Photoelectrochemical Biosensor For Hg²⁺ Detection Based ZnO Modified Nanomaterials

Photoelectrochemical?PEC?detection is a newly emerging technique and rapidly developed on the basis of electrochemical.PEC biosensors possessing its proper merit on high sensitivity and selectively detection due to the total separation of the excitation source and detection signal,have been applied into the field of biomedical,food security,environmental monitoring and others.ZnO nanomaterials has advantages of low cost,nontoxicity,highly catalytic efficiency and favorable biocompatibility,but it can only be catalyzed by UV light.In this thesis,we focused on the preparation of nano ZnO-based composite materials which can be under catalyzed by visible light,and combines with of photoelectrochemical detection method,biomolecular signal amplification strategy were applied to the electrode a novel photoelectrochemical to constructe a novel PEC biosensor for Hg²⁺sensitive detection and trace analysis.The research is as follows:1.Highly sensitive PEC biosensor for Hg²⁺detection based on dual signal amplification strategy by exciton energy transfer coupled with dye sensitization effectGraphene oxide-ZnO-Cd S nanohybrid?GO-ZnO-Cd S?as photoelectric material was synthesized by simple hydrothermal method,Y-shape DNA was labeled by Au NPs,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 QDs.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.The results show that the photocurrent linearly increased with the increasing of Hg²⁺levels in the range of 5 pM⁵00 pM with the detection limit of 1.5 p M.More importantly,the developed biosensor showed the advantages of acceptable selectivity,repeatability and stability.2.Enhanced PEC biosensing platform based on Exonuclease III-assisted target recycling and DNA zyme-catalyzed amplification for detection of Hg²⁺Fe³⁺/Zn O-Ag was synthesized to provide photocurrent under visible light irradiation by deposition-precipitation method.T-T mismatched bases combine with Hg²⁺selectively,which could catalyze to the stepwise removal of mononucleotides of specific double-stranded DNA?dsDNA?.The photocurrent markedly decreased due to catalysis of hemin/G-quadruplex toward4-chloro-1-naphthol with H₂O₂.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.The detection platform only responses strongly to Hg²⁺among many other metal ions.And the developed biosensor could be applied in detecting of Hg²⁺in real samples,the recoveries of standard addition in water varied from 90%¹00%,which could meet the prefer feasibility and practicability in future.