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Naoyuki Ishida - One of the best experts on this subject based on the ideXlab platform.
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Forces between zinc sulphide surfaces; amplification of the Hydrophobic Attraction by surface charge
Physical chemistry chemical physics : PCCP, 2019Co-Authors: E-jen Teh, Naoyuki Ishida, William Skinner, Drew F. Parsons, Vincent S. J. CraigAbstract:Smooth Zinc Sulphide (ZnS) surfaces were prepared by magnetron sputtering and the interaction forces were measured between them as a function of pH. At the isoelectric point (iep) of pH 7.1 the attractive force was well described by the van der Waals interaction calculated using Lifshitz theory for a layered system. Away from the iep, the forces were fitted using DLVO theory extended to account for surface roughness. At pH 9.8 the surfaces acquire a negative charge and an electrostatic repulsion is evident. Below the iep the surfaces acquire a positive charge leading to electrostatic repulsion. The forces in the range 3.8 5 nm).
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Hydrophobic Attraction Measured between Asymmetric Hydrophobic Surfaces
Langmuir : the ACS journal of surfaces and colloids, 2018Co-Authors: Naoyuki Ishida, Kohei Matsuo, Koreyoshi Imamura, Vincent S. J. CraigAbstract:The interaction forces between silica surfaces modified to different degrees of Hydrophobicity were measured using colloidal probe atomic force microscopy (AFM). A highly Hydrophobic silica particle was prepared with octadecyltrichlorosilane (OTS), and the interaction forces were measured against silica substrates modified to produce surfaces of varying Hydrophobicity. The interaction forces between the highly Hydrophobic particle and a completely hydrophilic silicon wafer surface fitted well to the DLVO theory, indicating that no additional (non-DLVO) forces act between the surfaces. When the silicon wafer surface was treated to produce a contact angle of water on surface of 40°, an additional attractive force that is longer ranged than the van der Waals force was observed between the surfaces. The range and magnitude of the attractive force increase with the contact angle of water on the substrate. Beyond the effect on the contact angle, the hydrocarbon chain length and the terminal groups of Hydrophobic layer on the substrate only have a minor effect on the magnitude of the force, even when the substrate is terminated with polar carboxyl groups, provided the Hydrophobicity of the other surface is high.
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Effect of surface Hydrophobicity on short-range Hydrophobic Attraction between silanated silica surfaces
Advanced Powder Technology, 2015Co-Authors: Yuuhei Soga, Koreyoshi Imamura, Hiroyuki Imanaka, Naoyuki IshidaAbstract:Abstract The interaction forces between silanated silica surfaces without nanobubbles were measured using colloidal probe atomic force microscopy (AFM). To obtain Hydrophobic surfaces without nanobubbles, an aqueous solution was introduced between the surfaces following an exchange process involving several solvents. In the obtained approaching force curves, an attractive force was observed from a distance of 10–20 nm, which is an additional attractive force stronger than typical van der Waals Attractions. When the surface Hydrophobicity decreased, the range of this Attraction decreased slightly; the Attraction disappeared when the surface contact angle was below 90°. In contrast, measurements in the water–ethanol mixtures revealed that the Attraction persisted even when the contact angle was well below 90°. The possible origin of this force was discussed on the basis of the obtained results.
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Effect of Electrolyte and Alcohol in Solution on the Hydrophobic Attraction between Alkoxylated Silica Surfaces
Chemistry Letters, 2012Co-Authors: Naoyuki Ishida, Yasuyuki Kusaka, Hirobumi UshijimaAbstract:The interaction forces between silica surfaces when nanobubbles were removed from the surfaces were measured using an atomic force microscope. In the approaching force curves between the hydrophobi...
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Hydrophobic Attraction between silanated silica surfaces in the absence of bridging bubbles.
Langmuir : the ACS journal of surfaces and colloids, 2012Co-Authors: Naoyuki Ishida, Yasuyuki Kusaka, Hirobumi UshijimaAbstract:The interaction forces between silanated silica surfaces on which there were neither nanobubbles nor a gas phase were measured using colloidal probe atomic force microscopy (AFM). To obtain hydroph...
