Fabrication And Application Of Nonenzymatic Electrochemical Biosensing Materials Based On Graphene And Molybdenum Disulfide

The traditional small biological molecules,such as glucose and hydrogen peroxide（H₂O₂）,play an important role in living organisms.Glucose is not only the prerequisite of the energy supply for organisms,but also an important metabolite,which is closely related to diabetes mellitus.H₂O₂ is an important product of many enzymatic reactions and participates in the critical physiological processes such as the stomatal closure in plants and the apoptosis in animals.The health of organisms can be reflected by the existence and the content of the small biomolecules.Therefore,the rapid and accurate detection of glucose and H₂O₂ is of great significance in the medical health.At the same time,the detection of glucose and H₂O₂can also be used in the fields of food industry,fermentation control and biotechnology.In this paper,two novel composites based on the two-dimensional sheet structure（graphene and molybdenum disulfide）were designed,fabricated and used for enzyme-free electrochemical sensing of glucose and H₂O₂.The two kinds of the ternary composite were composed by the materials with high catalytic activity for small biomolecules and the graphene or Mo S₂ with large specific surface area and strong electron transport capability.The main research results are as follows:（1）The novel Ag-Cu O/r GO composites were designed and prepared.The composites with the particle size of about 10 nm were synthesized by hydrothermal method followed by calcination.The effects of different silver contents on the properties of the composites were investigated.The results showed that the best performances were obtained when the molar ratio of Ag/Cu reached 1/50.The small amount of Ag NPs in the composite can promote the electron transfer between the electrode and the active material.In addition,the catalytic activity of Ag-Cu O NPs can be also improved because Ag can promote the interaction between the active material and the glucose molecules in the solution.The Ag-Cu O/r GO composite modified electrode exhibits good enzyme-free electrochemical sensing performance for glucose with the extremely wide linear range of0.01-28 m M,the good sensitivity of 214.37μA m M^-1 cm^-2 and the minimum detection limit of 0.76μM.Meanwhile,the sensor presents good selectivity and stability,and can be used for the analysis of the actual blood samples.（2）The novel Ag-Ag₂S/Mo S₂ composites were designed and prepared.The composites were obtained by the self-assembly of the Mo S₂ aqueous solution and the Ag nano-dispersions.In the composite,the multi-layered Mo S₂ is distributed as a petal shape,and the Ag-Ag₂S NPs with the size of30×20 nm are uniformly grown on the petal-like layer.The Ag₂S with a low content exists mainly at the interface between the Ag NPs and the Mo S₂ sheets.The sensor possesses the best performance when the molar ratio of Ag NPs and Mo S₂ is 1/2.When the ratio is less than 1/2,the low content of Ag₂S is favor of the transmission of electrons.Excessive Ag₂S will lead to a sharp decline in the transmission capacity of electrons and suppress the sensing performance.The Ag-Ag₂S/Mo S₂ composite modified electrode exhibits a good enzyme-free electrochemical sensing performance for H₂O₂ with the extremely wide linear range of 0.01-160m M,the good sensitivity of 17.1μA m M^-1cm^-2 and the minimum detection limit of 4.8μM.Meanwhile,the sensor shows a good selectivity and stability.