Fine tuning of the size of zeolite L crystals in a large range is possible by changing the composition of the starting gel for otherwise constant reaction conditions. We describe a convenient way to prepare different crystalline materials in the size range of 30 nm up to 3000 nm. Representative data on the morphology, the pore volume, the size distribution and the optic I al antenna system behavior for light harvesting and transport are reported. We have extended the investigations on energy migration in pyronine-loaded zeolite L crystals as donor molecules, modified with oxonine as luminescent acceptors (traps) at the crystal ends. The preparation procedure reported and the extended zeolite materials now available lead to a large improvement of the energy migration efficiency.