Local polarity excess at the interface of water with a nonpolar solute

We present the results of numerical simulations of the electrostatics and dynamics of water surrounding Kihara solutes described by a Lennard-Jones layer at the surface of a hard-sphere core. The dipolar response of the hydration layer peaks at the solute surface, significantly exceeding bulk water in polarity. This effect can be observed by atomic force microscopy. The dynamics of water shells are slow close to the surface, but become faster with the growing layer thickness and approach the bulk limit for layers 1 nm thick. Slowing of the inner hydration shells strongly depends on the strength of solute-solvent attraction, offering a possibility of highly heterogeneous interfacial dynamics. (C) 2011 Elsevier B. V. All rights reserved.