Issue 23, 2010

Molecular diffusion in porous media by PGSEESR

Abstract

Diffusion in porous media is a general subject that involves many fields of research, such as chemistry (e.g. porous catalytic pallets), biology (e.g. porous cellular organelles), and materials science (e.g. porous polymer matrixes for controlled-release and gas-storage materials). Pulsed-gradient spin-echo nuclear magnetic resonance (PGSE NMR) is a powerful technique that is often employed to characterize complex diffusion patterns inside porous media. Typically it measures the motion of at least ∼1015 molecules occurring in the milliseconds-to-seconds time scale, which can be used to characterize diffusion in porous media with features of ∼2–3 μm and above (in common aqueous environments). Electron Spin Resonance (ESR), which operates in the nanoseconds-to-microseconds time scale with much better spin sensitivity, can in principle be employed to measure complex diffusion patterns in porous media with much finer features (down to ∼10 nm). However, up to now, severe technical constraints precluded the adaptation of PGSE ESR to porous media research. In this work we demonstrate for the first time the use of PGSE ESR in the characterization of molecular restricted diffusion in common liquid solutions embedded in a model system for porous media made of sub-micron glass spheres. A unique ESR resonator, efficient gradient coils and fast gradient current drivers enable these measurements. This work can be further extended in the future to many applications that involve dynamical processes occurring in porous media with features in the deep sub-micron range down to true nanometric length scales.

Graphical abstract: Molecular diffusion in porous media by PGSE ESR

Article information

Article type
Paper
Submitted
21 Oct 2009
Accepted
09 Mar 2010
First published
06 Apr 2010

Phys. Chem. Chem. Phys., 2010,12, 5998-6007

Molecular diffusion in porous media by PGSE ESR

Y. Talmon, L. Shtirberg, W. Harneit, O. Yu. Rogozhnikova, V. Tormyshev and A. Blank, Phys. Chem. Chem. Phys., 2010, 12, 5998 DOI: 10.1039/B922060G

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