This thesis presents the recent progress of diffusion measurements in nanoporous
host systems by micro-imaging. Interference microscopy is applied as a
powerful tool to record transient, intracrystalline concentration profiles of different
sorbate species in the porous framework of two different zeolites, viz. ZSM-5
(MFI) and ZSM-58 (DDR). These profiles, yielding high temporal and spatial
resolutions of about 10 s and 0.45 μm, follow the change of the refractive index
of the host-guest system during uptake and release of certain guest molecules.
With the thus accessible changes of concentration and particle fluxes, mass
transport parameters, such as intracrystalline diffusivity and surface permeability,
can be obtained by the use of the very fundamental equations on diffusion.
Additionally, in two examples of never before performed types of experiments,
further insights into challenging fields of host-guest interactions are
provided: The well known phase transition in MFI type zeolites covering high
benzene loadings is investigated in a single crystal study, allowing to follow the
change of the sorbate phase in great detail. Furthermore, in DDR zeolites, a
new way of data analysis facilitates to study the uptake and release of binary
mixtures. Here, from the two-dimension profiles obtained by interference microscopy,
the local concentrations of the sorbate species could be retrieved by
using the so-called ideal adsorbed solution theory
