Molecular Dynamics Simulation of Contact Angles of Water Droplets in Carbon Nanotubes

Werder, T.; Walther, Jens Honoré; Jaffe, Richard L.; Halicioǧlu, T.; Noca, Flavio; Koumoutsakos, Petros

doi:10.1021/nl015640u

Cited by 242 publications

(183 citation statements)

References 22 publications

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“…The SPC/E water model was used to describe the liquid water as this water model has been investigated comprehensibly [31][32][33][34][35] . The parameter for nitrogen gas was the Universal Force Field (UFF) model which was used by Wang et al 19 .…”

Section: Interaction Modelsmentioning

confidence: 99%

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Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

2013

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Interfacial gas enrichment (IGE) covering the entire area of hydrophobic solid-water interface has recently been detected by atomic force microscopy (AFM) and hypothesized to be responsible for the unexpected stability and anomalous contact angle of gaseous nanobubbles, and the significant change from DLVO to non-DLVO forces. In this paper, we provide further proof of the existence of IGE in the form of a dense gas layer (DGL) by molecular dynamic simulation.Nitrogen gas adsorption at the water-graphite interface is investigated using molecular dynamic simulation at 300 K and 1 atm normal pressure. The results show that a DGL with a density equivalent to a gas at pressure of 500 atm is formed and equilibrated with a normal pressure of 1 atm. By varying the number of gas molecules in the system, we observe several types of dense gas domains: aggregates, cylindrical cap gas domains and DGLs. Spherical cap gas domains form during the simulation but are unstable and always revert to another type of the gas domains.Furthermore, the calculated surface potential of the DGL-water interface, -17.5 mV, is significantly closer to 0 than the surface potential, -65 mV, of normal gas bubble-water interface. This result supports our previously stated hypothesis that the change in surface potential causes the switch from repulsion to attraction for an AFM tip when the graphite surface is covered by an IGE layer. The change in surface potential comes from the structure change of water molecules at the DGL-water interface as compared with the normal gas-water interface. In addition, the contact angle of the cylindrical cap high density nitrogen gas domains is 141degrees. This contact angle is far greater 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 than 85 degrees observed for water on graphite at ambient conditions and much closer to the 150 degrees contact angle observed for nanobubbles in experiments.

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Section: Interaction Modelsmentioning

confidence: 99%

“…Werder et al 34,35 . The standard Lorentz-Berthelot type mixing rules were used to obtain the LJ parameters between atoms of different species in both sets of potential parameters as shown in Table 1.…”

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confidence: 99%

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

2013

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“…Recent investigations have increased our understanding of confined water, showing that, in nanoscopic proportions, many water properties differ drastically from those of bulk water [10,11,12]. In particular, an excellent model is water confined in carbon nanotubes, which have been adopted in many previous studies [13,14,15,16,17,18,19,20,21,22,23,24,25,26]. Among these interesting investigations, Koga et al investigated water inside single-walled carbon nanotubes (SWCNTs) of diameter 1.1∼1.4 nm and found that water forms ice nanotubes composed by a rolled square ice sheet [14,15,16].…”

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Ferroelectric Ordering in Ice Nanotubes Confined in Carbon Nanotubes

Luo

Zhou

et al. 2008

Nano Lett.

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We report that ice nanotubes with odd number of side faces inside carbon nanotubes exhibit spontaneous electric polarization along its axis direction by using molecular dynamics simulations. The mechanism of this nanoscale quasi-one-dimensional ferroelectricity is due to low dimensional confinement and the orientational order of hydrogen bonds. These ferroelectric fiber structural materials are different from traditional perovskite structural bulk materials. 85.35.Kt, 61.46.Fg, 68.08.De Whether ferroelectric ice exists is a question that has long fascinated researchers [1,2,3,4]. Although one water molecule has a significant dipole moment, normal hexagonal ice Ih does not possess ferroelectricity and it is very difficult to get an ice phase even with a weak whole polarization. Several year ago, the ferroelectricity of ice films grown on ultra-clean platinum was detected, although only a small proportion (0.2%) of the molecules are aligned [5,6]. Most recently, Fukazawa et al. have succeeded in making Ice XI in the laboratory and suggests existence of ferroelectric ice in the universe [7].Confinement of matter on the nanometer scale can induce phase transitions not seen in bulk systems [8,9]. In biology as well as in natural and synthetic materials, water is often tucked away in tiny crevices inside proteins or in porous materials. Therefore, water confined in nanoscale quasi-one-dimensional (Q1D) channels is of great interest to biology, geology, and materials science. Recent investigations have increased our understanding of confined water, showing that, in nanoscopic proportions, many water properties differ drastically from those of bulk water [10,11,12]. In particular, an excellent model is water confined in carbon nanotubes, which have been adopted in many previous studies [13,14,15,16,17,18,19,20,21,22,23,24,25,26]. Among these interesting investigations, Koga et al. investigated water inside single-walled carbon nanotubes (SWCNTs) of diameter 1.1∼1.4 nm and found that water forms ice nanotubes composed by a rolled square ice sheet [14,15,16]. Recent neutron scattering studies, combined with molecular dynamics (MD) simulations, revealed that water in SWCNTs of diameter 1.4 nm forms a core-shell structure, in which the square ice sheet described by Koga et al. is coupled with a chainlike configuration at the center of the shell [27,28].Recently, investigations of nanoscale ferroelectric materials are very active due to its potential application [29,30,31]. Because of its particular structures, the ice nanotubes inside SWCNTs may exhibit ferroelectricity. * Electronic address: jdong@nju.edu.cnIn this paper, we report that ice nanotubes with odd number of side faces inside SWCNTs exhibit spontaneous electric polarization along its axis direction by using MD simulations. The origin of ferroelectricity of these ice nanotubes is due to the strong direction preferred hydrogen-bonds between water molecules and the Q1D confinement inside SWCNTs, which is different from traditional ferroelectric bulk materials, ...

