Fe3+ doped ZnO-Ag photocatalyst for photoelectrochemical sensing platform of ultrasensitive Hg2+ detection using exonuclease III-assisted target recycling and DNAzyme-catalyzed amplification

Herein we designed a novel photoelectrochemical sensing platform based on Fe3+ doped ZnO-Ag photocatalyst (Fe3+/ZnO-Ag) for ultrasensitive Hg2+ detection by using exonuclease III-assisted target recycling and DNAzyme-catalyzed amplification. Firstly, Fe3+/ZnO-Ag was synthesized to provide photocurrent under visible light irradiation. Secondly, target Hg2+ was determined by hairpin DNA probes on the Fe3+/ZnO-Ag modified ITO based on T-Hg2+-T, and then Hg2+ was released by the digestion of exonuclease III to double-stranded DNA. Finally, the photocurrent markedly decreased due to catalysis of hemin/G-quadruplex toward 4-chloro-1-naphthol. Under optimal conditions, the photocurrents were linearly related to Hg2+ concentrations form 0. 5 nM to 100 nM with a detection limit of 0. 1 nM at the 3Sblank criterion. More importantly, the developed biosensor exhibited good selectivity, repeatability, and stability, meanwhile, this analysis platform held great potential for testing real water samples in future.