A ZnIn₂S₄/Ag₂CO₃ Z-scheme heterostructure-based photoelectrochemical biosensor for neuron-specific enolase

An efficient photo-to-electrical signal is pivotal to photoelectrochemical (PEC) biosensors. In our work, a novel PEC biosensor was fabricated for the detection of neuron-specific enolase (NSE) based on a ZnIn₂S₄/Ag₂CO₃ Z-scheme heterostructure. Due to the overlapping band potentials of the ZnIn₂S₄ and Ag₂CO₃, the formed Z-scheme heterostructure can promote the charge separation and photoelectric conversion efficiency. And the concomitant Ag nanoparticles in Ag₂CO₃ provided multiple functions to enhance the PEC response of the Z-scheme heterostructure. It acts not only as a bridge for the transfer of carriers between ZnIn₂S₄ and Ag₂CO₃, promoting the constructed Z-scheme heterostructure, but also as electron mediators to accelerate the transfer of photogenerated carriers and improve the capture of visible light of the Z-scheme heterostructure by surface plasmon resonance (SPR). Compared with single Ag₂CO₃ and ZnIn₂S₄, the photocurrent of the designed Z-scheme heterostructure increased more than 20 and 60 times respectively. The fabricated PEC biosensor based on a ZnIn₂S₄/Ag₂CO₃ Z-scheme heterostructure exhibits sensitive detection to NSE, and presents a linear range of 50 fg·mL^-1 ~ 200 ng·mL^-1 with a limit of detection of 4.86 fg·mL^-1. The proposed PEC biosensor provides a potential approach for clinical diagnosis.