Triple signal enhancement in a dual-enzyme-mimicking single-atom Fe nanozyme-based photoelectrochemical aptasensor for ultrasensitive detection of aflatoxin B1.

Accurate and sensitive detection of aflatoxin B1 (AFB1) is essential for ensuring food safety. In this study, a nanozyme-based photoelectrochemical (PEC) aptasensor was developed through a triple signal amplification strategy. A hollow-structured h-CdS coupled with TiO2 formed a highly efficient heterojunction that enhanced light absorption, light scattering, and charge separation, resulting in significantly improved photoelectric conversion efficiency. A single-atom Fe-MNC nanozyme possessing both peroxidase- and oxidase-like activities was synthesized via a cascade anchoring strategy, successfully catalyzing a biocatalytic precipitation (BCP) reaction for signal amplification. Density functional theory (DFT) calculations further validated the energy band structure of the heterojunction and the catalytic superiority of Fe-MNC. Additionally, a hybridization chain reaction (HCR) was rationally designed based on the AFB1 aptamer to achieve target-specific recognition and probe amplification. By integrating these three synergistic elements, the constructed nanozyme-based PEC aptasensor enabled highly sensitive detection of AFB1 with a detection limit of 2.04 fg/mL and a linear range from 0.005 to 100 pg/mL. The sensor demonstrated excellent stability and selectivity and showed good agreement with HPLC results when applied to real sample analysis, highlighting its practical potential for food safety monitoring.