Electric Control of Wetting by Salty Nanodrops: Molecular Dynamics Simulations

Daub, Christopher D.; Bratko, D.; Luzar, Alenka

doi:10.1021/jp206242n

Cited by 60 publications

(75 citation statements)

References 87 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For a typical case as shown above: the case of a drop of roughly 26 nm in diameter and considering the planar limit of the fluid-vapor tension (72 mN·m . While this number seems to be different from those estimated from micrometer drop experiments [35] or from molecular simulation of atomistic water models [36,37]; it is appropriate to point out that values as low as ×10 −11 J·m −1 and as high as ×10 −5 J·m −1 have been reported [33], which place our results in the correct context. Obviously, there is scope for much more detailed research into this topic.…”

Section: Resultscontrasting

confidence: 80%

On the Calculation of Solid-Fluid Contact Angles from Molecular Dynamics

Santiso

Herdes

Müller

2013

Entropy

View full text Add to dashboard Cite

Abstract:A methodology for the determination of the solid-fluid contact angle, to be employed within molecular dynamics (MD) simulations, is developed and systematically applied. The calculation of the contact angle of a fluid drop on a given surface, averaged over an equilibrated MD trajectory, is divided in three main steps: (i) the determination of the fluid molecules that constitute the interface, (ii) the treatment of the interfacial molecules as a point cloud data set to define a geometric surface, using surface meshing techniques to compute the surface normals from the mesh, (iii) the collection and averaging of the interface normals collected from the post-processing of the MD trajectory. The average vector thus found is used to calculate the Cassie contact angle (i.e., the arccosine of the averaged normal z-component). As an example we explore the effect of the size of a drop of water on the observed solid-fluid contact angle. A single coarsegrained bead representing two water molecules and parameterized using the SAFT-γ Mie equation of state (EoS) is employed, meanwhile the solid surfaces are mimicked using integrated potentials. The contact angle is seen to be a strong function of the system size for small nano-droplets. The thermodynamic limit, corresponding to the infinite size (macroscopic) drop is only truly recovered when using an excess of half a million water coarse-grained beads and/or a drop radius of over 26 nm.

show abstract

Section: Resultscontrasting

confidence: 80%

On the Calculation of Solid-Fluid Contact Angles from Molecular Dynamics

Santiso

Herdes

Müller

2013

Entropy

View full text Add to dashboard Cite

show abstract

“…Hemispherical aqueous nanodroplets, on the other hand, show contact angle size dependence for small drops with contact area radius below r < 25 Å. 28,42,55 Although the size dependence weakens for low interfacial tensions, the cylindrical geometry, characterized by essentially straight contact lines, ensures a higher reliability independently on the system properties.…”

Section: B Methodsmentioning

confidence: 99%

Wettability of pristine and alkyl-functionalized graphane

Vanzo

Bratko

Luzar

2012

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

Graphane is a hydrogenated form of graphene with high bandgap and planar structure insensitive to a broad range of chemical substitutions. We describe an atomistic simulation approach to predict wetting properties of this new material. We determine the contact angle to be 73°. The lower hydrophobicity compared to graphene is explained by the increased planar density of carbon atoms while we demonstrate that the presence of partial charges on carbon and hydrogen atoms plays only a minor role. We further examine the effects of graphane functionalization by alkyl groups of increasing chain lengths. The gradual increase in contact angle with chain length offers a precise control of surface wettability. A saturated contact angle of 114° is reached in butylated form. We find the saturation of contact angle with respect to the length of the functional groups to coincide with the loss of water's ability to penetrate the n-alkyl molecular brush and interact with carbon atoms of the underlying lattice. Since no experimental data have yet become available, our modeling results provide the first estimate of the wettability of graphane. The results also show how its alkyl functionalization provides the basis for a variety of chemical modifications to tune hydrophilicity while preserving the planar geometry of the substrate.

show abstract

“…The contribution arising from water reflects not only strong packing effects but also the oscillatory orientation profile of interfacial water molecules. 47,63,68 The distribution of salt ions matches charge density profiles of water, with Na + ions favoring the domains cosine of the angle θ between water dipoles and the direction of the field, which is perpendicular to pore walls in the presence (solid black) or absence (dotted line) of electric field. Bottom: net charge-density profile (solid black) and charge densities due to water molecules (dotdashed red), and combined charge density due to salt ions of both types (Na + and Cl − , dotted blue).…”

Section: Resultsmentioning

confidence: 91%

Salt and Water Uptake in Nanoconfinement under Applied Electric Field: An Open Ensemble Monte Carlo Study

2015

Self Cite

View full text Add to dashboard Cite

Permeation of electrolytes in nanoporous materials underlies many applications in energy and materials technologies. Wetting of apolar nanopores can be enhanced by electric field, attracting water and ions from unperturbed electrolyte bath. We study absorption of water and NaCl in the pores by Expanded Ensemble Grand Canonical Monte Carlo simulation, which implements particle insertions and deletions through incremental changes in particles' coupling with the system. We determine the uptake of water and ions in the pores, and concomitant changes in pore thermodynamics, as functions of field strength in the pore and salinity in the external bath. Pressure increase and reduction of wetting free energy, σ, in the pore intensify near-quadratically with the field. Surprisingly, the influence of bulk salinity on σ can change qualitatively with pore width and field strength. Conforming to Gibbs adsorption isotherm, narrow pores with salt molality below that of the bath experience an increase in σ with rising bulk salinity. The field can change salt depletion to excess and consequently reverse the salinity dependence of wetting free energy from increasing to declining function of bulk molality. Field polarity continues to play a role, leading to asymmetric wettability at opposing walls as we previously observed in the absence of ions.

show abstract

Electric Control of Wetting by Salty Nanodrops: Molecular Dynamics Simulations

Cited by 60 publications

References 87 publications

On the Calculation of Solid-Fluid Contact Angles from Molecular Dynamics

On the Calculation of Solid-Fluid Contact Angles from Molecular Dynamics

Wettability of pristine and alkyl-functionalized graphane

Salt and Water Uptake in Nanoconfinement under Applied Electric Field: An Open Ensemble Monte Carlo Study

Contact Info

Product

Resources

About