Vincent S. J. Craig - One of the best experts on this subject based on the ideXlab platform.
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Forces between zinc sulphide surfaces; amplification of the Hydrophobic Attraction by surface charge
Physical chemistry chemical physics : PCCP, 2019Co-Authors: E-jen Teh, Naoyuki Ishida, William Skinner, Drew F. Parsons, Vincent S. J. CraigAbstract:Smooth Zinc Sulphide (ZnS) surfaces were prepared by magnetron sputtering and the interaction forces were measured between them as a function of pH. At the isoelectric point (iep) of pH 7.1 the attractive force was well described by the van der Waals interaction calculated using Lifshitz theory for a layered system. Away from the iep, the forces were fitted using DLVO theory extended to account for surface roughness. At pH 9.8 the surfaces acquire a negative charge and an electrostatic repulsion is evident. Below the iep the surfaces acquire a positive charge leading to electrostatic repulsion. The forces in the range 3.8 5 nm).
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Hydrophobic Attraction Measured between Asymmetric Hydrophobic Surfaces
Langmuir : the ACS journal of surfaces and colloids, 2018Co-Authors: Naoyuki Ishida, Kohei Matsuo, Koreyoshi Imamura, Vincent S. J. CraigAbstract:The interaction forces between silica surfaces modified to different degrees of Hydrophobicity were measured using colloidal probe atomic force microscopy (AFM). A highly Hydrophobic silica particle was prepared with octadecyltrichlorosilane (OTS), and the interaction forces were measured against silica substrates modified to produce surfaces of varying Hydrophobicity. The interaction forces between the highly Hydrophobic particle and a completely hydrophilic silicon wafer surface fitted well to the DLVO theory, indicating that no additional (non-DLVO) forces act between the surfaces. When the silicon wafer surface was treated to produce a contact angle of water on surface of 40°, an additional attractive force that is longer ranged than the van der Waals force was observed between the surfaces. The range and magnitude of the attractive force increase with the contact angle of water on the substrate. Beyond the effect on the contact angle, the hydrocarbon chain length and the terminal groups of Hydrophobic layer on the substrate only have a minor effect on the magnitude of the force, even when the substrate is terminated with polar carboxyl groups, provided the Hydrophobicity of the other surface is high.
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Direct measurement of Hydrophobic forces: a study of dissolved gas, approach rate and neutron irradiation
Langmuir, 1999Co-Authors: Vincent S. J. Craig, Barry W. Ninham, Richard M. PashleyAbstract:Theoretical interpretations of the, as yet, poorly understood long-range Hydrophobic Attraction are briefly reviewed. We report long-range Hydrophobic attractive forces between silica surfaces made Hydrophobic by adsorption of the cationic surfactants cetyltrimethylammonium bromide and cetylpyridinium chloride onto silica surfaces. The effects of dissolved gas, surface approach velocity, and neutron irradiation on the measured interaction have been studied in order to investigate possible non-electrostatic mechanisms for the long-range Hydrophobic Attraction. At large separations the presence of dissolved gas, neutron irradiation, and reduced approach velocities are, in each case, found to result in a stronger Attraction between the Hydrophobic surfaces. These results are consistent with mechanisms related to the metastability of the thin aqueous film separating the approaching Hydrophobic surfaces.
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Study of the Long-Range Hydrophobic Attraction in Concentrated Salt Solutions and Its Implications for Electrostatic Models
Langmuir, 1998Co-Authors: Vincent S. J. Craig, And Barry Ninham, Richard M. PashleyAbstract:Direct force measurements of the interaction between silica surfaces in low concentrations of the soluble cationic surfactant cetyltrimethylammonium bromide reveal a long-range strongly attractive Hydrophobic force extending out to 100 nm. Similar forces observed for cetylpyridinium chloride in 0.1 M electrolyte demonstrate that the Hydrophobic Attraction is undiminished in the presence of concentrated electrolyte. These results are discussed in relation to other investigations of the long-range Hydrophobic Attraction and lead to the conclusion that electrostatic double layer forces are unable to account for these attractive forces.
