Detection Of Glucose By Cu₂O/MWCNTs Nanocomposites And Their Modified Printed Electrodes

With the improvement of material living standards,the ranking of diabetes has been rising in diseases that generally endanger people's health.The number of patients in China has reached 120 million,ranking first in the world.In this environment,it is especially important to check the blood sugar levels in your own blood regularly.At present,there are two main sensors for detecting the concentration of glucose in the blood:glucose oxidase(GOx)-based and enzyme-free(NEG).The selectivity and sensitivity of the former are excellent,but the stability is extremely poor,because the enzyme is sensitive to humidity,temperature,p H and chemical toxicity,the detection result is easily affected by the environment and is inaccurate,and the biological enzyme immobilization process is delicate and cumbersome.These all limit the development of GOx biosensors.The enzyme-free sensor can detect the concentration of the glucose molecule by electrocatalytic oxidation directly on the electrode,and avoids the disadvantages of the enzyme-containing sensor,and is suitable for more extreme environments and occasions.Therefore,many researchers have turned their attention to the study of enzyme-free sensors.Most of the existing modifying materials are based on metals and their oxides,hydroxides and the like.There are mainly noble metals such as platinum(Pt),gold(Au)and palladium(Pd),transition metals such as nickel(Ni),copper(Cu),manganese(Mn),zinc(Zn),cobalt(Co)and the like.Cuprous oxide(Cu₂O)has a wide band gap of 2.17 e V,and has many advantages such as remarkable catalytic activity,simple preparation,low cost,etc.,and the nanostructure of Cu₂O has been proved to have great potential in the catalytic oxidation of glucose.Catalytic properties are directly related to specific surface area and morphology.In this thesis,an enzyme-free glucose sensor was prepared based on octahedron Cu₂O and its composite with multi-walled carbon nanotubes(MWCNTs),and the phosphate buffer(PBS)similar to the blood environment was used as the electrolyte to investigate the electricity of glucose.The effect of catalytic oxidation.Finally,the composite material is combined with printing technology,the printing electrode(SPE)is prepared by screen printing machine,and the composite electrode is screen-printed to construct Printed Cu₂O/MWCNTs/SPE enzyme-free glucose sensor.The main work is as follows:(1)Octahedron Cu₂O is prepared by a simple and convenient liquid phase reduction method.The crystal structure and morphology of the sample were characterized by XRD and SEM,which proved to be a complete octahedral shape.The cyclic voltammetry(CV)curve shows that the prepared octahedron Cu₂O has catalytic oxidation effect on glucose.The current-time(it)curve is used to conclude that the Cu₂O octahedral modified glassy carbon electrode(GCE)can be 10?M?4.25m M.The glucose solution at a concentration range of 4.25 m M produced a linear response with a calculated sensitivity of 179.9?A·m M^-1·cm^-2and a detection limit of5.6?M(S/N=3).(2)Preparation of Cu₂O/MWCNTs composites with MWCNTs as auxiliary materials.The effect of the amount of MWCNTs on the electrochemical catalytic performance of the product.The obtained samples were characterized by XRD,FESEM and TEM,and Cu₂O was successfully attached around MWCNTs.Using the cyclic voltammetry curve,the electrochemical properties of the obtained composites were better when the amount of MWCNTs was 30 mg.The GCE was modified by this sample.Cyclic voltammetry showed that the addition of MWCNTs greatly improved the catalytic oxidation of Cu₂O.The it curve showed that Cu₂O/MWCNTs/GCE could produce linear response to glucose solution in the range of 5?M?9.5 m M.The detection limit was 2.7?M(S/N=3)of 214.2?A·m M^-1·cm^-2.Moreover,it has excellent selectivity and can effectively prevent the interference of ascorbic acid(AA),uric acid(UA)and dopamine(DA),and has good stability and reproducibility.(3)Printing SPE with carbon-based conductive ink developed by the laboratory,printing composite material to modify SPE,and then printing a layer of insulating ink to make a printed sensor.The CV test showed that the sensor can effectively catalyze the oxidation of glucose.The it curve shows that the sensor can produce a linear response to the glucose solution in the range of 20?M?5.25 m M.The calculated sensitivity is 75.4?A·m M^-1·cm^-2,and the detection limit is 3.2?M(S/N=3).Moreover,it has excellent selectivity and can effectively prevent the interference of ascorbic acid(AA),uric acid(UA)and dopamine(DA),and has good stability and reproducibility.