title: Molecular diffusion in porous media by PGSE ESR.
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 approximately 10(15) molecules occurring in the milliseconds-to-seconds time scale, which can be used to characterize diffusion in porous media with features of approximately 2-3 mum 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 approximately 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.
authors.affiliation: Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Talmon
authors.forename: Lazar
authors.initials: L
authors.lastname: Shtirberg
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Harneit
authors.forename: Olga Yu
authors.initials: OY
authors.lastname: Rogozhnikova
authors.forename: Victor
authors.initials: V
authors.lastname: Tormyshev
authors.forename: Aharon
authors.initials: A
authors.lastname: Blank
mesh_terms: D004058:Diffusion; D004578:Electron Spin Resonance Spectroscopy; D037741:Fullerenes / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D016062:Porosity; D013997:Time Factors; D014320:Triphenylmethyl Compounds / Q000737:chemistry
chemical_list: D037741:Fullerenes; D014320:Triphenylmethyl Compounds; C069837:fullerene C60