Water at the interface with hydrophobic media is of utmost importance in many fields, from the air/water interface playing a key role in atmospheric processes, to the graphene/water interface in electrochemistry, and more generally hydrophobic silica/water interfaces (with low density of silanols) of relevance in geochemistry and pharmaceutical applications, just to cite a few examples.<br/>We provide a full rationalization of the molecular arrangement of water at the interface with different hydrophobic media, by coupling Density Functional Theory (DFT) based Molecular Dynamics simulations (DFT-MD) and vibrational Sum Frequency Generation Spectroscopy (vSFG). We have shown in our recent work [J. Phys. Chem. Lett. 8:3133 (2017)] the existence of a very specific 2-Dimensional H-Bond network (denoted 2DN afterwards) made by the water molecules at the interface with air. All water molecules located in the topmost layer at the interface with the air are connected within a H-Bond network parallel to the water surface. Once the 2DN structure is unraveled, many specific structural (water density, orientation), physical (surface potential, surface tension, vSFG response) and chemical (charge separation at recombination, proton trapping and proton hopping) properties of the air/water interface could be rationalized. We have unraveled the same 2DN at the water/α(0001)-Alumina interface.<br/>In this presentation, we will review these works and more recent works at several mineral/water interfaces where we show how and why the structural organization of interfacial water evolves from a very organized 2-Dimensional network to other organized/less organized networks, depending on the hydrophobicity/hydrophilicity properties of the mineral surfaces.

Hydrophobic aqueous interfaces by DFT-MD simulations and vSFG: 2-dimentional H-bond networks

255th National Meeting (2018)

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