Construction And Performance Study Of Cysteine Electrochemical Sensor Based On MIL-53(Fe)

L-cysteine is widely used in medicine,personal care products and foods.Abnormal cysteine levels could cause a range of diseases,including liver damage,cardiovascular disease,and Alzheimer.The content of cysteine in human blood is often used as a basis for clinical diagnosis.Therefore,it is of importance to detect the concentration of cysteine with a simple,sensitive,convenient,and accurate method.In this paper,electrochemical sensors based on metal organic framework MIL-53（Fe）was developed for cysteine detection in real samples.The preparation of materials,the selection of composite materials,the preparation of modified electrode,the optimization of working parameters of sensor and the electrochemical performance test were studied.Three parts of this study were as follows:The composite of MIL-53（Fe）and carbon nanotubes（CNTs）,MIL-53（Fe）/CNTs was synthesized by solvothermal method.The electronic conductivity of MIL-53（Fe）can be effectively improved by CNTs in the composite.The crystal structure and morphology of MIL-53（Fe）/CNTs were characterized by X-ray diffraction,scanning electron microscopy and X-ray photoelectron spectroscopy.Then an electrochemical sensor for cysteine detection was prepared by using MIL-53（Fe）/CNTs composite as the recognition element,Nafion solution as binder and glassy carbon electrode（GCE）as the base electrode.The electrochemical performance of the sensor was studied by cyclic voltammetry and other electrochemical analysis methods.The results showed that when the concentration range of cysteine was 20μM～100μM and 100μM～800μM,the linear equations were:y₁=0.0680x₁+33.6220（R²=0.9875）and y₂=0.0049x₂+41.9042（R²=0.9047）,the sensitivity was 0.0680μA·μM^-1 and0.0049μA·μM^-1,and the limit of detection was 13.5μM.In addition,the MIL-53（Fe）/CNTs/GCE sensor shows good stability,reproducibility and anti-interference,and the recoveries in practical samples were 98.1%～103.9%.The gold nanoparticles（Au NPs）were synthesized by citric acid reduction method,and MIL-53（Fe）/Au NPs was synthesized by the combination of MIL-53（Fe）and Au NPs.The crystal structure and morphology of MIL-53（Fe）/Au NPs were characterized by X-ray diffraction,scanning electron microscopy and X-ray photoelectron spectroscopy.Then,the electrochemical sensor which can detect cysteine was prepared by using MIL-53（Fe）/Au NPs composite as the recognition element,Nafion solution as binder and glass carbon electrode as the base electrode.The electrochemical performance of the sensor was studied by cyclic voltammetry and other electrochemical analysis methods.The results showed that when the concentration range of cysteine was 10μM～1400μM,the linear regression equation was y=0.01474x+4.844（R²=0.9931）,the sensitivity was 0.01474μA·μM^-1,and the detection limit was1.5μM.In addition,the MIL-53（Fe）/Au NPs/GCE sensor shows good stability,reproducibility and anti-interference,and the recoveries were 98.4%～100.3%.Cu doped MIL-53（Fe）materials,Cu@MIL-53（Fe）were synthesized by impregnation method.Cu@MIL-53（Fe）derivatives（Cu@MD）were synthesized by calcination at high temperature.The crystal structure and morphology were characterized by X-ray diffraction,scanning electron microscopy and X-ray photoelectron spectroscopy.Then,Cu@MD was used as recognition element,Nafion solution was used as binder,and glassy carbon electrode was used as the base electrode to prepare the electrochemical sensor for the detection of cysteine.The electrochemical performance of the sensor was studied by cyclic voltammetry and other electrochemical analysis methods.The results showed that when the concentration range of cysteine was 1μM～10μM and 10μM～400μM,the linear equations were:y₁=-2.824x₁+86.32（R²=0.9515）and y₂=-0.0824x₂+48.67（R²=0.9782）,the sensitivity was 2.824μA·μM^-1 and0.0824μA·μM^-1,and the detection limit was 1.37μM.In addition,the Cu@MD sensor shows good stability,reproducibility and anti-interference,and the recoveries were 95.7%～109.5%.The cysteine electrochemical sensor prepared in this study has good performance,and can be used for the detection of cysteine in actual food,which has important influence and significance on human health.