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 Fe 3+ doped ZnO-Ag photocatalyst (Fe 3+ /ZnO-Ag) for ultrasensitive Hg 2+ detection by using exonuclease III-assisted target recycling and DNAzyme-catalyzed amplification. Firstly, Fe 3+ /ZnO-Ag was synthesized to provide photocurrent under visible light irradiation. Secondly, target Hg 2+ was determined by hairpin DNA probes on the Fe 3+ /ZnO-Ag modified ITO based on T-Hg 2+ -T, and then Hg 2+ 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 Hg 2+ concentrations form 0. 5   nM to 100   nM with a detection limit of 0. 1   nM at the 3 S blank 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.