Sammanfattning
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.
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.
| Originalspråk | engelska |
|---|---|
| Sidor (från-till) | 10589-10597 |
| Tidskrift | The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory |
| Volym | 42 |
| Nummer | 111 |
| DOI | |
| Status | Published - 2007 |
Bibliografisk information
The information about affiliations in this record was updated in December 2015.The record was previously connected to the following departments: Chemical Physics (S) (011001060)
Ämnesklassifikation (UKÄ)
- Atom- och molekylfysik och optik