Interfacial electrostatic properties and ice nucleation efficiency on functionalized gold surfaces.

Surface properties play a critical role in determining the heterogeneous ice nucleation ability of a material, with important implications for atmospheric processes and climate models. However, understanding how these properties, such as surface chemistry, structure, and morphology, influence ice nucleation is experimentally challenging, as it depends on nanoscale variations that are difficult to control and characterize. To investigate these effects, drop-freezing experiments and scanning Kelvin probe microscopy (SKPM) were performed on atomically flat gold (Au) surfaces functionalized with self-assembled monolayers (SAMs) of alkanethiols (HS-(CH2)n-X) terminating in chemical groups of varying polarity (-NH2, -CONH2, -CH3, -COOH, -OH). The results revealed significant differences in ice nucleation efficiency depending on the terminal functional group, independently of surface wettability. Surface dipoles, inferred from SKPM surface potential measurements, exhibited a strong correlation with ice nucleation efficiency among polar functional groups, regardless of the polarity's sign. These findings offer molecular-level insights into ice nucleation mechanisms and suggest the potential to predict the ice nucleation performance of natural and engineered surfaces based on surface chemical functionality.