In order to improve the sensitivity of electrochemical impedance spectroscopy (EIS)-based biosensors, a number of structuring strategies to promote enlarging the electroactive surface area have been recently proposed. However, these approaches have not been applicable to graphene-based electrodes especially due to their ultrathin film thickness (usually <10 nm) and incompatibility with top-down based structuring methods. To challenge this limitation, in this work, we presented a novel means to increase the electroactive surface area and the sensitivity of graphene electrode-based EIS biosensors with obviation of any extrinsic structuring method, such as patterning or pore generation. Instead, graphene oxide (GO) nanosheets functionalized with octadecylamine (ODA) groups to alter the inter-sheet spacing were synthesized and assembled to stacked films. Then, GO films were thermally reduced to form the roughened surface to maximize the electroactive surface area and sensing sensitivity. As a proof of concept demonstration, the sensing performances of rGO electrodes with differential inter-sheet distance were assessed via EIS measurements for the detection of myoglobin (Mb), a representative biomarker of acute myocardial infarction. Taken together, the deliberate control of the extent of interlayer alkylation of stacked GO nanosheets proved to be an effective strategy to produce rGO electrodes with significantly enhanced and/or controlled surface area, giving rise to a remarkably high sensing performance with the detection limit of 2.37 pM concentration of Mb. The presented strategy is simple yet powerful and widely applicable to various types of target molecules, it is therefore expected to provide general platform for biomedical and environmental sensors.
- Electrochemical impedance spectroscopy
- Graphene oxide
- Inter-sheet distance