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Particle Size Controls on Water Adsorption and Condensation Regimes at Mineral Surfaces.

ABSTRACT: Atmospheric water vapour interacting with hydrophilic mineral surfaces can produce water films of various thicknesses and structures. In this work we show that mineral particle size controls water loadings achieved by water vapour deposition on 21 contrasting mineral samples exposed to atmospheres of up to ~16 Torr water (70% relative humidity at 25?°C). Submicrometer-sized particles hosted up to ~5 monolayers of water, while micrometer-sized particles up to several thousand monolayers. All films exhibited vibrational spectroscopic signals akin to liquid water, yet with a disrupted network of hydrogen bonds. Water adsorption isotherms were predicted using models (1- or 2- term Freundlich and Do-Do models) describing an adsorption and a condensation regime, respectively pertaining to the binding of water onto mineral surfaces and water film growth by water-water interactions. The Hygroscopic Growth Theory could also account for the particle size dependence on condensable water loadings under the premise that larger particles have a greater propensity of exhibiting of surface regions and interparticle spacings facilitating water condensation reactions. Our work should impact our ability to predict water film formation at mineral surfaces of contrasting particle sizes, and should thus contribute to our understanding of water adsorption and condensation reactions occuring in nature.

SUBMITTER: Yesilbas M

PROVIDER: S-EPMC5000481 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Particle Size Controls on Water Adsorption and Condensation Regimes at Mineral Surfaces.

Yeşilbaş Merve M Boily Jean-François JF

Scientific reports 20160826

Atmospheric water vapour interacting with hydrophilic mineral surfaces can produce water films of various thicknesses and structures. In this work we show that mineral particle size controls water loadings achieved by water vapour deposition on 21 contrasting mineral samples exposed to atmospheres of up to ~16 Torr water (70% relative humidity at 25 °C). Submicrometer-sized particles hosted up to ~5 monolayers of water, while micrometer-sized particles up to several thousand monolayers. All film ...[more]

PMID: 27561325

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Project description:The adsorption of amyloidogenic peptides, amyloid beta 1-40 (A?1-40), alpha-synuclein (?-syn), and beta 2 microglobulin (?2m), was attempted over the surface of nano-gold colloidal particles, ranging from d = 10 to 100 nm in diameter (d). The spectroscopic inspection between pH 2 and pH 12 successfully extracted the critical pH point (pHo) at which the color change of the amyloidogenic peptide-coated nano-gold colloids occurred due to aggregation of the nano-gold colloids. The change in surface property caused by the degree of peptide coverage was hypothesized to reflect the ?pHo, which is the difference in pHo between bare gold colloids and peptide coated gold colloids. The coverage ratio (?) for all amyloidogenic peptides over gold colloid of different sizes was extracted by assuming ? = 0 at ?pHo = 0. Remarkably, ? was found to have a nano-gold colloidal size dependence, however, this nano-size dependence was not simply correlated with d. The geometric analysis and simulation of reproducing ? was conducted by assuming a prolate shape of all amyloidogenic peptides. The simulation concluded that a spiking-out orientation of a prolate was required in order to reproduce the extracted ?. The involvement of a secondary layer was suggested; this secondary layer was considered to be due to the networking of the peptides. An extracted average distance of networking between adjacent gold colloids supports the binding of peptides as if they are "entangled" and enclosed in an interfacial distance that was found to be approximately 2 nm. The complex nano-size dependence of ? was explained by available spacing between adjacent prolates. When the secondary layer was formed, A?1-40 and ?-syn possessed a higher affinity to a partially negative nano-gold colloidal surface. However, ?2m peptides tend to interact with each other. This difference was explained by the difference in partial charge distribution over a monomer. Both A?1-40 and ?-syn are considered to have a partial charge (especially ?+) distribution centering around the prolate axis. The ?2m, however, possesses a distorted charge distribution. For a lower ? (i.e., ? <0.5), a prolate was assumed to conduct a gyration motion, maintaining the spiking-out orientation to fill in the unoccupied space with a tilting angle ranging between 5° and 58° depending on the nano-scale and peptide coated to the gold colloid.

Dataset Information

Particle Size Controls on Water Adsorption and Condensation Regimes at Mineral Surfaces.

Publications

Particle Size Controls on Water Adsorption and Condensation Regimes at Mineral Surfaces.

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