Molecular dynamics study on helium nanobubbles in water

Yamamoto, Takenori; Ohnishi, Shuhei

doi:10.1039/c1cp22018g

Cited by 18 publications

(13 citation statements)

References 35 publications

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“…28 Amber FF03 29 was used to model the interaction of the carbon of the pristine graphene (atom type CA), which has been shown previously to describe structure and dynamics of confined water very well. The same helium parameters were used recently 34 to study the stability of helium bubbles in water. During minimization, the pristine graphene sheets were held fixed to their initial positions using a harmonic constraint with a spring constant of 500 kcal mol À1 Å À2 .…”

Section: Simulation Detailsmentioning

confidence: 99%

Molecular mechanism of water permeation in a helium impermeable graphene and graphene oxide membrane

Raghav

Chakraborty

Maiti

2015

Phys. Chem. Chem. Phys.

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Layers of graphene oxide (GO) are found to be good for the permeation of water but not for helium (Science, 2012, 335(6067), 442-444) suggesting that the GO layers are dynamic in the formation of a permeation route depending on the environment they are in (i.e., water or helium). To probe the microscopic origin of this observation we calculate the potential of mean force (PMF) of GO sheets (with oxidized and reduced parts), with the inter-planar distance as a reaction coordinate in helium and water. Our PMF calculation shows that the equilibrium interlayer distance between the oxidized part of the GO sheets in helium is at 4.8 Å leaving no space for helium permeation. In contrast, the PMF of the oxidized part of the GO in water shows two minima, one at 4.8 Å and another at 6.8 Å, corresponding to no water and a water filled region, thus giving rise to a permeation path. The increased electrostatic interaction between water with the oxidized part of the sheet helps the sheet open up and pushes water inside. Based on the entropy calculations for water trapped between graphene sheets and oxidized graphene sheets at different inter-sheet spacings, we also show the thermodynamics of filling.

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Section: Simulation Detailsmentioning

confidence: 99%

Molecular mechanism of water permeation in a helium impermeable graphene and graphene oxide membrane

Raghav

Chakraborty

Maiti

2015

Phys. Chem. Chem. Phys.

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“…16,17 Ashbaugh and Pratt 4 find δ ≈ 0.6 Å at T = 300 K, which decreases with increasing temperature and changes sign at T ≈ 350 K. Huang et al 18 deduce δ = 0.9 Å at T = 298 K for SPC/E water from simulated solvation free energies of hydrophobic spheres. Yamamoto and Ohnishi 19 on the other hand find a maximum in the surface tension of helium bubbles in water as a function of bubble radius, which, considering the curvature expansion in Eqs. (1) or (3), corresponds to a negative Tolman length, in contrast to the previous studies.…”

Section: Introductionmentioning

confidence: 96%

The spontaneous curvature of the water-hydrophobe interface

Sedlmeier

Netz

2012

The Journal of Chemical Physics

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The temperature-dependent solvation of hydrophobic solutes in water is investigated by large-scale molecular dynamics simulations. A simultaneous fit of solvation free energies for spheres and cylinders with radii up to R = 2 nm yields a negative Tolman length on the order of 1 Å at room temperature, equivalent to a spontaneous curvature that favors water droplets over cavities. Pronounced crossover effects of the surface free energy are analyzed in terms of higher-order curvature corrections and water-discreteness effects.

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“…Here, d Using DFT, Talanquer et al [66] calculated the density profiles of unstable critical bubbles at R = R c , where the solute is accumulated in the bubble interior and its density exhibits a mild maximum at the interface. In their molecular dynamics simulation, Yamamoto and Ohnishi [67] realized stable helium-rich nanobubbles in water. They fixed the cell volume to find slightly negative pressures in the liquid region as in our Fig.6(a).…”

Section: Stress Tensor Around a Bubble And Laplace Lawmentioning

confidence: 99%

Density functional theory of gas–liquid phase separation in dilute binary mixtures

Okamoto

Ōnuki

2016

J. Phys.: Condens. Matter

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We examine statics and dynamics of phase-separated states of dilute binary mixtures using density functional theory. In our systems, the difference in the solvation chemical potential ∆µs between liquid and gas is considerably larger than the thermal energy kBT for each solute particle and the attractive interaction among the solute particles is weaker than that among the solvent particles. In these conditions, the saturated vapor pressure increases by an amount equal to the solute density in liquid multiplied by the large factor kBT exp(∆µs/kBT ). As a result, phase separation is induced at low solute densities in liquid and the new phase remains in gaseous states, while the liquid pressure is outside the coexistence curve of the solvent. This explains the widely observed formation of stable nanobubbles in ambient water with a dissolved gas. We calculate the density and stress profiles across planar and spherical interfaces, where the surface tension decreases with increasing the interfacial solute adsorption. We realize stable solute-rich bubbles with radius about 30 nm, which minimize the free energy functional. We then study dynamics around such a bubble after a decompression of the surrounding liquid, where the bubble undergoes a damped oscillation. In addition, we present some exact and approximate expressions for the surface tension and the interfacial stress tensor.

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Molecular dynamics study on helium nanobubbles in water

Cited by 18 publications

References 35 publications

Molecular mechanism of water permeation in a helium impermeable graphene and graphene oxide membrane

Molecular mechanism of water permeation in a helium impermeable graphene and graphene oxide membrane

The spontaneous curvature of the water-hydrophobe interface

Density functional theory of gas–liquid phase separation in dilute binary mixtures

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