摘要
The spatial monitoring of ion diffusion into an ultrathin film sample was demonstrated by our depth profiling method using variable observation angle fluorescence spectroscopy under normal incidence conditions. A 143-nm-thick LB multilayer model sample was prepared in which the fluorophore rhodamine B was homogeneously distributed in each layer. The model sample was then immersed into an aqueous solution of sodium tungstate, where the tungstate ion diffused into it and reacted with rhodamine B to form a nonfluorescent complex. Because of this chemical quenching effect, the homogeneous concentration distribution of rhodamine B was changed by the tungstate ion diffusion. Changes in concentration depth profiles of rhodamine B with diffusion time were measured by the variable observation angle fluorescence depth profiling method based on the reciprocal theory, which has a spatial resolution of the monolayer thickness level in the depth direction. As a result, the diffusion behavior of tungstate ion was monitored, and its diffusion coefficient in LB multilayers was obtained as (1.2 - 1.7) × 10 cm /s. © 1992 American Chemical Society.