• Korean Journal of Materials Research
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• v.17 no.9
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• pp.489-492
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• 2007

Temperature and injection current dependence of elctroluminescence(EL) spectral intensity of the $In_{0.27}Ga_{0.73}N/GaN$ multi-quantum-well(MQW) have been studied over a wide temperature and as a function of injection current level. EL peaks also show significant broadening into higher photon energy region with the increase of injection current. This is explained by the band-filling effect. When temperature is slightly increased to 300 from 15 K, the EL emission peak showed red-blue-red shift. It can be explained by the carrier localization by potential fluctuation of multiple quantum well and band-gap shrinkage as temperature increase. It is found that a temperature-dependent variation pattern of the EL efficiency under very low and high injection currents show a drastic difference. This unique EL efficiency variation pattern with temperature and current is explained field effects due to the driving forward bias in presence of internal(piezo and spontaneous polarization) fields.

• ETRI Journal
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• v.24 no.3
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• pp.221-225
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• 2002

We performed nonlinear transmission measurements and quantum-chemical calculations on dithienothiophene(DTT)-based molecules to gain insight into the effect of acceptor and donor groups on two-photon absorption(TPA) properties. The TPA intensity showed dispersion characteristics of the single-photon absorption spectrum. When the molecules included an asymmetric donor-acceptor pair, the single- and two-photon absorption maximum wavelengths were red-shifted more than when the molecules had a symmetric donor-donor structure. We interpreted this result as indicating that the $S_2$ state plays the dominating role in the absorption process of molecules with a symmetric structure. The experimental TPA ${\delta}$ values at the absorption peak wavelength showed a dependence on the structural variations. We found the self-consistent force-field theory and Hartree-Fock Hamiltonian with single configuration interaction formalism to be valid for evaluating TPA ${\delta}$. Although the quantum-chemical calculations slightly underestimated the experimental ${\delta}$ values obtained from nonlinear trans -mission measurements, they reasonably predicted the dependence of the ${\delta}$ value on the structural variations. We confirmed the role of molecular symmetry by observing that donor-donor substituted structure gave the highest experimental and theoretical TPA ${\delta}$ values and that the donor-acceptor substituted structure showed a greater red-shift in the TPA absorption maximum wavelength. Overall, the theoretical ${\delta}$ values of DTT-based molecules were in the order of $10^{-46}\;cm^4{\cdot}s{\cdot}photon^{-1}$ and are higher than that of AF-50 by nearly two orders of magnitude.

• Bulletin of the Korean Chemical Society
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• v.28 no.5
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• pp.816-820
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• 2007

Novel new red-light emitting perylene fluoroionophore N,N'-dipropyl-1,7-bis(calix[4]azacrown-5-crown-5)- 3,4,9,10-perylene tetracarboxy diimide (3) was prepared by reacting N,N'-dipropyl-1,7-dibromo-3,4,9,10- perylene tetracarboxy diimide (1) with calix[4]azacrown-5-crown-5. Also the alternating copolymer (4) with similar repeating unit was prepared reacting by calix[4]bisazacrown-5 with 1. Metal ion binding by 3 and 4 leads to a blue-shift of absorption band and emission spectra. When ionophoric characteristics were investigated by binding alkali, alkali earth metal and various metal ions, polymeric ionophores displayed large fluorescence decreasing effects with K+, Ag+ and Ba2+, which was rationalized by photo-induced charge transfer (PCT).

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.188-196
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• 2013

We have investigated the effects of formalin on the assembly of colloidal gold nanoparticles (AuNPs) prepared by laser ablation of a solid gold target in deionized water. Upon addition of formalin, the surface plasmon resonance (SPR) band at 519 nm for pure AuNPs decreases and shifts to red while a new broad SPR band appears at ~700 nm. The red-shift is prominent with increase in the incubation time. The average size of the initial AuNPs is around 12 nm but it increases to 23 nm after addition of formalin. It turns out that formalin acts as a cationic surfactant for AuNPs with negative surface charge in the colloidal solutions. Furthermore, through analysis of the Raman spectrum of formalin and the density functional theory calculations, we confirm that methanediol is the main species in formalin which is in charge of the aggregation of AuNPs.

• Textile Coloration and Finishing
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• v.17 no.6 s.85
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• pp.1-10
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• 2005

Disperse dyes derived from heterocyclic compounds such as phenylindole, pyridone, diaminopyridine, and carbazole have been known to exhibit high light fastness and bathochromic shift compared to the coursponding aminoazobenzene. The synthetic method to obtain diaminopyridine derivatives, which can be used as coupling components, was chlorination of pyridone with phosphorous oxychloride, followed by substitution with various primary amines. Four azo disperse dyes were synthesized by coupling four diaminopyridines with 2-cyano-4-nitroaniline as a diazo component. Structures of these dyes were confirmed by $^1H$ NMR spectroscopy. The wavelengths of maximum absorption of the synthesized disperse dyes were in the range of $517\~528nm$, and molar extinction coefficients were $45,700\~50,100$. The dyeability of four disperse dyes toward PET fiber was generally good. Wash and rubbing fastnesses were excellent, while light and dry heat fastness were good.

