CuInS2/Red Phosphorus Nanosheet Interleaved Heterostructures with Improved Interfacial Charge Transfer for Photoelectrochemical Aptasensing

Accelerating the migration of interfacial carriers in heterojunctions is crucial for achieving highly sensitive photoelectrochemical (PEC) sensing. In this study, we developed three-dimensional (3D)/two-dimensional (2D) CuInS₂/red phosphorus nanosheet (CuInS₂/RP NS) n-n heterojunction functional materials with enhanced interfacial charge transfer capabilities for PEC sensing. The 3D CuInS₂ serves as a conductive layer, providing excellent electronic conductivity and superior electron absorption and transport properties. In contrast, the ultrathin RP NS acts as a transport layer that enhances carrier mobility. The 3D/2D heterojunction ensures a large interface contact surface, shortening the carrier transport distance. A well-aligned band position generates a substantial built-in electric field, providing a significant driving force for efficient carrier separation and migration, thereby improving response sensitivity. A PEC aptamer sensor was constructed based on the synthesized heterostructure for ciprofloxacin detection. The detection limit of the CuInS₂/RP NS aptamer sensor for ciprofloxacin is 2.03 × 10^-15 mg·mL^-1, with a linear range from 1.0 × 10^-14 to 1.0 × 10^-5 mg·mL^-1. This work presents a strategy for enhancing the photoelectric response by modulating the interface structure of heterojunctions, thereby opening new prospects for the application of highly sensitive PEC sensors in antibiotic detection.