Filmes autossuportados a base de grafeno para detecção eletroquímica de Paraquat

Abstract

In this study, freestanding composite films of reduced graphene oxide (rGO), polyaniline (PAni), and nickel-cobalt (Ni-Co) nanoparticles were synthesized for the electrochemical detection of the herbicide Paraquat (PQ). The films were prepared through thermal reduction in an ambient atmosphere (O₂, 150 °C) combined with chemical reduction using ascorbic acid (AA). The laser direct writing (LDW) technique was applied to the surface of the rGO/PAni/NiCo films, and the electrode area was optimized by comparing 1 cm² and 0,5 cm² configurations. Scanning electron microscopy (SEM) characterization revealed a heterogeneous surface with well-dispersed metal nanoparticles. After LDW treatment, the films exhibited increased thickness and electrochemically active area, along with reduced sheet resistance. Electrochemical analyses using K₃[Fe(CN)₆]/K₄[Fe(CN)₆] redox probes demonstrated that the electrodes with a smaller area (0,5 cm²) performed better, displaying more defined redox peaks. The rGO/PAni/NiCo-Acet film achieved a detection limit of 120 nM for Paraquat (PQ), confirming its efficacy as an electrochemical sensor. Differential pulse voltammetry (DPV) further validated the device's capability to detect herbicides at low concentrations, highlighting its potential for environmental monitoring applications. This study demonstrates that combining graphene, conductive polymers, and nanoparticles is a promising strategy for developing high-performance electrochemical sensors. Future research could explore the application of these films in detecting other contaminants in complex matrices, as well as investigate the influence of different metal precursors on sensor selectivity.