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

Abstract

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.

Highly Durable Graphene Monolayer Electrode on Insulating Substrate under Long-term Hydrogen Evolution Cycling

“…It is known in carbon research that the preparation of the electrode has a strong effect on the ensuing electrochemical characteristics. 17,24,25 This is in contrast to non-crystalline metal electrodes, where polycrystalline or amorphous planar electrodes give similar electrochemical behavior rather independent of the preparation strategy. This work underlines the necessity to perform sample preparation carefully in order to assess the maximum achievable performance.…”

Graphene‐Mercury‐Graphene Sandwich Electrode for Electroanalysis

“…Monolayer graphene electrodes on Si/SiO 2 substrates with pre‐patterned metal contacts were prepared as outlined in our earlier works [3a,d] . (see Figure S1 in supporting information (SI) and experimental section for details).…”

“…However, the potential range on the cathodic side is limited due to oxygen reduction and hydrogen evolution reactions at the carbon surface. Chemical modification of graphene is being widely pursued to modify the electrochemical characteristics [3a,6] . For example, deposition of metal nanoparticles may impart improved electrocatalytic activity in carbon electrodes [7] .…”

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

“…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.…”