Synthesis Of Multi-walled Carbon Nanotubes Crosslinked COF Nanocomposites And Its Application In Electrochemical Sensing

Due to their advantages of easy operation,fast response,high sensitivity and good selectivity,electrochemical sensors have been widely studied and applied.For the development of electrochemical sensors,the selection of electrodes modified materials is crucial for its excellent performance.As an advanced porous new material,covalent organic frameworks（COFs）have attracted more and more attention in catalysis,gas storage and separation,drug delivery,supercapacitors and other fields because of their large surface area,low mass density,adjustable pores,predesigned structures,and high thermal stability.Unfortunately,COFs are rarely used in the field of electrochemical sensing owing to their poor conductivity,and resulted weak response signal and low sensitivity when modified on the electrodes surface.To solve this problem,in this thesis,some COFs were constructed by selecting conjugate structure units,and then the COFs were coupled with multi-walled carbon nanotubes with good electrical conductivity to prepare COFs composite materials for fabrication of electrochemical biosensors with excellent sensing properties.And these prepared sensors have been successfully applied to detect some environmental pollutants and biological small molecules.The specific research content of this thesis as following:（1）Using1,3,6,8-tetra（4-formylphenyl）pyrene（TFPPy）and4,4’-diaminobenzene（BD）as the building blocks,a covalent organic framework TFPPy-BD-COF was synthesized by amine-aldehyde condensation reaction.And by combiningwithmulti-walledcarbonnanotubes（MWCNT）,a TFPPy-BD-COF/MWCNT/GCE electrochemical sensor was fabricated,which exhibitied good electrochemical performance for simultaneous and highly sensitive detection of catechol（CC）and hydroquinone（HQ）.Under the optimal experimental conditions,the electrochemical sensor showed wide linear ranges（4.0-450μM）and low detection limits（0.36μM,0.38μM）for the detection of CC and HQ,and realized the simultaneous and rapid analysis of CC and HQ in yellow river water samples and tap water samples.（2）A novel amine-linked covalent organic framework TFPB-TAPB-COF was prepared by Schiff base reaction of 1,3,5-tris（4-formylphenyl）benzene（TFPB）and1,3,5-tris（4-aminophenyl）benzene（TAPB）as reaction monomers.Then by composition with oxidized multi-walled carbon nanotubes（Ox-MWCNT）a TFPB-TAPB-COF/Ox-MWCNT/GCE was prepared for electrochemical sensing of dopamine（DA）and uric acid（UA）.Due to the synergistic effect between the porous and large specific surface area of TFPB-TAPB-COF and the high conductivity of Ox-MWCNT,the developed electrochemical sensor exhibited good electrocatalytic performance and high analytical sensitivity for DA and UA detection with low detection limits of 0.073μM and 0.063μM,respectively,and can be used for simultaneous and rapid detection of DA and UA in dopamine injection and human urine samples.（3）A covalent organic framework TADH-COF was synthesized by using solvothermal method with 1,3,5-tris（4-aminophenyl）benzene（TAPB）and2,5-dihydroxyterephthalaldehyde（DHA）as monomers,and then Ni²⁺was introduced into TADH-COF to obtain Ni-TADH-COF composites through a post-synthesis modification strategy.Composition of hydroxylated multi-walled carbon nanotubes（OH-MWCNT）with the COF allowed a preparation of the Ni-TADH-COF/OH-MWCNT/GCE electrochemical sensor with sensitive electrochemical responses for guanine and adenine.The prepared sensor can be exploited for the simultaneous detection of guanine and adenine in hot denatured herring sperm DNA.The electrochemical response signal of the sensing platform was significantly amplified due to the synergistic interaction between the three materials.The resulted biosensor exhibited a wide linear range of 0.6-200μM and low detection limits of 0.16μM and 0.10μM for guanine and adenine,respectively.