Solvation structure and energetics of single ions at the aqueous liquid–vapor interface

Bauer, Brad A.; Ou, Shuching; Patel, Sandeep

doi:10.1016/j.cplett.2011.12.061

Cited by 16 publications

(21 citation statements)

References 34 publications

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“…Ions were treated as non-polarizable particles with interaction parameters based on those by Lamoureux and Roux 37 and validated for use with TIP4P-FQ 38-42 . For ions in TIP4P-QDP, the parameters were obtained from Reference 42 .…”

Section: Methodsmentioning

confidence: 99%

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Spherical Monovalent Ions at Aqueous Liquid–Vapor Interfaces: Interfacial Stability and Induced Interface Fluctuations

Patel

et al. 2013

J. Phys. Chem. B

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Ion-specific interfacial behaviors of monovalent halides impact processes such as protein denaturation, interfacial stability, surface tension modulation, and as such, their molecular and thermodynamic underpinnings garner much attention. We use molecular dynamics simulations of monovalent anions in water to explore effects on distant interfaces. We observe long-ranged ion-induced perturbations of the aqueous environment as suggested by experiment and theory. Surface stable ions, characterized as such by minima in potentials of mean force computed using umbrella sampling MD simulations, induce larger interfacial fluctuations compared to non-surface active species, conferring more entropy approaching the interface. Smaller anions and cations show no interfacial potential of mean force minima. The difference is traced to hydration shell properties of the anions, and the coupling of these shells with distant solvent. The effects correlate with the positions of the anions in the Hofmeister series (acknowledging variations in force field ability to recapitulate essential underlying physics), suggesting how differences in induced, non-local perturbations of interfaces may be related to different specific-ion effects in dilute biophysical and nanomaterial systems.

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Section: Methodsmentioning

confidence: 99%

“…For ions in TIP4P-QDP, the parameters were obtained from Reference 42 . Ion parameters in SPC/E were parameterized by Fyta et al 43,44 .…”

Section: Methodsmentioning

confidence: 99%

Spherical Monovalent Ions at Aqueous Liquid–Vapor Interfaces: Interfacial Stability and Induced Interface Fluctuations

Patel

et al. 2013

J. Phys. Chem. B

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“…20 This behaviour can be modified significantly by altering the forcefield parameters, and small changes in the ion effective diameter can induce large modifications in the interfacial structure. These observations are important for understanding the interfacial free energy of aqueous interfaces, 22,23 and the ion density enhancement at interfaces that can be inferred from simulations [24][25][26][27][28][29] and experiments. [30][31][32] Ion enrichment at the interface is consistent with the surprising amount of bromide chemistry occurring in sea salt aerosols, despite the relatively low concentration of bromide in sea water.…”

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confidence: 99%

Lithium Ion–Water Clusters in Strong Electric Fields: A Quantum Chemical Study

2015

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We use density functional theory to investigate the impact that strong electric fields have on the the structure and energetics of small lithium ion-water clusters, Li + · nH 2 O, with n=4, 6. We find that electric field strengths of ∼ 0.5 V/Å are sufficient to break the symmetry of the n = 4 tetrahedral energy minimum structure, which undergoes a transformation into an asymmetric planar cluster, consisting of three water molecules bound to lithium and one additional molecule in the second solvation shell.Interestingly, this cluster remains the global minimum configuration at field strengths 0.15 V/Å. The 6-coordinated cluster, Li + · 6H 2 O, features a similar transition to 5-and 4-coordinated clusters at field strengths ∼ 0.2 V/Å and ∼ 0.3 V/Å respectively, with the tetra-coordinated structure being the global minimum even in the absence of the field. Our findings are relevant to understanding the behaviour of the Li + ion in aqueous environments under strong electric fields and in interfacial regions where field gradients are significant.

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“…Larger ionic charge density species may amplify the hydrophobic interaction between nonpolar solutes and show different effects with smaller ionic charge density species . In a biological context, these specific ion effects such as those observed by Hofmeister relating to the “salting‐in” (increasing the solubility of proteins) and “salting‐out” (antisolvent crystallization, precipitation crystallization) of proteins in aqueous electrolyte solutions of varying ionic species and concentrations have been pursued from theoretical, modeling, and experimental approaches for decades; studies continue to probe the fundamental phenomenology of this effect ,, . Horinek et al investigated the free energetics for Na + , Cl –, Br – , and I − to transfer from bulk aqueous solution to a hydrophobic self‐assembled monolayer (SAM)‐water interface in an infinite dilution and reported that soft polarizable monovalent anions (I − and Br – ) prefer to accumulate around the hydrophobic interface.…”

Section: Introductionmentioning

confidence: 99%

Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions: Temperature effects using all‐atom molecular dynamics simulations

Cui

Wezowicz

et al. 2015

J Comput Chem

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In this study we examine the temperature dependence of free energetics of nanotube association by using GPU-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, intra-tube 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 also 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.

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Solvation structure and energetics of single ions at the aqueous liquid–vapor interface

Cited by 16 publications

References 34 publications

Spherical Monovalent Ions at Aqueous Liquid–Vapor Interfaces: Interfacial Stability and Induced Interface Fluctuations

Spherical Monovalent Ions at Aqueous Liquid–Vapor Interfaces: Interfacial Stability and Induced Interface Fluctuations

Lithium Ion–Water Clusters in Strong Electric Fields: A Quantum Chemical Study

Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions: Temperature effects using all‐atom molecular dynamics simulations

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