Design,Processing And Application Of Conjugated Polymers-Based Photoelectrochemical Sensors

The photoelectrochemical（PEC）process is the process of the charge transfer from photosensitive substances by light excitation.PEC bioanalysis is essentially a combination of the PEC process and traditional electrochemical analysis to achieve the corresponding target analyte detection,which is a rapidly developing and highly sensitive bioanalytical method with the advantages of fast response,low background and high sensitivity.However,PEC still faces many serious challenges,for example the efficiency of photo-electric conversion needs to be improved,the variety of recognition elements needs to be expanded,new devices and mechanisms need to be further developed and elucidated.Therefore,there has been an urgent need to develop advanced biosensors.In recent years,organic photoelectrochemical transistor（OPECT）bioanalysis displays its talent for the first time.Due to the inherent signal amplification of OPECT,as well as low cost,simple preparation process,low operating voltage（<1 V）,and easy device miniaturization and flexibility,they have been successfully applied to sensitive detection in the fields of enzyme sensing,immunoassay,and nucleic acid analysis.Conjugated polymers are a class of polymeric materials with highly delocalized electronπ-πconjugated structures,which have excellent electrical and optical properties,would be structurally designed to modulate light absorption,emission and photo-electric properties.Therefore OPECT have gained much attention in recent years.Based on this,we use conjugated polymers to construct a novel and highly sensitive method to detect biomolecules with higher detection sensitivity.Two specific works are carried out in the work as follows:1.Polymer dots synergized with a Ni O hole transporting layer and poly（amido amine）dendrimer for sensitive photocathodic detection of tyrosinase level in serumPolymer dots（Pdots）are functional materials with good photostability,low toxicity,good biocompatibility,a simple preparation process and tunable optoelectronic properties.The Pdots/Ni O HTL electrode is prepared by liquid phase deposition and annealing treatment of Ni O nanosheets on fluorine-doped tin oxide（FTO）,then layer-by-layer assembly of Pdots.Pdots form a new type of p-p heterojunction with Ni O HTL,significantly enhancing the photo-electric conversion efficiency.The active amino group in the hyperbranched polyamide-amine PAMAM molecules would covalently bind to the carboxyl group of Pdots and covalently connect to the electron acceptor BQ,which makes the PAMAM/Pdots/Ni O/FTO photosensitive electrode with excellent PEC stability.Due to the synergistic effect of Pdots/Ni O and PAMAM,the PEC enzyme sensor has good selectivity and high sensitivity for TYR detection,with a linear range of 0.1～1000 U L^-1and detection limit as low as 0.03 U L^-1.The PEC enzyme sensor is also suitable for TYR detection of actual human serum samples.2.Conjugated acetylenic polymers efficiently gated organic photochemical transistors for sandwich immunoassay of human immunoglobulin GConjugated acetylene polymers（CAPs）are rigid polymer-based semiconductor materials containing aromatic rings and C≡C groups in the main chain.Theπ-electron conjugated skeletons in the molecular range of the structures confer them excellent optical and electrical properties.In this work,poly（1,4-diethynylbenzene）（p DEB）fabricated by copper-mediated Glaser polycondensation forms a novel p-p heterojunction with Ni O HTL,which can efficiently modulate OPECT.Linking with a sandwich immunoassay,the labeled alkaline phosphatase can catalyze sodium thiophosphate to generate hydrogen sulfide（H₂S）,which will react with the diacetylene group in p DEB through the Michael addition reaction,resulting in the inhibited the photoelectric conversion efficiency.This leads to a reduction in the effective gate voltage and suppression of the channel current I_D,ultimately reflecting the target detection HIg G information with a highly sensitive response of I_D.The developed p DEB/Ni O gated OPECT biosensor has a high current gain of 6.8×10³,a linear range of HIg G detection from 70 fg m L^-1to 10 ng m L^-1,and a detection limit of28.5 fg m L^-1.