Abstract : Based on DNAzyme-induced disassembly of the "Z-scheme" TiO2 /Au/CdS QDs system, a facile and sensitive photoelectrochemical biosensor was developed for lead ion assay. Abstract : Herein, based on DNAzyme-induced disassembly of the "Z-scheme" TiO2 /Au/CdS QDs system, a facile and sensitive photoelectrochemical biosensor was developed for lead ion assay and a low detection limit of 0.13 pM was obtained.