Chemical reactivity imprint lithography on graphene: Controlling the substrate influence on electron transfer reactions

The chemical functionalization of graphene enables control over electronic properties and interactions with other materials. Graphene's chemical reactivity is strongly influenced by the underlying substrate. In this paper, we show a stark difference in the rate of electron transfer chemistry with aryl diazonium salts on monolayer graphene supported on a broad range of substrates. Reactions proceed rapidly when graphene is on SiO$_{2}$ and Al$_{2}$O$_{3}$ (sapphire), but negligibly on alkyl-terminated and hexagonal boron nitride (hBN) surfaces. The effect cannot be explained by the overall graphene doping levels alone, and can instead be described using a reactivity model accounting for substrate-induced electron-hole puddles in graphene. Raman spectroscopic mapping is used to characterize the effect of the substrates on graphene. Reactivity imprint lithography (RIL) is demonstrated as a technique for spatially patterning chemical groups on graphene by patterning the underlying substrate, and is applied to the covalent tethering of proteins on graphene.