Turning Waste into Sensors: Sustainable Pesticide Detection Using Orange Peel-Derived Laser-Induced Graphene

The growing impacts of climate change, combined with the environmental burden of global pollutants such as agricultural pesticides, have intensified the demand for sustainable and innovative technologies for their monitoring and mitigation. In this study, we introduce a low-cost, easy-to-fabricate, and rapid sensor platform utilizing orange peel (OP)an abundant agricultural by-productas a sustainable substrate for the fabrication of laser-induced graphene (LIG). The sensor was designed to detect organophosphate pesticides, namely Malathion and Chlorpyrifos, using electrical impedance spectroscopy (EIS) combined with principal component analysis (PCA) in an electronic tongue sensor array. To improve the structural integrity and reproducibility of the developed sensor, the OP was pretreated with paraffin prior to the laser writing process. Morphological, spectroscopic, and electrical characterizations confirmed the successful formation of conductive graphitic structures. LIG-based devices demonstrated linear sensitivity in the nanomolar range (1 to 20 nmoL^-1) and retained discriminative capability even in complex matrices, such as tap water. The proposed sensor is simple to fabricate, cost-effective, and enables in situ production using waste biomaterials, offering an accessible and environmentally friendly solution for pesticide monitoring.