Paramagnetic adsorption sites in microporous crystalline solids studied by electron paramagnetic resonance spectroscopy – from single crystals to oriented thin films

Technological applications of microporous materials in molecular sieving and catalytic processes rely more and more on thin films and membranes instead of widely used pellets made from pressed powders. This trend in engineering sets new challenges for the spectroscopic investigation of aluminosilcate and aluminophosphate thin films and small single crystals including the characterization of paramagnetic ions and their interaction with adsorbates and reactants by EPR spectroscopy. Such information is of uttermost importance for the understanding of the adsorptive and catalytic properties of the porous materials. In order to meet this challenge, X-band cw EPR probe heads with higher spin sensitivity will be developed for the studies of such oriented thin films and small crystals in vacuum and at low temperatures. The probe head design will be based on two strategies: (A) the adoption of the planar micro resonators recently introduced by D. Suter and (B) the use of dielectric resonators with high permittivity accommodated together with the samples in sealed quartz containers. By extending EPR spectroscopy to small single crystals and oriented thin films information about the orientation of the magnetic interaction tensors with respect to the crystallographic axes frame will become available and in that way will offer significantly improved opportunities to determine the cation sites and the structure and dynamics of the adsorption complexes formed in zeolite and AlPO porous materials.

A. Pöppl

Prof. Dr. Andreas Pöppl

Universität Leipzig, Institut für Experimentalphysik II Linnéstr. 5, 04103 Leipzig
Tel.: +49 341 97-32608 Email: poeppl@physik.uni-leipzig.de
Fax: +49 341 97-32649 Website: http://