1,721,075 research outputs found
Synthesis of 8-hydroxyquinoline functionalised DO3A ligand and Eu(III) and Er(III) complexes: Luminescence properties
No full textThe synthesis of a new DO3A-based macrocyclic ligand bearing a 8-hydroxyquinoline residue together with the preparation of its Eu(3+) and Er(3+) neutral complexes are described. In a previous report IF. Rizzo, A. Papagni, F. Meinardi, R. Tubino, M. Ottonelli, G.F Musso, G. Dellepiane. Synth. Met. 147 (2004) 1431, we have shown that lanthanide complexes display very high stability combined with a good luminescence in aqueous solution under UV radiation, which indicate an energy transfer process from the excited 8-hydroxyquinoline moiety to the metal. In this work, we correlate the ability to transfer the energy from the sensitizer to lanthanide ion with pH behaviour of the antenna. Furthermore, the variation of pH in Eu(3+) complex supports the hypothesis of presence of charge-transfer transitions. The good Solubility and sensitized emission in different solvents (organic and water) are very important aspects for their technologic applications as luminescent probes or NIR-emitting devices. (C) 2009 Elsevier B.V. All rights reserved
OPTICAL PROPERTIES AND LONG-LIVED CARRIER GENERATION EFFICIENCY IN ORIENTED POLYACETYLENE
No full textFemtosecond vibrational and torsional energy redistribution in photoexcited oligothiophenes
No full textDFB laser action in a flexible fully plastic multilayer
No full textAn all-plastic distributed-feedback flexible multilayer laser (FML), able to keep its lasing characteristics even upon strong bending from planarity, is proposed and the possibility of using this system to make solid-state dye lasers is suggested
Vibrational spectrum and hydrogen bonding in solid α-naphtol
No full textThe i.r. spectrum of α-naphthol has been obtained at different temperatures and at different degrees of deuteration. A method is proposed for determining the orientation of the crystallographic axis with respect to the incident beam. The absorption bands due to hydrogen bonded groups are then analysed in terms of a simple dipole-dipole model
Electrical characterization of organic semiconductors by transient current methods
No full textThis paper presents a method for characterizing the transport properties of organic semiconductors by means of large-signal electrical transients. For validating the method, poly(phenylene-vinylene) (PPV) was chosen as a test material, thanks to its widely investigated properties. Large voltage steps are applied to Au/PPV/Au test structures and, from the resulting current transient, the carrier mobility is measured. Transient phenomena are shown to give insight on the physical properties of the material and on the technological characteristics of the device, while requiring a simpler test system in comparison to other methods, like impedance spectroscopy and time-of-flight measurements
Upconversion-induced fluorescence in multicomponent systems: Steady-state excitation power threshold
Get PDFWe have analyzed the dynamics of the upconversion-induced delayed fluorescence for a model multicomponent organic system, in which high concentrations of triplet states can be sustained in steady-state conditions. At different excitation powers, two regimes have been identified depending on the main deactivation channel for the triplets, namely, the spontaneous decay and the bimolecular annihilation. The excitation power density at which triplet bimolecular annihilation becomes dominant is the threshold (I(th)) to have efficient upconversion generation. The simple equation obtained for I(th) allows us to predict the theoretical efficiency of a generic system on the basis of few parameters of the constituent molecules
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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