Electrochemical Sensing Research Based On Covalent Organic Framework Materials

Covalent organic frameworks(COFs)linked by covalent bonds is a class of designable crystalline polymers with structural periodicity.Due to their high porosity,low density,insolubility,semiconductivity and robust stability,COFs have emerged as new organic porous materialswith applications in gas storage,catalysis and devices optoelectronic.Two-dimensional(2D)COFs are formed by covalent bonds of organic units to form a 2D extension plane,which can form a one-dimensional nanopore by layer-to-layer deposition.In recent years,due to the advantages of COFs linked by imine bonds,2D COFs are of great interest to electrochemical workers.However,due to the weak conductivity and biocompatibility of COFs,the application of such materials in the field of sensors is limited.Therefore,we have done the following work to improve the performance of COFs and apply it to electrochemical sensing research.The specific work is as follows:(1)In this work,a sensitive and selective covalent organic framework(TAPB-DMTP-COFs)modified carbon paste electrode was evaluated as a novel electrochemical sensor for the determination of lead in an aqueous medium.Lead was accumulation on the TAPB-DMTP-COFs surface by the complexation with the amine groups,and detected by differential pulse anodic stripping voltammetry.Due to the distinct structure features of COFs,the resulting sensor revealed a fast electron transfer rate and outstanding adsorption capacity for lead.The influence of various experimental parameters(the content of COFs,pH of the electrolyte solution,accumulation potential,and accumulation time)on the peak current was investigated in the overall analysis procedure.After a series of experiments,this method shows a wide linear range of 0.0050 to 2.0?mol L-1,low detection limit of 1.9 nmol L-1,and the relative standard deviation was 3.10%for 0.50?mol L-1 of lead(n=11).This method not only displays the feasibility of COFs based sensor for trace levels of metal ions detection but also broadens the scope of applications of COFs based hybrid materials in electroanalytical chemistry.(2)In this work,novel gold nanoparticles-doped TAPB-DMTP-COFs composite was successfully prepared via COFs as the host matrix to support the growth of gold nanoparticles.With the strong electrostatic interaction between gold nanoparticles and unsaturated amine group present on TAPB-DMTP-COFs,the gold nanoparticles were successfully immobilized onto the surface of TAPB-DMTP-COFs under vigorous stirring.Then,this novel composite was used to constitute an advanced electrochemical sensor and presented a good electrocatalytic activity toward the oxidation of chlorogenic acid(CGA)in the phosphate buffer solution(pH 7.0).After a series of experiments,this electrochemical sensor displays a wide linear range of 0.010-40?mol L-1,low detection limit of 0.0095 ?mol L-1.Moreover,the sensor exhibits an excellent stability and maintains its catalytic activity at least 100 cycles.Our work not only provides a simple way to detect CGA quantitatively in real samples,but also paves a new platform for COFs-based composite in biosensor.(3)In this work,a novel core-shell-structured composite Fe3O4-NH2@TAPB-DMTP-COFs was synthesized by using a superparamagnetic Fe3O4-NH2 as core to encapsulate TAPB-DMTP-COFs on its surface.TAPB-DMTP-COFs was encapsulated into Fe3O4-NH2 surface through self-assembly condensation between aldehyde group and amino group of Fe3O4,and the resultant material were characterized by powder X-ray diffraction(XRD),Fourier infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS).Given the cooperative effect of TAPB-DMTP-COFs and Fe3O4-NH2,the proposed catalyst material(Fe3O4-NH2@TAPB-DMTP-COFs)was firstly employed as electrochemical sensing platform for luteolin.The modified electrode based on Fe3O4-NH2@TAPB-DMTP-COFs displays a wide linear range of 0.010-2.0 ?mol L-1 and 2.0-70 ?mol L-1.The limit of detection(LOD)can be down to 0.0072 ?mol L-1.It may open up a new way for the sensitive and accurate detection of luteolin in the field of biomedical diagnostics.