Construction Of Multi-walled Carbon Nanotubes Electrochemical Sensor And Application To The Analysis Of Small Biological Molecules

The sp² hybridized carbon atoms in multi-walled carbon nanotubes（MWCNTs）,with unpaired electrons in the p-orbital of each carbon atom,determines its excellent physiological properties and its wide application as an electrochemical sensing material.By compounding with other materials,they can exhibit better physicochemical properties and become ideal materials for electrode modification.The electrochemical sensor based on the composite material of multi-walled carbon nanotubes can realize the detection of small biological molecules.The excellent electrical signals result from the good electrical conductivity of MWCNTs,which allows for electron transport capabilities,on the one hand,the hollow cylinder structure of MWCNTs,which provides a larger number of reaction sites.The abnormal biological small molecules in human body can bring some diseases,so it is very necessary to detect them,which is expected to provide ideas for medical diagnosis.Electrochemical sensors have the characteristics of fast response speed,high sensitivity and simple operation.Therefore,the aim of this thesis is to prepare three composites based on MWCNTs to construct different electrochemical sensors to accomplish highly sensitive detection of small biological molecules.The main research contents are as follows:1.The introduction of the conception of nanomaterials is briefly discussed,and the structure,properties and applications of carbon nanotubes,detection methods for biological small molecules and the principles of electrochemical sensors and modified electrodes are outlined.On this basis,further research advances in the electrochemical detection of biomolecules based on MWCNTs composites are reviewed.2.A non-enzymatic glucose sensor（CuO/MWCNTs/GCE）was constructed by compounding copper oxide（CuO）and multi-walled carbon nanotubes（MWCNTs）.CuO has a stable and reversible redox activity under alkaline conditions and can reduce the overpotential of the redox reaction.The linear range of CuO/MWCNTs/GCE for the detection of glucose was 0.5-5000μM,and the detection limit was 0.17μM（S/N=3）.CuO/MWCNTs/GCE has simple preparation process,good selectivity,stability,and achieved the detection of Glu in human serum samples.3.Ruthenium oxide（RuO₂）has high catalytic activity and the excellent electrical conductivity of MWCNTs can improve the electron transfer rate of RuO₂ and maintain its electrocatalytic properties.Due to the synergistic effect of RuO₂ and MWCNTs,the RuO₂/MWCNTs composite was prepared for the efficient and stable electrochemical detection of DA.It is proved that DA is adsorbed on the surface of RuO₂/MWCNTs/GCE,and the possible oxidation mechanism was the conversion of dopamine to dopamine quinone.Compared to RuO₂/GCE and MWCNTs/GCE,the electrocatalytic performance of RuO₂/MWCNTs/GCE for DA oxidation was significantly,and the quantitative detection of DA can be realized.Moreover,RuO₂/MWCNTs/GCE enabled the detection of DA in serum samples.4.It was synthesized by a simple hydrothermal method of yttrium vanadate（YVO₄）,and combined with MWCNTs to establish a new method for the detection of ascorbic acid（AA）,dopamine（DA）,and uric acid（UA）separately and simultaneously.The uniform distribution of YVO₄ on the surface of MWCNTs resulted in their large specific surface area,fast electron transfer rate,and excellent electrical conductivity,which improved their electrocatalytic performance.YVO₄/MWCNTs/GCE exhibits wide linear range,low detection limit,and good anti-interference ability.It can achieved the detection of AA,DA,and UA in human serum samples,which has some practical applicability.5.This paper provides a new method for the preparation of carbon nanotube composites and the detection of glucose,dopamine,ascorbic acid,and uric acid by electrochemical sensors.In view of the existing problems of related research areas,the experiment is scientifically discussed and looked forward to the future work combined with cutting-edge work and the results of this work.