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Blue Light Emission (blue + light_emission)
Selected AbstractsChemInform Abstract: Efficient Blue Light Emission from Silicon.CHEMINFORM, Issue 40 2001L. Rebohle Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Diphenylamino End-Capped Oligofluorenes with Enhanced Functional Properties for Blue Light Emission: Synthesis and Structure,Property RelationshipsCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2005Zhong Hui Li Abstract A novel series of monodisperse asymmetrically and symmetrically substituted diphenylamino end-capped oligofluorenes, OF(2)-NPhR, R = H or An (An = 9-anthryl) and OF(n)-NPh, n = 2,4, has been synthesized by a convergent approach using palladium-catalyzed Suzuki cross-coupling. End-capping of oligofluorenes with diphenylamino group(s) has been shown to offer advantages in terms of lowering their first ionization potentials, enhancing thermal stability, and inducing good amorphous morphological stability. By tuning the number of diphenylamino end-caps and the chain length, the optimal conjugated length for optical and luminescence properties has been determined. Of all the hitherto reported oligofluorenes capable of serving as non-doped blue emitters, OF(3)-NPh, with an optimal conjugated length, exhibits some of the best hole-transport and blue-emitting properties. A maximum luminance of 7500 cd,m,2 and a luminance efficiency up to 1.8 cd,A,1 have been achieved. [source] Novel Fabrication of Size-Tunable Silica Nanotubes Using a Reverse- Microemulsion-Mediated Sol,Gel Method ,ADVANCED MATERIALS, Issue 9-10 2004J. Jang Size-tunable silica nanotubes have been fabricated using a novel reverse-microemulsion-mediated sol,gel method (see Figure). This facile approach is adaptable to large-scale fabrication, and the diameter of silica nanotubes is tunable through the use of different apolar solvents. The photoluminescence spectrum of the nanotubes displays three emission bands, including a stable and strong blue light emission at 435 nm. [source] Matrix dependence of blue light emission from a novel NH2 -functionalized dicyanoquinodimethane derivativeJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2006Marek Szablewski Abstract The reactions of primary and secondary amines with (cyclohexa-2,5-diene-1,4-diylidene)-dimalononitrile (TCNQ) lead to mono- and disubstituted dicyanoquinodimethane derivatives and fluorescence emission has been observed for several of these compounds. We report the luminescence properties, synthesis and crystal structure of the novel dicyanoquinodimethane derivative 2-{4-[amino-(2,6-dimethyl-morpholin-4-yl)-methylene]-cyclohexa-2,5- dienylidene}-malononitrile (Ammor), a unique example of an asymmetric dicyanoquinodimethane derivative in which one of the nitrile groups has been replaced with an NH2 moiety, which provides a reactive centre for potential further substitution or tethering to larger molecules or polymers. The luminescence properties of the title compound were investigated in a variety of environments, including alcohol solutions at room temperature and a glass-forming solvent at low temperature. The fluorescence quantum yields and Stokes' shifts of the blue emission were found to be very sensitive to the matrix. The crystal structure of the subject compound was determined, revealing that the molecules are non-planar in the ground state. The environmentally sensitive emission is discussed in terms of the conformational change during photoexcitation and the constraint imposed on this by the matrix. This behaviour is also compared with that of other related amino-functionalized dicyanoquinodimethane derivatives. Copyright © 2006 John Wiley & Sons, Ltd. [source] Synthesis and properties of nitrogen-linked poly(2,7-carbazole)s as hole-transport material for organic light emitting diodesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2009Tsuyoshi Michinobu Abstract A novel class of carbazole polymers, nitrogen-linked poly(2,7-carbazole)s, was synthesized by polycondensation between two bifunctional monomers using the palladium-catalyzed amination reaction. The polymers were characterized by 1H NMR, Infrared, Gel permeation chromatography, and MALDI-TOF MS and it was revealed that the combination of the monomer structures is important for producing high molecular weight polymers. Thermal analysis indicated a good thermal stability with high glass transition temperatures, e.g., 138 °C for the higher molecular weight polymer P2. To pursue the application possibilities of these polymers, their optical properties and energy levels were investigated by UV-Vis absorption and fluorescence spectra as well as their electrochemical characteristics. Although the blue light emission was indeed observed for all polymers in solution, the quantum yields were very low and the solid films were not fluorescent. On the other hand, the HOMO levels of the polymers estimated from the onset potentials for the first oxidation in the solid thin films were relatively high in the range of ,5.12 to ,5.20 eV. Therefore, light emitting diodes employing these polymers as a hole-transport layer and iridium(III) complex as a triplet emitter were fabricated. The device of the nitrogen-linked poly(2,7-carbazole) P3 with p,p,-biphenyl spacer, which has a higher HOMO level and a higher molecular weight, showed a much better performance than the device of P2 with m -phenylene spacer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3880,3891, 2009 [source] Light emission from different ZnO junctions and nanostructuresPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009M. Willander Abstract We will discuss our experimental results for optical spectra produced by hole-injection from different p-type organic and inorganic materials into n-type ZnO nanowires. The influence of different growth techniques and conditions on the nanowires and their emission spectral characteristics will then be analyzed and discussed. The latest findings on the mixture of the green emission band responsible for visible light emission from ZnO and the blue light emission from the organic polymer will be presented. Different high brightness light emitting diodes (HB-LEDs) from our grown ZnO nanowires are demonstrated. The p-type multi layer organic structures contain PEDOT:PSS as hole injectors combined with a hole transporting layer, and in some structures, a final top electron blocking/hole barrier stepping layer is placed. The purpose of this layer is to adjust the hole and electron emission from the corresponding junction side to optimize the LED performance. Structural scanning electron microscopy (SEM), electrical (I ,V characteristics), photoluminescence (PL) and electroluminescence (EL) characteristics of these devices are displayed. Theoretically, we study the superfluidity of a two-dimensional system of excitonic polaritons in an optical microcavity with an embedded quantum well. Using the effective low-energy action for thermodynamic phase fluctuations, we obtain an expression for the analogue of the superfluid density in the system in terms of the "current,current" correlation function. The Kosterlits,Thouless transition temperature to the superfluid state as a function of the controlling parameters is calculated. Two methods are considered for producing traps for a polariton system in an optical microcavity. The behaviour of a two-component Bose condensate of photons and excitons is analyzed theoretically for both types of the trap. The Bose condensate is described by the coupled system of equations of the Gross,Pitaevskii type. The approximate wave functions and the spatial profiles of coupled photon and exciton condensates are obtained. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High efficiency violet to blue light emission in porous SiC produced by anodic methodPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010T. Nishimura Abstract Porous fluorescent (f-) SiC containing N and B was produced by anodic oxidation. The average crystal size can be controlled by adding K2S2O8 as an oxidant to dilute HF solution during the anodic process. With the reduction of the average crystal size of the porous crystal, the PL peak wavelength becomes shorter, and its intensity increases. Such behavior can be explained by the quantum size effect of donor-acceptor-pair recombination. Finally, we confirmed the superior fluorescent property of blue light emission in porous f-SiC crystal (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||