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Maximum Emission (maximum + emission)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Synthesis and characterization of the soluble fluorescent poly[2-decyloxy-5-(2,-(6,-dodecyloxy)naphthyl)-1,4-phenylenevinylene]

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007
Hung-Te Chang
Abstract A new soluble fluorescent polymer, poly[2-decyloxy-5-(2,-(6,-dodecyl-oxy)naphthyl)-1,4-phenylenevinylene] (DDN-PPV), with no tolane-bisbenzyl (TBB) structure defects is prepared by the dehydrohalogenation of 1,4-bis(bromomethyl)-2-decyloxy-5-(2,-(6,-dodecyloxy)naphthyl)benzene (as monomer) in this study. The aforementioned monomer is synthesized via such chemical reactions as alkylation, bromination, and Suzuki coupling reactions. The structure and properties of the DDN-PPV are examined by 1H NMR, FTIR, UV/vis, TGA, photoluminescence (PL), and electroluminescence (EL) analyses. The two asymmetric decyloxy and 6,-dodecyloxynaphthyl substituents on the phenylene ring make the DDN-PPV soluble in organic solvents and eliminate the TBB structure defects. With the DDN-PPV acting as a light-emitting polymer, a device is fabricated with a sequential lamination of ITO/PEDOT/DDN-PPV/Ca/Ag. The EL spectrum of the device shows a maximum emission at 538 nm. The turn on voltage of the device is about 16.6 V. Its maximum brightness is 14 cd/m2 at a voltage of 18.2 V. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2734,2741, 2007 [source]

Novel fluorescent (p -phenylene ethynylene)-calix[4]arene-based polymer: Design, synthesis, and properties

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2008
Alexandra I. Costa
Abstract A novel fluorescent (p -phenylene ethynylene)-calix[4]arene-based polymer (CALIX-PPE) has been successfully synthesized by cross-coupling polymerization of bis-calix[4]arene 1 with 1,4-diethynylbenzene. The polycondensation was carried out in toluene/NEt3 at 35 °C for 24 h, using PdCl2(PPh3)2/CuI as the catalytic system, furnishing CALIX-PPE in excellent isolated yields (higher than 95%, several runs). The yellow polymer is freely soluble in several nonprotic organic solvents. The GPC trace of the isolated polymer showed a monomodal distribution and a number-average molecular weight of 23,300 g mol,1 (Mw/Mn = 2.05). No evidence was found in the structural analysis (FTIR and 1H/13C NMR) regarding the formation of alkyne homocoupled segments along the polymer chain. For comparative purposes, the synthesis of an analogous poly(p -phenylene ethynylene) containing p - t -butyl-phenoxymethyl side chains (TBP-PPE) was also undertaken. A great similarity was found between the photophysical properties of CALIX-PPE and TBP-PPE in solution (UV,vis and laser induced luminescence), clearly demonstrating their unique dependence on the structure and conformation of the conjugated PPE backbone. The fluorescence spectra of polymers are of nearly identical shape, displaying their maximum emission around 420 nm. The calculated solution photoluminescence quantum yields of CALIX-PPE and TBP-PPE are of similar magnitude (,F(CALIX-PPE) = 0.43; ,F(TBP-PPE) = 0.51). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6477,6488, 2008 [source]

The role of aluminium and titanium in the point defects of gamma irradiated natural quartz

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005
G. O. Sawakuchi
Abstract In this work, the origin of the smoky colour acquired by quartz when exposed to extremely high doses (20 kGy) of ionising radiation is studied. Five paramagnetic centres were detected in the electron paramagnetic resonance (EPR) spectrum of irradiated quartz: [AlO4]0, [TiO4,/Li+]0A, [GeO4,/Na+]0A, [GeO4,/Li+]0C, and E,1. Optical absorption revealed a complex spectrum with superposition of bands. With the technique of thermoluminescence, at least three peaks at around 180, 260 and 320 °C were detected. The peak at around 180 ºC has maximum emission at 470 nm and the peaks at around 260 and 320 °C have maximum emissions at 450 nm. Through correlations between the obtained results with these techniques, it was possible to confirm previous results from the literature, i.e., that the smoky colour of quartz is strongly related to the centre [AlO4]0. Besides, it was verified an excellent correlation between the thermal decay of [AlO4]0 and [TiO4,/Li+]0A, suggesting that at a temperature around 200 ºC the Li leaves the Ti centre and recombines with the aluminium centre destroying the smoky colour of irradiated quartz. On the other hand and differently from the literature this process does not correlate to any of the thermoluminescence peaks. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]