A CuO-mediated photothermal and photocurrent-polarity-switching photoelectrochemical dual-mode immunosensor for the detection of chloramphenicol in food based on Cu-ZnIn2S4/TiO2 heterojunction.

Leveraging the dual functionality of CuO as a catalytic probe for 3,3',5,5'-tetramethylbenzidine (TMB) oxidation and a photocurrent-polarity-switching agent, a dual-mode sensing platform integrating photothermal and photoelectrochemical (PEC) strategies was developed for chloramphenicol (CAP) detection. The system employs a Cu-ZnIn2S4/TiO2-modified electrode as the PEC interface and CuO-labeled CAP antibody (CuO-mAb) as a bifunctional probe. In the presence of CAP, competitive immunorecognition immobilizes CuO-mAb on the electrode. The anchored CuO catalyzes TMB oxidation to oxidized TMB (oxTMB), which acts as a photothermal agent, enabling photothermal detection via temperature increase under 808 nm laser irradiation. This mode achieved a linear range of 2 pg/mL-20 ng/mL and a detection limit of 1.54 pg/mL. Simultaneously, CuO switches the photocurrent polarity of the electrode from anodic to cathodic due to favorable band alignment, facilitating PEC detection with a linear range of 0.2 pg/mL-10 ng/mL and a detection limit of 0.173 pg/mL. The dual-mode design enables cross-validation between photothermal and PEC signals, significantly enhancing detection reliability and accuracy. This platform demonstrates great potential for sensitive, selective, and accurate CAP monitoring in food safety applications.