Design and construction of Z-scheme BiS/nitrogen-doped graphene quantum dots: Boosted photoelectric conversion efficiency for high-performance photoelectrochemical aptasensing of sulfadimethoxine.

Rational design and fabrication of Z-scheme visible-light-driven photoactive materials have drawn much attention owing to their great potential in handling environment and energy crisis. In this work, Z-scheme BiS/nitrogen-doped graphene quantum dots (NGQDs) with superior photoelectric conversion efficiency were designed and fabricated, which demonstrated enhanced photoactivity compared with BiS owing to the improved separation efficiency of photogenerated electron and hole pairs. The emphasis was put on designing Z-scheme BiS/NGQDs, and then the mechanism of Z-scheme charge transfer mode was verified by the electron spin resonance (ESR) technique. On this basis, the proposed sensor exhibited a wide linear range of 0.1-120 nM and a detection limit of 0.03 nM (S/N = 3) for SDM, with high sensitivity (0.075 μA nM ), good selectivity and stability. Moreover, the proposed PEC aptasensor using BiS/NGQDs as the photoelectrode achieved sensitive and selective determination of sulfadimethoxine in milk samples. This work could provide some ideas for designing other Z-scheme photoactive species and insights into the charge transfer mechanism of Z-scheme. Furthermore, the promising applicability of PEC aptasensor using photoactive species could be extended to other accurate monitoring for contaminants.