Understanding and controlling the substrate effect on graphene electron-transfer chemistry via reactivity imprint lithography

Graphene has exceptional electronic, optical, mechanical and thermal properties, which provide it with great potential for use in electronic, optoelectronic and sensing applications. The chemical functionalization of graphene has been investigated with a view to controlling its electronic properties and interactions with other materials. Covalent modification of graphene by organic diazonium salts has been used to achieve these goals, but because graphene comprises only a single atomic layer, it is strongly influenced by the underlying substrate. Here, we show a stark difference in the rate of electron-transfer reactions with organic diazonium salts for monolayer graphene supported on a variety of substrates. Reactions proceed rapidly for graphene supported on SiO2 and Al2O3 (sapphire), but negligibly on alkyl-terminated and hexagonal boron nitride (hBN) surfaces, as shown by Raman spectroscopy. We also develop a model of reactivity based on substrate-induced electron–hole puddles in graphene, and achieve spatial patterning of chemical reactions in graphene by patterning the substrate. The chemical modification of graphene is important for its use in many applications. Now it is shown that the reactivity of graphene towards covalent modification varies widely depending on its underlying support substrate, and that the substrate can be patterned to induce spatial control of chemical reactions in graphene.