Nanostructured Laser-Induced Porous Graphene Electrochemical Sensor for the Detection of Heavy Metals and Paraquat

Abstract The rapid and reliable detection of toxic contaminants in food and cosmetic products remains challenging because of complex sample matrices and the need for scalable and high-performance electrode materials. Herein, a nanostructured laser-induced porous graphene (LIG) electrode was fabricated directly on a polyimide sheet through a simple, chemical-free single-step CO2 laser-writing process for the electrochemical detection of cadmium (Cd2+), lead (Pb2+), and paraquat (PQ) in two buffer electrolytes with single sensing platform. The laser-writing process generated a three-dimensional porous graphene architecture with interconnected conductive networks, structural defects, and oxygen-containing functional groups, collectively enhancing the electrochemically active surface area and facilitating rapid interfacial electron-transfer kinetics. Using square-wave anodic stripping voltammetry, the LIG electrode enabled simultaneous determination of Cd2+ and Pb2+ over a linear range of 1–6 μM with detection limits of 43.7 and 29.69 nM, respectively. The proposed electrode exhibited satisfactory selectivity for Cd2+ and Pb2+ in the presence of potential interferents. For paraquat, the LIG electrode exhibited a linear response over the concentration range of 5–70 μM with a detection limit of 0.21 μM, together with good selectivity against the investigated ionic and molecular species, reproducibility, and satisfactory long-term stability. The LIG electrode enabled to recover the spiked Cd2+, Pb2+, and PQ in the extracted/digested food and cosmetic samples, using the standard addition method. These findings establish a clear structure–property–performance relationship, demonstrating that chemical-free laser-induced graphitization provides a scalable strategy for fabricating nanostructured graphene electrodes for electrochemical sensing applications in environmental and food safety monitoring.