A split-type photoelectrochemical sensor based on In₂S₃/PCN-224 Z-scheme heterojunction for ultrasensitive detection...

A ultrasensitive split-type photoelectrochemical (PEC) sensor was constructed for ampicillin (AMP) detection, utilizing a metal-organic framework (MOF)-confined In₂S₃/PCN-224 Z-scheme heterojunction as the photoactive material. The prepared In₂S₃/PCN-224 was demonstrated with high charge separation efficiency and a stable PEC signal response due to the unique electron flow direction of the Z-scheme configuration. To further enhance the detection sensitivity, target-mediated in-situ ion exchange via Cd²⁺ ions was employed to modulate the photoactivity of In₂S₃/PCN-224. In the presence of AMP, the aptamers labeled with CdCO₃ were released from the DNA double-strand and then dissociated into Cd²⁺ ions after acid treatment. Ion exchange reactions will occur upon introducing the solution into the In₂S₃/PCN-224 surface. Another photoactive material may be produced on the electrode surface to amplify the original PEC signal. The resulting split-type PEC sensor exhibited an impressive linear range (0.5-200 ng mL^-1) with a low limit of detection (LOD, 0.09 pg mL^-1, S/N = 3). This work presents a promising strategy for the development of PEC biosensors, offering practical applications in the environmental analysis of antibiotics.