Construction And Performance Study Of Phenolic Compound Electrochemical Biosensor

Phenolic compounds,including monophenols and bisphenols,are widely used chemical raw materials which are mainly used in cosmetics,leather and other manufacturing industries.With the development of manufacturing,the use of phenolic compounds is becoming more widespread.However,due to certain chemical properties of phenolic compounds,such as refractory,highly toxic,etc.,its widespread use has brought a series of serious problems to the environment,and it may accumulate in human body with the water,bringing a series of health problems.Therefore,the phenol content in water and soil must be maintained at a normal concentration range.Real-time detection of phenol content in water and soil has certain practical significance for environmental construction and human health.In this thesis,we constructed phenolic electrochemical biosensors for the analysis and detection of actual samples based on nano-carbon materials and bioactive substances.Research has been carried out on the synthesis of materials,the selection and fixation of bioactive substances,the main points are as follows:Graphene is a conductive material with high specific surface area,good electrical conductivity and high mechanical strength.It is often used as a modification material for enzyme electrodes.Doping graphene with hetero atoms such as B,S and N atoms can improve its some disanvantages,such as weak electrochemical activity,easy to agglomerate,difficult to process and so on.In this study,nitrogen-doped graphene material was synthesized with polyaniline as a nitrogen source,and graphite oxide was reduced by a hydrothermal method,followed by high temperature calcination.Then,because the horseradish peroxidase can be oxidized by H₂O₂ to catalyze the oxidation of the phenolic compounds,so we combined the horseradish peroxidase with the prepared nitrogen-doped graphene material and chitosan to prepare an enzyme modified electrode for detecting hydroquinone.The electrochemical properties of the electrode were studied by electrochemical methods such as cyclic voltammetry.The results shows that the detection range of hydroquinone was 9×10^-55.075×10^-3 mol/L,the linear equation is I_pc（μA）=-5.89C（mmol/L）-11.37,the correlation coefficient is R²=0.998;the detection limit is 1×10^-5 mol/L（S/N=3）;the sensitivity is 84.14 mA·mol^-1·cm^-2,apparent Michaelis-Menten constant K_M^app was 14.9×10^-55 M;at the same time,this system as a detection method for bisphenol compounds had a strong anti-interference ability as well as good reproducibility and stability.Polyphenol oxidase can catalyze the bisphenol compounds to form quinone compounds in the presence of oxygen or catalyze the monophenols oxidase to bisphenols and further oxidize to quinone compounds.Based on this,the prepared nitrogen-doped graphene material was used as a carrier,and polyphenol oxidase was used as a catalyst to prepare an enzyme-modified electrode for detecting phenol under cross-linking of glutaraldehyde.The electrochemical properties of the modified electrode were studied by electrochemical methods such as cyclic voltammetry and so on.The results show that the biosensor had a lower detection limit of1.21×10^-6 mol/L（S/N=3）;a large detection range from 2×10^-5 to 7.7×10^-4 mol/L,the linear equation is Ipc（μA）=-36.696C（mmol/L）-1.295,the coefficient is R²=0.993;the sensitivity is524.285 mA·mol^-1·cm^-2,apparent Michaelis-Menten constant K_M^app was 33.9×10^-55 M.The results of cyclic voltammetry also show that this biosensor possesses a very good sensitivity,repeatability and anti-interference ability.In order to further improve the electrochemical performance of the phenol biosensor,such as the sensitivity and the detection range,the material was further optimized,and the graphene/carbon nanotube composite material was prepared by in-situ chemical reduction method.The morphology and functional groups were characterized by scanning electron microscopy,Raman and so on.The tyrosinase was combined with the prepared reduced graphene/carbon nanotube composite material,and chitosan was used as a binder to prepare an enzyme-modified electrode for detecting phenol.The results of cyclic voltammetry show that the biosensor had a lower detection limit of 1.38×10^-8 mol/L（S/N=3）;a large detection range from 2×10^-5 to 1.14×10^-3 mol/L,the linear equation is I_pc（μA）=-28.002C（mmol/L）-1.249,the coefficient is R²=0.998;the sensitivity is 400.029 mA·mol^-1·cm^-2,apparent Michaelis-Menten constant K_M^app was 8.7×10^-55 M;.At the same time,the system as a detection method for phenolic compounds has a grate anti-interference ability with only produces a current change of 0.2%、1.4%、3.6%、0.6%and 1.0%for FeCl₃、KNO₃、Na₃PO₄、CuSO₄ and ZnCl₂,respectively.At the same time,the electrochemical test results show that the sensor also has good reproducibility and stability.The enzyme biosensor of phenolic compound prepared in this study is expected to be used for the detection of phenolic compounds,including phenol,hydroquinone,catechol,etc.,and provides the control and good application prospects for the detection of phenolic compounds.It is of great impact and significance of the study of phenolic compound sensors.