For the first time, by the application of interference microscopy, direct monitoring of three-dimensional guest diffusion in nanoporous host-guest systems has become possible. The primary experimental evidence accessible using this technique was the integral over the concentration in the direction of observation. In the present letter, an algorithm was presented which provided direct access to the local concentrations. For the system under study, methanol in the silico-aluminophosphate zeotype SAPO STA-7, the intracrystalline concentration evolving during a sorption experiment was calculated by the suggested method and the resulting data was used to determine the concentration dependence of the principal values of the diffusion tensor as well as of the surface permeability.

Three-Dimensional Diffusion in Nanoporous Host-Guest Materials Monitored by Interference Microscopy. L.Heinke, P.Kortunov, D.Tzoulaki, M.Castro, P.A.Wright, J.Kärger: EPL, 2008, 81[2], 26002 (6pp)