Multilayer Adsorption On Plane Surfaces By Capacity Measurements. I. Adsorption On Glass At High Relative Pressures

Garbatski, U.; Folman, M.

doi:10.1021/j150540a023

Cited by 19 publications

(9 citation statements)

References 1 publication

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“…The thickness d of the water film decreased from 5 to 1.5 nm in the as-grown and the 560 °C annealed crystals, respectively. The as-grown value is in accord with thickness estimations for water surface layers on hydrophilic silica at about 35% relative humidity (2–10 nm). − References and also reported a clear decrease of the film thickness on progressively dehydroxylated silica. As observed in Figure , left, reducing water adsorption affected more pronouncedly to the neck between the spheres (its volume decreased in a factor of 20 after treatment at T a = 560 °C) than to the film around them (with about a 3-fold volume loss).…”

Section: Resultssupporting

confidence: 83%

In Situ Optical Study of Water Sorption in Silica Colloidal Crystals

2012

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We apply a recent optical technique to investigate fundamental water adsorption/desorption phenomena on submicrometer Stöber silica sphere surfaces of varying hydrophilicity. Thermally annealed (partially dehydroxylated) silica colloidal crystals are used as test systems for the sensitivity of their photonic properties to water. The allocation of physisorbed water on the crystal spheres is inferred in situ during water desorption by simple optical spectroscopy. Silica dehydroxylation and water desorption were found to have dissimilar effects on the water distribution, which is therefore unique for each hydrophilicity and hydration state. Physisorbed water in hydrophilic (fully hydroxylated) compacts tended to accumulate between adjacent spheres forming large necks, whereas it distributed more uniformly (small necks) in hydrophobic (dehydroxylated) ones. Counterintuitively, water films on the spheres surface were released faster upon desorption in the case of hydrophilic crystals. With this exception, water desorption was identical irrespective of silica hydroxylation or water content. Remarkably, the separation between spheres in the nonclose-packed crystals exclusively depended on water content and not on hydrophilicity. These results are compatible with water transport from the spheres surface to the necks, which is gradually hindered in hydrophobic crystals. Our method revealed extreme accuracy allowing us to measure nanometer-scale changes like thin surface water films (from 5 to 0 nm) or slight sphere shrinkage upon annealing of less than 2% (4 to 7 nm), which are hardly discernible with other techniques like dynamic light scattering or electron microscopy.

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Section: Resultssupporting

confidence: 83%

In Situ Optical Study of Water Sorption in Silica Colloidal Crystals

2012

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“…However, such a thickness clearly exceeds the literature values: although the possibility of stable multilayer water films has been sufficiently assessed at similar RH s on silica and other hydrophilic surfaces, their thickness was typically ≤1 nm (at most, ca. 2 nm). Nonetheless, such a comparison must be taken with caution since these studies were performed on flat, open surfaces (see discussion in Section ).…”

Section: Exploring the Water In Colloidal Crystalsmentioning

confidence: 97%

Exploration and Exploitation of Water in Colloidal Crystals

2015

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Water on solid surfaces is ubiquitously found in nature, in most cases due to mere adsorption from ambient moisture. Because porous structures have large surfaces, water may significantly affect their characteristics. This is particularly obvious in systems formed by separate particles, whose interactions are strongly influenced by small amounts of liquid. Water/solid phenomena, like adsorption, condensation, capillary forces, or interparticle cohesion, have typically been studied at relatively large scales down to the microscale, like in wet granular media. However, much less is known about how water is confined and acts at the nanoscale, for example, in the interstices of divided systems, something of utmost importance in many areas of materials science nowadays. With novel approaches, in-depth investigations as to where and how water is placed in the nanometer-sized pores of self-assembled colloidal crystals have been made, which are employed as a well-defined, versatile model system with useful optical properties. In this Progress Report, knowledge gained in the last few years about water distribution in such nanoconfinements is gathered, along with how it can be controlled and the consequences it brings about to extract new or enhance existing material functionalities. New methods developed and new capabilities of standard techniques are described, and the water interplay with the optical, chemical, and mechanical properties of the ensemble are discussed. Some lines for applicability are also highlighted and aspects to be addressed in the near future are critically summarized.

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“…On a hydrophilic surface such as glass, a value of ca. 0.3 N m -1 would seem appropriate. , Since we treat relatively large values of macroscopic contact angle, θ o , in this study, the former value would seem more suitable. Taking β 2 ≈ 0.2 and γ = 73 mN m -1 (at ambient temperature), eq 23 sets an upper ratio of h 2 / h 1 for regime 1 of ca.…”

Section: Solution Matchingmentioning

confidence: 99%

Spreading of Water: Condensation Effects

Shanahan

2001

Langmuir

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Although the macroscopic, bulk behavior of liquids wetting (or dewetting) can be adequately explained by viscous flow, the intricate details near the solid/liquid/fluid triple line (TL) are still not totally appreciated.These two aspects correspond to the bases of the hydrodynamic approach and of the molecular kinetics approach, respectively, to explain spreading. We have suggested a complementary model to that of molecular kinetics, based on the modified curvature of a dynamic, wetting meniscus near the TL, which leads to local condensation of vapor from the surrounding atmosphere, further contributing to motion. An earlier paper dealt with liquids whose thin film behavior (i.e., near the TL) is dominated by long-range van der Waals forces. Here, we turn our attention to the spreading of water. Basic equations are modified to allow for non-negligible meniscus slope and then applied to a model for water, consisting of two different, thickness dependent, disjoining pressure isotherms.

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Multilayer Adsorption On Plane Surfaces By Capacity Measurements. I. Adsorption On Glass At High Relative Pressures

Abstract: The adsorption of water vapor at relative pressures from 0.505 to 0.9976 and of isopropyl alcohol from 0.2 to 0.993 on glass plates is measured by change in electrical capacity. Layer thicknesses up to hundreds of A. are found. Experimental details are given.

Cited by 19 publications

References 1 publication

In Situ Optical Study of Water Sorption in Silica Colloidal Crystals

In Situ Optical Study of Water Sorption in Silica Colloidal Crystals

Exploration and Exploitation of Water in Colloidal Crystals

Spreading of Water: Condensation Effects

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