Two-Dimensional Hierarchical Semiconductor with Addressable Surfaces

Surfaces play a key
role in determining material properties, and
their importance is further magnified in the two-dimensional (2D)
limit. Though monolayers are entirely composed of surfaces, there
is no chemical approach to covalently address them without breaking
intralayer bond. Here, we describe a 2D semiconductor that offers
two unique features among 2D materials: structural hierarchy within
the monolayer and surface reactive sites that enable functionalization.
The 2D semiconductor is composed of a single layer of strongly interconnected
Re6Se8 clusters arranged in an oblique lattice
capped by substitutionally labile Cl atoms. We show that a simple
ligand substitution strategy borrowed from traditional coordination
chemistry can be used to modify the surface of the 2D material while
preserving its internal structure. The potential generality of this
approach establishes a promising route toward multifunctional 2D materials
with tunable physical and chemical properties and may also facilitate
better electrical top contact to 2D semiconductors.