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PL Quantum Yields (pl + quantum_yield)
Selected AbstractsHigh 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] Luminescent Monomer and Poly(methacrylate) Containing 1,3,4-Oxadiazole and Stilbene Units: Synthesis and Optical PropertiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2004John A. Mikroyannidis Abstract Summary: A monomer M as well as a poly(methacrylate) P carrying the same chromophore, that consists of 1,3,4-oxadiazole and stilbene units, were efficiently synthesized. They dissolved in common organic solvents such as THF, chloroform, dichloromethane, 1,1,2,2-tetrachloroethane and chlorobenzene. P showed a Tg value of 145,°C. Both M and P were stable up to approximately 300,°C and afforded anaerobic char yield of about 40% at 800,°C. Their optical properties were comparable. They emitted intense violet-blue light in THF solution with a PL maximum at 413 nm and a PL quantum yield of 0.29 for M and 0.73 for P. Thin films of them displayed optical band gap of 3.03 eV and blue-light emission with a PL maximum around 440 nm. The PL curves of both samples were progressively red-shifted with increasing the solvent polarity. The influence of the annealing on the PL emission spectrum of M and P thin films was investigated. [source] Oligophenylenevinylenes in Spatially Confined Nanochannels: Monitoring Intermolecular Interactions by UV/Vis and Raman Spectroscopy,ADVANCED FUNCTIONAL MATERIALS, Issue 6 2008Mariya Aloshyna Abstract Perhydrotriphenylene-based channel-forming inclusion compounds (ICs) and thin films made of polyphenylenevinylene (PPV)-type oligomers with terminal alkoxy groups are investigated and compared in a combined experimental and theoretical approach. Interchromophore interactions and host-guest interactions are elucidated by UV/Vis and Raman spectroscopy. The impact of the local environment of the chromophore on the optical and photophysical properties is discussed in light of quantum-chemical calculations. In stark contrast to thin films where preferential side-by-side orientation leads to quenching of photoluminescence (PL) via non-emissive traps, the ICs are found to be attractive materials for opto-electronic applications: they offer high chromophore concentrations, but at the same time behave as quasi-isolated entities of tightly packed, well-oriented objects with high PL quantum yields and the possibility of color tuning. [source] Carbazolevinylene-based polymers and model compounds with oxadiazole and triphenylamine segments: Synthesis, photophysics, and electroluminescenceJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2008Panagiotis D. Vellis Abstract Two new soluble alternating carbazolevinylene-based polymers POXD and PTPA as well as the corresponding model compounds MOXD and MTPA were synthesized by Heck coupling. POXD and MOXD contained 2,5-diphenyloxadiazole segments, while PTPA and MTPA contained triphenylamine segments. All samples displayed high thermal stability. The polymers had higher glass transition temperature (Tg) than their corresponding model compounds. The samples showed absorption maximum at 364,403 nm with optical band gap of 2.62,2.82 eV. They emitted blue-green light with photoluminescence (PL) emission maximum at 450,501 nm and PL quantum yields in THF solution of 0.15,0.36. The absorption and the PL emission maxima of PTPA and MTPA were blue-shifted as compared to those of POXD and MOXD. The electroluminescence (EL) spectra of multilayered devices made using four materials exhibited bluish green emissions, which is well consistent with PL spectra. The EL devices made using poly(vinyl carbazole) doped with MOXD and MTPA as emitting materials showed luminances of 12.1 and 4.8 cd m,2. POXD and PTPA exhibited 25.4, and 96.3 cd m,2, respectively. The polymer containing the corresponding molecules in the repeating group showed much higher device performances. Additionally, POXD and MOXD exhibited better stability of external quantum efficiency (EQE) and luminous efficiency with current density resulting from enhancing the electron transporting properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5592,5603, 2008 [source] Cationic, water-soluble, fluorene-containing poly(arylene ethynylene)s: Effects of water solubility on aggregation, photoluminescence efficiency, and amplified fluorescence quenching in aqueous solutionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2006Yan-Qin Huang Abstract Three novel fluorene-containing poly(arylene ethynylene)s with amino-functionalized side groups were synthesized through the Sonogashira reaction. They were poly{9,9-bis[6,-(N,N -diethylamino)hexyl]-2,7-fluorenylene ethynylene}- alt - co -{2,5-bis[3,-(N,N -diethylamino)-1,-oxapropyl]-1,4-phenylene} (P1), poly{9,9-bis[6,-(N,N -diethylamino)hexyl]-2,7-fluorenylene ethynylene} (P2), and poly({9,9-bis[6,-(N,N -diethylamino)hexyl]-2,7-fluorenylene ethynylene}- alt - co -(1,4-phenylene)) (P3). Through the postquaternization treatment of P1,P3 with methyl iodide, we obtained their cationic water-soluble conjugated polyelectrolytes (WSCPs): P1,,P3,. The water solubility was gradually improved from P3, to P1, with increasing contents of hydrophilic side chains. After examining the ultraviolet,visible absorption and photoluminescence (PL) spectra, fluorescence lifetimes, and dynamic light scattering data, we propose that with the reduction of the water solubility from P1, to P3,, they exhibited a gradually increased degree of aggregation in H2O. The PL quantum yields of P1,,P3, in H2O displayed a decreasing tendency consistent with the increased degree of aggregation, suggesting that the pronounced degree of aggregation was an important reason for the low PL quantum yields of WSCPs in H2O. Two structurally analogous water-soluble trimers of P2, and P3,, model compounds 2,7-bis(9,,9,-bis{6,-[(N,N -diethyl)- N -methylammonium] hexyl}-2,-fluorenylethynyl)-9,9-bis{6,-[(N,N -diethyl)- N -methylammonium]hexyl}fluorene hexaiodide and 1,4-bis(9,,9,-bis{6,-[(N,N -diethyl)- N -methylammonium]hexyl}-2,-fluorenylethynyl)benzene tetraiodide, were synthesized. The amplified fluorescence quenching of these WSCPs by Fe(CN)64, in H2O was studied by comparison with a corresponding analogous trimer. The effects of aggregation on the fluorescence quenching may be two-edged in these cases. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5778,5794, 2006 [source] Synthesis, optical properties, and electroluminescence of conjugated poly(p -phenylenevinylene) derivatives containing 1,3,4-oxadiazole and pyridine rings in the main chainJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2004John A. Mikroyannidis Abstract Three new poly(p -phenylenevinylene) derivatives,PO, POD, and POP,with oxadiazole and pyridine rings along the main chain were synthesized via Heck coupling. The polymers were amorphous and dissolved readily in common organic solvents. They showed relatively low glass-transition temperatures (up to 42 °C) and satisfactory thermal stability. Solutions of the polymers emitted blue-greenish light with photoluminescence (PL) emission maxima around 460 nm and PL quantum yields of 0.28,0.49. Thin films of the polymers displayed PL emission maxima at 461,521 nm, and their tendency to form aggregates was significantly influenced by the chemical structure. Light-emitting diodes with polymers PO and POP, with an indium tin oxide/poly(ethylenedioxythiophene) (PEDOT)/polymer/Ca configuration, emitted yellow and green light, respectively, and this could be attributed to excimer emission. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3212,3223, 2004 [source] | ||||||||||