| 1. |
- Johansson, DM, et al.
(författare)
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Synthesis of soluble phenyl-substituted poly(p-phenylenevinylenes) with a low content of structural defects
- 2002
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 35:13, s. 4997-5003
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of two new soluble poly(p-phenylenevinylenes) (PPVs) are reported. The polymers are poly(2-2',5'-bis(octyloxy)benzene)-1,4-phenylenevinylene) (BOP-PPV) and poly(2-(2',5'-bis(octyloxy)benzene)-5-methoxy-1,4-phenylenevinylene) (BOPM-PPV). Both polymers have been polymerized at high and low temperatures to study the formation of structural defects. It is shown that both methoxy groups as side chains and low polymerization temperatures decrease the content of defects in the final polymer. As a consequence, the polymers with lower concentration of defects exhibit higher electroluminescence yields in light-emitting diodes. In addition to this, the polymers with a low content of defects exhibited longer operational lifetimes in these devices. The highest photoluminescence quantum yield in the solid state and electroluminescence efficiency were found to be 72% and 1.74%, respectively.
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| 2. |
- Chen, LC, et al.
(författare)
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Excitation transfer in polymer photodiodes for enhanced quantum efficiency
- 2000
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Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 12:15, s. 1110-
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Tidskriftsartikel (refereegranskat)abstract
- The realization of polymer solar cells is the driving force behind this research. In an idea inspired by photosynthesis, the authors have constructed efficient bilayer photodiodes by a well-chosen combination of conjugated polymers (see Figure) in the donor layer. Forster energy transfer within the donor layer allows the absorbed light to be channeled to the C-60 acceptor layer, improving the total photoconversion of the blend device.
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| 3. |
- Johansson, DM, et al.
(författare)
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Influence of polymerization temperature on molecular weight, photoluminescence, and electroluminescence for a phenyl-substituted poly(p-phenylenevinylene)
- 2001
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Ingår i: Macromolecules. - 0024-9297 .- 1520-5835. ; 34:11, s. 3716-3719
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Tidskriftsartikel (refereegranskat)abstract
- We present the synthesis and characterization of poly(2-(2",5'-bis(2"-ethylhexyloxy)phenyl)-1,4-phenylenevinylene) (BEHP-PPV) polymerized at different temperatures. The photoluminescence efficiencies in the solid state of BEHP-PPV obtained at 144 and 0 degreesC are 28% and 60%, respectively. H-1 NMR measurements showed a lower concentration of structural defects for BEHP-PPV obtained at lower temperatures, which can explain the increased photoluminescence efficiencies for these polymers. Polymerization temperatures below 0 degreesC decrease the molecular weight without changing the photoluminescence efficiency to any large extent. The electroluminescence efficiencies follow the trend in the photoluminescence efficiencies.
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| 4. |
- Johansson, DM, et al.
(författare)
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Synthesis and characterization of polyfluorenes with light-emitting segments
- 2001
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Ingår i: Macromolecules. - 0024-9297 .- 1520-5835. ; 34:6, s. 1981-1986
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Tidskriftsartikel (refereegranskat)abstract
- Two new polymers consisting of poly(9-(2'-ethylhexyl)-9-hexylfluorene) (EHH-PF) with a small amount of substituted poly(p-phenylenevinylene) (PPV) segments have been synthesized and characterized. The synthetic route was designed to allow the incorporation of only one (or zero) PPV segments per polymer chain. Photoluminescence measurements showed that energy transfer from the PF segments to the more narrow band-gap PPV segments did occur, both in solution and in film. In the solid state, all emissions were detected from the PPV segments with photoluminescence quantum yields up to 68%. One of the polymers has been used as the active material in a microcavity laser device. The threshold for lasing is 2 muJ/cm(2).
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| 5. |
- Nosslin, Bertil, et al.
(författare)
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A generic model for C-11 labelled radiopharmaceuticals for imaging receptors in the human brain
- 2003
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Ingår i: Radiation Protection Dosimetry. - 1742-3406. ; 105:1-4, s. 587-591
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Tidskriftsartikel (refereegranskat)abstract
- A large number of rachopharmaceuticals labelled with C-11 (half-time 0.340 h) are being developed for positron emission tomographic studies of different types of receptor in the human brain. For most of these agents, the available biokinetic data are insufficient to construct realistic compound-specific biokinetic models for calculating the internal radiation dose delivered to persons undergoing investigation. A generic model for brain receptor substances that predicts the internal dose with sufficient accuracy for general radiation protection purposes has, therefore, been developed. Biokinetic data for 13 C-11-radiopharmaceuticals used clinically for imaging different brain receptors indicate that, despite differences in chemical structure. their uptake and retention in the human brain and other tissues are broadly similar. The proposed model assumes instantaneous deposition of 5% of the injected radioactivity in the brain, with the remaining radioactivity being rapidly and uniformly distributed throughout all other tissues. Elimination from all tissues is assumed to occur with a half-time of 2 h. It is further assumed that 75% of the injected C-11 is excreted in the urine, and 25% via the gall bladder, with a half-time of 2 h. This model yields all effective dose of 4.5 X 10(-3) mSv MBq(-1), with doses of 3.2 X 10(-2), 1.7 X 10(-2), 8.7 X 10(-3), 5.2 X 10(-3), and 3.8 X 10(-3) mGy MBq(-1) to the urinary bladder, gall bladder, kidneys, brain and ovaries, respectively. These closes are well within the range of those reported using compound-specific models for the radiopharmaceutals studied.
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