Fabrication of the Cu2O/polyvinyl pyrrolidone-graphene modified glassy carbon-rotating disk electrode and its application for sensitive detection of herbicide paraquat

A polyvinyl pyrrolidone (PVP) functionalized graphene nanosheets (GNs) and cuprous oxide (Cu2O) sub-microparticles (micro-Cu2O/PVP-GNs) modified glassy carbon-rotating disk electrode (GC-RDE) was successfully fabricated. The electrochemical sensor based on PVP-GNs and micro-Cu2O was then developed for the investigation of the electrochemical behavior and the sensitive detection of herbicide paraquat (PQ). By cyclic voltammetry (CV) and differential pulse voltammetry (DPV), it was found that the modified electrode provided an electron-transfer microenvironment to accelerate the electrochemical catalytic reaction of PQ. The DPV signals of PQ on the micro-Cu2O/PVP-GNs modified GC-RDE were significantly enhanced. The enhanced DPV signals represented the excellent analytical performance of PQ detection in the range of 1.0 × 10−6–2.0 × 10−4 mol L−1, with a low limit of detection (LOD) of 2.65 × 10−7 mol L−1 (S/N = 3), and the acceptable reproducibility (RSD = 2.02%, n = 5). The proposed method has been used to determine the residual amount of PQ in cabbage leaves samples. By the treatment of the experimental data, the electrochemical reaction mechanism of PQ involves a diffusion-controlled quasi-reversible process and a two-electron-transfer process.