Au Quantum Dot/Nickel Tetraminophthalocyanaine–Graphene Oxide-Based Photoelectrochemical Microsensor for Ultrasensitive Epinephrine Detection

[Image: see text] Owing to the importance of epinephrine as a neurotransmitter and hormone, sensitive methods are required for its detection. We have developed a sensitive photoelectrochemical (PEC) microsensor based on gold quantum dots (Au QDs) decorated on a nickel tetraminophthalocyanine–graphene oxide (NiTAPc-Gr) composite. NiTAPc was covalently attached to the surface of graphene oxide to prepare NiTAPc-Gr, which exhibits remarkable stability and PEC performance. In situ growth of Au QDs on the NiTAPc-Gr surface was achieved using chemical reduction at room temperature. The synthesized materials were characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and electrochemical impedance spectroscopy. Au QDs@NiTAPc-Gr provided a much greater photocurrent than NiTAPc-Gr, making it suitable for the ultrasensitive PEC detection of epinephrine. The proposed PEC strategy exhibited a wide linear range of 0.12–243.9 nM with a low detection limit of 17.9 pM (S/N = 3). Additionally, the fabricated PEC sensor showed excellent sensitivity, remarkable stability, and good selectivity. This simple, fast, and low-cost strategy was successfully applied to the analysis of human serum samples, indicating the potential of this method for clinical detection applications.