Electrochemical Functionalization of Graphene at the Nanoscale with Self-Assembling Diazonium Salts

Abstract

We describe a fast and versatile method to functionalize high-quality graphene with organic molecules by exploiting the synergistic effect of supramolecular and covalent chemistry. With this goal, we designed and synthesized molecules comprising a long aliphatic chain and an aryl diazonium salt. Thanks to the long chain, these molecules physisorb from solution onto CVD graphene or bulk graphite, self-assembling in an ordered monolayer. The sample is successively transferred into an aqueous electrolyte, to block any reorganization or desorption of the monolayer. An electrochemical impulse is used to transform the diazonium group into a radical capable of grafting covalently to the substrate and transforming the physisorption into a covalent chemisorption. During covalent grafting in water, the molecules retain the ordered packing formed upon self-assembly. Our two-step approach is characterized by the independent control over the processes of immobilization of molecules on the substrate and their covalent tethering, enabling fast (t < 10 s) covalent functionalization of graphene. This strategy is highly versatile and works with many carbon-based materials including graphene deposited on silicon, plastic, and quartz as well as highly oriented pyrolytic graphite.

A Straightforward Approach to Multifunctional Graphene

“…The reactivity of graphene has shown to be strongly correlatedt ot he number of layers constituting each sheet, and it decreases dramatically with the increasing of the number of layers. [2][3][4] For this reason, an extensive varietyo fo rganic reactions has been reported in the literature for monolayered graphene, [4][5][6][7] but not all these reactions can be applied satisfactorily for as cale-upp roduction from bulk graphene. In this context, the reduction of graphite using alkaline metals yielding graphite intercalation compounds (GICs), followedb y the quenching of the intermediatelyg enerated graphenide [8] with electrophiles,i sa na ppropriate alternative to enhance the functionalization degree in bulk graphene dispersions.…”

Functionalization of graphene: does the organic chemistry matter?

“…The diazotization reaction is a widely applied protocol for the functionalization of sp 2 carbon in the graphene sheet [9,46–48]. This phenomenon is desirable due to the commercial accessibility of the reactants (aromatic amines).…”

Bioelectronics and Interfaces Using Monolayer Graphene

“…The controlled patterning of functional groups on graphene has also attracted much attention. As an example, the control of the adsorption and subsequent electrochemical reduction of the aryl diazonium salt with a long aliphatic chain 4‐docosyloxy‐benzenediazonium tetra fluoroborate (DBT) was proposed as a strategy for molecular orientation on graphene . The other important aspect of covalent coupling of molecules on to graphene concerns the possibility to control the local deposition at the basal plane or at the edge of the electrodes for future molecular electronics .…”