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Molecular aggregates, dendrimers, and motors: optical dynamics and control

By Ramūnas Augulis


The combination of efficiency, reliability, and ubiquity of biological systems continues to inspire new branches of fundamental and technological research in all possible aspects, ranging from molecular electronics to bio-inspired solar cells. One of the most fascinating processes in nature is photosynthesis. This is the process where sunlight, the energy source for the biosphere, is converted into the chemical energy so vital for life on earth. The light-harvesting, transfer, and conversion processes in various natural systems might look different, but the key mechanisms stay the same – the optical energy is harvested in a light harvesting antenna complex, composed of a set of pigments, then the excitation energy is transferred down a cascade of chromophores to the reaction center where it is used for charge separation needed for the biochemical reactions. Although in general terms the process sounds rather simple, the detailed understanding of the whole picture is quite complicated. This is primarily due to the complexity of natural photosynthetic units. For a “proof of principle”, however, it suffices to mimic certain parts of the photosynthesis process in an artificial device. This does not require using the same components and arrangements as found in natural systems. Much simpler model systems can be used to explore or to employ a very specific function, which would be difficult to access in for example a living cell. Processes as complicated as self-replication in biological systems can, for instance, be replaced with self-assembly in artificial molecule-based devices. However, these simplified systems sacrifice versatility and robustness, and generally have a more limited functionality. This thesis focuses on a number of synthetic model systems mimicking aspects of light-harvesting, energy transfer, and motional processes found in nature. The model systems used are dendrimers, molecular aggregates, and molecular motors. Dendrimers can be considered as simple model systems mimicking the excitation energy transfer cascade found in natural light-harvesting complexes. Molecular aggregates are similar to natural light harvesting and energy transport units. They may potentially be used as molecular wires for energy harvesting and transport in optical devices. In addition, they are of fundamental interest as model materials to study the nature of excitons in systems of reduced dimensionality. Finally, light-driven rotary molecular motors are attractive as model systems for studies on light-to-motion energy conversion processes, as well as for their potential applications in nanotechnology.

Topics: Zelforganiserende systemen, Moleculaire motoren, Excitatie , Fluorescentie , Relaxatie ,; Laser spectrometrie, Aggregaten , Dendrimeren,; Proefschriften (vorm); spectrochemische analyse
Year: 2008
OAI identifier: oai:ub.rug.nl:dbi/490efac925fa4
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