Research On Metal-organic Frame As Sensitive Material For Electrochemical Sensor

Electrochemical sensors technology is implemented by changing the electrical signal generated by the reaction of an identifying element on the electrode with the target analyte.The energy changing element of the sensor converts the detected electrical signal into a digital message so as to achieve the qualitative and quantitative study of the target analyte.It is a new detection technology with low cost,high sensitivity,wide linear range,convenience and fast response.Based on these advantages,electrochemical sensor analysis technology is not only widely used in the detection of small biological molecules,but also widely used in agriculture,food and petroleum industry,as well as environmental and biomedical fields.Among so many electrode materials,Metal-organic frameworks（MOF）have became one of the most commonly used electrode materials due to their large internal surface area,controllable pores and diverse chemical structures.MOF are porous solid materials consisting of organic ligands and metal ions by forming coordination bonds.However,the poor conductivity of MOF severely limits their application in electrochemistry.In order to improve electrical conductivity,MOF are often combined with other highly conductive nanomaterials as sensors’electrode materials.Based on this,three kinds of electrochemical sensors were constructed by loading nanomaterials on different MOF,which respectively realized the sensitivity detection of uric acid,isoniazid and ascorbic acid.Specific research contents are as follows:1.Specific recognition of uric acid molecules by Ni-MOF sensor modified by Au NPsIn this work,we synthesized Ni-MOF with cube structure by simple method,using H₃BTC as organic ligand,and successfully loaded Au NPs with particle size of 8.45 nm on its surface.X-ray Diffraction,X-ray photoelectron spectroscopy and Scanning electron microscope characterization showed that Au/Ni-MOF composite nanomaterials with small particle size,uniform dispersion and high crystallinity were successfully synthesized.Then,a series of experimental conditions were optimized,including p H,sweep speed,material’s mass ratio and electrode modification amount.The optimal p H of the designed sensor was 7.When detecting UA,the peak current increased with the increase of sweep speed,and the oxidation process of UA was consistent with the surface chemical process.In view of the stability of the system,100 mv/s was selected as the optimal sweep speed.The optimal mass ratio of Au NPs to Ni-MOF was 1:4,the optimal concentration of electrode material was 2 mg/m L,and the optimal volume was5μL.The linear range of the sensor is 15μM～500μM with the lowest detection limit of 5.6μM（S/N=3）.Compared with other UA electrochemical sensors,it has a relatively wider linear range and lower detection limit.Besides,the sensor has good selectivity to AA,DA and Glu,and also has good stability and reproducibility.Finally,the sensor was successfully applied to the detection of UA in human serum,and the results of recovery and RSD were satisfactory.2.Specific recognition of isoniazid by Ni-MOF sensor modified by multi-wall carbon nanotubesNi-MOF with porous spherical structure and particle size of 13.46 nm were synthesized by a simple solvothermal method using PTA as organic ligand and Ni（NO₃）₂·6H₂O as metal center.MWCNT was loaded onto MOF successfully by electrostatic adsorption under stirring conditions.Because of the MWCNT is introduced into the MWCNT,the oxidation peak current is increased by increasing the electron transfer rate of INH on the electrode.SEM,XRD and XPS characterization showed that MWCNT/Ni-MOF was synthesized successfully.The test conditions of the sensor,including p H,sweep speed,electrode modification and ratio between materials were optimized.Under the optimal experimental conditions,the linear range of INH on the sensor is 20μM～350μM by DPV,and there is a linear relationship between the peak current and the target concentration:y=0.0218x+0.5662,（R²=0.9956）.Results show that the oxidation of INH on the sensor is a surface-controlled process.INH is oxidized to isonicotinic acid on the electrode in the end.It has been measured that the designed sensor has good performance in anti-jamming ability,stability and reproducibility.Finally,MWCNT/Ni-MOF was successfully applied to the actual test of INH tablets.3.Ascorbic acid detection of composite nanomaterial sensor based on graphene oxide and Cu-MOFIn this experiment,with PTA as the organic ligand and copper acetate as the metal center,Cu-MOF with small balls was synthesized by simple precipitation method,and then combined with r GO under stirring conditions.Then Cu-MOF was successfully loaded on the surface of r GO.SEM,XRD and XPS showed that the material was successfully synthesized.Next,a series of experimental conditions for AA detection were optimized,including p H,sweep speed,modification amount on electrode and ratio between materials.When the sensor detects AA,the optimal p H is 7,the optimal ratio between materials is 6:1,and the current response is maximum when the electrode modification amount is 3mg/m L.Since the scanning rate is proportional to the oxidation current,the oxidation of AA on the sensor is a surface-controlled process.And the linear range of AA measured by the sensor is 5～250μM,while the lowest detection limit is3.76μM（S/N=3）.Compared with other AA sensors,the sensor has a wider linear range and a lower detection limit.Moreover,the sensor has good selectivity,stability and reproducibility.Finally,the sensor constructed in this experiment has been successfully applied to the actual detection of vitamin C tablets,so the sensor has good practical application value.