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Blue Emission (blue + emission)
Kinds of Blue Emission Selected AbstractsStable Blue Emission from a Polyfluorene/Layered-Compound Guest/Host Nanocomposite,ADVANCED FUNCTIONAL MATERIALS, Issue 7 2006E. Aharon Abstract In this study a blue-light-emitting conjugated polymer, poly(9,9-dioctylfluorene), is confined to the interlayer space of inorganic, layered metal dichalcogenide materials, metallic MoS2, and semiconducting SnS2. The nanocomposites are prepared through Li intercalation into the inorganic compound, exfoliation, and restacking in the presence of the polymer. X-ray diffraction and optical absorption measurements indicate that a single conjugated polymer monolayer, with an overall extended planar morphology conformation, is isolated between the inorganic sheets, so that polymer aggregation or ,,, interchain interactions are significantly reduced. Photoluminescence (PL) measurements show that the appearance of the undesirable green emission observed in pristine polymer films is suppressed by incorporating the polymer into the inorganic matrix. The blue emission of the intercalated polymer is stable for extended periods of time, over two years, under ambient conditions. Furthermore, the green emission is absent in the PL spectra of nanocomposite films heated at 100,°C for 7,h in air with direct excitation of the keto defect. Finally, no green emission was observed in the electroluminescence spectrum of light-emitting devices fabricated with a polymer-intercalated SnS2 nanocomposite film. These results support the proposed hypothesis that fluorenone defects alone are insufficient to generate the green emission and that interchain interactions are also required. [source] Enhanced Blue Emission from Transparent Oxyfluoride Glass,Ceramics Containing Pr3+:BaF2 NanocrystalsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2010Kaushik Biswas Transparent glass,ceramics containing Pr3+:BaF2 nanocrystals in the chemical composition of SiO2,BaF2,K2CO3,La2O3,Sb2O3 oxyfluoride glass systems have been prepared from melt quenching and with a subsequent heat-treatment method. The luminescence and structural properties of these materials have been evaluated and the results are reported. Rietveld analysis of X-ray diffraction patterns and investigation of transmission electron microscopy confirmed the presence of BaF2 nanocrystals dispersed in the heat-treated glass matrices. Measured UV-Vis-NIR absorption spectra exhibited nine bands of the transitions 3H4,3P2, (1I6, 3P1), 3P0, 1D2, 1G4, 3F3, 3F2, 3H6, and 3H5 from all the samples with nondegenerated 1I6 and 3P1 levels in the glass,ceramics. The photoluminescence spectra show an enhancement in the intensities upon ceramization, indicating the incorporation of Pr3+ ions into BaF2 nanocrystals that possess a low phonon energy (346 cm,1). This has further been corroborated from the observation of a significant threefold increase in the relative intensity ratio of blue (3P0,3H4) to red (1D2,3H4, 3P0,3H6) emissions from glass,ceramics compared with the glass. This is due to a significant decrease of multiphonon nonradiative relaxation from the 3P0 to the 1D2 level of Pr3+ in glass,ceramics. Time-resolved spectra exhibit 3P0 -level decays faster than the 1D2 level. [source] Blue Emission of a Soluble Poly(p -phenylene) with a Cross-Conjugated Bisimidazole-Based ChromophoreMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2007Frank Dierschke Abstract A novel poly(p -phenylene) (6) has been synthesized by a cruciform combination of a polyphenylene backbone with 2,2,-(p -phenylene)-bis(4,5-diphenylimidazole) (5) as an additional, orthogonal chromophore. Polymer 6 showed in solution and in the solid state, a blue-green emission, which is obviously arising from the second bisimidazole-based chromophore. UV-Vis spectroscopy, and cyclic voltammetry revealed that the optical and electronic properties of 6 were fully determined by the incorporated 2,2,-(1,4-phenylene)bisimidazole structure. The bisimidazole unit led to high solubility and, despite the steric demand of the substituents, at the same time to the blue-green emission of the poly(p -phenylene) (6). In addition, the oxidation of 6 with potassium ferricyanide yielded a low bandgap polymer with a quinoid-type structure and a bandgap of 1.6 