Switching between Boosting and Suppression of Sensitivity and Selectivity of Inkjet-Printed Graphene Electrodes for Biomolecule Detection

Sensitivity and selectivity are key parameters for electrochemical sensors, typically dictated by the properties of the sensing electrode's surface. Here, we demonstrate for the first time that the enhancement of both parameters for detecting surface-sensitive analytes can be repeatedly switched "on" and "off" on-demand by applying defined rapid and simple heating protocols to inkjet-printed graphene electrodes. Electroactive benchmark probes, which provide different interaction mechanisms with graphene surfaces are applied to characterize both electrodes. The voltammetric detection of uric acid (UA) with switched-on electrodes culminates in a more than 60-fold lower detection limit (0.39 µM) and 60-fold higher sensitivity (34.4 mA cm^-2 mm^-1) compared to the one switched-off, offering optimal sensing characteristics at low concentrations. Excellent selectivity is demonstrated for multi-component mixtures of UA, ascorbic acid (AA), dopamine (DA) and xanthine (XA). In contrast, switched-off electrodes provide reproducible signals and a wide linear range at high concentrations, complementing the switched-on electrodes for applications where high concentrations are of interest. Spectroscopy and scanning probe microscopy techniques are applied to correlate the reversible surface modifications with the observed differences in the electrochemical performances. Finally, as practical advantage of the enhancement effect, the detection of electrochemically redox markers for viable bacterial cells is presented. The reproducible large-scale production of disposable graphene electrodes, coupled with the ability to modulate quickly and simply the electrochemical performance on request offers great opportunities for a broad range of electrochemical applications.