We report the direct exclusive modification of the edge of a single graphene monolayer with nanoparticles or organic functionalities under ambient conditions.

We present here the electrochemistry at a photolithographically created isolated monolayer graphene edge (GrEdge). The millimeter-long GrEdge is found to behave like a nanowire, exhibiting very high mass transport rates, characteristic of nanoelectrodes. Accordingly, the voltammetric response at such electrodes is dictated by the kinetics of heterogeneous electron transfer (HET). We observe high electron transfer rates at GrEdge electrodes, at least 14 cm/s for the outer-sphere probe ferrocenemethanol and 0.06 cm/s or higher for the innersphere probe Fe(CN) 6 3− . Upon selective modification of the edge with gold nanoparticles, the HET is found to be reversible, with the voltammetric curve showing a typical mass-transport-limited Nernstian response for both kinds of probes. Subsequently, the electrodes are evaluated as electrochemical sensors for the detection of reduced form of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD). The nanoscale geometry with a unique diffusional profile of the unmodified GrEdge enables the sensing of NADH down to micromolar concentrations. Taken together, our simple strategy for the realization of graphene edge electrodes enables the availability of a versatile high-aspect one-dimensional nanoelectrode with the capability to study fast electron transfer kinetics. Moreover, such electrodes allow for facile detection of small amounts of electroactive species and hence will find applications in chemical sensing and biosensing.

Electron transfer rates at graphene are found to vary with pH, attributed to electrostatic effects at the graphene-liquid interface.