eV. [source] High Quantum Yield Blue Emission from Water-Soluble Au8 Nanodots.CHEMINFORM, Issue 41 2003Jie Zheng Abstract For Abstract see ChemInform Abstract in Full Text. [source] InN@SiO2 Nanomaterials as New Blue Light EmittersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2008Prabhakaran Munusamy Abstract In this article we report blue photoluminescence (, 450 nm) from InN@SiO2 nanomaterials. The InN@SiO2 nanomaterials were prepared by a simple precipitation reaction followed by a solid-state reaction. Various control experiments demonstrate that the interface between the InN and SiO2 seems to play a crucial role in the origin of the blue emission from the InN@SiO2 nanomaterial. The InN@SiO2 nanomaterial was characterized by using analytical methods such as TEM, XRD, Raman, XPS, and photoluminescence spectroscopy, which confirmed the existence of InN on SiO2 with a small excess of nitrogen relative to indium.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Regiospecific Three-Component Access to Fluorescent 2,4-Disubstituted Quinolines via One-Pot Coupling-Addition-Cyclocondensation-Sulfur Extrusion Sequence,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2010Sven Rotzoll Abstract 2,4-Di- and 2,4,7-trisubstituted quinolines are readily synthesized in a regioselective fashion from acyl chlorides, terminal alkynes, and 2-aminothiophenols by a consecutive, microwave-assisted one-pot three-component Sonogashira coupling-Michael addition,cyclocondensation sequence and following sulfur extrusion in moderate to good yields. The terminal sulfur extrusion step was studied by DFT computations. The absorption spectra of 2,4-disubstituted quinolines can be rationalized by DFT-ZINDO-CI calculations and all derivatives show intense blue emission upon UV excitation. [source] Stable, Glassy, and Versatile Binaphthalene Derivatives Capable of Efficient Hole Transport, Hosting, and Deep-Blue Light EmissionADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Bin Wei Abstract Organic light-emitting diodes (OLEDs) have great potential applications in display and solid-state lighting. Stability, cost, and blue emission are key issues governing the future of OLEDs. The synthesis and photoelectronics of a series of three kinds of binaphthyl (BN) derivatives are reported. BN1,3 are "melting-point-less" and highly stable materials, forming very good, amorphous, glass-like films. They decompose at temperatures as high as 485,545,°C. At a constant current density of 25,mA,cm,2, an ITO/BN3/Al single-layer device has a much-longer lifetime (>80,h) than that of an ITO/NPB/Al single-layer device (8,h). Also, the lifetime of a multilayer device based on BN1 is longer than a similar device based on NPB. BNs are efficient and versatile OLED materials: they can be used as a hole-transport layer (HTL), a host, and a deep-blue-light-emitting material. This versatility may cut the cost of large-scale material manufacture. More importantly, the deep-blue electroluminescence (emission peak at 444 nm with CIE coordinates (0.16, 0.11), 3.23 cd A,1 at 0.21,mA cm,2, and 25200,cd,m,2 at 9,V) remains very stable at very high current densities up to 1000,mA,cm,2. [source] A Stimuli-Responsive, Photoluminescent, Anthracene-Based Liquid Crystal: Emission Color Determined by Thermal and Mechanical ProcessesADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Yoshimitsu Sagara Abstract Here, a photoluminescent liquid crystal that exhibits a change of emission color on the metastable,stable phase transition induced by external stimuli is prepared. A 2,6-diethynylanthracene derivative with amide groups and dendritic side chains exhibits a columnar phase on slow cooling from the isotropic phase and shows blue emission in this columnar phase. In contrast, a cubic phase is obtained by rapid cooling from the isotropic phase. In the cubic phase, the 2,6-diethynylanthracene cores form excimers, resulting in yellow emission. While the columnar phase is a stable liquid-crystalline (LC) phase, the cubic phase is a metastable LC phase. It is found that a change of the photoluminescent color from yellow to blue is observed on the cubic-columnar phase transition induced by heating or mechanical shearing for this 2,6-diethynylanthracene derivative in the cubic phase. This change of photoluminescent color is ascribed to the inhibition of