Square-shaped Cu2MoS4 loaded on three-dimensional flower-like AgBiS2 to form S-scheme heterojunction as a light-driven photoelectrochemical sensor for efficient detection of serotonin in biological samples

Serotonin (5-HT) is a crucial neurotransmitter in the body, with its levels being particularly significant for life safety. Here, we designed the AgBiS₂/Cu₂MoS₄ S-scheme heterojunction by uniformly immobilizing lamellar Cu₂MoS₄ on the surface of three-dimensional (3D) flower-like AgBiS₂ using a simple physical mixing technique. In this case, AgBiS₂ and Cu₂MoS₄ are bonded together by electrostatic attraction to form an active surface with a large specific surface area. Subsequently, the detector 5-HT bound to AgBiS₂/Cu₂MoS₄/GCE undergoes hole oxidation and the photocurrent signal increases significantly. Meanwhile, the reaction mechanism of AgBiS₂/Cu₂MoS₄ composite material was investigated through density functional theory calculations. The AgBiS₂/Cu₂MoS₄/GCE sensor demonstrates a low detection limit of 0.046 nM and a wide linear range (0.0001-8 μM). Furthermore, by comparing UV-Vis spectrophotometry and fluorescence spectroscopy for the detection of 5-HT in human serum, it was proved that the sensor has an impressive recovery rate.