Noble Gas Provides a Solution to the Synthesis-On-Inert-Surfaces Challenge for Extended Covalent Nanostructures

A key milestone in the field of On-Surface Synthesis (OSS) is the development of generic protocols for covalent coupling on inert surfaces. Typically, metal surfaces are used in OSS, but the strong interactions distort the intrinsic properties of the synthesized nanostructures and therefore compromise their applicability. Inert surfaces, on the other hand, preserve the nanostructures' unique properties, but present challenges during synthesis: Activation energies are generally higher than on metal surfaces, hence thermally activated coupling on inert surfaces is severely hampered by competing premature desorption of the reactants. Using the coupling of 1,3,5-tris(4-mercaptophenyl)benzene (TMB) via carbon-sulfur-carbon thioether bonds, we demonstrate that annealing in a noble gas atmosphere instead of in a vacuum kinetically inhibits desorption. This allows covalent coupling on both inert graphite and even more weakly interacting graphene surfaces. We anticipate generic potential for this approach, with future experiments exploring the expandability of ambient pressure annealing to a portfolio of other coupling protocols.