Electrophilic radical coupling at the edge of graphene

Abstract

We report the selective functionalization of an edge of graphene via the electrografting of 4-nitrobenzene diazonium tetrafluoroborate. The edge - a single line of carbon atoms - forms during the process of cutting a graphene monolayer with an atomically sharp microtome knife. Embedded in a polymeric matrix, the just cut bare graphene edge efficiently transfers electrons to a ferricyanide probe in solution. By monitoring the electron exchange reactions of the edge upon functionalization, we observe an annihilation of the reduction and oxidation peaks of the ferricyanide probe, characteristic of the formation of a nitroaryl passivation layer on the edge of graphene. For the first time, the chemical state of a single line of carbon atoms is influenced and monitored using an electrochemical cell, therefore bypassing the usual requirements of atomic resolution characterization techniques, which often demand very clean graphene samples and vacuum processing.

Grafting of Diazonium Salts on Surfaces: Application to Biosensors

“…This graphene-edge electrode was modified by electrochemical reduction of 4-nitrobenzenediazonium. The cyclic voltammetry of 4-nitrophenyl films was observed, and the signal of the redox probe Fe(CN) 6 3−/4− was completely inhibited, indicating a blocking of the electrode by the grafted film; this was confirmed by the Raman spectrum that indicated an increase of the D-band [36]. From Reference [31] with permission of Elsevier.…”

pH sensitivity of edge-gated graphene field-effect devices with covalent edge-functionalization

“…31,66 The observed trend of reduction of the magnitude of cathodic current with every CV cycle suggests that the deposition of the diazonium-derived species at the edge gradually passivates the edge, hindering the possibility of electron transfer at the edge. 24,26 We expect that the aminophenyl moieties attach selectively to the edge of the graphene sheet in a covalent manner, since the rest of the graphene surface is passivated by the photoresist. 24 Evidence for this is obtained from Raman spectroscopy and FET data.…”

“…8,[20][21][22] The specialized nature of the monolayer graphene edge has been in the focus of several recent investigations. [23][24][25][26][27][28][29] Since it is not feasible to obtain a free-standing atomic carbon edge, a certain portion of the basal plane needs to be present in order to support the edge. For electrochemical studies in a liquid environment, the capability to address the edge of a single graphene sheet exclusively has been demonstrated in a few occasions.…”

“…For electrochemical studies in a liquid environment, the capability to address the edge of a single graphene sheet exclusively has been demonstrated in a few occasions. [23][24][25][26][27]29 In these works, exclusive exposure of the graphene edge to the electrolyte was achieved by protecting a part of the basal plane (e.g. with a photoresist) and etching or cutting away the remaining open part of the basal plane.…”

Fast Electron Transfer Kinetics at an Isolated Graphene Edge Nanoelectrode with and without Nanoparticles: Implications for Sensing Electroactive Species

“…For example, bulk electrodes have been fabricated with a multitude of graphene edges using edge-plane pyrolytic graphite (EPPG), solution-processed graphene oxide, or multilayer graphene. − The realization of an isolated graphene edge, on the other hand, is not that straightforward since it is important to isolate the effect of the basal plane completely while simultaneously having the capability to address a single sheet. There are a few demonstrations of devices realized based on isolated monolayer graphene edges. − Recently, we demonstrated a photolithographic method to realize single graphene edge (GrEdge) devices by appropriate passivation of the basal plane . The graphene edge in such devices is usually composed of a random mixture of zigzag and armchair configurations.…”