Permanent Pattern‐Resolved Adjustment of the Surface Potential of Graphene‐Like Carbon through Chemical Functionalization

Sensing at the Surface of Graphene Field‐Effect Transistors

“…The introduction of such chemical moieties on the graphene surface or edge is often referred to as graphene functionalization. [109,110] Chemical functionalization of graphene is commonly achieved using either covalent [23][24][25][26][27]28] or non-covalent [29][30][31][32] strategies. The resulted graphene materials contain specific recognition moieties for biochemical sensing, but still share, to a large extent, the same carbon honeycomb backbone and the electrical properties, especially the field effect, of graphene.…”

“…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).…”

“…3d). During the electrografting of graphene with 4-nitrobenzene diazonium tetrafluoroborate (4-NBD), [28] bare SiO 2 -supported graphene showed a stronger reactivity with the diazonium salt than graphene resting on OTS-protected SiO 2 (Fig. 3e).…”

“…[22] Additionally, graphene (at least ideal graphene) has a crystal lattice free of dangling bonds and is therefore intrinsically chemically inert. This inertness has been a driving force for the first attempts aiming at biointerfacing graphene with specific recognition moieties, via both covalent [23][24][25][26][27]28] and non-covalent [29][30][31][32] approaches, using different biochemical molecules and chemical treatments.…”

Janus graphene from asymmetric two-dimensional chemistry

“…Physisorption of chemical species on graphene would provide a facile way to alter its electronic properties 12 , however, covalent chemical modification shows a great advantage in achieving permanent stabilisation for long-term usage 13 . Previous attempts towards fundamental research on covalent functionalisation of graphene mainly involved the development of new modification strategies (for example, hydrogenation [14][15][16][17] , fluorination [18][19][20] , chlorination 21,22 , diazotization [23][24][25][26][27] and other cycloaddition reactions [28][29][30][31] ), covalent addition of edge and defects 27,32 , fabrication of chemical superlattices 26,33 and quantum effects in graphene modification 17,34 . Of the various significant research activities on graphene chemistry that have been conducted, nearly no work to date has been focused on the asymmetric chemistry of this ideal 2D atomic crystal via covalently attaching different functional groups on its two faces simultaneously.…”