Direct and quantitative AFM measurements of the concentration and temperature dependence of the hydrophobic force law at nanoscopic contacts

Stock, Philipp; Utzig, Thomas; Valtiner, Markus

doi:10.1016/j.jcis.2015.01.032

Cited by 55 publications

(54 citation statements)

References 47 publications

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“…l Hy for hydrophobic surfaces is expected to be between 3 to 10 Å; 27 Stock et al showed that it is close to 7.2 AE 1.2 Å. 21 Our findings of l Hy = 7 to 8 Å for the hydrophobic region of X SO 3 H o 0.4 compare well to the literature values. In the intermediate region, i.e.…”

Section: Nanoscale Surface and Solvent Characteristicssupporting

confidence: 86%

“…In our previous work with longer hydrocarbon chains, we recorded weak repulsive contributions within the attractive regime, albeit not as pronounced an effect as reported here. 21 Similar short-range hydrophobic repulsion has been recently observed in experiments probing the hydrophobic force of diamond-like carbon. 24 Fig .…”

Section: Nanoscale Surface and Solvent Characteristicssupporting

confidence: 67%

“…As a result, the F-D characteristics switch from attractive to repulsive due to steric hydration repulsion originating from strongly surface-bound molecules, which can be described by an extended DLVO Hydra model (eqn (1)). [20][21][22][23] This approach includes van der Waals (vdW) attraction, electrostatic double layer repulsion, and an additional hydration interaction parameter (Hy):…”

Section: Nanoscale Surface and Solvent Characteristicsmentioning

confidence: 99%

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Characterizing the hydrophobic-to-hydrophilic transition of electrolyte structuring in proton exchange membrane mimicking surfaces

Ostertag

Ling

Domke

et al. 2018

Phys. Chem. Chem. Phys.

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The surface density of charged sulfonic acid head groups in a perfluorosulfonic acid (PFSA) proton exchange membrane determines the hydrophilicity of the ionic channels and is thus critical for the structuring and transport of water and protons. The mechanism through which the head group density affects the structuring of water and ions is unknown, largely due to experimental challenges in systematically varying the density in an appropriate model system resembling the ionic channels. Here, we present a model system for PFSA membrane ionic channels using self-assembled monolayers with a tunable surface density of sulfonic acid and methyl groups to tune surface hydrophilicity. Atomic force microscopy force-distance measurements were used to quantify the hydration forces and deduce the interfacial electrolyte structure. The measured force profiles indicate a pronounced change of the electrolyte layering density at the surface with an unexpectedly sharp hydrophobic-to-hydrophilic transition when the surface shows a contact angle of ∼37°. Using an extended Derjaguin-Landau-Verwey-Overbeek model including the Hydra force, we quantify diffuse double layer charges and characteristic hydration lengths as a function of sulfonic acid group density on the surface. Translating our results to PFSA membranes, these findings have two implications: (1) the density of sulfonic acid head groups can have a dramatic effect on the local solvent structuring of water inside the ionic channels and (2) they support a view where two types of water (solution) exist in PFSA ionic channels - a structured (shell/surface) and a non-structured (bulk) water. This offers an interesting perspective on how different head group densities lead to changes in water and proton transport and macroscopic membrane conductivity properties based on hydration layer characteristics.

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Section: Nanoscale Surface and Solvent Characteristicssupporting

confidence: 86%

Section: Nanoscale Surface and Solvent Characteristicssupporting

confidence: 67%

Section: Nanoscale Surface and Solvent Characteristicsmentioning

confidence: 99%

See 1 more Smart Citation

Characterizing the hydrophobic-to-hydrophilic transition of electrolyte structuring in proton exchange membrane mimicking surfaces

Ostertag

Ling

Domke

et al. 2018

Phys. Chem. Chem. Phys.

