Preparation Of Group VIB Metal Oxides/carbons And Their Electrochemical Sensing Properties For Dopamine

As a kind of catecholamine neurotransmitter,the abnormal concentration of Dopamine(DA)in human blood will cause many diseases.Therefore,the development of materials with good sensing performance for the construction of DA electrochemical sensor has become a research hotspot.VIB group transition metal oxides have been used in the field of electrochemistry due to their simple structure,easy control and good biocompatibility.However,their poor electrical conductivity has a great limitation on the improvement of electrocatalytic performance.Combining with carbon materials is one manner to solve this problem.However,the carbon materials generally have the disadvantages of complex preparation and high cost.Therefore,in this thesis,low-cost glucose was used as carbon source,and VIB transition metal oxides were combined with carbon by hydrothermal method.Finally,three kinds of composites with high conductivity and electrocatalytic activity were successfully prepared.Their morphology,composition,structure and electrochemical properties were characterized via various analytical and measurement means.The main contents are as follows:(1)The homogeneous spherical Cr2O3/C composite was obtained by calcinating the precursor,which was synthesized by hydrothermal method with chromium nitrate as the source and glucose as the carbon source,at 400? in air.It has a morphology with good dispersion,and the diameter was 50?70 nm.The material was modified on the surface of glassy carbon electrode and(GCE)used for DA detection.The sensor has good selectivity,high sensitivity and stability for DA.The DPV response value of the sensor is linearly correlated with the concentration of DA in the range of 0.1?1014 ?mol·L-1.The detection of limit to DA is 0.03 ?mol·L-1(S/N=3).(2)Using ammonium molybdate as molybdenum source and glucose as carbon source,MoO2/carbon spheres(MoO2/CSs)composite with rough surface and uniform size was synthesized by hydrothermal method combined with calcination at 650? in N2.The particle size of the composite is 350?450 nm,and MoO2 nanoparticles are loaded on the surface of carbon spheres.The MoO2/CSs composite is modified on GCE to construct electrochemical sensor,which shows good catalytic ability for DA.The linear relationship for DA is great in the concentration ranges of 0.34?96.14 ?mol·L-1 and 96.14?668.14 ?mol·L-1,with the detection limit of 0.04 ?mol·L-1(S/N=3).At the same time,the sensor also has excellent anti-interference ability and stability.(3)Using sodium tungstate as tungsten source and glucose as carbon source,hydrothermal method followed with calcination at 650? in N2 was used to synthesize the composite of carbon spheres supported oxide nanoparticles(WO2-NaxWO3/CSs)with rough surface and the particle size of 300?500 nm.The electrochemical tests show the composite modified GCE sensor possesses good stability and reproducibility,and displays good linear relationship in the concentration ranges of 0.004?15.4 ?mol·L-1 and 15.4?106.4 ?mol·L-1,with the detection limit of 0.0013 ?mol·L-1(S/N=3).Furthermore,the above three kinds of composite modified electrodes were successfully applied to the detection of DA in animal serum samples,and ideal recovery rates are obtained.The electrocatalytic oxidation mechanism of DA on the electrode surface was studied.It was found by calculation that the reaction of DA on the electrode involves two electrons and two protons.