Fig. 5.

Density fluctuations and cavity formation at different interfaces. (A) Probability distributions of number of heavy atoms in 3.3 Å-radius spherical volumes in bulk water and near interfaces. (B) The excess chemical potential of a methane-sized WCA solute normal to the surface, relative to that in the bulk. Curves are translated horizontally, such that minimum is at z* = 0. This corresponds to the solute being in contact with SAM, and SAM density being roughly 5% of its bulk density. This latter criterion was used for −OH and −CONH₂ surfaces, for which a minimum is not observed. (C and D) The excess chemical potential of repulsive WCA (58) solutes of different sizes (σ = 0.25, 0.373, 0.560, 0.746, and 0.932 nm) relative to its value in bulk water as a function z at hydrophobic −CF₃ and hydrophilic −CONH₂ interfaces, respectively. The arrow points to increasing solute size. The curves are translated horizontally as above.