Interaction of single water molecules with silanols in mesoporous silica

Abstract

Deep Inelastic Neutron Scattering measurements of water confined in mesoporous silica have been carried out. The experiment has been performed at room temperature on dry and on hydrated samples in order to investigate the interaction between the protons and the silanol groups of the confining surface. With this aim we could control the hydration of the pores in such a way as to adsorb 3.0 water molecules per nm(2), corresponding to a 1 to 1 ratio with the silanol groups of the surface. DINS measurements directly measure the mean kinetic energy and the momentum distribution of the protons. A detailed analysis of the hydrated sample has been performed in order to separate the contributions of the protons in the system, allowing us to determine the arrangement of water molecules on the silanol groups. We find that the hydrogen bond of the water proton with the oxygen of the silanol group is much stronger than the hydrogen bonds of bulk water.

Spherical momentum distribution of the protons in hexagonal ice from modeling of inelastic neutron scattering data

“…In recent years, several DINS experiments have addressed the study of bulk water in stable liquid, 7 solid, 8 and supercooled liquid 13,14 phases and in confined geometry. [15][16][17][18] In parallel, novel simulation techniques have been employed to calculate the n(p) using open path integral simulations 19 implemented with first principles molecular dynamics 20 within the path integral Car-Parrinello molecular dynamics (PICPMD) framework. 21 The path integral simulation has access to the three dimensional n( p), and thus provides complementary information to the spherically averaged n(p) obtained via DINS a) Author to whom correspondence should be addressed.…”

Water thermoporosimetry as a tool of characterization of the textural parameters of mesoporous materials

“…Higher pressure exerted on the layers makes them ''ticker'' that lead to the situation that a bigger population of water layer experiences the interaction with silanol groups from pore walls. As it was said before, the hydrogen bond created between the water proton and the oxygen of the silanol group is much stronger than the hydrogen bonds present between molecules of water [32][33][34][35][36]. It means that the more water layers interact with silanols, the bigger the thickness of the non-freezing liquid layer is.…”

“…It is known that the mesoporous materials have abundant number of silanol groups because of the amorphous surface structure; therefore, a large amount of water can be sorbed on them followed by capillary condensation [31]. It is known from the work of Pantalei et al [32] that it is possible to separate the contribution of the protons in the water-mesoporous silica system and thus to determine of the arrangement of water molecules in respect to silanols groups. It is based on their observation that the hydrogen bond created between the water proton and the oxygen of the silanol group is much stronger than the hydrogen bonds present between molecules of bulk water.…”

Dehydration and Rehydration of an Ion-Leachable Glass Used in Glass-Ionomer Cements

“…The reaction with the polyacid solution is likely to promote some formation of silanol groups on the dehydrated glass as the setting reaction proceeds, but this does not result in high strength cements. It is known that silanol groups are able to become involved in a range of hydrogen-bonded environments [25] and also that hydrogen bonds formed by silanol groups with water are stronger than hydrogen bonds in bulk water [26]. However, the fact that they need to be formed in situ within the cement made from dehydrated glass seems to inhibit their usefulness in promoting high strength in the set cement.…”