Modified laser-induced graphene as scaffold for the sensitive and selective sensing of pharmaceutical products

Diclofenac is a widely used pharmaceutical pollutant that is frequently detected in wastewater and natural waters; however, its reliable on-site quantification remains challenging because of costly instrumentation, labor-intensive sample preparation, and electrodes with limited electron-transfer efficiency. In this study, we report a simple, scalable, and mask-free strategy for constructing high-performance electrochemical electrodes based on laser-induced graphene (LIG) produced by direct laser graphene writing on polyimide. The porous three-dimensional LIG scaffold was subsequently functionalized with Co(II)-chelated graphitic carbon nitride (Co(II)@g-C₃N₄) to introduce redox-active sites and enhance interfacial charge transfer. Structural and electrochemical analyses revealed a seven-fold increase in the electrochemically active surface area and markedly improved heterogeneous electron-transfer kinetics after functionalization. Owing to these synergistic effects, the hybrid LIG electrodes enabled highly sensitive square-wave voltammetric detection of diclofenac over a wide linear range (1–200 μM), with a low detection limit of 0.10 μM (S/N = 3) and two distinct sensitivity regions. The sensor exhibited excellent selectivity toward diclofenac in the presence of common interferents and demonstrated reliable performance in pharmaceutical formulations and spiked human urine samples. This study highlights laser-induced graphene as a versatile and environmentally friendly electrode scaffold for advanced electrochemical sensing platforms in the pharmaceutical and environmental monitoring fields.