Molecular Dynamics Simulations of Water Structure and Diffusion in a 1 nm Diameter Silica Nanopore as a Function of Surface Charge and Alkali Metal Counterion Identity

Marie Collin, Stéphane Gin, Baptiste Dazas, Thiruvillamalai Mahadevan, Jincheng Du, Ian Charles Bourg

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Water confined in nanopores - particularly in pores narrower than 2 nm - displays distinct physicochemical properties that remain incompletely examined despite their importance in nanofluidics, molecular biology, geology, and materials sciences. Here, we use molecular dynamics simulations to investigate the coordination structure and mobility of water and alkali metals (Li, Na, K, Cs) inside a 1 nm diameter cylindrical silica nanopore as a function of surface charge density, a model system particularly relevant to the alteration kinetics of silicate glasses and minerals in geologic formations. We find that the presence of a negative surface charge and adsorbed counterions within the pore strongly impacts water structure and dynamics. In particular, it significantly orients water O-H bonds toward the surface and slows water diffusion by almost 1 order of magnitude. Ion crowding in the charged nanopore enhances the tendency of counterions to coordinate closely with the silica surface, which moderates the impact of ions on water dynamics. Co-ions are strongly excluded from the nanopore at all surface charges, suggesting that the 1 nm diameter cylindrical silica nanopores likely exhibit nearly ideal semipermeable membrane transport properties.

Original languageEnglish (US)
Pages (from-to)17764-17776
Number of pages13
JournalJournal of Physical Chemistry C
Volume122
Issue number31
DOIs
StatePublished - Aug 9 2018

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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