Sensitive and selective neurotransmitter epinephrine detection at a carbon quantum dots/copper oxide nanocomposite

Herein, the electrochemical detection of epinephrine (EP) at a carbon quantum dots/copper oxide nanocomposite (CQDs/CuO) modified glassy carbon electrode (GCE) was investigated. The carbon quantum dots (CQDs), copper oxide nanoparticles (CuO NPs), and their composite (CQDs/CuO) were characterized using scanning electron microscopy (SEM), Fourier-Transform infrared spectroscopy (FT-IR), UV–visible spectroscopy, X-ray diffraction (XRD) spectroscopy, Transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). A limit of detection (LoD) of 15.99 µM over a linear dynamic range (LDR) of 10–100 µM was obtained at GCE/CQDs/CuO using the square wave voltammetry (SWV) for EP electroanalysis at pH 7. The theoretical evidence for the conventional weak epinephrinequinone (EPQ) reduction peak and EPQ cyclization was investigated using the density functional theory (DFT) calculations. This sensor was also applied for the analysis of EP in chicken blood serum and EP injection with percentage recovery of 101.23 and 93.54 %, respectively. In addition to its outstanding long-term stability, good reproducibility, and ease of fabrication, the detection of EP in the presence of ascorbic acid (AA) was achieved at this sensor. The proposed sensor also demonstrated the ability to simultaneously detect epinephrine (EP), dopamine (DA), and uric acid (UA).