Construction And Application Of Molecularly Imprinted Electrochemical Sensors Based On Carbon-based Composite Material

In recent years,electrochemical sensors have been widely used in many fields,such as medicine,food and environment and so on,due to the simple instrument,fast response,and low cost.The construction of electrochemical sensors with high recognition performance and high sensitivity is one of the research focuses in the sensing field.Using molecularly imprinted polymer（MIP）as the recognition element of electrochemical sensor can improve the selectivity of the sensor,and modifying the electrode with carbon-based composite material can improve the sensitivity of the sensing substrate.In this paper,green raw materials（such as chitosan,grapefruit peel,prolifera,etc.）were used as the source of carbon quantum dots（CQDs）.A series of carbon-based composite materials were prepared by compounding CQDs with transition metal sulfides/oxides through solvothermal reaction.These materials have a variety of excellent properties,such as environmental friendly,low cost,and good electrochemical performance.Combined with molecular imprinting technology,molecularly imprinted electrochemical sensors with high sensitivity and good selectivity based on carbon-based composites were constructed,and the performance was investigated.The main research contents are as follows:（1）Construction and performance of folic acid molecularly imprinted electrochemical sensor based on MoS₂-CQDs composite materialsMoS₂-CQDs composites were prepared by using MoS₂ and chitosan as raw materials.The effets of molar ratio of MoS₂ and CS,reaction temperature and reaction time on the electrochemical performance of MoS₂-CQDs composites were investigated.The results showed that when the molar ratio of MoS₂ to CS was 2:1,the reaction temperature was 200°C and the reaction time was 12 h,the electrochemical performance of the prepared composites were the best.Then the morphology,structre and performance of the materials were characterized by transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,Fourier transform infrared spectroscopy（FT-IR）,X-ray diffractometer（XRD）,cyclic voltammetry（CV）and electrochemical impedance spectroscopy（EIS）.The MoS₂-CQDs composites were used as electrode modification materials to prepare modified electrodes.The MIP film was then fabricated in situ on the surface by electropolymerzition with folic acid acting as template molecule and o-phenylenediamine as functional monomer.A molecularly imprinted electrochemical sensor（MIP/MoS₂-CQDs-CS/GCE）was established for folic acid detection.Under the optimal conditions,a calibration curve of the logarithm of the current difference（LogΔI）versus the folic acid concentration（C）was obtained in the range of 60-5000μM with a detection limit of（LOD）（3S/N）0.09μM.The linear regression equation is LogΔI=-0.0002C-4.3706,R²=0.9903.Furthermore,the proposed MIP/MoS₂-CQDs-CS/GCE sensor possesses low cost,favorable sensitivity,selectivity and stability.（2）Construction and performance of glucose molecularly imprinted electrochemical sensor based on MnFe₂O₄-CQDs composite materialsMnFe₂O₄-CQDs composites were prepared by one-step solvothermal method with ferric chloride,manganese chloride and grapefruit peel powder as raw materials.The morphology,structure and properties of the as-prepared MnFe₂O₄-CQDs composites were characterized by TEM,FT-IR,XRD,XPS,CV and EIS.The prepared MnFe₂O₄-CQDs composites were used as electrode modification materials to prepare modified electrodes.A molecularly imprinted electrochemical sensor（MIP/MnFe₂O₄-CQDs-CS/GCE）for glucose detection was prepared with glucose as template molecule and 3-aminophenylboronic acid as functional monomer.Under the optimal conditions,the peak current decreases gradually with the increase of glucose concentration in the concentration range of 0.1-600μM.The current difference（ΔI）is linear with the logarithm of glucose concentration（Log C）,ΔI=3.3626Log C-10.3535,R²=0.9753,and the calculated LOD（3S/N）was 0.043μM.The proposed MIP/MnFe₂O₄-CQDs-CS/GCE sensor possesses simple preparation,favorable sensitivity,relativley wide linear range and high selectivity.（3）Construction and performance of bisphenol A molecularly imprinted electrochemical sensor based on NiFe₂O₄-CQDs composite materialsNiFe₂O₄-CQDs composites were prepared by one-step solvent method with nickel chloride,ferric chloride and prolifera as raw materials.The morphology,structure and properties of the prepared NiFe₂O₄-CQDs composites were characterized by TEM,FT-IR,XRD,XPS,CV and EIS.The NiFe₂O₄-CQDs composites were used as electrode modification materials to prepare modified electrodes.A molecularly imprinted electrochemical sensor（MIP/NiFe₂O₄-CQDs-CS/GCE）was developed for the determination of bisphenol A（BPA）.BPA was used as template molecule,while o-phenylenediamine and dopamine were used as the binary functional monomers.Under the optimal conditions,the peak current decreases gradually with the increase of the concentration of BPA.The logarithm of the current difference（LogΔI）exhibit a well linear relationship toward the logarithm of the concentration of BPA（Log C）in the range from 0.1 n M-60μM,with a LOD（3S/N）of 0.083μM and a correlation coefficient of 0.9935.The electrochemical sensor possesses simple preparation,good stability,selectivity,high sensitivity and relativley wide linear range.