Surface-Induced Anisotropic Orientations of Interfacial Ethanol Molecules at Air/Sapphire(11̅02) and Ethanol/Sapphire(11̅02) Interfaces

Abstract

Sum frequency vibrational spectroscopy was used to study the interfacial arrangement of ethanol 2

Interaction of Water with the Gypsum (010) Surface: Structure and Dynamics from Nonlinear Vibrational Spectroscopy and Ab Initio Molecular Dynamics

“…Indeed, Figure S12 shows the SFG spectra for gypsum (010) at high relative humidity (RH ≈ 98%) recorded with SSP polarization as a function of the azimuthal angle ϕ, demonstrating that the adsorbed water is clearly anisotropic, with the H-bonded OH bands showing a minimum at ϕ ≈ 40° (which is the average direction of these OH groups) and the nearly free OH bands showing a minimum at ϕ ≈ 120°. Similar surface-induced anisotropy of adsorbed ethanol from vapor on the sapphire (11̅02) surface was also observed by SFG spectroscopy . Therefore, the distinct polarization dependence for each OH peak at high RH and their anisotropy indicate that they result from OH groups that have different molecular orientations and H-bonding strengths.…”

“…However, the significant changes in the spectra up to RH ≈ 50% suggest the formation of a monolayer of adsorbed water around that value of RH. Multilayer adsorption in equilibrium with vapor occurs only very close to saturation, 36,80,81 and perhaps a slight change in the SPS and PPP spectra at ϕ = 30°from RH 50% to >90% indicates initial multilayer formation.…”

“…Similar surface-induced anisotropy of adsorbed ethanol from vapor on the sapphire (11̅ 02) surface was also observed by SFG spectroscopy. 81 Therefore, the distinct polarization dependence for each OH peak at high RH and their anisotropy indicate that they result from OH groups that have different molecular orientations and H-bonding strengths. This could not occur if the adsorbed water layer were liquid-like, with high orientational and positional diffusion, suggesting that the adsorbed water layer maintains a good orientational order.…”

“…Only recently did another SFG study identify surface-induced anisotropic ethanol adsorption on the sapphire (11̅ 02) surface at room temperature. 81 Therefore, due to the significant environmental and technological relevance of gypsum, we hope that such detailed information obtained herein about the interaction of gypsum with water adsorbed from vapor at room temperature could be useful to the understanding of several physico-and geochemical processes.…”

Surface-Induced Anisotropic Binding of a Rhenium CO2-Reduction Catalyst on Rutile TiO2(110) Surfaces

“…SFG is thus surface-specific, giving it a distinct advantage over other optical techniques and making it an ideal tool for elucidating a molecular-level picture of structure and dynamics for molecule–semiconductor as well as molecule–metal systems. − Although it is typically used to determine the average molecular tilt angle for molecules on isotropic surfaces, it can also be used to determine the degree of anisotropy in these interfacial systems. Specifically, by monitoring the molecular sum frequency response as a function of the surface azimuthal angle, the anisotropic orientation distribution can be deduced. − …”