excimer formation on the metastable,stable LC phase transition. [source] Harvesting Excitons Via Two Parallel Channels for Efficient White Organic LEDs with Nearly 100% Internal Quantum Efficiency: Fabrication and Emission-Mechanism AnalysisADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Qi Wang Abstract By incorporating two phosphorescent dyes, namely, iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C2,]picolinate (FIrpic) for blue emission and bis(2-(9,9-diethyl-9H -fluoren-2-yl)-1-phenyl-1H -benzoimidazol-N,C3)iridium(acetylacetonate) ((fbi)2Ir(acac)) for orange emission, into a single-energy well-like emissive layer, an extremely high-efficiency white organic light-emitting diode (WOLED) with excellent color stability is demonstrated. This device can achieve a peak forward-viewing power efficiency of 42.5,lm,W,1, corresponding to an external quantum efficiency (EQE) of 19.3% and a current efficiency of 52.8,cd,A,1. Systematic studies of the dopants, host and dopant-doped host films in terms of photophysical properties (including absorption, photoluminescence, and excitation spectra), transient photoluminescence, current density,voltage characteristics, and temperature-dependent electroluminescence spectra are subsequently performed, from which it is concluded that the emission natures of FIrpic and (fbi)2Ir(acac) are, respectively, host,guest energy transfer and a direct exciton formation process. These two parallel pathways serve to channel the overall excitons to both dopants, greatly reducing unfavorable energy losses. It is noteworthy that the introduction of the multifunctional orange dopant (fbi)2Ir(acac) (serving as either hole-trapping site or electron-transporting channel) is essential to this concept as it can make an improved charge balance and broaden the recombination zone. Based on this unique working model, detailed studies of the slight color-shift in this WOLED are performed. It is quantitatively proven that the competition between hole trapping on orange-dopant sites and undisturbed hole transport across the emissive layer is the actual reason. Furthermore, a calculation of the fraction of trapped holes on (fbi)2Ir(acac) sites with voltage shows that the hole-trapping effect of the orange dopant is decreased with increasing drive voltage, leading to a reduction of orange emission. [source] Synthesis of Multiaryl-Substituted Pyridine Derivatives and Applications in Non-doped Deep-Blue OLEDs as Electron-Transporting Layer with High Hole-Blocking AbilityADVANCED MATERIALS, Issue 4 2010Na Li Two multiaryl-substituted pyridine derivatives, applied as electron transport materials (ETMs; see figure) with good hole- blocking ability in high-performance deep-blue OLEDs, are characterized. The maximum current efficiencies of the devices based on the new compounds are over 70% higher than previously reported devices using traditional ETMs instead. The CIE coordinates of the devices based on the new compounds are close to the NTSC standards of (0.14, 0.08) for blue emission. [source] The preparation of ZnGa2O4 doped with Mn-Mg and Tm for green and blue phosphorsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2006Binod Kumar Singh Non-member Abstract Phosphor powders of zinc gallate (ZnGa2O4) with Mg and Mn for green and Tm-Mg for blue luminescence were prepared by solid state reaction method for their improved luminescent properties. Green-luminescence emitting ZnMnGa2O4 reached maximum intensity at Mn = 0.005 mol% and further improvement was achieved by the addition of Mg2+. Tm-Mg based zinc gallate phosphor exhibited a strong blue emission, centered at ,420 nm with the maximum intensity achieved for 0.003 mol% of Mg and 0.015 mol% of Tm. This study established the possibilities of controlling the luminescent characteristics of zinc gallate by adding various elements. