Solvation structure of nanoscopic hydrophobic solutes in supercritical water: Results for varying thickness of hydrophobic walls, solute-solvent interaction and solvent density

The solvation behavior of hydrophobic graphite sheets and carbon nanotubes in supercritical water has been studied using molecular dynamics simulations. In particular, the effects of varying solute-water interactions and thickness of solute layers on the wetting and dewetting behavior and solvation structures under supercritical conditions have been investigated. The water density and distributions of hydrogen bonds around these solutes are analyzed and compared for a wide range of supercritical water densities at 673 K and also for ambient water. We found both wetting and drying of confined narrow pore regions of the solutes depending on the surface-solvent interaction potentials. The basic solvation patterns are found to be somewhat similar to that under ambient condition although the details are found to depend on water density and nature of solute-water interactions. The thickness of the walls is found to have only minor effects on the wetting characteristics. (C) 2012 Elsevier B.V. All rights reserved.