A self-powered photoelectrochemical oxytetracycline aptasensor: An integrated heterojunction photoanode of metal-organic framework derived ZnO nanopolyhedra/graphitic carbon nitride with high carrier density.

The development of effective strategies for the detection of oxytetracycline (OTC) in soil is of great importance for preserving agri-environmental safety and human health. Herein, a novel photoactive material of metal-organic framework (MOF) derived ZnO nanopolyhedra/graphitic carbon nitride (ZnO/g-CN) heterojunction was designed by mixing calcination of zeolite imidazole framework-8 (ZIF-8) and melamine. A self-powered photoelectrochemical aptasensor for the sensitive and selective detection of OTC in soil was proposed using ZnO/g-CN as the photoanode. The photoactivity of the MOF derived ZnO nanopolyhedra was regulated effectively by the introduction of g-CN, which resulted in a 7-fold increase in the photocurrent of the ZnO nanopolyhedra at a bias potential of 0 V. It was assigned to the higher carrier density of ZnO/g-CN. By virtue of the amplified photocurrent of ZnO/g-CN, the specificity of the OTC aptamer and the anti-interference ability of the self-powered sensing method, the designed aptasensor demonstrated the advantages of a wide linear range (0.005-200 nM), low limit of detection (1.49 × 10 nM), good selectivity and good reproducibility. For real soil sample analysis, satisfactory recoveries were obtained and further verified by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).