Direct Z-scheme In2S3/Bi2S3 heterojunction-based photoelectrochemical aptasensor for detecting oxytetracycline in water

The threats of the discharge of antibiotics to the environment and ecology cannot be ignored. Accurate detection of the antibiotic concentration in the matrix is important to determine the contamination status. In this work, we proposed an In2S3/Bi2S3 heterojunction-based photoelectrochemical (PEC) sensor to detect antibiotics in water. The Z-scheme heterostructure promoted the separation of photo-generated carriers and achieved a stronger light response. Gold nanoparticles electrodeposited on the heterojunction surface as anchoring points slightly increased the photocurrent due to its metallic properties and surface plasmon resonance effect. Oxytetracycline (OTC), a broad-spectrum antibiotic was used as the target to test the performance of PEC sensor. Specific junction aptamer was used as the probe to recognize OTC to avoid the interference of complex components in matrix. The composition of In2S3/Bi2S3 heterojunction and the measurement conditions were optimized before the detection of OTC. The presence of OTC resulted in the increase in steric hindrance and the decrease in photocurrent. The PEC aptasensor showed a linear detection range of 0.04–10 nM and a calculated detection limit of 0.007 nM for OTC. In addition, the PEC aptasensor could distinguish OTC from other antibiotics and exhibited a stable light response under 20 continuous on-off irradiations. The practicability of the PEC aptasensor was verified by detecting OTC in river water. The proposed Z-scheme In2S3/Bi2S3 heterojunction-based PEC aptasensor can offer analysis applications for other antibiotics in water by substituting the corresponding aptamer.