Broad Emission (broad + emission)

Distribution by Scientific Domains
Polymers and Materials Science50%

Terms modified by Broad Emission

  • broad emission band
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    Selected Abstracts

    Exploiting a Dual-Fluorescence Process in Fluorene,Dibenzothiophene- S,S -dioxideCo-Polymers to Give Efficient Single Polymer LEDs with Broadened Emission

    ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009
    Simon M. King
    Abstract A description of the synthesis of random (9,9-dioctylfluorene-2,7-diyl),(dibenzothiophene- S,S -dioxide-3,7-diyl) co-polymers (p(F-S)x) by palladium-catalyzed Suzuki cross-coupling polymerization where the feed ratio of the latter is varied from 2 to 30,mol % (i.e., x,=,2,30) is given. Polymer light emitting devices are fabricated with the configuration indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid)/p(F,S)x/Ba/Al. The device external quantum efficiency increased as the ratio of the S co-monomer was increased, up to a maximum of 1.3% at 100,mA cm,2 for p(F-S)30 and a brightness of 3 770,cd m,2 (at 10,V). The S units impart improved electron injection, more balanced mobilities, and markedly improved device performance compared to poly(9,9-dioctylfluorene) under similar conditions. These co-polymers display broad emission, observed as greenish-white light, which arises from dual fluorescence, viz. both local excited states and charge transfer states. Utilizing dual emission can reduce problems associated with Förster energy transfer from high-energy to-low energy excited states. [source]

    White Luminescence from Sol,Gel-Derived SiOC Thin Films

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009
    Aylin Karakuscu
    A new approach to obtain visible luminescence from sol,gel-derived SiOC films is proposed. In order to investigate the influence of Si and C content, Si- and C-rich SiOC films were prepared as well as stoichiometric SiOC films. High intense white luminescence is obtained where the emission color can be controlled by the experimental parameters such as the starting sol,gel-composition and the pyrolysis temperature. In stoichiometric SiOC films, low pyrolysis temperature yields UV-blue luminescence, whereas high temperatures favor green-yellow luminescence. On the contrary, in Si-rich SiOC films, intense white luminescence is obtained with a broad emission from 430 to 900 nm and an external quantum efficiency (EQE) of 11.5%. Relatively, stoichiometric SiOC films showed an EQE of 5%. Finally, C-rich SiOC films did not show noticeable luminescence due to absorption by carbon clusters. [source]

    Broadband Near-IR Emission in Tm/Er-Codoped GeS2,In2S3 -Based Chalcohalide Glasses

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009
    Yinsheng Xu
    The near IR emission spectra of Tm/Er-codoped GeS2,In2S3 -based chalcohalide glasses are studied with an 808 nm laser as excitation source. A broad emission with a full-width at half-maximum of ,170 nm is recorded in a 0.5Tm2S3,0.1Er2S3 -codoped 70GeS2,20In2S3,10CsBr (in mol%) glass. The luminescence mechanisms are discussed with different CsI concentration, different halogen atoms, and different In content. These results suggest that both halogen (X) atoms and [InSxX4,x] structural units can enhance the emission intensity located at 1460 nm. [source]

    Discriminant analysis of autofluorescence spectra for classification of oral lesions in vivo

    LASERS IN SURGERY AND MEDICINE, Issue 5 2009
    J.L. Jayanthi MSc, MPhil
    Abstract Background and Objectives Low survival rate of individuals with oral cancer emphasize the significance of early detection and treatment. Optical spectroscopic techniques are under various stages of development for diagnosis of epithelial neoplasm. This study evaluates the potential of a multivariate statistical algorithm to classify oral mucosa from autofluorescence spectral features recorded in vivo. Study Design/Methods Autofluorescence spectra were recorded in a clinical trial from 15 healthy volunteers and 34 patients with diode laser excitation (404,nm) and pre-processed by normalization, mean-scaling and its combination. Linear discriminant analysis (LDA) based on leave-one-out (LOO) method of cross validation was performed on spectral data for tissue characterization. The sensitivity and specificity were determined for different lesion pairs from the scatter plot of discriminant function scores. Results Autofluorescence spectra of healthy volunteers consists of a broad emission at 500,nm that is characteristic of endogenous fluorophores, whereas in malignant lesions three additional peaks are observed at 635, 685, and 705,nm due to the accumulation of porphyrins in oral lesions. It was observed that classification design based on discriminant function scores obtained by LDA-LOO method was able to differentiate pre-malignant dysplasia from squamous cell carcinoma (SCC), benign hyperplasia from dysplasia and hyperplasia from normal with overall sensitivities of 86%, 78%, and 92%, and specificities of 90%, 100%, and 100%, respectively. Conclusions The application of LDA-LOO method on the autofluorescence spectra recorded during a clinical trial in patients was found suitable to discriminate oral mucosal alterations during tissue transformation towards malignancy with improved diagnostic accuracies. Lasers Surg. Med. 41:345,352, 2009. © 2009 Wiley-Liss, Inc. [source]

    Photoluminescence of Ho3+:YVO4 crystals

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007
    S. Polosan
    Abstract Emission spectra of Ho3+ -doped YVO4 crystals are studied in the visible and infrared spectral regions. Besides the emission bands at 544 nm and at about 1950 and 2017 nm due to Ho3+, we observed a broad emission band at 610 nm at low temperatures like 15 K in the highly doped crystals with the Ho3+ concentrations of more than 0.5 mol%. The excitation band for this broad emission is located at 390 nm which is near the edge of band gap of the crystal. It is suggested that the 610 nm band is attributed to defects related to oxygen vacancies around V4+ ions. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    [Re6Q7O(3,5-Me2PzH)6]Br2·3,5-Me2PzH (Q = S, Se) , New Octahedral Rhenium Cluster Complexes with Organic Ligands: Original Synthetic Approach and Unexpected Ligand Exchange in the Cluster Core

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2005
    Yuri V. Mironov
    Abstract Two new octahedral rhenium cluster complexes, [Re6S7O(3,5-Me2PzH)6]Br2·3,5-Me2PzH (1) and [Re6Se7O(3,5-Me2PzH)6]Br2·3,5-Me2PzH (2), with the organic ligand 3,5-dimethylpyrazole (3,5-Me2PzH), have been synthesised by reaction of rhenium chalcobromides Cs3[Re6(µ3 -Q7Br)Br6] (Q = S, Se) with molten dimethylpyrazole. During the reaction, all six apical bromine ligands of the cluster complexes are substituted by the organic ligand, which is coordinated through the aromatic nitrogen atom N2. Additionally, the inner ligand µ3 -Br in the cluster core [Re6(µ3 -Q7Br)]3+ is substituted by oxygen, giving cluster cores [Re6(µ3 -Q7O)]2+ with mixed chalcogen/oxygen ligands. Compounds 1 and 2 have been characterised by single-crystal X-ray diffraction analysis. They are isostructural and crystallise with four formula units in the unit cell. Absorption spectra and luminescence characteristics of these two cluster compounds have been investigated in methanol. Absorption starts below 400 nm. For both compounds, broad emissions were found. The fluorescence decays of the two compounds follow a diexponential decay behaviour. The main fluorescence intensity decays have longer fluorescence lifetimes of 3.07 ± 0.03 (1) and 3.96 ± 0.02 µs (2). Studying the thermal stability of both compounds in vacuo showed that the release of 3,5-dimethylpyrazole ligands begins near 200 °C, and decomposition, with the removal of 7 molecules of 3,5-Me2PzH, is complete at 330 °C. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]