Crafting 3D Hierarchical NiO@MXene Derived TiO ₂ /Graphene Heterostructured Electrode for Ultrasensitive Paraquat and Heavy Metal Detection

Abstract The fabrication of electrochemical sensing electrode with high sensitivity is vital for environmental monitoring of toxic contaminants in water and food sources. Here, a 3D hierarchical NiO@MXene derived TiO ₂ /graphene (NMG) heterostructured electrode is developed using laser writing technique. The NMG heterostructured electrode is employed for voltammetric detection of both pesticide and heavy metals. For pesticide detection, NMG is employed to monitor paraquat (PQ) in 0.1 m phosphate buffer using stripping voltammetry, achieving a remarkable limit of detection of 0.0092 µ m under optimized conditions. Its practical applicability is demonstrated by successfully detecting PQ in real samples of aqueous coriander leaf extract. Interestingly, NMG exhibits high selectivity, repeatability, and reproducibility, highlighting its potential as a robust electrode for PQ detection. Furthermore, NMG facilitates individual and simultaneous detection of heavy metals, including Cd ²⁺ , Pb ²⁺ , Cu ²⁺ , and Hg ²⁺ with detection limits as 0.0036, 0.0018, 0.0043, and 0.0027 µ m , respectively, in the 0.1−2 µ m range using 0.1 m acetate buffer solution. The synergistic material combination with their complimentary physicochemical properties of NMG significantly enhance the electrochemical performance, making NMG as an effective electrode for sensitive and selective detection of PQ and heavy metals.