N. V. Churaev - One of the best experts on this subject based on the ideXlab platform.
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A modified method for computation of contact angles of aqueous electrolyte solutions on quartz
Colloid Journal, 2000Co-Authors: N. V. Churaev, V. D. SobolevAbstract:A modified technique is proposed for computing contact angles of aqueous electrolyte solutions on charged solid surfaces with varying degrees of hydrophilicity. Along with earlier equations for molecular and structural forces, the modified method also uses a more general expression for electrostatic forces, which is not confined to the condition of a low solution concentration. The resultant expression allows us to compute contact angles for aqueous solutions in a wide range of concentrations and pH values. The applicability range is determined for the previously obtained simplified expression describing electrostatic forces in films. An approach to computer search for parameters of structural forces of hydrophilic repulsion and Hydrophobic Attraction in wetting films on the basis of experimental values is developed.
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Prediction of wetting conditions on the basis of disjoining pressure isotherm. Computations
Colloid journal of the Russian Academy of Sciences, 1995Co-Authors: N. V. Churaev, V. D. SobolevAbstract:Computations of the contact angles were performed based on the Frumkin-Derjaguin approach and using disjoining pressure isotherms Π(h) for wetting films. The contact angles were calculated for low-concentration aqueous electrolyte solutions on a quartz surface of different hydrophilicity accounting for the forces of molecular repulsion, electrostatic Attraction, and structural forces. The Π(h) isotherms, thicknesses of equilibrium wetting films h 0 , and equilibrium contact angles Θ 0 as dependent on the difference of film surface potentials Δψ and the magnitude of parameter Kλ characterizing structural forces of hydrophilic repulsion (Kλ > 0) and Hydrophobic Attraction (Kλ 60° are formed due to the forces of Hydrophobic Attraction. The parameters of the forces of Hydrophobic Attraction in aqueous films are close to those for water interlayers between two Hydrophobic surfaces. For contact angles Θ 0 < 40°, a noticeable effect of the forces of electrostatic Attraction takes place. Good wetting of the surfaces is provided by the forces of structural repulsion.
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Hydrophobic forces in colloids and wetting films
Colloid journal of the Russian Academy of Sciences, 1995Co-Authors: N. V. ChuraevAbstract:Structural forces play a predominant role in colloids and wetting films when contact angles characterizing the hydrophilicity of the solid surfaces lie in the range θ 40°. In the first case, forces of hydrophilic structural repulsion are exhibited, while in the second case, forces of Hydrophobic Attraction are revealed. The DLVO theory, which accounts only for molecular and electrostatic forces, may be applied in the intermediate range. Short-range forces of Hydrophobic Attraction are characterized in colloids and wetting films by the same parameters. K and λ. This may be attributed to the fact that at high contact angles wetting films are contiguous (as in colloids), with two Hydrophobic surfaces, i.e., with a substrate and a water-gas interface. It is assumed that similar effects of lyophilic and lyophobic forces may be observed for other polar liquids
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Contact angles and surface forces
Advances in Colloid and Interface Science, 1995Co-Authors: N. V. ChuraevAbstract:Abstract The modern state of the theory of wetting phenomena is considered with special attention to the approach based on the theory of surface forces. Contribution of the effects of molecular, electrostatic and short-range structural forces to wetting films stability and forming contact angles is discussed. The magnitudes of contact angles may be predicted on the basis of isotherms of disjoining pressure of wetting films that include Hamaker constants, electrical potentials of solid-liquid and liquid-gas interfaces, and experimental constants that characterize the structural forces of hydrophilic repulsion and Hydrophobic Attraction. The constants seem to be the same as in the case of interaction of colloidal particles. In the framework of the suggested approach, the influence of surfactants on wetting phenomena was considered.
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On the Relation between Surface Forces and Wetting
Mendeleev Communications, 1994Co-Authors: N. V. ChuraevAbstract:Structural forces play a dominant role in the range of contact angles θ 40° (Hydrophobic Attraction); the intermediate region corresponds to the field of application of the DLVO (Derjaguin–Landau–Verwey–Overbeek) theory. The short-range Hydrophobic forces in the wetting films of water seem to be the same as in colloids; this can be explained by assuming an unstable wetting film to be disposed between two Hydrophobic surfaces: the Hydrophobic solid substrate and the water–air interface.
