Cobalt-doped tungsten trioxide nanorods decorated with Au nanoparticles for ultrasensitive photoelectrochemical detection of aflatoxin B1 based on aptamer structure switch

Abstract Herein, we report cobalt-doped tungsten trioxide (Co-WO3) nanorods/Au nanoparticles (AuNPs) for sensitive photoelectrochemical (PEC) sensing of aflatoxin B1 (AFB1) based on aptamer structure switch and horseradish peroxidase (HRP)-induced biocatalytic precipitation. Because of the decreased band gap and the increased visible light absorption of Co-WO3 nanorods, Co-WO3 nanorods show higher PEC activity than WO3 nanorods under the visible light irradiation. Co-WO3 nanorods decorated with AuNPs offer superior PEC activity to Co-WO3 nanorods due to the surface plasmon resonance effect. To construct a PEC aptasensor, short DNA strands (DNA1) are immobilized on the Co-WO3-AuNPs modified indium-tin oxide electrode. HRP-labeled aptamer hybridizes with the DNA1 on the photoelectrode in the absence of AFB1, and precipitations generated by HRP catalysis can quench the photocurrent of the photoelectrode. In the presence of AFB1, HRP-labeled aptamer does not hybridize with the DNA1 due to the formation of aptamer-AFB1 complex, and thus high photocurrent signal is achieved. The PEC aptasensor for AFB1 detection shows a broad linear range from 5 fg mL−1 to 10 ng mL−1, with a detection limit of 1 fg mL−1 (S/N = 3). We believe the high-performance Co-WO3/AuNPs active material coupled with the simple PEC sensing strategy will provide a promising sensing platform for detecting small biomolecules.