Novel dual type-II WO3/g-C3N4/Cu2O-Au heterojunction-based photoelectrochemical aptasensor for ultra-sensitive AFB1 detection in Astragalus matrix.

Given the extreme toxicity and carcinogenicity of aflatoxin B1 (AFB1) in foodstuffs and medicinal products, ultrasensitive detection for it is critically important. Herein, we engineered a type-II dual WO3/g-C3N4/Cu2O-Au heterojunction via hydrothermal synthesis and photoreduction, which synergistically integrates the structural stability of WO3, the visible-light response of Cu2O, the optimal band alignment of g-C3N4, and the plasmonic enhancement effect of Au nanoparticles. Leveraging the band structure differences among these constituent semiconductor components, this architecture enables efficient separation of photogenerated electron-hole pairs, resulting in a 6.7-fold enhancement in photocurrent compared to pristine WO3. Integrating this optimized photoelectrochemical (PEC) sensor platform with aptamer-based specific recognition, the biosensor achieves ultrasensitive quantification of AFB1 across a 7-order-of-magnitude linear range (10⁻⁵ ng/mL to 100 ng/mL) and an ultra-low limit of detection (LOD) of 2.29 fg/mL. Validation through highly sensitive determination of AFB1 in real Astragalus samples (a widely used Traditional Chinese Medicine (TCM)) yielding recoveries ranging from 98.5% to 102.1% verifies its applicability for quality control of medicinal products. This work presents a high-performance PEC biosensor for AFB1 and establishes a generalized component integration strategy for designing heterostructured nanomaterials aimed at detecting ultra-trace mycotoxins in complex food and pharmaceutical matrices.