A sensitive electrochemical sensor manufactured from multi-wall carbon nanotubes-polyethylenimine nanocomposite for malachite green detection

• A novel electrochemical method for detecting trace malachite green is presented. • High selectivity, stability and repeatability of sensor was observed. • A large linear range (0.01–6.0 μM) and a relatively low LOD (2.58 nM). • The developed sensor can be applied in water and fish samples. Due to the high toxicity of malachite green (MG), it is of great significance to determine MG in aquaculture for the sake of food safety and human health. In this study, multi-walled carbon nanotubes (MWCNTs)-polyethylenimine (PEI) composites were modified on the surface of a glassy carbon electrode (GCE). Morphology of the modified electrode was observed by scanning electron microscopy (SEM). The ability of the sensor in detecting MG was investigated by chronocoulometry (CC), cyclic voltammetry (CV) and by differential pulse voltammetry (DPV). The experimental results indicated an excellent catalytic performance of the modified electrode in MG oxidation. The peak current of MG obtained on the MWCNTs-PEI/GCE has been enhanced greatly compared with that of MWCNTs/GCE. A large linear range from 0.01 μM to 6.0 μM and a relatively low limit of detection of 2.58 nM were observed under the optimum conditions. In addition, this sensor shows many advantages in MG detection with samples of water and fish, such as good accuracy and reproducibility, excellent anti-interference ability and rapid response, and the recoveries obtained were between 95.5% and 104.0%.