Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions

Temperature effects using all-atom molecular dynamics simulations

Shu Ching Ou, Di Cui, Matthew Wezowicz, Michela Taufer, Sandeep Patel

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

In this study, we examine the temperature dependence of free energetics of nanotube association using graphical processing unit-enabled all-atom molecular dynamics simulations (FEN ZI) with two (10,10) single-walled carbon nanotubes in 3 m NaI aqueous salt solution. Results suggest that the free energy, enthalpy and entropy changes for the association process are all reduced at the high temperature, in agreement with previous investigations using other hydrophobes. Via the decomposition of free energy into individual components, we found that solvent contribution (including water, anion, and cation contributions) is correlated with the spatial distribution of the corresponding species and is influenced distinctly by the temperature. We studied the spatial distribution and the structure of the solvent in different regions: intertube, intratube and the bulk solvent. By calculating the fluctuation of coarse-grained tube-solvent surfaces, we found that tube-water interfacial fluctuation exhibits the strongest temperature dependence. By taking ions to be a solvent-like medium in the absence of water, tube-anion interfacial fluctuation shows similar but weaker dependence on temperature, while tube-cation interfacial fluctuation shows no dependence in general. These characteristics are discussed via the malleability of their corresponding solvation shells relative to the nanotube surface. Hydrogen bonding profiles and tetrahedrality of water arrangement are also computed to compare the structure of solvent in the solvent bulk and intertube region. The hydrophobic confinement induces a relatively lower concentration environment in the intertube region, therefore causing different intertube solvent structures which depend on the tube separation. This study is relevant in the continuing discourse on hydrophobic interactions (as they impact generally a broad class of phenomena in biology, biochemistry, and materials science and soft condensed matter research), and interpretations of hydrophobicity in terms of alternative but parallel signatures such as interfacial fluctuations, dewetting transitions, and enhanced fluctuation probabilities at interfaces.

Original languageEnglish (US)
Pages (from-to)1196-1212
Number of pages17
JournalJournal of Computational Chemistry
Volume36
Issue number16
DOIs
StatePublished - Jun 1 2015
Externally publishedYes

Fingerprint

Carbon Nanotubes
Temperature Effect
Nanotubes
Salt
Thermal effects
Molecular Dynamics Simulation
Molecular dynamics
Carbon nanotubes
Carbon
Salts
Association reactions
Atoms
Computer simulation
Fluctuations
Tube
Water
Temperature Dependence
Spatial Distribution
Spatial distribution
Free energy

Keywords

  • graphics processing unit
  • hydrophobic association
  • ion adsorption
  • single-walled carbon nanotube
  • temperature dependence

ASJC Scopus subject areas

  • Chemistry(all)
  • Computational Mathematics

Cite this

Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions : Temperature effects using all-atom molecular dynamics simulations. / Ou, Shu Ching; Cui, Di; Wezowicz, Matthew; Taufer, Michela; Patel, Sandeep.

In: Journal of Computational Chemistry, Vol. 36, No. 16, 01.06.2015, p. 1196-1212.

Research output: Contribution to journalArticle

Ou, Shu Ching ; Cui, Di ; Wezowicz, Matthew ; Taufer, Michela ; Patel, Sandeep. / Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions : Temperature effects using all-atom molecular dynamics simulations. In: Journal of Computational Chemistry. 2015 ; Vol. 36, No. 16. pp. 1196-1212.
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