Molecular simulation of water adsorption on hydrophilic and hydrophobic surfaces of silicon: IR-spectral explorations

Molecular-dynamics simulations have been performed for full liquid water adsorbed onto two planar silicon surfaces, with varying hydrogen- and hydroxyl-termination (mimicking different extents of hydrophobicity and hydrophophilicity). It was found that there was water-density ‘ordering’ perpendicular to both surfaces–heavily dependent on the degree of hydrophobicity. The position and the width of the three solvation layers closest to the different surfaces depends, again, on the hydrophobicity of the surface. IR spectra of the first monolayer of adsorbed water indicate similarities to more confined-water dynamical behaviour, but without becoming ice-like. Moving away from the surface, the water behaviour converges on that of liquid water, albeit with some intermediate characteristics; this was seen for both hydro-phobic and –philic surfaces.