The role of adsorption compression in nanocapillarity

Aranovich, G. L.; Donohue, Marc D.

doi:10.1016/j.jcis.2005.05.045

Cited by 11 publications

(7 citation statements)

References 46 publications

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“…One of possible effects which will require additional investigation is possible adsorbent expansion/ contraction caused by both pressure variation and interaction of the solid with the sorbed fluid. 28…”

Section: ■ Results and Discussionsupporting

confidence: 91%

Direct Measurements of Pore Fluid Density by Vibrating Tube Densimetry

et al. 2012

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The densities of pore-confined fluids were measured for the first time by means of vibrating tube densimetry (VTD). A custom-built high-pressure, high-temperature vibrating tube densimeter was used to measure the densities of propane at subcritical and supercritical temperatures (between 35 and 97 °C) and carbon dioxide at supercritical temperatures (between 32 and 50 °C) saturating hydrophobic silica aerogel (0.2 g/cm(3), 90% porosity) synthesized inside Hastelloy U-tubes. Additionally, supercritical isotherms of excess adsorption for CO(2) and the same porous solid were measured gravimetrically using a precise magnetically coupled microbalance. Pore fluid densities and total adsorption isotherms increased monotonically with increasing density of the bulk fluid, in contrast to excess adsorption isotherms, which reached a maximum and then decreased toward zero or negative values above the critical density of the bulk fluid. The isotherms of confined fluid density and excess adsorption obtained by VTD contain additional information. For instance, the maxima of excess adsorption occur below the critical density of the bulk fluid at the beginning of the plateau region in the total adsorption, marking the end of the transition of pore fluid to a denser, liquidlike pore phase. Compression of the confined fluid significantly beyond the density of the bulk fluid at the same temperature was observed even at subcritical temperatures. The effect of pore confinement on the liquid-vapor critical temperature of propane was less than ~1.7 K. The results for propane and carbon dioxide showed similarity in the sense of the principle of corresponding states. Good quantitative agreement was obtained between excess adsorption isotherms determined from VTD total adsorption results and those measured gravimetrically at the same temperature, confirming the validity of the vibrating tube measurements. Thus, it is demonstrated that vibrating tube densimetry is a novel experimental approach capable of providing directly the average density of pore-confined fluids, and hence complementary to the conventional gravimetric or volumetric/piezometric adsorption techniques, which yield the excess adsorption (the Gibbsian surface excess).

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Section: ■ Results and Discussionsupporting

confidence: 91%

Direct Measurements of Pore Fluid Density by Vibrating Tube Densimetry

et al. 2012

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“…It has been shown that this model enables reasonable predictions in the framework of the grand canonical ensemble and yields a simple analytical solution [12]. Also it still includes the essential physics and, hence, can illustrate qualitatively the important elements of the behavior of molecules between walls, including the relation between molecular compression and oscillation of adhesive force.…”

Section: Grand Canonical Ensemble For Molecules In Nanoconfinementmentioning

confidence: 95%

“…(10) contains not only a linear term in 1/r, but also a quadratic one, 1/r 2 , which can make this approximation more accurate at small r. Equation (10) takes into account Laplace's pressure, but ignores adsorption compression which becomes significant in the limit of small r (in nanocapillaries) [12]. As at a very small radius of capillary, the strong attraction to the walls causes liquid molecules to compress and attain higher densities than that of the bulk phase.…”

Section: The Kelvin Equation For a Compressible Liquid In A Capillarymentioning

confidence: 99%

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Generalization of Kelvin's equation for compressible liquids in nanoconfinement

Chen

Wetzel

Aranovich

et al. 2006

Journal of Colloid and Interface Science

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“…polymers compared to the microporous equivalents [132] . Therefore, the contribution of capillary adsorption to moisture sorption becomes very significant in nanocapillaries [133] , especially where interactions between the liquid-solid interface are stronger than the liquid-liquid interface interactions [134] . The effects of P / P 0 , temperature, and pore geometry were also investigated for argon, krypton, and nitrogen that were confined in porous silica materials.…”

Section: Figurementioning

confidence: 99%

Why is the nanoscale special (or not)? Fundamental properties and how it relates to the design of nano-enabled drug delivery systems

Otto

Villiers

2013

Nanotechnology Reviews

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Why is the nanoscale special (or not) ?Fundamental properties and how it relates to the design of nano-enabled drug delivery systems Abstract: Nanoscience studies describe natural phenomena at the submicron scale. Below a critical nanoscale limit, the physical, chemical, and biological properties of materials show a marked departure in their behavior compared to the bulk. At the nanoscale, energy conversion is dominated by phonons, whereas at larger scales, electrons determine the process. The surface-to-volume ratio at the nanoscale is immense, and interfacial interactions are markedly more important than at the macroscopic level, where the majority of the material is shielded from the surface. These properties render the nanoparticles to be significantly different from their larger counterparts. Nano-enabled drug delivery systems have resulted from multidisciplinary cooperation aimed at improving drug delivery. Significant improvements in the thermodynamic and delivery properties are seen due to nanotechnology. Hybrid nanodelivery systems, i.e., membranes with nanopores that can gate stimuli-responsive drug release could be a future development. Nanotechnology will improve current drug delivery and create novel future delivery systems. The fundamental properties and challenges of nanodelivery systems are discussed in this review.

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The role of adsorption compression in nanocapillarity

Cited by 11 publications

References 46 publications

Direct Measurements of Pore Fluid Density by Vibrating Tube Densimetry

Direct Measurements of Pore Fluid Density by Vibrating Tube Densimetry

Generalization of Kelvin's equation for compressible liquids in nanoconfinement

Why is the nanoscale special (or not)? Fundamental properties and how it relates to the design of nano-enabled drug delivery systems

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