Preparation And Application Of Photoelectrochemical Biosensors Based On Semiconductor Composite

Photoelectrochemical（PEC）bioanalysis has been boomng in recent years,compared to conventional electrochemical and fluorescence,it has better sensitivity,accuracy,and biological affinity.PEC biosensor usually composed of two parts,one is photoelectric active material and another is biometric identification element,different combinations of them can be used for quantitative and qualitative analysis of a variety of biochemicals.In order to broaden the application of PEC technology and improve the sensing performance,it can be started from the development of new photoelectric materials,new technology integration,new strategy exploration and so on.In this paper,from the perspective of developing new photoelectric chemical sensors,the 3D photocathode biosensor and the ultra-micro PEC biosensor which can be used for single cell analysis are constructed by using carbon fiber meshwork and nanopipette substrate respectively.The specific work is as follows:（1）Herein,we introduced a customized approach for simple preparation of three-dimensional（3D）NiO nanoflakes（NFs）/carbon fiber meshwork（CFM）and its application as a universal photocathode strategy for photoelectrochemical（PEC）bioanalysis.To be specific,3D NiO NFs/CFM was fabricated by a sequential liquid phase deposition with a following annealing process,then sensitized by Bi OI to obatain a 3D Bi OI/NiO NFs/CFM electrode.Next,futher integrated with an alkaline phosphatase（ALP）/tyrosinase（TYR）bi-enzyme cascade system,to achieve a sensitive split-type cathodic PEC bioanalysis for the analysis of ALP.This method can monitor ALP concentrations down to 3×10^–5U L^–1with a linear response range of0.001–10 U·L^–1.Moreover,this proposed bioanaylsis strategy performed good selectivity,stability and excellent performance for real sample analysis.This research features the facile preparation of 3D NiO NFs/CFM that could acts as a universal matrix for photocathodic analysis,and is envisioned to stimulate more effort for advanced 3D photocathode for PEC bioanalysis and beyond.（2）This work introduces the design and development of a 3D hierarchical CdS/NiO heterojunction and its application in a self-powered cathodic photoelectrochemical（PEC）bioanalysis.Specifically,NiO nanoflakes（NFs）were in situ formed on carbon fibers via a facile liquid-phase deposition method followed by an annealing step and subsequent integration with CdS quantum dots（QDs）.For enzymatic detection of glucose as a model target,glucose oxidase（GOx）was further functionalized onto the photocathode.Upon light illumination,this self-powered system performs much enhanced power output in comparison with NiO alone,and the as-developed photocathodic biosensor achieved target detection with high sensitivity and selectivity with linear range from 5×10^-7M to 1×10^-3M and lowest detection limit at 5×10^-8M.This is owing to the construction of a hierarchical CdS/NiO heterojunction,which simultaneously acted as an ideal platform for GOx accommodation and enzymatic catalysis reaction.This work is expected to stimulate more passion in the development of innovative hierarchical heterostuctures for advanced self-powered photocathodic bioanalysis.（3）We used the symmetric cone tube drawn by nanopipette as the electrode to assembled ultra-miniature PEC biosensor and successfully applied to the monitoring of reactive oxygen species（ROS）in single cells.First,the inner and outer walls of the nanopipette were uniformly coated with platinum,and then the inner wall was further modified with a layer of ethyldimercaptan,so that a sulfhydryl groups could exposure in the inner wall surface.And then,the electrode tip was treated with wax to control the exposure area and effectively reduce the biological noise caused by the adsorption of complex biochemical substances in the cell.Next,mercaptothiylated Ti O₂nanoparticles（Ti O₂-MPTES）were infused into the nanopipette and inserted into the cells for detection.When ROS enters the nanopipette tip,Ti O₂-MPTES will be agglomerated with each other and the mercapto groups in the inner wall surface quickly by the form of disulfide bonds,and improve the photocurrent signal.In this work,we modified the photoelectric active material into the tip of nanopipette and applied into single cell analysis,successfully detected the ROS in Hela cells.