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [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 electroluminescent properties of polyfluorene-based conjugated polymers containing bipolar groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2009Sheng-Tung Huang Abstract A bipolar dibromo monomer, bis-(4-bromophenyl)[4-(3,5-diphenyl-1,2,4- triazole-4-yl)-phenyl]amine (9), containing electro-rich triphenylamine and electro-deficient 1,2,4-triazole moieties was newly synthesized and characterized. Two fluorescent fluorene-based conjugated copolymers (TPAF, TPABTF) were prepared via facile Suzuki coupling from the dibromo bipolar monomer, 4,7-dibromo-2,1,3-benzothiadiazole (BTDZ), and 9,9-dioctylfluorene. They were characterized by molecular weight determination, IR, NMR, DSC, TGA, solubility, absorption and photoluminescence spectra, and cyclic voltammetry. The polymers showed good solubility in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran, and dichlorobenzene at room temperature. They had glass transition temperatures (Tg) higher than 135 °C and 5% degradation temperatures in nitrogen atmosphere were higher than 428 °C. Single layer polymer light-emitting diodes (PLED) of ITO/PEDOT:PSS/polymer/metal showed a blue emission at 444 nm and Commission Internationale de I'Eclairage (CIE) 1931 color coordinates of (0.16, 0.13) for TPAF. The device using TPABTF as emissive material showed electroluminescence at 542 nm with CIE1931 of (0.345, 0.625), low turn-on voltage of 5 V, a maximum electroluminance of 696 cd/m2, and a peak efficiency of 2.02 cd/A. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6231,6245, 2009 [source] High quantum yield photoluminescence of new polyamides containing oligo-PPV amino derivatives and related oligomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2009Antonio Roviello Abstract The synthesis and the chemical physical characterization of new photoluminescent (PL) chromophores and polymers are reported. Chromophores (oligo-PPV symmetric derivatives ending with amino groups) are strong blue emitters with a PL quantum yield of ,70% in dioxane solution. They have been used to prepare polyamides by reaction with aliphatic acyl dichlorides in which emitting and non emitting units are alternated. PL properties of the synthesized polyamides have been evaluated in solution and reveal a strong blue emission (PL quantum yield ,60%), To increase the solubility of these systems, oligomers have been purposely prepared and then characterized. They show a peculiar white emission when excited in DMF solution; to get insight into this interesting behavior, asymmetric monoacetylated chromophores have been prepared as model compounds for the chromophoric end groups of the polyamide chains. The emission spectra of these compounds reveal a broad excimeric yellow emission which is responsible, along with the blue emission of the inner chromophoric units, of the overall white emission of the oligomers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2677,2689, 2009 [source] PCPP derivatives containing carbazole pendant as hole transporting moiety for efficient blue electroluminescenceJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2009Jinwoo Kim Abstract The syntheses and characterization of poly((2,6-(4,4-bis(4-((2-ethylhexyl)oxy)phenyl)-4H -cyclopenta[def]phenanthrene))- co -(2,6-(4,4-bis(4-(((9-carbazolyl)hexyl)oxy)phenyl))-4H- cyclopenta[def]phenanthrene)) (BCzPh-PCPPs) and poly((2,6-(4,4-bis(4-((2-ethylhexyl)oxy)phenyl)-4H -cyclopenta[def]phenanthrene))- co -(2,6-(4-(4-(((9-carbazolyl)hexyl)oxy)phenyl)-4-(4-((2-ethylhexyl)oxy)phenyl)-4H- cyclopenta[def]phenanthrene))) (CzPh-PCPPs), with carbazole unit as pendants, are presented. The carbazole moiety, which can improve the hole injection ability, was introduced as a pendant on the PCPP backbone. The devices of the polymers with the configurations of ITO/PEDOT:PSS/polymers/Ca/Al generate EL emission with maximum peaks at 400,450 nm, CIE coordinates of (x = 0.11,0.29, y = 0.11,0.33), low turn-on voltages of 4,6 V, maximum brightness of 60,810 cd/m2, and luminescence efficiencies of 0.04,0.22 cd/A. The PL spectra of CzPh-PCPPs films did not show any peak at around 550 nm, which corresponds to keto defect or aggregate/excimer formation, even after annealing for 30 h at 150 °C in air. Out of the series, CzPh-PCPP1 (PCPP derivative with 10% of carbazole moiety as pendant) shows blue emission with the maximum brightness of 810 cd/m2 at 9 V, and the highest luminescence efficiency of 0.22 cd/A at 395 mA/cm2. