  Freestanding graphene membranes were successfully functionalized with
platinum nanoparticles (Pt NPs). High-resolution transmission electron
microscopy revealed a homogeneous distribution of single-crystal Pt NPs that
tend to exhibit a preferred orientation. Unexpectedly, the NPs were also found
to be partially exposed to the vacuum with the top Pt surface raised above the
graphene substrate, as deduced from atomic-scale scanning tunneling microscopy
images and detailed molecular dynamics simulations. Local strain accumulation
during the growth process is thought to be the origin of the NP
self-organization. These findings are expected to shape future approaches in
developing Pt NP catalysts for fuel cells as well as NP-functionalized graphene
based high-performance electronics.
