Differentiating Solvation Mechanisms at Polar Solid/Liquid Interfaces

Abstract

Resonance enhanced second harmonic generation (SHG) has been used to identify solvation mechanisms at different solid/liquid interfaces. Solvation interactions are characterized as being either nonspecific and averaged over the entire solute cavity or specific, referring to localized, directional interactions between a solute and its surroundings. SHG spectra report the electronic structure of solutes adsorbed to silica/organic solvent interfaces, and different solutes are chosen to probe either interfacial polarity or interfacial hydrogen bond donating/accepting opportunities. SHG results show that interfacial polarity probed by p-nitroanisole depends sensitively on solvent structure, whereas hydrogen bonding interactions probed by indoline are insensitive to solvent identity and instead are dominated by the hydrogen bond donating properties of the polar silica substrate. The bulk solvation interactions were modeled with a series of ab initio calculations that characterized solute electronic structure within a dielectric continuum and in the presence of explicit, individual solvent molecules. Collectively, these measurements and calculations create a comprehensive picture of how solvation mechanisms vary at different polar, solid surfaces.

Structure of Liquid Propionitrile at Interfaces. 2. Experiment

“…In the case of propionitrile, specific interactions arise from the polar and hydrogen-bond-donating nature of the silica surface. 37 We can use the amplitudes of the two exponentials in the OKE decays to estimate the thickness of the surface layer with inhibited dynamics (r s ) using the equation 60…”

Unusual Structure and Dynamics at Silica/Methanol and Silica/Ethanol Interfaces—A Molecular Dynamics and Nonlinear Optical Study

“…[23][24][25][26] More recently, VSFS and other 2 nd order nonlinear optical methods have been employed to study molecular-level interactions at buried silica/liquid alcohol interfaces. 20,[27][28][29][30][31][32] Using this surface specific technique, vibrational modes of species in asymmetric environments have been observed and used to discern the structure and organization of interfacial molecules. Of all the short chain alcohols, methanol exhibits the most peculiar behavior, with data from experiments and simulations leading to conflicting descriptions of solvent structure at this solid/liquid interface.…”

In Situ Wettability Investigation of Aging of Sandstone Surface in Alkane via X-ray Microtomography

“…Nevertheless, it was upheld that the distinctive surface behavior and physicochemical properties, which are subject to chain length, make alkanes a suitable organic phase for wetting and two-dimensional ordering studies [2,21,40]. In addition, adsorbed alkane molecules can interact directly with the silica surface as well as adjacent adsorbed molecules [41,42]. Moreover, standard adsorption free energy ∆G • ads of alkanes (for hexane to decane) on silica surface decrease with the increase in chain length in the range of −10 to −25 kJ/mol [43,44].…”