Morphology-Controlled Hydration at Gold Nanoparticle Interfaces: Facet-Resolved Structure and Dynamics of Water

Interfacial hydration of gold nanoparticles is an important aspect that can impact adsorption and molecular transport at aqueous interfaces. Nevertheless, the response of water molecules to the evolving ratios of terraces, edges, and vertices of nanoparticles due to variations of particle sizes is insufficiently studied. In this study, molecular dynamics simulations were carried out to investigate the interfacial hydration of three Wulff-cut gold nanoparticles with increasing size. A facet-specific analysis, together with an isolated water reference state and a frustration energy measure, was used to quantify the deviation of hydrated interfacial water from its optimal isolated adsorption state due to constraints imposed by the surrounding solvent network. With increasing nanoparticle size, the surface structure became richer in facets and poorer in edges, thus forming different hydration environments at [111], [100], and edge areas. The extended facets supported more spatially continuous hydration layers, whereas undercoordinated sites locally disrupted water organization. Water motion near the surface was found to be dominantly lateral rather than surface-normal, indicating that nanoparticle morphology guides molecular transport within the hydration layer. These results show that interfacial hydration is governed not only by nanoparticle size, but also by the distribution of specific surface environments. The findings provide a molecular-level description of morphology-dependent hydration at aqueous gold nanoparticle interfaces.