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.