Intrazeolite diffusion kinetics of dye molecules in the nanochannels of zeolite L, monitored by energy transfer

Intracrystalline diffusion kinetics of two cationic dyes in an aqueous medium were studied by means of energy transfer from an electronically excited donor to an acceptor located in one-dimensional crystalline channels. Different stages of the diffusion processes were visualized by using fluorescence microscopy. The picture illustrates the counter diffusion of the dye (hatched block) and water molecules (circles) in such a one-dimensional channel; the diffusion of the water molecules past the dye (1 → 2) is the rate-determining step rather than the period between encountering different dyes (2 → 3).