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1327,1342, 2009 [source] Synthesis and characterization of novel germanium-containing poly(p -phenylenevinylene) derivativesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2008Hoon-Je Cho Abstract Novel blue-emitting germanium-containing poly(p -phenylenevinylene) (PPV) derivatives with well-defined conjugation lengths were synthesized via Wittig-condensation polymerizations. The polymers can be color-tuned by the introduction of various chromophores into the PPV-based polymer backbones. The photoluminescence (PL) spectra of the polymers, GePVK (containing carbazole moieties), GeMEH (containing dialkoxybenzene moieties), and GePTH (containing phenothiazine moieties), were found to exhibit blue, greenish blue, and green emissions, respectively. GePTH produces more red-shifted emission than GeMEH and GEPVK, resulting in green emission, and the solution and solid state PL spectra of GePVK consist of almost blue emission. The electroluminescence spectra of GeMEH and GePTH contain yellowy green and yellow colors, respectively. Interestingly, GePVK exhibits white emission with CIE coordinates of (0.33, 0.37) due to electroplex emission in the light-emitting diodes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 979,988, 2008 [source] Fluorene-based liquid crystalline networks with linearly polarized blue emissionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2007Marta Millaruelo Abstract A series of fluorene-based luminophores containing methacrylic end groups have been prepared and incorporated into uniaxially oriented liquid crystalline films by in situ photopolymerization. Various structural modifications on the 2-(4-cyanophenyl)fluorene core, which include alkyl chains at the 9-position and elongation of the rigid core with one additional phenyl ring, have been investigated to generate emitters with adjusted liquid crystal compatibility, improved luminescence and dichroic properties. Polarized blue-emitting films were produced that had an acceptable photostability, and it was found that the polarization emission was better for samples with low (5%) cross-linker contents. Polarization of the luminescence was favored by the liquid crystalline properties of the luminophore. In addition, the detrimental effect of the alkyl substituent at the fluorene core on the mesomorphism and on the emission polarization can be overcome by lengthening the ,-system. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4804,4817, 2007 [source] Phenothiazine- S,S -dioxide- and fluorene-based light-emitting polymers: Introduction of e, -deficient S,S -dioxide into e, -rich phenothiazineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2007Jonghee Lee Abstract A novel series of poly(10-hexyl-phenothiazine- S,S -dioxide-3,7-diyl) and poly(9,9,-dioctyl-fluorene-2,7-diyl- alt -10-hexyl-3,7-phenothiazine- S,S -dioxide) (PFPTZ-SS) compounds were synthesized through Ni(0)-mediated Yamamoto polymerization and Pd(II)-catalyzed Suzuki polymerization. The synthesized polymers were characterized by 1H NMR spectroscopy and elemental analysis and showed higher glass transition temperatures than that of pristine polyfluorene. In terms of photoluminescence (PL), the PFPTZ-SS compounds were highly fluorescent with bright blue emissions in the solid state. Light-emitting devices were fabricated with these polymers in an indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration. The electroluminescence (EL) of the copolymers differed from the PL characteristics: the EL device exhibited a redshifted greenish-blue emission in contrast to the blue emission observed in the PL. Additionally, this unique phenothiazine- S,S -dioxide property, triggered by the introduction of an electron-deficient SO2 unit into the electron-rich phenothiazine, gave rise to improvements in the brightness, maximum luminescence intensity, and quantum efficiency of the EL devices fabricated with PFPTZ-SS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1236,1246, 2007 [source] Blue-emitting AlN:Eu2+ Powder Phosphor Prepared by Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010Hyoung-SeoK Do Blue-emitting AlN:Eu2+ powder phosphor was synthesized by spark plasma sintering (SPS) using AlN, Si3N4, and Eu2O3 as the starting materials, and its luminescence properties were investigated. A single-phase Eu- and Si-co-doped AlN powder was successfully fabricated by SPS in the range of 1650°,1800°C for 5 min. The AlN:Eu2+ obtained exhibited a strong blue emission at 480 nm under the excitation of ,exc=340 nm and an electron beam. The highest photoluminescence intensity was observed