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Kirstein, Johanna (2007): Diffusion of single molecules in nanoporous mesostructured materials. Dissertation, LMU München: Fakultät für Chemie und Pharmazie



Single-molecule methods play a growing role in materials science because they can reveal structural and dynamic features which are obscured by ensemble averaging in conventional spectroscopic techniques. In this work, such methods were used to study the dynamics of single dye molecules (guests) within different surrounding porous matrices (hosts) using wide-field microscopy and single-molecule tracking. A significant amount of tracking data was collected and sophisticated methods to analyse the data according to diffusion theory were developed. A method was established to directly correlate the diffusion information that is provided by single-molecule trajectories with the images of the porous host systems obtained by transmission electron microscopy (TEM). Furthermore, the results from single-molecule tracking experiments were compared with diffusion measurements using pulsed-field gradient NMR in the same samples. The data presented in this thesis thus provide for the first time a detailed picture of the real mesoporous structure and its effects on the dynamic behavior of dye molecules at the nanometre to micron scale, e.g.~information about pore connectivity and accessibility. The methodology established here is expected to provide detailed insights into the dynamics of other important host-guest systems, such as bioactive molecules in porous materials for drug delivery or reactants in porous catalysts.