The optical and excitation energy transport of self-assembled molecular aggregates have received much attention over recent years. These properties are governed by the nature and dynamics of collective excited states, known as excitons. Self-assembled nanotubes with diameters of the order of ten nanometer and lengths up to micrometers, have received particular attention in this context. These systems can be prepared synthetically from a variety of dye molecules and also occur in natural systems, for instance in the light-harvesting antennae of photosynthetic bacteria. The excitonic properties, such as delocalization size, energy spectrum, and dynamics, sensitively depend on the molecular packing within the assembly, which often cannot be resolved directly with current imaging techniques. Modeling plays an important role in interpreting experiments and suggesting new routes for design. <br/> <br/>In this talk, I will address recent progress in probing and modeling the excitonic properties of several synthetic and natural nanotubular molecular aggregates. Particularly, I will address the robustness of these systems against localization by disorder, reflected in the strong polarization dependent behavior of their optical response and understood from the exciton density of states near the band edge. This may have a strong effect on the excitation energy transport, reflected in the exciton diffusion constant. Furthermore, I will show how fluorescence excitation experiments on single nanotubular assemblies reveal information on molecular packing and disorder therein. Finally, I will address recent progress in multiscale first-principles calculations of the optical properties of large tubular molecular aggregates, in which a combination of molecular dynamics calculations and quantum modeling is applied. This allows to determine the molecular packing with a high degree of accuracy.

Optics and energy transport of excitons in self-assembled molecular nanotubes

2019 Fall National Meeting

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