in the phosphor sintered at 1700°C, which was comparable to that of the phosphor prepared by gas pressure sintering at 1750°C for 4 h. [source] Preparation, Characterization, and Photocatalytic Properties of CaNb2O6 NanoparticlesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2009In-Sun Cho CaNb2O6 nanoparticles with a size range of 30,50 nm were synthesized by heat treatment at 600°C after a solvothermal process and their optical and photocatalytic properties were investigated. The prepared powders were characterized by X-ray powder diffractometer, field-emission scanning electron microscope, transmission electron microscope, UV-Vis diffuse reflectance spectroscopy, Fluorescence spectroscopy, and Raman spectroscopy. Compared with a powder of the same material prepared by a solid-state reaction (SS) method, the nanoparticles exhibited a higher Brunauer,Emmett,Teller (BET) surface area, more efficient light absorption, and enhanced photocatalytic activity for producing H2 from pure water under UV irradiation. The photoluminescence spectra revealed that a radiative recombination process is dominant in the powder prepared by the SS method (strong blue emission at 300 K) under UV light irradiation, while no obvious emission was observed in the nanoparticles. This decrease of the radiative recombination as well as the higher optical absorption ability and higher BET surface area resulting from the reduced dimensionality led to enhanced photocatalytic activity of the nanoparticles. [source] Energy Transfer Process for the Blue Up-Conversion in Calcium Aluminate Glasses Doped with Tm3+ and Nd3+JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2001Woon Jin Chung Excitation of Tm3+ to 3H4 using the 791 nm pump source showed the frequency up-converted blue emission (,480 nm) due to the Tm3+:1G4,3H6 transition in Tm3+/Nd3+ codoped CaO·Al2O3 glasses. Intensity and lifetime changes with rare-earth concentrations suggested the efficient energy transfer of Tm3+:3H4, Nd3+:4F5/2 and Nd3+:4F3/2, Tm3+:1G4. The latter transfer enabled Tm3+ to reach its 1G4 level, and the blue emission became possible through the 1G4,3H6 transition. Quantitative analysis with rate equations proved that these two transitions were the most efficient among all the possible energy transfer routes between Tm3+ and Nd3+. Calculated up-conversion efficiency of the Tm3+/Nd3+ combination in CaO·Al2O3 glass was 6.6 × 10,3, and it was ,4 orders of magnitude larger than those reported for other oxide glasses. [source] Highly Fluorescent Conjugated Pyrenes in Nucleic Acid Probes: (Phenylethynyl)pyrenecarbonyl-Functionalized Locked Nucleic AcidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2008Irina Abstract In recent years, fluorescently labeled oligonucleotides have become a widely used tool in diagnostics, DNA sequencing, and nanotechnology. The recently developed (phenylethynyl)pyrenes are attractive dyes for nucleic acid labeling, with the advantages of long-wave emission relative to the parent pyrene, high fluorescence quantum yields, and the ability to form excimers. Herein, the synthesis of six (phenylethynyl)pyrene-functionalized locked nucleic acid (LNA) monomers M1,M6 and their incorporation into DNA oligomers is described. Multilabeled duplexes display higher thermal stabilities than singly modified analogues. An increase in the number of phenylethynyl substituents attached to the pyrene results in decreased binding affinity towards complementary DNA and RNA and remarkable bathochromic shifts of absorption/emission maxima relative to the parent pyrene fluorochrome. This bathochromic shift leads to the bright fluorescence colors of the probes, which differ drastically from the blue emission of unsubstituted pyrene. The formation of intra- and interstrand excimers was observed for duplexes that have monomers M1,M6 in both complementary strands and in numerous single-stranded probes. If more phenylethynyl groups are inserted, the detected excimer signals become more intense. In addition, (phenylethynyl)pyrenecarbonyl,LNA monomers M4, M5, and M6 proved highly useful for the detection of single mismatches in DNA/RNA targets. [source] Hydrothermal Synthesis, Crystal Structures and Photoluminescence of Two Novel Metal-organic Supramolecular Frameworks Based on Mixed Ligands of Dipyrazino[2,3- f:2,,3,-h]quinoxaline and