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          Institute: MPI für Dynamik komplexer technischer Systeme     Collection: Physical and Chemical Foundations of Process Engineering     Display Documents



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ID: 537447.1, MPI für Dynamik komplexer technischer Systeme / Physical and Chemical Foundations of Process Engineering
Composition, Structure, and Mobility of Water−Acetonitrile Mixtures in a Silica Nanopore Studied by Molecular Dynamics Simulations
Authors:Melnikov, S. M.; Höltzel, A.; Seidel-Morgenstern, A.; Tallarek, U.
Language:English
Date of Publication (YYYY-MM-DD):2011
Title of Journal:Analytical Chemistry
Volume:83
Issue / Number:7
Start Page:2569
End Page:2575
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:To investigate the effect of the nanoscale confinement on the properties of a binary aqueous−organic solvent mixture, we performed molecular dynamics simulations of the equilibration of water−acetonitrile (W/ACN) mixtures between a cylindrical silica pore of 3 nm diameter and two bulk reservoirs. Water is enriched, and acetonitrile is depleted inside the pore with respect to the bulk reservoirs: for nominal molar (~volumetric) ratios of 1/3 (10/90), 1/1 (25/75), and 3/1 (50/50), the molar W/ACN ratio in the pore equilibrates to 1.5, 3.2, and 7.0. Thus, the relative accumulation of water in the pore increases with decreasing water fraction in the nominal solvent composition. The pore exhibits local as well as average solvent compositions, structural features, and diffusive mobilities that differ decidedly from the bulk. Water molecules form hydrogen bonds with the hydrophilic silica surface, resulting in a 0.45 nm thick interfacial layer, where solvent density, coordination, and orientation are independent of the nominal W/ACN ratio and the diffusive mobility goes toward zero. Our data suggest that solute transport along and across the nanopore, from the inner volume to the interfacial water layer and the potential adsorption sites at the silica surface, will be substantially different from transport in the bulk.

Copyright © 2011 American Chemical Society [accessed April 15th 2011]
External Publication Status:published
Document Type:Article
Communicated by:Andreas Seidel-Morgenstern
Affiliations:MPI für Dynamik komplexer technischer Systeme/Physical and Chemical Foundations of Process Engineering
External Affiliations:Philipps-Universität Marburg,
Department of Chemistry,
Hans-Meerwein-Straße, 35032 Marburg, Germany

Otto-von-Guericke-Universität Magdeburg,
Institut für Verfahrenstechnik,
Universitätsplatz 2, 39106 Magdeburg, Germany
Identifiers:LOCALID:60/11
URL:http://dx.doi.org/10.1021/ac102847m
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