Arantzazu Zabala Ruiz

Controlling Size and Morphology of Zeolite L

The synthesis of zeolite L crystals of high purity and well-defined morphology is described. Four procedures are detailed, leading to (a) large elongated cylindrical crystals, (b) medium-sized disc-shaped crystals, (c) nano-sized crystals, and (d) medium-sized cylindrical-shaped crystals.

Electronic excitation energy transfer from dye-loaded zeolite L monolayers to a semiconductor

In device engineering, a high degree of supramolecular organisation is required to achieve certain desired macroscopic properties. Dye-loaded zeolite L host-guest materials have been successfully used in the realisation of efficient light-harvesting antenna systems. A new hierarchy of structural order is introduced by arranging the zeolite L crystals into densely packed, oriented monolayers on a substrate. We developed methods to synthesise such monolayers, to fill them with dyes and to terminate them with a luminescent stopcock. By the subsequent insertion of different types of dye molecules in a zeolite L monolayer, the first unidirectional antenna system was realised. Such antenna materials open possibilities for the design of a novel thin layer, silicon based solar cell, where the excitation energy can only migrate in one direction towards the zeolite-semiconductor interface. The electronic excitation energy is then transmitted to the semiconductor by Forster resonance energy transfer (FRET) via stopcock molecules attached to the channel ends. Direct transfer of electrons is prevented by an insulating layer. We report here on the UV-VIS absorption as well as NIR luminescence spectroscopy results obtained from such materials.

Luminescence quenching measurements on zeolite L monolayers

The luminescence quenching of the oxygen sensitive Ru2+ complex (Ru-ph4-TMS) used as a stopcock and attached to a zeolite L monolayer has been investigated. The luminescence lifetime of the attached Ru-ph4-TMS was the same under N2 and under O2 atmosphere. This remarkable result is attributed to the shielding provided by the channels of the zeolite L crystals arranged as a monolayer. The emitting 3MLCT state of the Ru-ph4-TMS stopcock is localized on the ligand bearing the phenyl groups forming the tail of this complex, which deeply penetrates into the zeolite L channel.