Electrodeposited copper nanocubes on multi-layer graphene: A novel nanozyme for ultrasensitive dopamine detection from biological samples

In this paper, copper nanocubes (CuNCs) were grown on top of few-layer and multi-layer graphene (FLG and MLG) nanomaterial by electrodeposition, to develop a sensitive and selective nanozyme based electrochemical sensor for the determination of dopamine from plasma samples. The copper electrodeposition process was intensively studied and optimized to obtain cubic shape CuNPs on top of graphene that increased the active area of the sensor. The surface of the nanomaterial was investigated with several microphysical characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX), and Fourier-transform infrared (FTIR), Raman, and X-ray photoemission spectroscopies (XPS). Further, the nanozyme sensor based on CuNCs-Gr/SPCE was electrochemically characterized using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), and the response towards the oxidation of DA was investigated using the differential pulse voltammetry (DPV) technique. The signal recorded with CuNCs-Gr/SPCE was linear in a wide range (0.001 – 100 µM), with a low limit of detection of 0.33 nM and a very high sensitivity of 196 mA/moL-1. The developed sensor showed high selectivity towards DA in presence of other neurotransmitters. The detection of DA in human plasma samples was obtained with 95.8–100.2 % recovery percentage, proving the reliability of the method.