Pyridine-2,5-dicarboxylic AcidCHINESE JOURNAL OF CHEMISTRY, Issue 9 2008Xiu-Li WANG Abstract Two novel metal-organic frameworks [Zn2(Dpq)2(2,5-pda)2(H2O)2]·2H2O (1) (dipyrazino[2,3- f:2,3,- h]quinoxaline=Dpq) and [Cd2(Dpq)2(2,5-pda)2]·2H2O (2) (pyridine-2,5-dicarboxylic acid=2,5-H2pda) have been obtained from hydrothermal reactions of two different metal(II) nitrates with the same mixed ligands Dpq and 2,5-H2pda, and structurally characterized by elemental analyses, TG, IR spectroscopy, and single-crystal X-ray diffraction analyse. Single-crystal X-ray analyses show that the metal ions are bridged by different coordination modes of 2,5-pda to form a dimer in 1, 2D rhombic grid in 2, respectively. In the compound 1, adjacent dimers are packed through hydrogen bonds and - aromatic stacking interactions to form a distorted , -Po supramolecular structure. In the compound 2, adjacent polymer layers are further linked by hydrogen bonds to form a distorted , -Po 3D supramolecular framework stabilized by - stacking interactions. The different structures of compounds 1 and 2 illustrate the influence of the metal ions and ligands on the self-assembly of polymeric coordination architectures. In addition, the title compounds exhibit blue emission in the solid state at room temperature. [source] Blue Luminescence of ZnO Nanoparticles Based on Non-Equilibrium Processes: Defect Origins and Emission ControlsADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Haibo Zeng Abstract High concentrations of defects are introduced into nanoscale ZnO through non-equilibrium processes and resultant blue emissions are comprehensively analyzed, focusing on defect origins and broad controls. Some ZnO nanoparticles exhibit very strong blue emissions, the intensity of which first increase and then decrease with annealing. These visible emissions exhibit strong and interesting excitation dependences: 1) the optimal excitation energy for blue emissions is near the bandgap energy, but the effective excitation can obviously be lower, even 420,nm (2.95,eV,<,Eg,=,3.26,eV); in contrast, green emissions can be excited only by energies larger than the bandgap energy; and, 2) there are several fixed emitting wavelengths at 415, 440, 455 and 488,nm in the blue wave band, which exhibit considerable stability in different excitation and annealing conditions. Mechanisms for blue emissions from ZnO are proposed with interstitial-zinc-related defect levels as initial states. EPR spectra reveal the predominance of interstitial zinc in as-prepared samples, and the evolutions of coexisting interstitial zinc and oxygen vacancies with annealing. Furthermore, good controllability of visible emissions is achieved, including the co-emission of blue and green emissions and peak adjustment from blue to yellow. [source] Phenothiazine- S,S -dioxide- and fluorene-based light-emitting polymers: Introduction of e, -deficient S,S -dioxide into e, -rich phenothiazineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2007Jonghee Lee Abstract A novel series of poly(10-hexyl-phenothiazine- S,S -dioxide-3,7-diyl) and poly(9,9,-dioctyl-fluorene-2,7-diyl- alt -10-hexyl-3,7-phenothiazine- S,S -dioxide) (PFPTZ-SS) compounds were synthesized through Ni(0)-mediated Yamamoto polymerization and Pd(II)-catalyzed Suzuki polymerization. The synthesized polymers were characterized by 1H NMR spectroscopy and elemental analysis and showed higher glass transition temperatures than that of pristine polyfluorene. In terms of photoluminescence (PL), the PFPTZ-SS compounds were highly fluorescent with bright blue emissions in the solid state. Light-emitting devices were fabricated with these polymers in an indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration. The electroluminescence (EL) of the copolymers differed from the PL characteristics: the EL device exhibited a redshifted greenish-blue emission in contrast to the blue emission observed in the PL. Additionally, this unique phenothiazine- S,S -dioxide property, triggered by the introduction of an electron-deficient SO2 unit into the electron-rich phenothiazine, gave rise to improvements in the brightness, maximum luminescence intensity, and quantum efficiency of the EL devices fabricated with PFPTZ-SS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1236,1246, 2007 [source] | |||||||||||||||||||||||||