Fluorescence microscopy investigation on the manipulation of guest species on zeolites

We applied a fluorescence microscopy method to investigate the possibility of molecular manipulation such as intentional transfer of molecules from one zeolite crystal to another. Photophysical and photochemical processes of guest species incorporated in the zeolites were exploited as indicator reactions in order to yield a luminescence color characteristic of individual zeolite particles. Two types of migration mechanisms were observed: a through-space diffusional-transfer mode between separated zeolite crystals and a molecular injection process from a loaded crystal to another unloaded crystal, both in contact. A preferential direction of guest migration was found to exist for a few cases: for instance, aromatics such as phenanthrene and chrysene migrate from the sodium form of zeolite X (Na⁺-X) to thallium-exchanged zeolite X (Tl⁺-X). On the other hand, the migration-assisted formation of charge-transfer complexes between electron-donating arenes such as phenanthrene and chrysene, and electron-accepting 1,2,4,5-tetracyanobenzene, both incorporated into separate zeolite Na⁺-X crystals, takes place as a result of the migration of the donors. The fluorescence microscopy method utilizing photochemistry in zeolites was found to be a powerful technique for the qualitative investigation of the intercrystalline migration and possibly applicable to the observation of particleto-particle molecular manipulation processes.