Easy-to-prepare graphene-based inkjet-printed electrodes for diclofenac electrochemical sensing

Inkjet-printed electrodes (IPEs) from flexible Kapton® as substrate and easy to prepare graphene oxide (GO)-based inks (K/GO) were prepared using a standard desktop printer. Subsequently, they were submitted to a post-processing thermal treatment (K/GO_TR400) and assessed as disposable working electrodes (WEs) for diclofenac (DCF) indirect electrochemical detection at pH 7.0 (close to physiological pH value). DCF monitoring is attracting much interest, due to its classification as contaminant of emerging concern in water sources. The performance of the printed active sensor material was compared to that of thermally reduced (at 400°C) graphene oxide (TRGO-400, in a powder form), which has been successfully used as glassy carbon electrode (GCE) modifier for the detection of DCF. This electrode worked linearly withing the concentration range between 5–25 µM with an LOD value of 2.25 µM. Moreover, the morphology and chemical composition of the obtained IPEs were characterized by means of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) and compared with GCE/TRGO-400. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements using a miniaturized 3-electrode cell of the post-processed IPEs showed a promising electrochemical performance for DCF sensing. Thus, this study demonstrated the effective partial recovery of the valuable properties of graphene on the IPEs after the thermal treatment and the successful production of flexible and disposable electrodes for target analyte detection. Therefore, this is a promising alternative to conventional modified GCEs, as it offers a facile approach for the fabrication of cutting edge graphene-based electrodes and widens the available portfolio of electrochemical sensors towards detection of water contaminants of emerging concern.