Molecularly Imprinted\nElectrochemical Sensor Based\non Cu<sub><i>x</i></sub>O/MXene Nanocomposite for Sensing\nof Melatonin

A molecularly imprinted electrochemical sensor was designed\nfor\nthe quantitative and efficient detection of melatonin (MT) based on\na Cu<sub><i>x</i></sub>O/MXene modified screen-printed carbon\nelectrode (MIP/Cu<sub><i>x</i></sub>O/MXene/SPCE). Herein,\nthe Cu<sub><i>x</i></sub>O/MXene nanocomposite was prepared\nvia a hydrothermal method. The Cu<sub><i>x</i></sub>O was\nuniformly dispersed on the surface and the interlayers of the MXene,\nforming hybrid heterostructures. The encapsulated Cu<sub><i>x</i></sub>O increased the interlayer distance of the MXene matrix to\nbring more active sites and accelerated the oxidation reaction of\nmelatonin molecules, and thereby the electrochemical response of the\nsensor was improved. The MIP was constructed by electropolymerization\nof <i>o</i>-phenylenediamine (<i>o</i>-PD) in\nthe presence of MT on the surface of the Cu<sub><i>x</i></sub>O/MXene/SPCE. The morphology and chemical composition of the\nhybrid film were characterized by scanning electron microscopy and\nX-ray photoelectron spectroscopy; the electrochemical behaviors of\nthe sensor were evaluated by cyclic voltammetry and electrochemical\nimpedance spectroscopy. Under the optimal conditions, the MIP/Cu<sub><i>x</i></sub>O/MXene/SPCE sensor had a wide linear detection\nrange of 5–700 μM and a low detection limit of 0.029\nμM (S/N = 3) for MT. The sensor also showed excellent selectivity,\nreproducibility, and stability. Finally, it was successfully applied\nfor MT detection in human urine with satisfactory recovery. Overall,\nthis study provided a sensitive and efficient strategy for the determination\nof MT.