Research On Photoelectrochemical Sensor Based On Nano-Mimetic Enzyme

In recent years,synthetic enzymes based on nanomaterials not only have have the function of simulation,but also overcome the inherent defects of natural enzymes,which have attracted extensive attention.Nanozymes not only have the same mimetic activity as natural enzymes,but also have many advantages such as low cost,high stability,unique surface chemistry,biocompatibility and easy surface regulation,which make them widely used in the field of biosensors.Photoelectrochemical detection technology is an emerging analytical method,which utilizes the mutual conversion of optical signals and electrical signals to achieve the detection of corresponding substances.Glucose is an important substance to maintain normal human activities,so the detection of glucose content in the human body is very important in our daily life.In this thesis,based on bismuth oxyiodide（Bi OI）,Ce-ATP,cerium oxide（Ce O₂）,glucose oxidase（GOX）and other substances,nanozymes and photoelectrochemical sensors were combined to construct a sensitive and specific enzyme sensor to realize the detection of glucose in human serum.The main work is as follows:1、Firstly,the Bi OI nanolayer was prepared on the FTO electrode by the successive ionic layer adsorption reaction（SILAR）method.Bi OI as a photosensitive material,it has efficient absorption in the visible light region and has a narrow band gap.When it excited by light,electrons and holes undergo directional transfer,electrons are directionally transferred to the conduction band（CB）and holes are directed to the valence band（VB）.The H₂O₂generated by the reaction in the solution acts as an electron acceptor,captures electrons in the conduction band,and is further oxidized to generate reactive oxygen species O₂.-.Ce-ATP was synthesized by a simple method and modified with Bi OI to form nanocomposites.It is verified that Bi OI and Ce-ATP have peroxidase activity by color reaction,and then their photoelectrochemical responses to H₂O₂are measured respectively.It is proved that after the formation of nanocomposites,the sensitivity of the sensor to the photocurrent response of H₂O₂is enhanced,and they play a synergistic catalytic role.The synthesized GOX@Ce-ATP is modified on the Bi OI electrode to realized the detection of glucose.Under the catalysis of GOX,glucose and O₂react to generate gluconic acid and H₂O₂.With the increase of glucose concentration,more H₂O₂is generated in the reaction and the photocurrent signal is enhanced,which is a signal-enhancing enzyme sensor for glucose detection.Under the optimal reaction conditions,the prepared sensor exhibited a lower detection limit of 0.071μM,and when the concentration of glucose was increased from0.5μM to 1 m M,the photocurrent response of the sensor was proportional to the logarithm of the glucose concentration,achieving sensitive and specific detection of glucose,it can be used for the detection of glucose content in human serum.2、Ce O₂was synthesized by a simple hydrothermal method,which has the function of peroxidase and combined with Bi OI to form nanocomposites.Due to the matching of their energy levels,when excited by light,the electrons and holes of Bi OI and Ce O₂will move directionally,the electrons on the conduction band（CB）of Ce O₂can be transferred to the CB of Bi OI,and then continue to transferred to the electrode.Ce O₂can accelerate the electron transfer of Bi OI,thereby enhancing the photocurrent response of the electrode.Using electrostatic adsorption,GOX-Ce O₂was synthesized by self-assembly method and modified on Bi OI electrode.The mixture of different concentrations of glucose and excess chromogenic agent DAB was dropped on the GOX-Ce O₂/Bi OI electrode,glucose and O₂can be catalyzed by GOX to generate gluconic acid and H₂O₂.Under the catalysis of peroxide analog enzyme Bi OI and Ce O₂,the intermediate product H₂O₂reacts with the chromogenic agent DAB,and finally generates brown insoluble precipitate on the electrode surface,which impedes electron transfer and reduces the photocurrent.As the concentration of glucose increases,more precipitates are formed,and the current is smaller,it is a signal-reduced enzyme sensor for glucose detection.Under the optimal reaction conditions,the prepared sensor exhibited a lower detection limit of0.0014μM,and when the concentration of glucose was increased from 0.01μM to 10 m M,the photocurrent response of the sensor was proportional to the logarithm of the glucose concentration,achieving the detection of glucose.The sensor has the advantages of high sensitivity,wide linear range and good specificity,providing an effective method for the detection of glucose content in human serum.