Analysis of the influence of dissimilar facets on the
adsorption,
stability, mobility, and reactivity of surface ligands is essential
for designing ligand-coated nanocrystals with optimal functionality.
Herein, para-nitrothiophenol and nitronaphthalene were chemisorbed
and physisorbed, respectively, on Au nanocrystals, and the influence
of different facets within a single Au nanocrystal on ligands properties
were identified by IR nanospectroscopy measurements. Preferred adsorption
was probed on (001) facets for both ligands, with a lower density
on (111) facets. Exposure to reducing conditions led to nitro reduction
and diffusion of both ligands toward the top (111) facet. Nitrothiophenol
was characterized with a diffusivity higher than that of nitronaphthalene.
Moreover, the strong thiol–Au interaction led to the diffusion
of Au atoms and the formation of thiol-coated Au nanoparticles on
the silicon surface. It is identified that the adsorption and reactivity
of surface ligands were mainly influenced by the atomic properties
of each facet, while diffusion was controlled by ligand–metal
interactions.