Photoelectrochemical immunosensor for chloramphenicol detection based on cation exchange reaction-mediacted photocurrent enhancement of ZnIn₂S₄/TiO₂/Ti₃C₂ MXene coupled with controlled-release strategy

A photocurrent enhancing photoelectrochemical (PEC) immunosensor was developed for chloramphenicol (CAP) detection based on cation exchange reaction. The efficient split-type PEC immunosensor combined with controlled-release strategy was established using the ZnIn₂S₄/TiO₂/Ti₃C₂ MXene (ZIS/T/M) composite as the photoactive material and CuO as the signal response probe. In the presence of target CAP, CuO-labeled CAP antibody (CuO-mAb) was introduced onto the microplate via a competitive-type immunoassay. Under acidic conditions, a large amount of Cu²⁺ released from CuO-mAb, which triggered a cation exchange reaction with the Zn²⁺ in ZIS/T/M-modified photoelectrode to generate Cu_xS, resulting in enhancing the photocurrent. As a result, the quantitative detection of CAP was achieved by detecting the photocurrent change. Under optimized conditions, the linear range of the sensor was 1 pg/mL to 50 ng/mL, and the detection limit was 0.24 pg/mL. The excellent PEC behavior of ZIS/T/M composite could be attributed to the fact that heterojunction formation improved the migration and separation of the photocarrier. Additionally, by virtue of the photocurrent-enhancing strategy via cation exchange reaction and the controlled releasing signal amplification method of ion, the PEC immunosensor has high sensitivity and satisfactory accuracy, offering great potential applications in the determination of CAP.