Perovskite-type BiFeO₃/ultrathin graphite-like carbon nitride nanosheets p-n heterojunction: Boosted visible-light-driven photoelectrochemical activity for fabricating ampicillin aptasensor

Developing effective sensing method for trace analysis of ampicillin (AMP) is urgent and significant due to its residue possess serious threats to human health. Herein, a p-n heterojunction, on the basis of p-type BiFeO₃ nanoparticles coupled n-typed ultrathin graphite-like carbon nitride (utg-C₃N₄) nanosheets, has been designed and synthesized via a simple electrostatic interaction strategy. Such p-n heterojunction has two advantages: one is capable to narrow the band gap of photoactive materials from 2.20 eV of BiFeO₃ down to 2.04 eV of BiFeO₃/utg-C₃N₄, leading to improve the efficiency of visible light utilization; and the other is to facilitate the charge separation rate, resulting in the boosted photoelectrochemical (PEC) performance of BiFeO₃/utg-C₃N₄. Under visible light illumination, the photocurrent of the resulted BiFeO₃/utg-C₃N₄ was 7.0-fold enhanced than that of pure BiFeO₃ nanoparticles, and indeed 2.3-fold enhanced comparing to BiFeO₃/bulk-C₃N₄. Based on excellent PEC properties of BiFeO₃/utg-C₃N₄, an on-off-on PEC aptasensor was successfully fabricated for ampicillin (AMP) determination with highly selectivity and sensitivity. The fabricated PEC aptasensor exhibited excellent PEC performance with a broad linear in the range from 1 × 10^-12 mol L^-1 to 1 × 10^-6 mol L^-1 as well as a low detection limit of 3.3 × 10^-13 mol L^-1 (S/N = 3), and also good feasibility in real sample. The excellent analytical performance indicated that PEC aptasensor on the basis of the visible light driven BiFeO₃/utg-C₃N₄ heterojunction can provide a promising biosensor platform for sensitive detection AMP in food and environment analysis.