Session Q7: Focus Session: Computational Design of Materials: Graphene - Strain, defect and interface engineering

11:15 AM–2:15 PM, Wednesday, February 29, 2012
Room: 207

Sponsoring Units: DMP DCOMP
Chair: Marco Buongiorno Nardelli, North Carolina State University

Abstract ID: BAPS.2012.MAR.Q7.10

Abstract: Q7.00010 : Thermally-driven Isotope Separation Across Nanoporous Graphene

1:03 PM–1:15 PM

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  Joshua Schrier
    (Haverford College)

Experiment and theory indicate that a single graphene sheet is impermeable to gases even as small as helium; pores are required for transmission of atoms and molecules. Nanoporous forms of graphene, such as two-dimensional polyphenylene (2D-PP), consist of a regular array of sub-nanometer pores which can be used for separating atoms and molecules by size. Because the nanoporous graphene barrier is only an atom-thick, quantum tunneling plays a role in the the transmission of atoms through the nanoporous barrier, even at room temperature. This talk describes how the mass-dependence of the tunneling, combined with a temperature gradient, can be used to separate isotope mixtures under conditions where classical transmission cannot. Using transition state theory, we show that the zero-point and tunneling contributions lead to isotopic separations in opposite directions with respect to the temperature gradient. We examine the separation of $^{3}$He/$^{4}$He across a 2D-PP membrane under modest temperature and pressure conditions. We will also describe 2D-PP bilayer structures that yield resonant tunneling of helium atoms, and new nanoporous graphene structures suitable for separating heavier noble-gas isotopes.

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