  The structure of liquid water in the proximity of an interface can deviate
significantly from that of bulk water, with surface-induced structural
perturbations typically converging to bulk values at about ~1 nm from the
interface. While these structural changes are well established it is, in
contrast, less clear how an interface perturbs the dynamics of water molecules
within the liquid. Here, through an extensive set of molecular dynamics
simulations of supercooled bulk and interfacial water films and nano-droplets,
we observe the formation of persistent, spatially extended dynamical domains in
which the average mobility varies as a function of the distance from the
interface. This is in stark contrast with the dynamical heterogeneity observed
in bulk water, where these domains average out spatially over time. We also
find that the dynamical response of water to an interface depends critically on
the nature of the interface and on the choice of interface definition. Overall
these results reveal a richness in the dynamics of interfacial water that opens
up the prospect of tuning the dynamical response of water through specific
modifications of the interface structure or confining material.
