ZnIn₂S₄/g-C₃N₄ heterojunction-enabled PEC-ECL sensing interface for quenching assay of fipronil

A ZnIn₂S₄/g-C₃N₄ heterojunction-enabled dual-mode photoelectrochemical-electrochemiluminescent (PEC-ECL) biosensor was constructed for the quenching detection of fipronil, in which the inputs of the target fipronil triggered double-step catalytic hairpin assembly (CHA) circuits, leading to the introduction of a MnO₂ nanoflower (NF) quencher. Leveraging the excellent changes in the signals, this biosensor exhibited a wide linear range with a detection limit of 6.8 fM in PEC mode and 6.2 fM in ECL mode. Furthermore, it allowed for fipronil analysis in lettuce and egg samples, exhibiting excellent consistency with the standard method, which confirmed its potential for food safety monitoring.