8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Thu 811:10-14:00P7.101Coaxial cross-diffusion through carbon nanotubesJavier Rodriguez, 1 Maria Dolores Elola, 1 and Daniel Laria 11 National Agency of Atomic Energy, Centro Atomico Constituyentes. , Av Gral Paz 1499.B1650KNA, San Martin, ArgentinaWe present results from non-equilibrium Molecular Dynamics experiments describing the relaxationof local concentrations at two reservoirs, initially filled with water (W) and acetonitrile(ACN), as they get connected through a membrane composed of (16, 16) carbon nanotubes. Withinthe hydrophobic nanotube cavities, the equilibrium concentrations contrast sharply to those observedat the reservoirs, with a clear enhancement of ACN, in detriment of W. From the dynamicalside, the relaxation involves three well differentiated stages: the first one corresponds to the equilibrationof individual concentrations within the nanotubes. An intermediate interval with Fickiancharacteristics follows, during which the overall transport can be cast in terms of coaxial oppositefluxes, with a central water domain segregated from an external ACN shell, in close contact withthe tube walls. We also found evidence of a third, much slower, mechanism to reach equilibration,which involves structural modifications of tightly bound solvation shells, in close contact with thenanotube rims.101