Water diffusion in rough carbon nanotubes

Mendonça, Bruno H. S.; Ternes, Patrícia; Salcedo, Evy; Oliveira, Alan Barros de; Barbosa, Márcia C.

doi:10.1063/1.5129394

Cited by 28 publications

(41 citation statements)

References 35 publications

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“…In addition, each water molecule is attached, on average, to 2.45 other water molecules through hydrogen bonds, as shown in Figure 4 . The slow dynamics of water in this small confinement is due to the rigidity of water molecules through the formation of an organized network depicted as a tubular shape shown in Figure S1 , considering that the cutoff length of an hydrogen bond is about 0.35 nm [ 32 ].…”

Section: Resultsmentioning

confidence: 99%

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Effect of Size and Temperature on Water Dynamics inside Carbon Nano-Tubes Studied by Molecular Dynamics Simulation

2021

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Water transport inside carbon nano-tubes (CNTs) has attracted considerable attention due to its nano-fluidic properties, its importance in nonporous systems, and the wide range of applications in membrane desalination and biological medicine. Recent studies show an enhancement of water diffusion inside nano-channels depending on the size of the nano-confinement. However, the underlying mechanism of this enhancement is not well understood yet. In this study, we performed Molecular Dynamics (MD) simulations to study water flow inside CNT systems. The length of CNTs considered in this study is 20 nm, but their diameters vary from 1 to 10 nm. The simulations are conducted at temperatures ranging from 260 K to 320 K. We observe that water molecules are arranged into coaxial water tubular sheets. The number of these tubular sheets depends on the CNT size. Further analysis reveals that the diffusion of water molecules along the CNT axis deviates from the Arrhenius temperature dependence. The non-Arrhenius relationship results from a fragile liquid-like water component persisting at low temperatures with fragility higher than that of the bulk water.

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Section: Resultsmentioning

confidence: 99%

“…Due to the confined geometry, the diffusion of water is minimal along the radial direction, and it is almost zero [ 32 ]. Therefore, here, we consider only the axial self-diffusion coefficient ( D ) along the z-direction.…”

Section: Methodsmentioning

confidence: 99%

Effect of Size and Temperature on Water Dynamics inside Carbon Nano-Tubes Studied by Molecular Dynamics Simulation

2021

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“…Experiments in slit pores show that water forms layers parallel to the walls [72]. Computer simulations of water between two nanoscopic hydrophobic plates reveal that these layers correspond to local minima in the free-energy profile as a function of the plate-plate separation w [73] and that the water mobility in a hydrophobic slit pore monotonically increases as w becomes larger [74,75,76,77,78,79,80,81,82,83]. Similar results hold for water confined in graphite [84] and quartz [45,46,76], with freezing of the dynamics at sub-nm confinement.…”

Section: Introductionmentioning

confidence: 99%

Water under extreme confinement in graphene: Oscillatory dynamics, structure, and hydration pressure explained as a function of the confinement width

Calero

Franzese

2020

Journal of Molecular Liquids

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Graphene nanochannels are relevant for their possible applications, as in water purification, and for the challenge of understanding how they change the properties of confined liquids. Here, we use all-atom molecular dynamics simulations to investigate water confined in an open graphene slit-pore as a function of its width w, down to sub-nm scale. We find that the water translational and rotational dynamics exhibits an oscillatory dependence on w, due to water layering.The oscillations in dynamics correlate with those in hydration pressure, which can be negative (hydrophobic attraction), or as high as ∼ 1 GPa, as seen in the experiments. At pore widths commensurable with full layers (around 7.0Å and 9.5Å for one and two layers, respectively), the free energy of the system has minima, and the hydration pressure vanishes. These are the separations at which the dynamics of confined water slows down. Nevertheless, the hydration pressure vanishes also where the free energy has maxima, i.e., for those porewidths which are incommensurable with the formation of well-separated layers, as w 8.0Å. Around these values of w, the dynamics is faster than in bulk, with water squeezed out from the pore. This behavior has not been observed for simple liquids under confinement, either for water in closed nano-pores. The decomposition of the free energy clarifies the origins of the dynamics speedups

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“…The radial diffusion is therefore enhanced at larger radii. The total suppression of radial displacements in cylindrical nanopores can be observed in case of even stronger nanoconfinement, such as in the case of narrow carbon nanotubes that accommodate only a single-file arrangement of water molecules; there, diffusivity typically becomes negligible in the very-long time (nanoseconds) compared to axial diffusion [ 32 , 52 ]. Nonetheless for hydrophilic silica pores (allowing for the formation of HBs between water and the pore walls), the axial diffusion is faster in larger nanopores [ 29 ].…”

Section: Resultsmentioning

confidence: 99%

Structure and dynamics of water confined in cylindrical nanopores with varying hydrophobicity

Tinti

Camisasca

Giacomello

2021

Phil. Trans. R. Soc. A.

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We report a detailed study of the main structural and dynamical features of water confined in model Lennard–Jones nanopores with tunable hydrophobicity and finite length ( L = 26 Å). The generic model of cylindrical confinement used is able to reproduce the wetting features of a large class of technologically and biologically relevant systems spanning from crystalline nanoporous materials, to mesoporous silica and ion channels. The aim of this work is to discuss the influence of parameters such as wall hydrophobicity, temperature, and pore size on the structural and dynamical features of confined water. Our simulation campaign confirmed the existence of a core domain in which water displays bulk-like structural features even in extreme ( R = 7.0 Å) confinement, while dynamical properties were shown to depend non-trivially on the size and hydrophobicity of the pores. This article is part of the theme issue ‘Progress in mesoscale methods for fluid dynamics simulation’.

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Water diffusion in rough carbon nanotubes

Cited by 28 publications

References 35 publications

Effect of Size and Temperature on Water Dynamics inside Carbon Nano-Tubes Studied by Molecular Dynamics Simulation

Effect of Size and Temperature on Water Dynamics inside Carbon Nano-Tubes Studied by Molecular Dynamics Simulation

Water under extreme confinement in graphene: Oscillatory dynamics, structure, and hydration pressure explained as a function of the confinement width

Structure and dynamics of water confined in cylindrical nanopores with varying hydrophobicity

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