Atomistic Simulations of the Surface Coverage of Large
Gold Nanocrystals
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Abstract
Here, the adsorption of alkanethiols
(from ethane to dodecanethiol)
on icosahedral gold nanocrystals with diameters up to 10 nm is studied
by molecular dynamics simulations in a vacuum. The surface coverage
of the nanocrystals obtained in the simulations is in good agreement
with experimental data. We show that the average surface per adsorbed
thiol does not markedly depend on the nanocrystal size and ligand
and is only about 10% lower than the value observed on a flat Au(111)
surface. We observe two different molecular organizations of the thiolates
on the edges and in the centers of the nanocrystal facets. The incompatibility
between both organizations explains the fact that the formation of
self-assembled monolayers usually observed on flat Au(111) surfaces
is hindered for nanocrystals smaller than 6 nm. We also show that
the organization of thiolates on the edges is at the origin of the
lower average surface per adsorbed thiol found for the nanocrystal