• Journal of the Korean Applied Science and Technology
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• v.13 no.1
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• pp.87-98
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• 1996

In this study, benzoxazolo carbocyanine dye was used as sensitizer for photographic emulsion, and the photographic characteristics were examined. The basic properties of sensitizer such as stability in various solvents were examined. The sensitizer was very stable in methanol, acetonitrile, acetone, dimethylformamide, and chloroform solution. Absorption spectra of benzoxazolo carbocyanine dye $2.5{\times}10^{-6}M$ and $5{\times}10^{-6}M$ concentrations in 10% aqueous methanol solutions containing $10^{-2}M$ potassium chloride show the monomer-J-aggregation characteristics. Compared to the absorption peak of the monomer in pure methanol solution, the red shifts of the monomer-J-aggregate peaks of benzoxazolo carbocyanine dye of $2.5{\times}10^{-6}M$ and $5{\times}10^{-6}M$ concentrations in 10% aqueous methanol solutions containing $10^{-2}M$ potassium chloride are 34nm respectively, and the sensitizing peak of benzoxazolo carbocyanine dye in photographic emulsion has red shift of 34nm. Therefore, if was concluded that benzoxazolo carbocyanine dye can be used as green sensitizing dye for the spectral sensitization of photographic emulsion.

• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.629-637
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• 1998

The HF-SCF, MP2 and B3LYP calculations have been performed on the two conceivable clusters $(HF)_2(CO)$ trimers as well as their dimer complexes FH…FH, FH…CO and FH…OC applying $6-31+G^{\ast}^{\ast}$, and $6-311+G^{\ast}^{\ast}$ basis sets. A variety of ground state properties of these trimer complexes have been listed, and compared with corresponding properties of isolated monomers and combined dimers. It was calculated that FH…CO is more stable than FH…OC by average 0.85 kcal/mol and F-H…F-H…C≡O is more stable than F-H…F-H…O≡C by 1-2 kcal/mol. The C≡O stretching bands of the F-H…F-H…C≡O and F-H…F-H…O≡C were red shifted by 24, $37\;cm^{-1}$ compared with the FH…CO and FH…OC respectively. Also, H-F stretching bands were red shifted by 54 and $353\;cm^{-1}$.

• Korean Journal of Microbiology
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• v.33 no.4
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• pp.252-256
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• 1997

The white rot fungus Coriolus hiysutus decolorized several recalcitrant dyes. Four different types of dyes, including azo, triphenyl methane, heterocyclic, and polymeric dye, were treated by the mycelial preparation. Triphenyl methane dye, bromophenol blue lost over 95% of its color. Congo red and Poly R-478 were decolorized less than bromophenol blue, 57 and 55%, respectively. However, heterocyclic dye, methylene blue was not decolorized significantly and only red shift was observed. Extracellular laccase and peroxidase activities were appeared maximally in high level of dye decolorization media. In electrophoretic experiments, common active bands of laccase and peroxidase were found in all dye decolorized medium. These results indicated that the culture conditions which yield high levels of laccase and peroxidase activity lead to high levels of dye decolorization, and these two enzymes might be play an important roles in dye decolorization.

• Journal of the Korean Applied Science and Technology
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• v.16 no.4
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• pp.273-279
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• 1999

In order to study a reversible photoisomerization of disperse red l(DR 1) attached on natural polymers, cellulose acetate containing DR l(DR 1/CA adduct) was prepared, and the changes of UV/VIS spectra of its solution(benzene, DMAc). thick film, and LB film were investigated by alternate irradiation with two different wave length lights. DR 1/CA adduct was prepared through tosylation of partially hydrolyzed cellulose acetate followed by reaction with DR 1 at $100^{\circ}C$ in pyridine. From the UV/VIS spectra of DR 1/CA adduct dissolved in DMAc solvent including phosphoglyceride before and after irradiation at 360nm and 45Onm, we found out the changes of UV/VIS spectra were reversible. In addition, the change of UV/VIS spectra of this adduct solution was strongly depended on the sorts of solvents and temperature. As the temperature was increased, UV/VIS spectra of this adduct solution in DMF showed blue shift. These results provided this solution could be applied to a temperature sensor. In the thick film case, we also obtained similar results with solution case. LB monolayer and trilayer from DR 1/CA adduct was obtained by scattering the solution including phosphoglyceride on water surface at the surface pressure of 8mN/m. After irradiation on that LB monolayer and trilayer, the reversible photoisomerization was also detected. From these results we concluded DR 1/CA adduct was suitable for the application to data storage and optical switch, etc.

• Journal of the Korean Graphic Arts Communication Society
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• v.18 no.1
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• pp.113-120
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• 2000

A previous paper was reported in being sensetized photopolymer, poly(vinyl cinnamoyl acetate) (PVCiA)1) with some squarylium dyes such as 1,3-bis(4 or 6-trifluouomethy1-1,3,3-trimethylindo) squarylium dyes(TFSQ). Here, we synthesized new 1,3-bis(4 or 6-nitro-1,3,3-trimethylindo) squarylium dyes(NISQ) to sensetize photopolymer, such as poly(vinyl cinnamoyl acetate). Absorption's coefficient of (NISQ8) is 8.5x105, the sensitivity of PVCiA added with NISQ8(3%) was highly sensitized 8 times than not added, and 2 times than TFSQ8(3%). Maybe, high absorption'scoefficient and red shift of NISQs with strongly withdrawing group to TFSQs afford to the high sensitivity of PVCiA.