An ultra-sensitive electrochemical sensor based on 2D g-C3N4/CuO nanocomposites for dopamine detection

A facile sensor based on two-dimensional (2D) g-C3N4/CuO nanocomposites was proposed for electrochemical detection of dopamine (DA). The 2D g-C3N4/CuO nanocomposites were fabricated by a pyrolysis technique using melamine and cupric acetate monohydrate as precursors. The 2D g-C3N4/CuO nanocomposites prepared have a larger conductivity and a narrower band-gap than that of pure g-C3N4, resulting in higher electrochemical activity for sensing of DA. The response of this sensor is linear over the range of 2.00 × 10−9 to 7.11 × 10−5 mol L−1 with a detection limit of 1.00 × 10−10 mol L−1. The ultra-high sensitivity can be attributed to an electron transfer process on the surface of the sensor, where the 2D g-C3N4/CuO is a powerful electron donor and the oxidized DA quinone functions as an efficient electron acceptor, as confirmed by density functional theory (DFT) calculations. The sensor showed a high selectivity to DA over common interfering biological small molecules (including glucose, uric acid and ascorbic acid), as the DA quinone possesses the most positive electrostatic potential and the smallest electron-injection-barrier between the 2D g-C3N4/CuO and DA quinone, which was also supported by DFT calculations. The proposed novel sensor provides a facile yet ultra-sensitive electrochemical sensing method for detecting trace DA in real biological samples.