Figure 7.

(a) Top view of the cross-section of the water multilayer on the NS model, as obtained from the last snapshot of the DFTB molecular dynamics simulation. Oxygen atoms of the adsorbed water molecules and OH groups are color-coded according to their distance from the closest titanium atom. Titanium, oxygen, and hydrogen atoms of the nanoparticle are shown as cyan, red, and white spheres, respectively. Hydrogen bonds are represented as dashed black lines. (b) Probability distribution P(cos θ) of the angle θ between the O–H bond vector and the vector connecting water O atom to the center of the NS model for the molecules of the water multilayer adsorbed on the NS model within layer I (bottom panel, in black), Layers II and III (as red and violet points, respectively, in the middle panel) and layers IV and V (as green and orange points, respectively, in the top panel). cos θ equals to 1 means that the O–H bond is directed outwards, whereas a value close to −1 means that the O–H bond is oriented toward the center of the nanosphere.