Neal T. Skipper - One of the best experts on this subject based on the ideXlab platform.
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The aggregation of methane in aqueous solution
Journal of the Chemical Society Faraday Transactions, 1997Co-Authors: Ricardo L. Mancera, A. D. Buckingham, Neal T. SkipperAbstract:Molecular dynamics simulations, 1.0 ns long, of methane particles in water show the existence of a tendency for aggregation of these solutes which increases with temperature in the range 319–351 K. This is measured by a rise in the contact-configuration peak in the methane–methane radial distribution function at the expense of a decrease in the solvent-separated configuration peak. The observed solute–solute interaction reaches a maximum at 351 K before decreasing in magnitude at 358 K. These observations are consistent with an entropy-driven Hydrophobic Attraction.
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Computer simulation of methane—water solutions. Evidence for a temperature-dependent Hydrophobic Attraction
Chemical Physics Letters, 1993Co-Authors: Neal T. SkipperAbstract:Abstract Molecular dynamics simulation has been used to study a system of 256 water molecules and four Lennard-Jones methane molecules at 275, 297 and 317 K. Results are presented for the water—water, water—methane and methane—methane radial distribution functions. These show that on the time scale of the simulations (≈ 150 ps) the tendency for methane particles to aggregate increases with temperature. This behaviour is consistent with an entropically driven Hydrophobic interaction between the solute particles.
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computer simulation of methane water solutions evidence for a temperature dependent Hydrophobic Attraction
Chemical Physics Letters, 1993Co-Authors: Neal T. SkipperAbstract:Abstract Molecular dynamics simulation has been used to study a system of 256 water molecules and four Lennard-Jones methane molecules at 275, 297 and 317 K. Results are presented for the water—water, water—methane and methane—methane radial distribution functions. These show that on the time scale of the simulations (≈ 150 ps) the tendency for methane particles to aggregate increases with temperature. This behaviour is consistent with an entropically driven Hydrophobic interaction between the solute particles.
Vassili Yaminsky - One of the best experts on this subject based on the ideXlab platform.
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Is the long-range Hydrophobic Attraction related to the mobility of Hydrophobic surface groups?
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1997Co-Authors: Hugo K. Christenson, Vassili YaminskyAbstract:Abstract Literature data show that there is a correlation between the lack of stability, as indicated by contact angle hysteresis, of a Hydrophobic surface and the occurrence of a long-range (⩾20 nm) Attraction. In the case of Hydrophobic monolayers adsorbed from solution in situ, it has been shown that a shift of the adsorption/desorption equilibrium on approach of the two surfaces can lead to a long-range Attraction. For those surfaces where no adsorption/desorption equilibrium exists (Langmuir-Blodgett films, silylated surfaces, polymer surfaces), rearrangement or lateral diffusion of surface groups may be possible. If the local density of Hydrophobic groups is adjusted to give a decrease in free energy on approach of two surfaces, the result is an attractive interaction between the surfaces. Surfaces with no mobility of Hydrophobic groups do not give rise to a long-range Attraction, as has been demonstrated experimentally for some polymer surfaces. These ideas explain the occurrence of a long-range Attraction between one Hydrophobic surface and one hydrophilic surface, as well as in nonaqueous solvents.
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Cavitation, polywater and Hydrophobic Attraction by bridging by flimsy shells
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1997Co-Authors: Vassili YaminskyAbstract:An overview of experimental activity in the field of surface forces over the past twenty years reveals a consistent picture of the Hydrophobic phenomenon. Capillary bridging is an important component of the Attraction that operates from large distances. An experimental example is presented that rationalises observations on non-DLVO forces.
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Onset of Hydrophobic Attraction at low surfactant concentrations
Langmuir, 1996Co-Authors: Vassili Yaminsky, C. Jones, F. Yaminsky, Barry W. NinhamAbstract:We report here on the interaction between silica surfaces in a range of CTA+ (cetyltrimethylammonium cation) concentrations up to the point of zero charge (5 × 10-5 M) in a background electrolyte (...
