Role of spatial ionic distribution on the energetics of hydrophobic assembly and properties of the water/hydrophobe interface

Brad A. Bauer, Shuching Ou, Sandeep Patel

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

We present results from all-atom molecular dynamics simulations of large-scale hydrophobic plates solvated in NaCl and NaI salt solutions. As observed in studies of ions at the air-water interface, the density of iodide near the water-plate interface is significantly enhanced relative to chloride and in the bulk. This allows for the partial hydration of iodide while chloride remains more fully hydrated. In 1 M solutions, iodide directly pushes the hydrophobes together (contributing -2.51 kcal mol -1) to the PMF. Chloride, however, strengthens the water-induced contribution to the PMF by ∼-2.84 kcal mol -1. These observations are enhanced in 3 M solutions, consistent with the increased ion density in the vicinity of the hydrophobes. The different salt solutions influence changes in the critical hydrophobe separation distance and characteristic wetting/dewetting transitions. These differences are largely influenced by the ion-specific expulsion of iodide from bulk water. Results of this study are of general interest to the study of ions at interfaces and may lend insight to the mechanisms underlying the Hofmeister series.

Original languageEnglish (US)
Pages (from-to)1892-1906
Number of pages15
JournalPhysical Chemistry Chemical Physics
Volume14
Issue number6
DOIs
StatePublished - Feb 14 2012

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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