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“…Several groups have studied the effect of surface temperature on the equilibrium contact angles either experimentally 12 – 16 , or even using molecular dynamic simulations 17 – 20 . However, there is still some disagreement between the authors about the dependency of the equilibrium contact angle on the system temperature for a given system pressure.…”

Section: Introductionmentioning

confidence: 99%

A new model to predict the influence of surface temperature on contact angle

Villa

Marengo

Coninck

2018

Sci Rep

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The measurement of the equilibrium contact angle (ECA) of a weakly evaporating sessile drop becomes very challenging when the temperatures are higher than ambient temperature. Since the ECA is a critical input parameter for numerical simulations of diabatic processes, it is relevant to know the variation of the ECA with the fluid and wall temperatures. Several research groups have studied the effect of temperature on ECA either experimentally, with direct measures, or numerically, using molecular dynamic simulations. However, there is some disagreement between the authors. In this paper two possible theoretical models are presented, describing how the ECA varies with the surface temperature. These two models (called Decreasing Trend Model and Unsymmetrical Trend Model, respectively) are compared with experimental measurements. Within the experimental errors, the equilibrium contact angle shows a decrease with increasing surface temperatures on the hydrophilic surface. Conversely the ECA appears approximately constant on hydrophobic surfaces for increasing wall temperatures. The two conclusions for practical applications for weakly evaporating conditions are that (i) the higher the ECA, the smaller is the effect of the surface temperature, (ii) a good evaluation of the decrease of the ECA with the surface temperature can be obtained by the proposed DTM approach.

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“…[9]), with a thickness of 0.7 nm suggested as an average [9,132]. A simple weighted average of the viscosity is shown to agree well with the numerical results: Although a conclusive law for hydrophobic interactions is yet to be achieved [286], an exponentially decaying behaviour is usually observed in direct measurements [287][288][289]. There has been also a longlasting debate on the range of hydrophobic interactions.…”

Section: Variation Of Viscosity µsupporting

confidence: 53%

Pore-scale investigation of complex flow behaviour in porous media

Aminpour¹

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Fluid flow in porous media has been studied extensively across a wide range of disciplines. Numerous natural and artificial systems are controlled or affected by flow in various porous media: for example, seepage flow in soil, the multi-phase flow of oil-gas-water in oil reservoirs, contaminant transport within groundwater and solute movement through biological tissues. While the pore-scale flow behaviours are dominating transport mechanisms, the knowledge in this scale is not comprehensive particularly in complex flow regimes. This study, through novel numerical approaches alongside with experiments in same scales, provides contributions to knowledge to understand the behaviours of flow in dynamic porous media, interfacially active (wettable/non-wettable media), and oscillatory boundary conditions. Unexpected rate-dependent local flow anomalies in form of rotational and counter-currents in porous media within the Darcy regime identified using Particle Image Velocimetry experiments raised the main question of this study: Is a variable tortuosity (pore-flow structure) possible for Darcy flow? The question stimulates more attention when considering that the accepted permeability models (e.g Kozeny-Carman) attribute a constant permeability to a constant flow micro-structure (pore streamlines). To explore the feasibility of such behaviours, we portrayed a set of scenarios based on the properties of the mentioned PIV experiments which were performed using a) deformable and b) super-hydrophilic hydro-gel beads comprising the particulate porous media in a flow system suspected as c) fluctuating head boundary conditions. The research plan is then defined so that with a systematic study of the following three areas, the main research question can be resolved: a) the effects of non-fixed (dynamic) Financial support This research was funded by the Australian Research Council via the Discovery Projects ('DPI120102188: Hydraulic erosion of granular structures: experiments and computational simulations' and 'DP140100490').

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Direct and quantitative AFM measurements of the concentration and temperature dependence of the hydrophobic force law at nanoscopic contacts

Cited by 55 publications

References 47 publications

Characterizing the hydrophobic-to-hydrophilic transition of electrolyte structuring in proton exchange membrane mimicking surfaces

Characterizing the hydrophobic-to-hydrophilic transition of electrolyte structuring in proton exchange membrane mimicking surfaces

A new model to predict the influence of surface temperature on contact angle

Pore-scale investigation of complex flow behaviour in porous media

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