Simultaneous Electrochemical Exfoliation of Graphite and Formation of Azide-Functionalized Graphene Flakes and Their Application in Sensing.

Electrochemical exfoliation has emerged as a facile method for graphene production. This work presents a one-step electrochemical synthesis of bulk azidated graphene by exfoliating graphite foil in a sodium sulfate/sodium azide aqueous solution. This approach circumvents the limitations associated with traditional methods that utilize graphene oxide (GO) as a precursor, which often require subsequent reduction steps that can compromise the electrical conductivity and potentially convert azide groups to amines. Here, we directly introduced azide functionalities onto the graphene surface during the exfoliation process, yielding high quantities of conductive few-layer graphene. To demonstrate the utility of this azidated graphene, we successfully performed copper-(I)-catalyzed alkyne-azide cycloaddition (CuAAC) click chemistry to attach a thiourea-based selector molecule for the selective gas detection of cyclohexanone, a nonexplosive vapor marker. The resulting sensor exhibited a selective response toward cyclohexanone with a low limit of detection of 4.5 ppm. The enhanced affinity for cyclohexanone was attributed to its higher polarizability compared with other volatile organic compounds. This work highlights the advantages of a simple and cost-effective electrochemical route for producing functionalized graphene using click chemistry with preserved electrical conductivity, opening up possibilities for a range of applications that would benefit from a tailored functional surface.