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 chemicalgroups on graphene by patterning the underlying substrate, and is applied to the covalent tethering of proteins on graphene.

Sensing at the Surface of Graphene Field‐Effect Transistors

“…Instead of providing an extensive list of the methods available to induce such modifications, we will continue with discussing a grafting strategy, frequently applied to covalently attach chemical moieties to graphene surface (or edges) via free-radical reactions. [27,28,109,121,[122][123][124][125] Graphene grafting uses alkyl or aryl diazonium salts as grafting agents, where the diazonium salt precursor is first chemically or electrochemically reduced (liberating nitrogen gas), to form a reactive alkyl or aryl radical that reacts with the aromatic system of the graphene sheet (the conductive channel of the transistor device fabricated on a 200 nm SiO 2 /highly doped Si substrate as shown in Fig. 3c).…”

“…II). The reaction efficiency depends on several parameters: the number of graphene layers, [122] the electrostatic environment, [123] and the defect density on the graphene surface. [124] A previous study exploited the graphene reactivity, induced by electrostatic charge doping on different substrates using reactivity imprint lithography (RIL).…”

“…[124] A previous study exploited the graphene reactivity, induced by electrostatic charge doping on different substrates using reactivity imprint lithography (RIL). [123] The RIL technique made use of a polydimethylsiloxane (PDMS) stamp to pattern octadecyltrichlorosilane (OTS) lines on a SiO 2 /Si substrate (Fig. 3d).…”

“…OTS increases the distance between the graphene sheet and the charged impurities in the SiO 2 substrate, rendering the portion of graphene resting on it less reactive to the 4-NBD. [123] Similarly, in case of GO (or rGO), grafting chemistries are best represented by localized reactivity of the carboxyl, carbonyl, and other oxygen-containing groups by substitution reactions. [124] …”

Structure of graphene and its disorders: a review

“…The asymmetry between the conduction band () and the valence band (), which is especially pronounced in the vicinity of the point, which is attributed to the non-zero overlap parameter . However, the electronic band structure of graphene can be simply altered by applying electric field [6,57–61] or providing substrates [62,63], and precisely engineered by introducing disorders into the hexagonal lattice [64–68], which will be discussed in detail in later sections.…”