Direct Z-scheme NiTiO3/polyaniline heterojunction based photoelectrochemical aptasensor for the efficient detection of ochratoxin A in corn and soil

Preparation of Z-scheme heterojunctions requires band-gap matched semiconductors with tedious procedures, which is challenging for the application of photoelectrochemical (PEC) sensing. Herein, a sensitive PEC aptasensor for ochratoxin A (OTA) detection was constructed based on direct Z-scheme NiTiO3/polyaniline (NiTiO3/PANI) heterojunction. NiTiO3/PANI was firstly prepared via electrostatic adsorption between monomers; PANI with high conductivity and hydrophilicity can engineer the surface of NiTiO3 to enhance the separation of charge carriers and enlarge the PEC signal (e.g., 71.8-fold higher of that at NiTiO3). By virtue of superior properties, a NiTiO3/PANI-based PEC aptasensor was developed by using the recognition event of OTA with aptamer to vary photocurrent. When OTA is present, the aptamer is pulled away from the electrode interface by OTA, leading to a decrease in steric hindrance and the recovery of photocurrent, thereby enabling the detection of OTA. The constructed PEC aptasensor offered a linear range of 1 pg mL−1–2000 pg mL−1 with a detection limit of 0.33 pg mL−1. Moreover, this PEC aptasenosr displayed satisfactory selectivity and stability. The strategies to fabricate high-performance direct Z-scheme heterojunction as well as PEC aptasensor offer new solutions for the efficient detection of mycotoxins in the field of food safety and environmental protection.