• Bulletin of the Korean Chemical Society
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• 제9권5호
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• pp.317-322
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• 1988

Premicellar precipitation, resolubilization and luminescing behaviors of $RuL_3^{2+}$ (L = bpy, phen, $Me_2bpy$) in aqueous alkylsulfate and sulfonate solutions were studied. Addition of the anionic surfactants to $RuL_3\;^{2+}$ solutions caused initial precipitation which was redissolved by further addition of the surfactants. The apparent solubility products $K_{sp}$'s of the precipitates were evaluated assuming 1:2 salt formation. The values were smaller as the ligand is more hydrophobic and the length of hydrocarbon chain of the surfactant is longer. The $K_{sp}$ values for L = bpy were constant over wide surfactant concentration range. However, those for L = $Me_2bpy$ and also for phen, but to less extent, increased with the surfactant concentration. The resolubilization of 1:2 salts was followed by red-shift of emission band and extensive emission quenching above critical concentration of the surfactants. The critical concentration was lower for more hydrophobic surfactant. For L = $Me_2bpy$, the blue-shifted emission band with enhanced emission intensity was observed in intermediate surfactant concentration region. The high ionic strength of media prevented the precipitate formation, but facilitated the red-shift of the emission bands. The results support that the precipitate is dissolved by accretion of surfactant anions to the salts to form water-soluble surfactant-rich $RuL_3$-surfactant anionic species. These species appeared to aggregate cooperatively to produce large clusters which exhibited the red-shifted emission.

• Journal of Photoscience
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• 제12권2호
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• pp.57-61
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• 2005

The ground and excited state dipole moments of Coumarin 450 (C 450) laser dye were measured at room temperature in several solvents of varying dipole moments. The ground state dipole moment (${\mu}_g$) is estimated by using the modified Onsagar model and the excited state dipole moments (${\mu}_e$) were estimated by the method of solvatochromism as well as by utilizing the microscopic solvent polarity parameter ($E^N_T$). Further, the deviation of some of the points from the linearity of the $E^N_T$ versus Stokes shift indicates the existence of specific type of solute-solvent interaction. The excited state dipole moment of C 450 were found to be higher than those of the ground state and is interpreted in terms of the resonance structure of the molecule. A reasonable agreement has been observed between the values obtained by the method of solvatochromism and modified Onsagar model. It is observed that, corresponding to cyclohexane solution, the fluorescence maxima shift towards the red region with increasing the polarity of the solvents, hence the transition involved are of ${\pi}-{\pi}^*$ type.

• Current Photovoltaic Research
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• 제5권2호
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• pp.43-46
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• 2017

Large absorption band shift has been observed for the azo-dye (disperse red-13, DR-13) attached on the surface of silica spheres. Urethane linkage has been utilized to form covalent bond between azo-dye (-OH) and 3-isocyanatopropyltriethoxysilane (ICPTES, -N=C=O). The synthesized ICPTES-DR-13 (ICPDR) molecules were attached to the silica spheres by the hydrolysis and condensation reaction. Although the absorption peak of DR-13 in methanol is at 510 nm, the absorption peak of the ICPDR-silica spheres shifts to 788 nm. The large absorption peak shift is due to the formation of intramolecular charge-transfer band with large aggregated ICPDR.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.49-52
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• 1987

In this work, the characteristics of a six step inverter fed brushless DC motor are analyzed and the control of amplitude of inverter input voltage and phase shift of a six step inverter is discussed. The effects of the motor performance, efficiency and power factor, are studied.

• 공업화학
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• 제28권5호
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• pp.571-575
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• 2017

본 연구에서는 초음파 조사법을 사용하여 cadmium telluride (CdTe) 양자점을 합성하였다. 전구체의 비율과 합성 시간을 주 변수로 하여 그에 따른 CdTe 양자점의 광학적 특성과 구조적 특성을 분석하였다. 모든 cadmium (Cd)과 tellurium(Te) 함량비율의 실험에서 합성 시간이 증가함에 따라 CdTe 양자점의 성장에 의해 밴드갭 감소현상이 관찰되었고, 발광 특성을 확인한 결과 510~610 nm 파장 범위에서 장파장으로 이동함을 보였다. 또한 Te의 비율이 증가함에 따라 장파장이동이 빠르게 일어나는 것을 확인하였다. Photoluminescence (PL) 피크 강도를 확인하였을 때 합성시간이 180 min~240 min 사이에서 가장 높은 강도를 보였다. X-ray diffraction (XRD)와 transmission electron microscopy (TEM)으로 구조적 특성을 확인한 결과 zinc blend 구조의 CdTe 양자점을 나타내었으며, 합성시간이 210 min일 때 양자점의 크기는 약 2.5 nm로 균일하게 분산되어 있었으며 fast fourier transform (FFT) 이미지를 확인한 결과 뚜렷한 결정성을 확인하였다.

