Electrochemical Sensing Application Based On Functionalized Imine Covalent Organic Framework

Two-dimensional covalent organic framework(2D COF)is a class of organic porous crystalline material,which is covalently connected by B-O,C=N,C-N,C=C,C-O or B=N bonds.Due to its high porosity,large specific surface area,adjustable structure,abundant active sites,good crystallinity and abundant ?-electron arrays,COF has great application prospects in many fields,including drug delivery,optoelectronics,sensors,energy storage and conversion,gas storage,separation and catalysis,etc.Due to its low conductivity,COFs are rarely used in construction of electrochemical sensor.In order to make full use of excellent adsorption performance of COF for signal amplification in electrochemical sensors,functionalizing COF materials is an effective strategy to improve its inherent low conductivity.In recent years,some new development trends have appeared in the field of electrochemical sensing.In order to further improve the conductivity of COF and expand its applicability,we designed and synthesized a series of functionalized imine COF complex based on imine COF(for example,COF-conductive polymer composite,COF-enzyme-metal nanoparticle composite,COF-metal oxide nanoparticle-enzyme composite).The obtained composite materials possess high surface area and excellent electrical conductivity,it can construct an electrochemical sensor for sensitive determination of specific analytes.The main content of the paper is as followsChapter 2 TAPB-DMTP-COF@PANI as a novel electrochemical probe for highly sensitive detection of acetaminophenThe unique properties of two-dimensional covalent organic framework(COF)provide potential opportunities for the development of new electrode materials.In this work,a core-shell structure complex TAPB-DMTP-COF@PANI(TAPB,1,3,5-tris(4-aminophenyl)benzene;DMTP,2,5-dimethoxyterephaldehyde)was prepared by solvothermal polymerization.The structural characteristics of TAPB-DMTP-COF@PANI were proved by XRD,FTIR,XPS and TEM.And TAPB-DMTP-COF@PANI/GCE can realize the electrochemical trace analysis of acetaminophen.TAPB-DMTP-COF@PANI not only promotes the interaction between acetaminophen and the absorption site through ?-? conjugation effect and hydrogen bonding,but also overcomes the disadvantage of poor conductivity of COF.Under the optimal conditions,a low limit of detection of 0.036 ?mol L-1 and wide linear range of 0.10-2500 ?mol L-1 were obtained.Other interfering substances have little effect on the electrochemical platform,and the method can be successfully applied to the detection of acetaminophen tablets,human blood and urine.This improvement makes COF based core-shell composites a promising candidate material for electrochemical detection.Chapter 3 Triple-signaling amplification strategy based electrochemical sensor design:boosting synergistic catalysis in metal-metalloporphyrin-covalent organic framework for sensitive bisphenol A detectionCovalent organic framework(COF)is a promising type of porous material with customizable surface characteristics.Confining multiple catalytic units within mesoporous COF can generate abundant active sites and improve catalytic performance.In this work,a COF with both metalloporphyrin and metal nanoparticles complex denoted as Hemin/TAPB-DMTP-COF/AuNPs(TAPB:1,3,5-tris(4-amino-phenyl)benzene,DMTP:2,5-dimethoxyterephaldehyde)has been successfully fabricated through a hierarchical encapsulation method.The as-synthesized composite was then employed to construct an electrochemical sensing platform for efficient detection of bisphenol A(BPA).Under the optimal conditions,the Hemin/TAPB-DMTP-COF/AuNPs sensor presented a linear range of 0.01-3 ?mol L-1 and a low detection limit of 3.5 nmol L-1.The satisfactory signal amplification is on the basis of a triple-signaling amplification strategy in terms of abundant Fe3+ sites of Fe-porphyrin,high conductivity of AuNPs and large specific surface area of TAPB-DMTP-COF.The proposed method was applied to measure the content of BPA in different water samples with satisfying recovery from 95.5 to 104.0%,suggesting great promising of the sensor for practical application.Chapter 4 An effective and reliable platform for enzyme-induced electrochemical sensor for hydroquinone detection in water samples based on magnetic nanoparticles embedded in covalent organic skeletonsIn this work,a novel ternary core-shell-shell composite formed by Fe3O4,TAPB-DMTP-COF and HRP(Fe3O4@TAPB-DMTP-COF@HRP)was reported to modify glassy carbon electrodes for the electrochemical detection of nano-scale hydroquinone Hydroquinone is a developer widely used in photography,lithography,cosmetics,as well as antioxidant in industries application.Hydroquinone enters the human body mainly through inhalation or skin contact and may cause harm to human health.The composites were characterized by a series of analytical techniques.The oxidation current of hydroquinone was linearly related to the concentration in the range of 5-1100 ?mol L-1.The lowest detection limits were 1.5 nmol L-1.Compared with high performance liquid chromatography(HPLC),this sensor can be used as a nanoscale detection platform for hydroquinone in various environmental and biological liquids.