The Study Of Novel Electrochemical Sensors Based On Covalent Organic Polymer

Electrochemical sensing is an analysis technology that combines electronic identification materials and electrical signal conversion systems.It has the advantages of high sensitivity,convenient operation,fast analysis,and easy miniaturization.Commonly used electronic recognition materials include biological enzymes,antigens,antibodies or certain catalytically active materials such as nanoenzymes.The performance of the sensor is usually closely related to the stability of the active material.When materials accumulate on the surface of the electrode,their electroactive centers will be covered,resulting in a decrease in catalytic activity;and when the interaction between the materials is weak,the material on the electrode will fall off,making the stability and reproducibility of the electrode poor.Therefore,the traditional electrode faces the problem of how the enzyme and the electronic mediator are uniformly and stably immobilized on the surface of the electrode.In this paper,we use Schiff base polymers and covalent organic framework materials as the substrate,and at the same time load highly efficient active catalytic materials to construct a series of electrochemical sensors with large specific surface area and strong immobilization capacity,used in the detection of glucose,small biological molecules,various drugs and food additives.The specific work is as follows:1.A new redox active Schiff base polymer(SBP_PPDA-PDA)was prepared by condensing p-phenylenediamine and 1,10-phenanthroline-2,9-diformaldehyde.SBP_PPDA-PDAwas studied by scanning electron microscope,transmission electron microscope and atomic force microscope.The results show that SB_PPPDA-PDA has a two-dimensional sheet structure.The electrochemical performance of SBP_PPDA-PDAwas characterized by cyclic voltammetry,showing multiple pairs of redox peaks and good catalytic oxygen reduction ability.Based on the redox activity of SBP_PPDA-PDA,an electrochemical p H sensor was constructed using SBP_PPDA-PDA,with a linear range of 2-9.At the same time,a new type of ratio electrochemical glucose sensor was constructed by immobilizing glucose oxidase on the SBP_PPDA-PDA modified electrode.The ratio electrochemical sensor based on GOD/SBP_PPDA-PDA/SPE has a fast response,a wide linear range,from 22.5μM to 5.00m M,and the detection limit is 7.58μM.2.The copper nitrate hexahydrate is incorporated into the ordered holes of the covalent organic framework(COF_TD)through coordination,and the carbon nanosheet（Cu NPs/CN）material of copper nanoparticles is encapsulated by the method of high-temperature carbonization.The material shows a carbon sheet structure loaded with small nanoparticles of about 10 nm.At the same time,COF_TD was used to coordinate a series of metals,and these complexes were calcined and reduced to obtain two-dimensional carbon nanoflake-coated small-sized metal nanoparticles—MNPs/CN to simultaneously detect dopamine and uric acid.The two active substances are in MNPs.The surface of the MNPs/CN/GCE modified electrode has an independent oxidation-reduction process,and the related sensor has good sensitivity.Finally,Cu NPs/CN/GCE has been used in the construction of a drug furazolidone sensor.The proposed electrical sensor has a wide linear range from 61.5n M-200μM,and has good reproducibility and repeatability.3.Firstly,Ni-doped ZIF-8 was calcined as a template to synthesize a nickel-zinc-doped porous carbon material（NZC）with a regular dodecahedron morphology,and hybridized with COF_TM to form a core-shell structure of NZC@COF_TM composite Core-shell material,Ni dispersed uniformly in NZC is used as a catalytically active material,and the synergistic effect of elemental Zn and porous carbon improves the electron transport efficiency of the material.At the same time,NZC retains the three-dimensional structure of ZIF-8,and the COF_TM with a flexible two-dimensional structure on the surface wraps the NZC material like a net to improve the stability of the NZC.At the same time,the active surface rich in bare N and O atoms has a good enrichment effect on the detection substance.The material was subsequently used in electrochemical sensors and biosensors to quantitatively detect paracetamol and Tert-butylhydroquinone.The results prove that the enzyme-free biosensor constructed based on NZC@COF_TM/GCE exhibits good sensitivity,with a wide linear range of 24.5 n M-130 m M and 5.34 n M-110μM,respectively.