• 한국환경보건학회지
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• 제27권1호
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• pp.36-43
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• 2001

Chitosans were prepared from red crab chitin under various alkali treatment conditions(different alkali concentrations, reaction times and temperatures) and theirphysicochemical properties were investigated. The nitrogen content and deacetylation degree of red crab chitin were 6.15% and 22.17A%, respectively. By the IR spectra, red crab and reference chitin showed the sharp bands at 1650 $cm^{-1}$ / and 1550 $cm^{-1}$ /, which are characteristic of chitin. The nitrogen contents of prepared chitosans ranged from 6.19~7.48%. Thedeacetylation degree was increased from 63~76% and 48~78% with increasing reaction time and temperature, whereas viscosity was decreased. The nitrogen content and yield of red crab chitosan perpared from chitin with 50% NaOH, 1:25(w/v) for 3.0 hr at 120$cm^{-1}$ / were 7.26% and 85.0%, respectively. and viscosity, deacetylation degree and molecular weight, 67.0 mPa.s, 75.0% and 6.5$\times$10$^{5}$ Dalton, respectively. From the IR spectra, the amide absorption bands of red crab and reference chitosan became very weak, similarly. And at solid state $^{13}$ C-NMR spectra, C=O(carbonyl carbon) signals absent, whereas $CH_3$(methyl carbon) was residues. Chemical shift of $^{13}$ C-NMR spectra of red crab and reference chitosans were in good agreement with slight experimental deviation.

• 대한화학회지
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• 제26권5호
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• pp.274-281
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• 1982

펜타메틸벤젠 및 헥사메틸벤젠과 요오드 및 일염화요오드와의 각계를 사염화 탄소용액에서 자외선 분광광도법에 의하여 연구한 결과 1:1 분자 착물이 형성됨을 알았다. 이들 착물 생성에 의한 흡수최대는 온도가 상승함에 따라 blue shift 되므로 이에 따른 각 온도에서의 평형상수를 구하였다. 이 값으로 부터 이들 착물 생성에 대한 열역학적 파라미터를 산출한 결과 각 온도에서 폴리메틸벤젠과 요오드 및 일염화요오드 사이에 생성된 착물의 상대적 안정도는 ICl이 $I_2$보다 크다는 것을 알 수 있다. 이 사실은 폴리메틸벤젠에 대한 그들의 상대적 산성도를 나타내며 할로겐 원자의 전기 음성도의 차이에 의하여 설명할 수 있다. 그리고 이 계열의 연구결과를 종합하면 벤젠에 치환된 메틸기의 수가 증가함에 따라 ${\lambda}_{max}$는 red shift 하였고 이들 착물의 상대적 안정도가 다음 순서로 증가함을 알 수 있었다.Benzene < Toluene < Xylene < Durene < Mesitylene < Pentamethylbenzene < Hexamethylbenzene. 이에 따른 결과에 대하여 고찰하였다.

• Bulletin of the Korean Chemical Society
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• 제16권10호
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• pp.972-976
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• 1995

A trace amount of 4-biphenylcarboxylate having a pre-twisted biphenyl moiety was attached to a poly(methyl methacrylate) side chain and the fluorescence properties of the chromophore were investigated in various solvents such as ethyl acetate and butyl chloride. At room temperature, the polymer exhibited a distinct red shift of the short wavelength emission (325 nm) and an enhanced emission intensity around 430 nm upon excitation at the absorption red edge. The temperature dependence of the intensity ratio (R) of the 325 nm emission to the 430 nm emission was observed when exciting at the red edge over the temperature range between -20 and 60 ℃. However, the temperature dependence was not observed when exciting at the shorter wavelength. The Arrhenius plot of the R value shows the activation energy of 6.0 kJ/mol which is in good agreement with the energy required for the twist of the biphenyl moiety. Together with the results of red edge excitation effects it was concluded that the pre-twisted geometry of the biphenyl moiety is preserved by the restriction of the polymer chain to facilitate the formation of the twisted intramolecular charge transfer (TICT) state upon excitation.

• 한국전기전자재료학회논문지
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• 제28권9호
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• pp.581-586
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• 2015

We studied optical and electrical properties of two-wavelength white tandem organic light-emitting diodes using red and blue materials. White fluorescent OLEDs were fabricated using Alq3 : Rubrene (3 vol.% 5 nm) / SH-1 : BD-2 (3 vol.% 25 nm) as emitting layer (EML). White single fluorescent OLED showed maximum current efficiency of 9.7 cd/A, and tandem fluorescent OLED showed 18.2 cd/A. Commission Internationale de l'Eclairage (CIE) coordinates of single and tandem fluorescent OLEDs was (0.385, 0.435), (0.442, 0.473) at $1,000cd/m^2$, respectively. White hybrid OLEDs were fabricated using SH-1 : BD-2 (3 vol.% 10 nm) / CBP : $Ir(mphmq)_2(acac)$ (2 vol.% 20 nm) as EML. White single hybrid OLED showed maximum current efficiency of 7.8 cd/A, and tandem hybrid OLED showed 26.4 cd/A. Maximum current efficiency of tandem hybrid OLED was more twice as high as single OLED. CIE coordinates of single hybrid OLED was (0.315, 0.333), and tandem hybrid OLED was (0.448, 0.363) at $1,000cd/m^2$. CIE coordinates in white tandem OLEDs compared to those for single OLEDs observed red shift. This work reveals that stacked white OLED showed current efficiency improvement and red shifted emission than single OLED.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(2)
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• pp.517-520
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• 2004

Organosilicate films are promising porous low-dielectric materials, which can replace the silicon dioxide films. It was researched that organosilicate films have two different chemical shifts according to the increase of the flow rate ratio. There are the red shift due to the electron deficient substitution group, and the blue shift of the electron rich substitution group. Among these chemical shifts, the blue shift from $1000 cm^{-1}$ to $1250 cm^{-1}$ was related with the formation of pores. The methyl radicals of the electron-rich substitution group terminate easily the Si-O-Si cross-link, and the Si-O-C cage-link near $1057 cm^{-1}$ is originated from the cross-link breakdown due to much methyl radicals.