TiO2 nanotube templated electron donor/acceptor architectures

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We plan to make use of recent progress in the preparation of well-defined, spatially separated TiO2 nanotubes for the deposition of photoactive organic molecules onto the walls and into the inner and outer space of the tubes. This template approach will allow us to study photoinduced electron transfer in an unprecedented environment and could ultimately lead to the fabrication of the elusive interdigitated heterojunction solar cell. TiO2 nanotubes will be grown in the group of Schmuki, and the inner wall of TiO2 nanotubes will be decorated with monolayers of tailor-made organic electron donors prepared by von Delius. In these simple architectures, we will collaboratively investigate how molecular properties such as spacer length or anchoring group, affect the kinetics and the efficiency of photoinduced electron transfer (spectroscopy and kinetics) to the semiconductor substrate. While von Delius will design and synthesize electron acceptor/anchor group conjugates, Schmuki will employ a corking protocol recently developed in his group to selectively deposit electron donors onto the inner walls and electron acceptors onto the outer walls of the TiO2 nanotubes. "Elemental mapping" by means of EDS-TEM, as recently demonstrated in proof-of-principle experiments, will play a central role in providing evidence for the desired selective immobilization. In addition to the structural characterization, we will study to which extent and with which donor/acceptor pairs, photoinduced electron transfer occurs across the TiO2 walls. In the final stage of the project, von Delius will make use of his extensive experience with orthogonal dynamic covalent reactions to design and synthesize sophisticated bifunctional molecules for the selective filling of the inner and outer space of Schmuki's TiO2 nanotubes. The size of donor/acceptor domains will be fine-tuned collaboratively, in order to optimize exciton lifetime, thus potentially paving the way towards the realization of an interdigitated heterojunction solar cell.