| Abstract
| - Single dye molecules incorporated into a mesoporous matrix can act as highly sensitive reportersof their environment. Here, we use single TDI molecules incorporated as guests into hexagonal mesoporousfilms containing highly structured domains. The dye molecules allow us to map the size of these domainswhich can extend to over 100 μm. Investigation of the translational and orientational dynamics via singlemolecule fluorescence techniques gives structural as well as dynamical information about the host material.In an air atmosphere, the guest molecules show no movement but perfect orientation along the pore direction.The diffusion of the TDI molecules can be induced by placing the mesoporous film in a saturated atmosphereof chloroform. In single molecule measurements with very high positioning accuracy (down to 2−3 nm) themovement of molecules could be observed even between neighboring channels. This reveals the presenceof defects like dead ends closing the pores or small openings in the silica walls between neighboringchannels, where molecules can change from one channel to the next. A statistical analysis demonstratesthat the diffusion of TDI in the mesoporous film cannot be described with a 1D-random diffusion but ismore complicated due to the presence of adsorption sites in which the TDI molecules can be occasionallytrapped.
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