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

Abstract

The chemical functionalization of graphene enables control over electronic properties and sensor recognition sites. However, its study is confounded by an unusually strong influence of 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 is contrary to expectations based on doping levels 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. of graphene chemical reactivity. This method allows chemical reactions on graphene to be spatially patterned over large areas without the use of disruptive resist materials or etchants. We use RIL to spatially control the conjugation of enhanced green fluorescent protein (EGFP) on graphene directly from solution,