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“…The geometrical shape of the meniscus and the position of the liquid surface were found by fitting the contour lines corresponding to = ͑1 / 2͒ bulk with circular arcs. 19 To ensure the smoothness of the contour lines, at least 5 ϫ 10 5 samples of the liquid density were taken in calculating the average, and the points within 5 Å from the wall and 2 Å from the center axis were neglected in the fitting procedure.…”

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confidence: 99%

Contact angles, ordering, and solidification of liquid mercury in carbon nanotube cavities

Kutana

Giapis

2007

Phys. Rev. B

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Optimized model potentials for mercury-mercury and mercury-carbon interactions are used in molecular dynamics simulations to study wetting and solidification of liquid mercury encapsulated in single-walled carbon nanotubes. The contact angle of mercury in the nanotube cavity increases linearly with wall curvature. The solid-liquid transition becomes less well defined as nanotube diameter decreases, while the melting temperature drops exponentially. A concentric cylindrical-shell structure is predicted for solidified mercury in small ͑20,20͒ nanotubes, while a polycrystalline structure appears in larger ͑40,40͒ nanotubes. DOI: 10.1103/PhysRevB.76.195444 PACS number͑s͒: 65.80.ϩn, 02.70.Ns, 64.70.Dv Liquid mercury does not wet graphite spontaneously. Indeed, fresh mercury forms droplets on highly ordered pyrolytic graphite with a contact angle of 152.5°. 1 Being equivalent to graphene scrolls, carbon nanotubes too cannot be wetted spontaneously by mercury, or for that matter, by any liquid metal with surface tension greater than 180 mN/ m. 2 However, wetting and filling of the inner cavity of a carbon nanotube with mercury have been shown to occur as a result of electrowetting. 3 Continuous columns of liquid mercury form inside carbon nanotubes with their open end immersed into a mercury droplet, following the application of a voltage exceeding a threshold value between the nanotube and the droplet. Once confined in a nanotube cavity, the wetting behavior of a nonwetting fluid becomes of fundamental and practical interest for nanofluidics. Furthermore, studies of freezing or melting transitions of metals under onedimensional confinement could lead to the discovery of new crystalline phases and possibly to the existence of a solidliquid critical point. 4 New solid metal phases could lead to unexpected mechanical, electrical, magnetic, and catalytic properties.Ordering and crystallization of materials in carbon nanotube cavities have attracted intense theoretical interest. New ice phases, including ordered ice nanotubes, were predicted to form by freezing water inside carbon nanotubes. 5 Simulations of CCl 4 in nanotube cavities showed liquid ordering in concentric layers, which solidify into two-dimensional hexagonal crystals unlike those observed for bulk crystallization. 6 Depending on the nanotube diameter, helical-strand, cylindrical-shell, and fcc structures were predicted for Cu and Au confined inside nanotube cavities. 7,8 Experimental evidence for the existence of such new structures in nanotube cavities has been sparse. Using highresolution transmission electron microscopy, Fan et al. 9 demonstrated the formation of a double-strand helix of iodine atoms inside a ͑10,10͒ single-walled nanotube ͑SWCNT͒. In slightly larger SWCNTs, Guan et al. 10 found a new crystalline phase of iodine, in addition to a triple-strand helix. Using x-ray diffraction, Maniwa et al. 11 studied water freezing in SWCNT bundles and found a new peak appearing in the diffraction spectrum at 235 K, which was attributed to the formati...

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Molecular Dynamics Simulation of Contact Angles of Water Droplets in Carbon Nanotubes

Cited by 242 publications

References 22 publications

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

Ferroelectric Ordering in Ice Nanotubes Confined in Carbon Nanotubes

Contact angles, ordering, and solidification of liquid mercury in carbon nanotube cavities

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