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- Borgström, Magnus, 1973-
(författare)
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Controlling Charge and Energy Transfer Processes in Artificial Photosynthesis : From Picosecond to Millisecond Dynamics
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes an interdisciplinary project, where the aim is to mimic the initial reactions in photosynthesis. In photosynthesis, the absorption of light is followed by the formation of charge-separated states. The energy stored in these charge-separated states is further used for the oxidation of water and reduction of carbon dioxide. In this thesis the photo-induced processes in a range of supramolecular complexes have been investigated with time resolved spectroscopic techniques. The complexes studied consist of three types of units; photosensitizers (P) capable of absorbing light, electron acceptors (A) that are easily reduced and electron donors (D) that are easily oxidised. Our results are important for the future design of artificial photosystems, where the goal is to produce hydrogen from light and water. Two molecular triads with a D-P-A architecture are presented. In the first one, a photo-induced charge-separated state was formed in an unusually high yield (φ>90%). In the second triad, photo-irradiation led to the formation of an extremely long-lived charge-separated state (τ = 500 ms at 140K). This is also the first synthetically made triad containing a dinuclear manganese unit as electron donor.Further, two sets of P-A dyads are presented. In both, the expected photo-induced reduction of the electron acceptor is diminished due to competing energy transfer to the triplet state of the acceptor.Finally, a P-P-A complex containing two separate photosensitizers is described. The idea is to produce high-energy charge-separated states by using the energy from two photons.
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- Larsen, Jane, et al.
(författare)
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Extending the Light-Harvesting Properties of Transition-Metal Dendrimers
- 2007
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Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 8:18, s. 2643-2651
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Tidskriftsartikel (refereegranskat)abstract
- We report a study of the electronic energy-transfer dynamics within the transition-metal polypyridine complex OsRu3pyr6 (Os[(dpp)Ru(bpy{pyrene})2]38+, where dpp=2,3-bis(2-pyridyl)pyrazine and bpy=2,2-bipyridine) after excitation with UV light. By using a broadband visible femtosecond probe, we are able to simultaneously detect both the energy transfer from the peripheral aromatic ligands to the Os center and the sub-picosecond energy transfer from the initially excited Ru-bpy ligand-centered state to the Os triplet metal-to-ligand charge-transfer (MLCT) state. Pyrene energy transfer occurs from both the nonrelaxed and the relaxed S1 states on timescales of 6 and 45 ps, respectively. In both cases, the energy transfer is described by means of Förster energy transfer theory. Sub-picosecond energy transfer within the OsRu3 metal-ligand core most likely includes a direct energy transfer between the higher-lying ligand-centered states on Ru and Os, in addition to the transfer between the MLCT states. The absorption cross-sections in both the UV and the visible spectral regions are enhanced by attaching the aromatic pyrene ligands. Furthermore, energy transfer is directed only towards the Os core, which ultimately leads to an exclusive population of the Os-based triplet MLCT state, thus making the OsRu3pyr6 transition metal-polypyridine dendrimer an obvious candidate for artificial light-harvesting systems.
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- Thapper, Anders, et al.
(författare)
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Artificial Photosynthesis for Solar Fuels – an Evolving Research Field within AMPEA, a Joint Programme of the European Energy Research Alliance
- 2013
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Ingår i: Green. - : Walter de Gruyter GmbH. - 1869-8778 .- 1869-876X. ; 3:1, s. 43-57
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Tidskriftsartikel (refereegranskat)abstract
- On the path to an energy transition away from fossil fuels to sustainable sources, the European Union is for the moment keeping pace with the objectives of the Strategic Energy Technology-Plan. For this trend to continue after 2020, scientific breakthroughs must be achieved. One main objective is to produce solar fuels from solar energy and water in direct processes to accomplish the efficient storage of solar energy in a chemical form. This is a grand scientific challenge. One important approach to achieve this goal is Artificial Photosynthesis. The European Energy Research Alliance has launched the Joint Programme “Advanced Materials & Processes for Energy Applications” (AMPEA) to foster the role of basic science in Future Emerging Technologies. European researchers in artificial photosynthesis recently met at an AMPEA organized workshop to define common research strategies and milestones for the future. Through this work artificial photosynthesis became the first energy research sub-field to be organised into what is designated “an Application” within AMPEA. The ambition is to drive and accelerate solar fuels research into a powerful European field – in a shorter time and with a broader scope than possible for individual or national initiatives. Within AMPEA the Application Artificial Photosynthesis is inclusive and intended to bring together all European scientists in relevant fields. The goal is to set up a thorough and systematic programme of directed research, which by 2020 will have advanced to a point where commercially viable artificial photosynthetic devices will be under development in partnership with industry.
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