Visible Light-driven Photoelectrochemical Ampicillin Aptasensor Based on an Artificial Z-scheme Constructed from Ru(bpy)-sensitized BiOI Microspheres

Dye sensitization is an alternative strategy to improve photoelectric activity of semiconductors and, particularly, to enhance the activity towards visible light domain. Herein, an artificial Z-scheme bipyridine ruthenium (Ru(bpy)) sensitizing narrow-gap bismuth oxy-iodide (BiOI) microspheres was constructed by a simple electrostatic interaction strategy for the first time. The electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) analysis showed that this design of such Z-scheme structure was helpful to enhance the interfacial charge transfer and improve the photoelectric conversion efficiency. In addition, due to the sensitization of Ru(bpy), the band gap was narrowed from 1.8 eV of BiOI microspheres to 1.3 eV of BiOI/Ru(bpy) microspheres, leading to improve the utilization of visible light. So that, the photocurrent of the resulted BiOI/Ru(bpy) was 13.0 times that of pure BiOI microspheres. In view of the outstanding photoelectrochemical (PEC) performance of BiOI/Ru(bpy) and the high specificity of the aptamer, the PEC aptasensor for ampicillin (AMP) merits the excellent detection performance including a broad linear ranging from 1 × 10 nM to 100 nM as well as a low detection limit of 3.3 × 10 nM (S/N = 3). This work not only provides a novel way to construct and design highly efficient photoactive materials for PEC detection, but also broadens the application of Z-scheme in the field of sensing.