Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Micro and Nanofluidics I

CPP 26.4: Talk

Wednesday, March 24, 2010, 14:45–15:00, H39

Charge transport and diffusion of ionic liquids in nanoporous silica membranes — •Ciprian Iacob, Joshua Sangoro, Sergej Naumov, Rustem Valiullin, Jörg Kärger, and Friedrich Kremer — Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, 04103, Leipzig, Germany

Charge transport in 1-hexyl-3-methylimidazolium hexafluorophosphate ionic liquid in oxidized nanoporous silicon membranes - prepared by electrochemical etching of (100) p-type silicon- is investigated in a wide frequency and temperature range by a combination of broadband dielectric spectroscopy and pulsed field gradient nuclear magnetic resonance (PFG NMR). By applying the Einstein-Smoluchowski relation to the dielectric spectra, diffusion coefficient is obtained in quantitative agreement with independent PFG NMR measurements. More than 10-fold systematic decrease in the diffusion coefficient from the bulk value is observed in silica nanopores. This is explained within the framework of a model taking into account decreased mobility at the interface of the pore and the nanoporous membrane due to the ability of the hydrogen-bonded ionic liquid to attach to SiO2 surfaces. By that, it becomes possible to probe the size of the adsorption layer and its temperature dependence. This has direct technological implications to the use of ionic liquids in fuel cells and nanobatteries.