Biochar copper nanocomposite modified sensor for the green electroanalytical sensing of paraquat

Abstract

Paraquat (PQ) is a widely used herbicide categorized as an environmental contaminant due to its high toxicity and risk to aquatic ecosystems and human health. In this study, we developed a Screen-printed Disposable Polyethylene Terephthalate (SD-PET) sensor using a green sodium alginate/graphite conductive ink. To maximize performance, the electrode surface was modified with a bamboo biochar composite incorporating copper nanoparticles (BC-CuNPs). Under optimized differential pulse voltammetry (DPV) conditions, the BC-CuNPs sensor outperformed the other configurations, displaying excellent linearity for PQ detection from 10 to 250 µmol L−1 (R2 = 0.988), a sensitivity of 0.0234 µA µmol−1 L, and limits of detection (LOD) and quantification (LOQ) of 7.65 µmol L−1 and 25.48 µmol L−1, respectively. Selectivity studies against common aquatic interferents (chloroquine, levofloxacin, and sulfamethoxazole) and tap water assays indicated mild matrix effects, though the device successfully quantified the analyte under competitive conditions. UV–Vis spectrophotometry validated the accuracy of the proposed method as an independent reference technique. Furthermore, the environmental sustainability of the device was quantitatively confirmed by green chemistry metrics, achieving a high AGREE score of 0.71 and a favorable ComplexGAPI profile. Despite presenting a limited shelf life over 21 days, the developed SD-PET/BC-CuNPs sensor stands out as a highly efficient, eco-friendly, and viable alternative for on-site environmental monitoring of paraquat.