The Silica-Water Interface: How the Silanols Determine the Surface Acidity and Modulate the Water Properties

Autoren

Marialore Sulpizi
Marie-Pierre Gaigeot
Michiel Sprik

DOI

10.1021/ct2007154

eISSN

1549-9626

ISSN

1549-9618

Ausgabe der Veröffentlichung

3

Zeitschrift

Journal of Chemical Theory and Computation

Sprache

en

Online publication date

2012

Paginierung

1037 - 1047

Datum der Veröffentlichung

2012

Status

Published

Herausgeber

American Chemical Society (ACS)

Herausgeber URL

http://dx.doi.org/10.1021/ct2007154

Datum der Datenerfassung

2023

Titel

The Silica–Water Interface: How the Silanols Determine the Surface Acidity and Modulate the Water Properties

Ausgabe der Zeitschrift

8

Datenquelle: Crossref

Abstract

Silica is the most abundant metal oxide and the main component of the Earth's crust. Its behavior in contact with water plays a critical role in a variety of geochemical and environmental processes. Despite its key role, the details of the aqueous silica interface at the microscopic molecular level are still elusive. Here we provide such a detailed understanding of the molecular behavior of the silica-water interface, using density functional theory based molecular dynamics (DFTMD) simulations, where a consistent treatment of the electronic structure of solvent and surface is provided. We have calculated the acidity of the silanol groups at the interface directly from the DFTMD simulations, without any fitting of parameters to the experimental data. We find two types of silanol groups at the surface of quartz: out-of-plane silanols with a strong acidic character (pKa = 5.6), which consequently results in the formation of strong and short hydrogen bonds with water molecules at the interface, and in-plane silanols with a pKa of 8.5, forming weak hydrogen bonds with the interfacial water molecules. Our estimate of the quartz point of zero charge (1.0) is found in good agreement with the experimental value of 1.9. We have also shown how the silanols orientation and their hydrogen bond properties are responsible for an amphoteric behavior of the surface. A detailed analysis has identified two species of adsorbed water molecules at the solid-liquid interface, which using the language of vibrational spectroscopy can be identified as "liquid-like" and "ice-like" water or, in other words, water molecules forming respectively weak and strong H-bonds with the oxide surface. These two populations of water are in turn responsible for two distinct peaks in the infrared spectrum of interfacial water and thus provide a molecular explanation of the experimental sum frequency generation spectrum recorded in the literature. In the specific case of quartz, we show that the liquid-/ice-like behavior is the result of the silanol groups ability to donate or accept hydrogen bonds with different strengths, which consequently modulates the vibrational properties of the adsorbed water layer.

Addresses

Johannes Gutenberg University , Staudinger Weg.7, D 55099, Mainz, Germany.

Autoren

Marialore Sulpizi
Marie-Pierre Gaigeot
Michiel Sprik

DOI

10.1021/ct2007154

eISSN

1549-9626

Externe Identifier

PubMed Identifier: 26593364

Funding acknowledgements

Engineering and Physical Sciences Research Council: EP/F038356/1

Open access

false

ISSN

1549-9618

Ausgabe der Veröffentlichung

3

Zeitschrift

Journal of chemical theory and computation

Sprache

eng

Medium

Print-Electronic

Online publication date

2012

Paginierung

1037 - 1047

Datum der Veröffentlichung

2012

Status

Published

Datum der Datenerfassung

2015

Titel

The Silica-Water Interface: How the Silanols Determine the Surface Acidity and Modulate the Water Properties.

Sub types

Journal Article

Ausgabe der Zeitschrift

8

Datenquelle: Europe PubMed Central

Abstract

Silica is the most abundant metal oxide and the main component of the Earth's crust. Its behavior in contact with water plays a critical role in a variety of geochemical and environmental processes. Despite its key role, the details of the aqueous silica interface at the microscopic molecular level are still elusive. Here we provide such a detailed understanding of the molecular behavior of the silica-water interface, using density functional theory based molecular dynamics (DFTMD) simulations, where a consistent treatment of the electronic structure of solvent and surface is provided. We have calculated the acidity of the silanol groups at the interface directly from the DFTMD simulations, without any fitting of parameters to the experimental data. We find two types of silanol groups at the surface of quartz: out-of-plane silanols with a strong acidic character (pKa = 5.6), which consequently results in the formation of strong and short hydrogen bonds with water molecules at the interface, and in-plane silanols with a pKa of 8.5, forming weak hydrogen bonds with the interfacial water molecules. Our estimate of the quartz point of zero charge (1.0) is found in good agreement with the experimental value of 1.9. We have also shown how the silanols orientation and their hydrogen bond properties are responsible for an amphoteric behavior of the surface. A detailed analysis has identified two species of adsorbed water molecules at the solid-liquid interface, which using the language of vibrational spectroscopy can be identified as "liquid-like" and "ice-like" water or, in other words, water molecules forming respectively weak and strong H-bonds with the oxide surface. These two populations of water are in turn responsible for two distinct peaks in the infrared spectrum of interfacial water and thus provide a molecular explanation of the experimental sum frequency generation spectrum recorded in the literature. In the specific case of quartz, we show that the liquid-/ice-like behavior is the result of the silanol groups ability to donate or accept hydrogen bonds with different strengths, which consequently modulates the vibrational properties of the adsorbed water layer.

Autoren

Marialore Sulpizi
Marie-Pierre Gaigeot
Michiel Sprik

Autoren-URL

https://www.ncbi.nlm.nih.gov/pubmed/26593364

DOI

10.1021/ct2007154

ISSN

1549-9618

Ausgabe der Veröffentlichung

3

Zeitschrift

J Chem Theory Comput

Sprache

eng

Country

United States

Paginierung

1037 - 1047

Datum der Veröffentlichung

2012

Status

Published

Datum, an dem der Datensatz öffentlich gemacht wurde

2015

Titel

The Silica-Water Interface: How the Silanols Determine the Surface Acidity and Modulate the Water Properties.

Sub types

Journal Article

Ausgabe der Zeitschrift

8

Datenquelle: PubMed

The Silica-Water Interface: How the Silanols Determine the Surface Acidity and Modulate the Water Properties

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