Double Z-scheme MOF-on-MOF heterojunction for ultrasensitive photoelectrochemical biosensing and photocatalytic degradation of aflatoxin B1

Abstract

Developing dual-functional catalysts for simultaneous detection and degradation of carcinogenic aflatoxin B1 (AFB1) is crucial for global food and environmental safety. Herein, we demonstrate the rational design and synthesis of a bifunctional MOF-on-MOF-derived ternary heterostructure for ultrasensitive photoelectrochemical (PEC) biosensing and efficient photocatalytic degradation of AFB1. The MOF-on-MOF-derived ternary synergistic system was constructed via an epitaxial growth strategy, where NH₂-BDC-Fe, Cu cores were initially anchored onto NH₂−MIL-125 satellite surfaces, followed by in situ deposition of Ag₂S nanoparticles onto the resulting Fe, Cu-MOF-on-Ti-MOF composite. Double Z-scheme heterojunction engineering substantially improves charge transfer rates while suppressing inherent electron-hole recombination in single MOF systems,providing critical support for performance optimization and application diversification. Furthermore, the multilayer nanoarchitecture intrinsic to MOF-on-MOF heterostructures orchestrates synergistic interfacial interactions that elevate photoelectrochemical (PEC) activity and drive enhanced photocatalytic degradation efficacy. When performing AFB1 analysis, the PEC biosensor incorporating this composite material and a specific aptamer demonstrates exceptional sensitivity, achieving an ultra-low detection limit of 0.29 fg/mL with a wide linear range spanning seven orders of magnitude (10⁻⁵ to 10² ng/mL). Furthermore, the NH₂−MIL-125/NH₂-BDC-Fe, Cu/Ag₂S composite exhibits outstanding photocatalytic degradation efficiency and stability toward AFB1. Detailed investigations into the PEC sensing mechanism, photocatalytic degradation pathways, and primary degradation products were conducted. This work not only advances the fundamental understanding of heterojunction engineering but also provides a practical and promising solution for AFB1 contamination control, offering dual-functional capabilities for both detection and elimination in food safety applications.