Ultra-sensitive photoelectrochemical aptamer biosensor for detecting E. coli O157:H7 based on nonmetallic plasmonic two-dimensional hydrated defective tungsten oxide nanosheets coupling with nitrogen-doped graphene quantum dots (dWO3•H2O@N-GQDs)

Light absorption and interfacial engineering of photoactive materials play vital roles in photoexcited electron generation and electron transport, and ultimately boost the performance of photoelectrochemical (PEC) biosensing. In this work, a novel high-performance photoelectrochemical (PEC) biosensing platform was fabricated based on nonmetallic plasmonic tungsten oxide hydrate nanosheets (WO3•H2O) coupling with nitrogen doped graphene quantum dots (N-GQDs) by a facile one-step hydrothermal approach. The localized surface plasmon resonance (LSPR) properties were achieved by oxygen vacancy engineered WO3·H2O (dWO3•H2O), which could greatly extend the light absorption from visible light to near-infrared light. Moreover, by coupling with N-GQDs, the as-fabricated heterojunction (dWO3•H2O@N-GQD) provided a much enhanced photoelectric response due to the efficient charge transfer. By conjugation with E.coli O157:H7 aptamer, a novel PEC aptasensor based on dWO3•H2O@N-GQD heterojunction was fabricated with a high sensitivity for detection of E.coli O157:H7. The limit of detection (LOD) of this PEC aptasensor is 0.05 CFU/mL with a linear detection range from 0.1 to 104 CFU/mL. Moreover, high reproducibility and good accuracy could also be achieved for analysis in milk samples. This work could provide a promising platform for the development of PEC bioanalysis and offer an insight into the non-metallic plasmonic materials based heterojunctions for high-performances PEC biosensing.