Photoelectrochemical aptasensing of tetracycline enabled by efficient photoanode: Integrating high visible light-harvesting Bi2S3 and metal-free g-C3N4 into Z-scheme heterojunction

• Efficient photoanode with high light-harvesting and enhanced photocurrent was fabricated. • A PEC aptasensor for sensitive and selective detection of TC was constructed. • The aptasensor had merits of low detection limit and good selectivity/stability. • Results of the aptasensor were in good agreement with UPLC-MS/MS for TC detection. The development of a reliable method for detecting tetracycline (TC) in fish is essential to ensure the safety of aquatic products and human health. Herein, a photoelectrochemical (PEC) aptasensor was fabricated for the efficient detection of TC based on a designed efficient photoanode with a novel high light-harvesting heterojunction of bismuth sulfide/graphitic carbon nitride (Bi 2 S 3 /g-C 3 N 4 ) as a photoactive material. The Bi 2 S 3 /g-C 3 N 4 exhibited enhanced photocurrent due to its increased light capture capability, high carrier density and especially low electron-hole recombination efficiency enabled by the Z-scheme electron transfer, which was verified by the UV–vis diffuse reflectance spectrum, Mott–Schottky plot, and electron spin resonance spectroscopy. Under optimal experimental conditions, the fabricated aptasensor had the advantages of a wide linear range of 0.01–10 nM, a low detection limit of 3 pM and good selectivity and reproducibility. When the aptasensor was applied to determine TC in fish, the results were in good agreement with the UPLC-MS/MS method, indicating the reliability of the PEC aptasensing method for detecting TC in real samples.