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| 2. |
- Larsen, Jane, et al.
(författare)
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Energy transfer within Zn-porphyrin dendrimers: Study of the singlet-singlet annihilation kinetics
- 2005
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Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 109:47, s. 10654-10662
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we explore energy transfer processes within a series of Zn-porphyrin-appended dendrimers by means of excitation intensity dependent transient absorption measurements. We report singlet-singlet annihilation on two distinct time scales of 18 +/- 5 ps and 130 +/- 10 ps in the dimer and the dendrimers. The two distinct processes reflect the presence of two structural conformer distributions. Analysis of the singlet-singlet annihilation transient kinetics shows that sequential annihilation occurs within subunits up to four Zn-porphyrins in the dendrimers. The onset of the singlet-singlet annihilation process depending on the size of the Molecule reveals a difference in the number Of Communicating Zn-porphyrins. We further report a full characterization of the transient absorption kinetics of the monomer over a spectral range from 450 to 730 nm.
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| 3. |
- Larsen, Jane, et al.
(författare)
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Solvent induced control of energy transfer within Zn(II)-porphyrin dendrimers
- 2006
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 433:1-3, s. 159-164
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Tidskriftsartikel (refereegranskat)abstract
- Solvent induced optimization of energy transfer properties in a series of Zn(II)-porphyrin-appended dendrimers has been studied by means of exciton-exciton annihilation. Upon changing from a polar solvent (tetrahydrofuran) to a non-polar solvent (3-methyl-pentane), the annihilation energy transfer rates increase by 28-44%. This is related to a decrease of the hydrodynamic radius, which enhances the communication between the Zn(II)-porphyrin chromophores. As a consequence, the overall energy transfer efficiency is increased, thereby yielding complete annihilation between all the chromophores in the smallest generation dendrimer.
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| 4. |
- Larsen, Jane, et al.
(författare)
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Structural Induced Control of Energy Transfer within Zn(II)-Porphyrin Dendrimers
- 2007
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Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 42:111, s. 10589-10597
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Tidskriftsartikel (refereegranskat)abstract
- We report on a study of singlet-singlet annihilation kinetics in a series of Zn(II)-porphyrin-appended dendrimers, where the energy transfer efficiency is significantly improved by extending the molecular chain that connects the light-harvesting chromophores to the dendrimeric backbone with one additional carbon. For the largest dendrimer having 64 Zn(II)-porphyrins, only 10% of the excitation intensity is needed in order to observe the same extent of annihilation in the dendrimers with the additional carbon in the connecting chain as compared to those without. Complete annihilation, until only one chromophore remains excited, now occurs within subunits of seven chromophores, when half of the chromophores are excited. The improvement of the annihilation efficiency in the largest dendrimer with 64 porphyrins can be explained by the presence of a the two-step delayed annihilation process, involving energy hopping from excited to nonexcited chromophores prior to annihilation. In the smallest dendrimer with only four chromophores, delayed annihilation is not present, since the direct annihilation process is more efficient than the two-step delayed annihilation process. As the dendrimer size increases and the chances of originally exciting two neighboring chromophores decreases, delayed annihilation process becomes more visible. The additional carbon, added to the connecting chain, results in more favorable chromophore distances and orientations for energy hopping. Hence, the improved energy transfer properties makes the Zn(II)-porphyrin-appended dendrimers with the additional carbon promising candidates as light-harvesting antennas for artificial photosynthesis.
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