A light-driven enzyme-free photoelectrochemical sensor based on HKUST-1 derived Cu2O/Cu@microporous carbon with g-C3N4 p-n heterojunction for ultra-sensitive detection of l-cysteine

l -cysteine (L-Cys) plays an important role in human health as well as in the biological environment. Here, a simple physical mixing technique was used to create the p-n heterojunction by homogeneously immobilizing cuprous oxide/copper@microporous carbon (Cu 2 O/Cu@mC) on the surface of a sheet of g-C 3 N 4 (CNS). Among them, the porous structure of Cu 2 O/Cu@mC after heat treatment is favorable for charge storage. Meanwhile, the carbon element in Cu 2 O/Cu@mC acts as a photosensitizer and electron mediator to extend visible light absorption. Compared with bulk g-C 3 N 4 (CNB), the sheet-like structure and high specific surface area of CNS can be used as a carrier for the binding of Cu 2 O/Cu@mC with L-Cys. Based on the interaction between L-Cys and Cu 2 O/Cu@mC through the formation of Cu–S bonds, Cu 2 O/Cu@mC/CNS was proposed as a light-driven enzyme-free photoelectrochemical sensor for the detection of L-Cys. In the best case, the Cu 2 O/Cu@mC/GCE sensor has a low limit of detection of 1.26 × 10 −9  M for L-Cys and a wide linear range (1.0 × 10 −8  M − 4.0 × 10 −6  M). The repeatability, reproducibility, stability, selectivity and specificity of the sensor were satisfactory. In addition, the potential applicability of the proposed photoelectrochemical sensor was evaluated in tap water and human serum.