Study On Photoelectrochemical Sensors Based On In Situ Sensitization Of Photoactive Materials

Photoelectrochemical（PEC）sensor quantifies the objects by changing corresponding photoelectric signals based on biometrics between the identifying element and the target molecule in the electrochemical conditions.In PEC analysis,excellent sensing mode,ideal optical electrode and efficient signal amplification strategy are the keys to improve performance of the sensor.As one of the effective PEC sensing strategy,in situ formation strategy has the advantages of simple operation and low background signal.However,most of the reported works based on in situ formation are signal off,which inevitably produce false positive signals,and limits the sensitivity of the sensors to a certain extent.In this paper,a series of signal enhanced PEC sensors were constructed based on the principle of in situ generation reaction.Combined with excellent photoelectrode,the liposome signal amplification strategy and dual target detection,the disease markers are sensitively detected.The main innovation points and research contents are as follows:1.A novel signal-increased PEC biosensor for L-cysteine（L-Cys）was proposed based on the Bi₂Mo O₆-Bi₂S₃heterostructure formed in situ on the ITO electrode.Firstly,Bi₂Mo O₆nanoparticles were prepared by a hydrothermal method and coated on a bare ITO electrode.When L-Cys existed,Bi₂S₃was formed in situ on the interface of the Bi₂Mo O₆/ITO electrode by a chemical displacement reaction.The Bi₂Mo O₆-Bi₂S₃heterostructure widened the light absorption range and efficient separation of photo-induced electron-hole pairs,resulting in a higher photocurrent response.Under the optimal conditions,the sensor for L-Cys detection has a linear range from 5.0×10^-11to1.0×10^-8mol L^-1and a detection limit of 5.0×10^-12mol L^-1.This strategy not only provides a method for L-Cys detection,but also broadens the application of the PEC bioanalysis based on in situ formation of photoactive materials.2.A dual-photoelectrode self-powered PEC biosensing system for protein detection was developed using liposome-assisted signal amplification strategy.The dual-photoelectrode self-powered device was constructed by integrating heterojunction of Ag₃PO₄with bromine doped g-C₃N₄（Ag₃PO₄/Br-CN）as a photoanode and Cu In S₂as a photocathode synchronously.Ag nanoparticles（Ag NPs）encapsulated liposomes as tags were labeled on the target protein through a sandwich immunoreaction implemented in a96-well plate.The Ag NPs encapsulated liposomes were used to generate the signal regulator Ag⁺for PEC detection.In the presence of Ag⁺,Ag Br was generated in situ on the interface of Ag₃PO₄/Br-CN to form Ag₃PO₄/Ag Br/Br-CN ternary heterostructures by the reaction between Ag⁺and Ag₃PO₄/Br-CN.The compact contact and the matchable band-edge levels of Ag₃PO₄,Ag Br,and Br-CN in the ternary heterostructures broaden the light absorption range and effectively restrain the electron-hole recombination of the photoanode,producing an improved photocurrent response.The large loading capacity of liposomes,the fine performance of the formed ternary heterostructures and the well-designed dual-photoelectrode self-powered PEC device endows the biosensing system with high sensitivity for protein detection.Using prostate specific antigen as model protein,the biosensing system exhibited a lowed detection limit of 3.4×10^-13g m L^-1with a linear range of 1×10^-12g m L^-1to 5×10^-8g m L^-1.The marriage of the self-powered system with the liposome-assisted strategy not only represented a generic method for protein detection,but also provided a novel path to fulfill the requirement of highly sensitive detection in the field of PEC analysis.3.To achieve the high sensitivity of biomolecule detection in PEC bioanalysis,exploiting high-efficiency photoelectron transfer nanomaterials is essential.Herein,a single atom photoactive material which incorporating Fe atoms into layered Bi₄O₅I₂（Bi₄O₅I₂-Fe SAs）was synthesized to construct an innovative PEC immunosensor for myoglobin（Myo）.Specifically,Ag NPs labeled detection antibody was introduced by sandwich immunoreaction,and then Ag NPs converted to Ag⁺in an acidic environment to participate in interfacial reactions with Bi₄O₅I₂-Fe SAs.Thereafter,Ag I was formed in suit which formed a heterojunction with Bi₄O₅I₂-Fe SAs improving the photocurrent,thus the detection of Myo is realized.Under the optimal conditions,the immunosensor revealed a wide linear range for Myo from 1.0×10^-11g m L^-1to 5.0×10^-8g mL^-1with a detection limit of 3.5×10^-12g m L^-1.The recoveries ranging from 91.0%to 110.0%for Myo in human serum samples validated the applicability of the biosensor.4.BiOBr/Bi material was synthesized by hydrothermal method.Based on Bi OBr/Bi/Ag Br and Bi OBr/Bi/Bi₂S₃heterojunction formed in situ on Bi OBr/Bi/ITO electrode,the sensitive detection of Myo and troponin（c Tn I）was realized.Mesoporous silica supported L-cysteine（L-Cys）and liposome coated Ag NPs were labeled on c Tn I and Myo antibodies as signaling probes,respectively,and introduced into the system by sandwich immune responses in 96-well plates.Ag Br and Bi₂S₃were generated in situ on the electrode by the reaction of Bi OBr/Bi with Ag⁺and S^2-,respectively.The resulting Bi OBr/Bi/Ag Br and Bi OBr/Bi/Bi₂S₃heterojunction effectively inhibited the recombination of electron hole pairs and produced enhanced photocurrent response.The proposed sensing strategy for the analysis of two kinds of objects opens a new way for PEC sensing.