Energy Collection, Transport, and Trapping by Supramolecular Organization of Dyes in Hexagonal Zeolite Nano Crystals

The incorporation of guest molecules into the cavities of molecular sieves leads to a large variety of highly interesting materials. Zeolite L - an aluminosilicate with one-dimensional channels of open diameter 7.1 Å - is a very versatile material for building highly organized host-guest systems. We present materials where organic dye molecules have been incorporated into the channels of zeolite L by means of diffusion, to build artificial photonic antenna systems. The channel entrance can be plugged by adding closure molecules that then connect the guest molecules inside with materials or molecules outside of the zeolite channels, since they can act as extensions of the interior of the zeolite crystal. The photophysical processes taking place in such dye-loaded zeolite L antennae can be studied either on single-micrometer- or submicrometer-sized crystals or on crystals dispersed in a solvent or coated as thin layers on a support. The energy-transfer process occurring is of the Förster-type, and its transfer rate can be tuned by separating the donor dyes and the acceptor dyes locally by varying amounts of spacer molecules. The distribution of the dye molecules and empty sites within a zeolite crystal has been modeled by means of a Monte Carlo simulation. The Förster energy migration and transfer steps are described as a random walk.