Novel Chemically Modified Electrodes For Electrochemical Detection Of Small Molecules

Fast and highly sensitive analytical methods are an important research field in food quality and safety detection.Electrochemical sensors based on chemically modified electrodes are a hot and key development direction in this research field.By chemically modifying the surface of conventional electrodes,chemically modified electrodes have higher sensitivity,specificity,and selectivity,while retaining the characteristics of rapid response,playing an increasingly important role in rapid food detection.This dissertation aims to develop a rapid electrochemical detection method for small molecules of dopamine and ascorbic acid,research and design simple chemical modification methods for the surface of ordinary glassy carbon electrodes,and prepare new chemically modified electrodes,and build on this basis Electrochemical sensor for the rapid and sensitive detection of the above two small molecules.The main research content and results of the thesis are as follows.The first part of the research work of the thesis proposes a simple and one-step potentiostatic oxidation method to prepare oxidized glassy carbon modified electrodes,and based on oxidized glassy carbon modified electrodes,an electrochemical method for rapid and sensitive electrochemical detection of dopamine is constructed.A suitable oxidation potential was applied to the surface of the ordinary glassy carbon electrode in the electrolyte solution to prepare an oxidized glassy carbon modified electrode.The electrochemical properties of the modified electrode were characterized by cyclic voltammetry and square wave voltammetry,and the influences of factors such as the p H value of the buffer solution and the oxidation time of potentiostatic oxidation on the electrocatalytic activity of the modified electrode were respectively explored.The experimental results show that the oxidized glassy carbon modified electrode has high catalytic activity for the electrochemical oxidation of dopamine.The electrochemical sensor based on this can quickly and sensitively detect dopamine in the solution,and can effectively eliminate the interference of ascorbic acid and uric acid electroactive substances,with good selectivity and specificity.The linear equation of the electrochemical sensor based on oxidized glassy carbon modified electrode for the detection of dopamine is Y=4.6884X+3.002(R~2=0.995),and the linear range is 0.1～15μM.The sensor is used for the determination of dopamine content in actual samples,and a good recovery rate can be obtained.The second part of the thesis proposed a simple,one-step potentiostatic reduction method to prepare"partially reduced graphene oxide"modified electrode,and based on the"partially reduced graphene oxide"modified electrode,an electrochemical sensor for fast and sensitive electrochemical detection of ascorbic acid was constructed.In the experiment,the graphene oxide suspension was first dripped onto the surface of the glassy carbon electrode to prepare a graphene oxide modified electrode,and then a reduction potential was applied to the surface of the oxidation modified electrode to reduce the graphene oxide film to prepare a reduced graphene modified electrode.By controlling the change of the reduction potential,the reduction degree of the graphene oxide film was adjusted,and the electrochemical properties of the reduced graphene modified electrodes with different reduction degrees and the influence of the electrochemical oxidation catalytic activity of ascorbic acid were investigated.The results show that the"partially reduced graphene oxide"modified electrode with a moderate degree of reduction has the highest electrocatalytic oxidation activity for ascorbic acid.The electrochemical sensor based on"partially reduced graphene oxide"modified electrode can be used for the rapid and highly sensitive electrochemical detection of ascorbic acid in solution.The electrochemical sensor can effectively eliminate the interference of ascorbic acid detection by electroactive substances such as uric acid,and has good selectivity and specificity.The linear equation of the electrochemical sensor based on"partially reduced graphene oxide"modified electrode for ascorbic acid detection is Y=11.624X+0.8896(R~2=0.9985),and the linear range is 0.1～10m M.The sensor is used for the determination of the ascorbic acid content in the actual sample,and the recovery rate is good.