Dual-mode PEC-colorimetric aptasensor for sensitive aflatoxin B1 detection via a BiVO4/Ni3(HHTP)2 heterojunction and PdAuCu nanoenzyme amplification.

Rapid, sensitive, and accurate detection of aflatoxin B1 (AFB1) is essential for ensuring food safety. In this study, we developed a dual-mode photoelectrochemical-colorimetric (PEC-CL) aptasensor for AFB1 detection constructed from a BiVO4/Ni3(HHTP)2 type-II heterojunction integrated with a PdAuCu (PAC) ternary alloy nanoenzyme. The BiVO4/Ni3(HHTP)2 formed a type-II band structure that effectively suppressed electron-hole recombination and enhanced the photocurrent response. The PAC nanoenzyme exhibiting peroxidase-like activity not only modulated the PEC signal by catalyzing the conversion of 4-chloro-1-naphthol to benzo-4-chlorohexadienon, but also catalyzed the oxidation of 3, 3', 5, 5'-tetramethylbenzidine to generate a distinct colorimetric response. Leveraging a target-triggered signal-switching mechanism based on aptamer recognition, this dual-mode aptasensor achieved wide dynamic ranges from 1 pg/mL to 500 ng/mL for PEC and 0.01 ng/mL to 500 ng/mL for CL with detection limits of 0.45 pg/mL (PEC) and 3.6 pg/mL (CL). This work provides a promising platform for early warning of mycotoxin contamination.