Dresden 2006 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 15: Dynamics and Diffusion

CPP 15.3: Talk

Wednesday, March 29, 2006, 14:30–14:45, ZEU 114

Diffusion of dye molecules through nanoporous TiO₂ networks — •M. Dürr, M. Obermaier, A. Schmid, A. Yasuda, and G. Nelles — Materials Science Laboratory, Sony Deutschland GmbH, D - 70327 Stuttgart

Nanosize-structured materials with their unique physical and chemical properties are recently attracting a growing interest. For many applications, diffusion of molecules in solution through such nanoporous materials can be of great importance, e.g. for the sensitization of nanoporous TiO₂ when used in dye-sensitized solar cells. To quantify the influence of the nanoporous TiO₂ network on the diffusion of both Ru-complexed bipyridine dye molecules as well as porphyrin molecules, we investigated the diffusion limitations to the adsorption of dye molecules on the surface of the TiO₂ nanoparticles. A simple model is shown to be capable of reproducing the uptake curves obtained by means of optical absorption spectrometry for materials with different porosity and average size of the nanoparticles. The effective diffusion constants are found to be reduced by up to 3 orders of magnitude in the porous layers when compared to diffusion in the pure solvent. Depending on the strength of the interaction between the dye molecules, two different modes of diffusion limitation can be distinguished. In the case of porphyrin molecules, the π − π - interaction energy was determined.