Bio-dye sensitized detection of Hg2+ based GO-ZnO-CdS nanohybrids

Mercuric ion (Hg2+) as one kind of environmental pollutants has attracted more and more attentions due to its persistence, mobility and biological enrichment. In this study, a novel photoelectrochemical biosensor for Hg2+ detection was constructed based on dye sensitization effect induced by Y-shaped DNA transformation as signal amplification strategy. Firstly, graphene oxide-ZnO-CdS nanohybrid (GO-ZnO-CdS) as photoelectric material was synthesized by simple hydrothermal method, and was employed to modify ITO electrode. Secondly, Y-shape DNA was labeled by Au NPs in the solution, and which crosslinked on the surface of GO-ZnO-CdS modified ITO electrode by carbodiimide coupling method, which resulted in the excitation energy transfer (EET) effect between Au NPs and CdS. Finally, in the presence of Hg2+, the structure of DNA on the modified electrode changed from Y-shape into hairpin accompanying the proximity of dye molecule based on T-Hg2+-T, which eliminated EET effect and triggered dye sensitization effect for enhancing photocurrent response. Under optimal conditions, the photocurrent linearly increased with the increasing of Hg2+ levels in the range of 5 pM − 500 pM with the detection limit of 1:5 pM(LOD = 3σblank/s). More importantly, the developed biosensor showed the advantages of acceptable selectivity, repeatability and stability.