Host-guest recognition-regulated TiO2@In2S3 S-scheme heterojunction photoactivity: A PEC-EC dual-mode split-type aptasensor for malathion

Abstract

Ensuring the sensitive and rapid detection of residual malathion (MLT) levels in both environment and food is crucial for ecological environment and food safety. Herein, host-guest recognition-regulated the photoactivity of TiO₂@In₂S₃ S-scheme heterojunction was applied to construct a photoelectrochemical (PEC) and electrochemical (EC) dual-mode split-type aptasensor for malathion bioassay. The S-scheme charge transfer mechanism, in conjunction with sulfur vacancies in the TiO₂@In₂S₃ heterojunction, not only broadens the light absorption range, but also facilitates efficient separation and migration of photogenerated carriers, thus enhancing the original photocurrent response of the sensor. In the presence of MLT, rhodamine B-labelled MLT aptamer (RhB-apta)-MLT conjugates were formed and acted as the guest, which was recognized by β-cyclodextrin as the host on the electrode surface. Leveraging the excellent electroactivity of RhB and its sensitization of TiO₂@In₂S₃, a PEC-EC dual-mode aptasensor for MLT assay was achieved. The proposed aptasensor exhibits a wide linear range (0.001 ~ 50 ng mL⁻¹), with a detection limit of 0.12 pg mL⁻¹ in PEC mode and 0.62 pg mL⁻¹ in EC mode. The combination of the two detection signals can complement and validate each other, thereby improving the sensitivity, accuracy, and reliability of malathion detection.