR.

• Journal of the Korean Chemical Society
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• v.38 no.1
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• pp.8-12
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• 1994

The structure-activity studies are described for the photoreaction of naturally occuring psoralen with thymine. Thymine <> psoralen <> thymine photodiadducts from DNA is studied as a model for the charge transfer interaction by the semiempirical methods (PM3-CI-UHF, etc.). The relative structural activities of psoralen, and photoadducts are analyzed in terms of their differing abilities of psoralen and photoadducts are investigated both with regard to their abilities to complex and to intercalate with thymine base. The photoadducts were inferred to be a trans-anti Psoralen(3,4) <> Thymine(5,6) and cis-anti Thymine(5,6) <> (4',5')Psoralen(3,4) <> Thymine.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.227-228
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• 1998

Lumbrokinase, potent fibrinolytic enzyme purified from earthworm, was immobilized onto polyurethane valves using photoreaction, photoreactive polyallyl-amino as a photoreactive linker. For evaluation of blood compatibility, lumbrokinase immobilized polymer valves were assembled into the total artificial heart (TAH). This TAH was implanted to 60kg healthy lamb for 1-3 days with the cardiac output 5 L/min. In the control lamb, the valves were untreated, in ore other, only valves on the right were treated, and in the remaining animal, only those on the left. To facilitate the thrombus formation, low doses of heparin were administered. For evaluation of the immobilized lumbrokinase, thrombus formation, proteolytic and fibrinolytic activity was measured. This data shows that lumbrokinase-treated polyurethane valves lead to decreased thrombus formation in vivo, and that their biocompatibility is therefore higher than that of untreated valves.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.5
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• pp.47-53
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• 2000

To overcome the shortage of conventional TWC that is activated at high temperature, higher than 25$0^{\circ}C$, photocatalyst is considered as an new technology. Because the photocatalytic reaction of photocatalyst is not a thermo mechanical reaction, it is necessary to heat the system to start the reaction. It can be activated just by ultra violet light that includes wavelengths shorter than 400 nanometers even at ambient temperature. In this study photocatalytic reduction of hydrocarbon was investigated with a model gas test. To understand the effects of co-existence gases on the hydrocarbon reduction by photoreaction, CO and NO, $O_2, H_2O$ gases those are components of exhaust gases of gasoline engine are supplied with C3H8/N2 to a photoreactor. The photoreactor contains $TiO_2$ photocatalyst powders and a UV bulb. The results show that oxygen is the most important factor to reduce HC emission with photocatalyst. Photocatalyst seems to have a good probability for automotive application to reduce cold start HC emissions.

• Polymer(Korea)
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• v.28 no.6
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• pp.545-550
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• 2004

The refractive index of thin copolymer film was controlled by photo-degradation of chromophores in the copolymer. FTIR and UV/Vis spectroscopy were employed to elucidate the effect of chemical structure on refractive index changes after photobleaching. The decrease of refractive index of the film by photobleaching can be ascribed to the decrease of polarizability of polymer molecules through breakage of C =C bond in the chromophore. Due to the selective photoreaction of the chromophores which align along the film plane, refractive index of the copolymer film measured in TE mode decreases faster than that in TM mode. Polarized ATR-FTIR spectroscopy was used to verify such a difference in refractive index of the film.

• YAKHAK HOEJI
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• v.40 no.1
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• pp.41-45
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• 1996

A high performance liquid chromatography using photoreduction fluorescence detection was described for the analysis of saikosaponins. Saikosaponins were separated on an $NH_2$ column using acetonitrile and aqueous 2-tert-butylanthraquinone(t-BAQ) as mobile phase. Column effluent was passed through a 40cm PTFE capillary tube coiled around a 10W UV lamp to reduce t-BAQ to a highly fluorescent dihydroxyanthracene derivative which was detected by a fluorescence detector. The optimal concentration of t-BAQ was found to be $6{\times}10^{-5}M$ and the optimal reaction time to be 2 seconds. The detection limit for saikosaponin a and d by this method was found to be about 280ng and 80ng. The dynamic linear range was over two orders and the correlation coefficient of the calibration curve of them was 0.998.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.75-80
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• 1992

The electrochemical spectral sensitization of a $SnO_2$ electrode with eosin B, a Xanthene dye, has been studied in acetonitrile. Measurements of the photocurrent have been carried out in the presence of supersensitizers such as thiourea, 1-allyl-2-thiourea, NaSCN, and NaI. The magnitude of the supersensitized photocurrent was greater than that of the sensitized photocurrent for all of the supersensitizers studied. However, the long time span of irradiation causes a significant decrease of the supersensitized photocurrent as well as the absorbance. These results, together with infrared spectra and fluorescence spectra, are taken into account to elucidate the mechanism of photoreaction between eosin B and supersensitizers in acetonitrile.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.819-824
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• 2010

We report the laser-induced formation of peanut-shaped gold nanoparticles (Au nanopeanuts) and gold nanowires (AuNWs), and their morphological properties. Pulsed laser irradiation of citrate-capped gold nanoparticles at 532 nm induces fragmentation, spherical growth, the formation of Au nanopeanuts, and the formation of AuNWs, sequentially. High-resolution transmission electron microscopy images reveal that the Au nanopeanuts are formed by instantaneous fusion of spherical nanoparticles in random orientation by laser heating. Furthermore, Au nanopeanuts are bridged in a linear direction to form AuNWs by an amorphous accumulation of gold atoms in the junction. The laser-produced Au nanopeanuts and AuNWs slowly disintegrate, restoring the spherical shape of the original Au nanoparticles when the laser irradiation is stopped. The addition of citrate effectively prevents them from transforming back to the nanospheres.