Silica and Related Surfaces: Interactions with Water

Legrand, A.P.

doi:10.1081/e-escs3-120000600

Cited by 2 publications

(4 citation statements)

References 13 publications

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“…Low-temperature spectral analyses of porous silicas indicate a 14–15 Å thick film composed of four to five layers of water molecules on the SiO 2 surface that differs structurally and dynamically from bulk water. − Like all porous silicas, PVG possesses interior and exterior hydroxylated surfaces that interact with water. − Correlating the pore volume in PVG with the weight changes induced by heating indicate two forms of water in the PVG matrix. Pore diameters in PVG range from 30 to 100 Å with the majority having diameters of 65 ± 15 Å. , Assuming a spherical pore with an average radius of 3.25 nm, a 1.4–1.5 nm layer of water on the PVG surface occupies 18.4% of the total pore volume, 144 nm 3 .…”

Section: Discussionmentioning

confidence: 99%

“…Yet, the moles of water present in the samples when the shoulder at 244 nm and the isosbestic points in the NIR become evident is less than that needed for monolayer coverage of PVG and similar to the number of silanol groups on the surface. Hence, the dependence of the NIR absorptions, in particular, on water must arise from interactions of the surface silanol and siloxane functionalities giving rise to the NIR absorptions (Figure ) and the water molecules in the 14–15 Å layer of “nonfreezable” water on the silica surface. − ,,,…”

Section: Discussionmentioning

confidence: 99%

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Photoluminescence of a Porous Vycor Glass; Surface-Enhanced Photocatalyzed Conversion of CO₂ to CH₄

et al. 2019

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Removing water from porous Vycor glass resolves the near-IR (NIR) spectrum revealing that the emissivity of nanoporous silicas derives from two energetically distinct silanol, SiOH(H 2 O) x , and siloxane, SiOSi(H 2 O) y , surface sites. The occurrence of isosbestic points and emission lifetimes independent of a water content implies that these sites do not randomly interact with water but are associated with a specific number of water molecules on the silica surface. Integer relationships between NIR absorptions that are overtones of the SiOH(H 2 O) x and SiOSi(H 2 O) y vibrations and the excitation spectra of the SiOH(H 2 O) x and SiOSi(H 2 O) y fluorescence indicate a facile exchange of electronic and vibrational energy with the majority of the excitation energy stored as O− H vibrational energy in a 14−15 Å layer of water on the silica surface. CO 2 quenches the SiOH(H 2 O) x , and SiOSi(H 2 O) y excited states by a proton transfer mechanism which initiates the CO 2 /CH 4 conversion. Although individual O−H vibrations do not have sufficient energy to promote the more energetic steps in the conversion, higher-order composite overtones indicate the presence of nonlinear processes that promote the transfer of hydrogen atoms and hydride ions from the silica/H 2 O surface sustaining the CO 2 /CH 4 conversion.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Photoluminescence of a Porous Vycor Glass; Surface-Enhanced Photocatalyzed Conversion of CO₂ to CH₄

et al. 2019

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“…Silica becomes charged in contact with an aqueous solution due to the protonation and deprotonation of the surface-exposed oxygen group and hydroxyls . The charged surface attracts electrolyte ions, resulting in an interfacial charge distribution known as the electrical double layer.…”

Section: Materials and Methodsmentioning

confidence: 99%

“…Silica becomes charged in contact with an aqueous solution due to the protonation and deprotonation of the surface-exposed oxygen group and hydroxyls. 33 The charged surface attracts electrolyte ions, resulting in an interfacial charge distribution known as the electrical double layer. The interfacial chemistry of the silica/electrolyte interface is often described using a thermodynamic model based on the assumption that charging and ion accumulations can be described as reactions with a characteristic equilibrium constant, and spatial charge distribution can be compartmented into inner- and outer-Helmholtz layers and a diffuse part.…”

Section: Materials and Methodsmentioning

confidence: 99%

Surface Hydroxylation-Induced Electrostatic Forces Thicken Water Films on Quartz

Cihan,

Zarzycki,

Hao

2024

Langmuir

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Aqueous films on mineral surfaces control the physical, chemical, and biological transport processes in the atmosphere, soil, and rocks. Despite the importance of thin films for various research and engineering fields, there are still unanswered questions regarding the roles of the different forces affecting the nature of water films. One of these, the focus of this study, is the development of abnormally thick water films on quartz surfaces. In this study, we developed a density-functionaltheory-based model to describe the time-dependent evolution of water films and identify the governing forces responsible for thickening films. We simulated the diffusion of water vapor from ambient air toward mineral surfaces and the formation and thickening of water films at various relative humidity values. Our model predicts an abnormal water film thickness on a hydroxylated quartz surface compared to a surface free of hydroxylation, which explains experimental observations. We further used the model to understand the key interaction forces at different stages of water film formation and thickening. Our model suggests that the attractive hydrogen bonding and van der Waals forces initiate a seed layer of water, and the electrostatic forces, generated by the hydroxylated and thus charged surface, lead to the thickening of water films. This generalizable model can provide insights into the peculiarities of water film development on various mineral surfaces.

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Silica and Related Surfaces: Interactions with Water

Cited by 2 publications

References 13 publications

Photoluminescence of a Porous Vycor Glass; Surface-Enhanced Photocatalyzed Conversion of CO₂ to CH₄

Photoluminescence of a Porous Vycor Glass; Surface-Enhanced Photocatalyzed Conversion of CO₂ to CH₄

Surface Hydroxylation-Induced Electrostatic Forces Thicken Water Films on Quartz

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Silica and Related Surfaces: Interactions with Water

Cited by 2 publications

References 13 publications

Photoluminescence of a Porous Vycor Glass; Surface-Enhanced Photocatalyzed Conversion of CO2 to CH4

Photoluminescence of a Porous Vycor Glass; Surface-Enhanced Photocatalyzed Conversion of CO2 to CH4

Surface Hydroxylation-Induced Electrostatic Forces Thicken Water Films on Quartz

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Photoluminescence of a Porous Vycor Glass; Surface-Enhanced Photocatalyzed Conversion of CO₂ to CH₄

Photoluminescence of a Porous Vycor Glass; Surface-Enhanced Photocatalyzed Conversion of CO₂ to CH₄