The Fabrication Of Three Novel Electrochemical Sensors And Their Electrocatalytic Properties For Dopamine,Uric Acid And Bisphenol A

Dopamine（DA）is one of the important neurotransmitters in human body.Its normal concentration should be kept in the range of 0.01-10μM.If DA is insufficiently secreted,it may cause major diseases such as schizophrenia and Parkinson’s disease.Uric acid（UA）is a common biological small molecule.The normal concentration in the human body is 10-100 times than that of DA,and its metabolic disturbance is the main cause of kidney disease and gout.Bisphenol A（BPA）is an important phenolic organic pollutants.Excessive emissions of BPA will cause serious environmental pollution and pose a great threat to human’s life and health.Therefore,the highly sensitive and selective determination of DA,UA and BPA is one of the research hotspots in the fields of medicine and environmental science.Among the various analytical methods,electrochemical methods have been widely adopted by researchers because of their unique advantages,such as high sensitivity,good selectivity,simple equipment and fast analysis.Highly efficient electrocatalytic materials are the key factor for constructing electrochemical sensors with high performance.In this thesis,three kinds of novel nanomaterials were prepared.Based on these nanomaterials,three new electrochemical sensors were fabricated and used to study the electrocatalytic properties of DA,UA and BPA,respectively.The three new methods of electrochemical detection were established and applied to the routine analysis of actual samples.This thesis was divided into five chapters.The main contents were as follows:The erbium phosphate（Er PO₄）nanoellipsoids were synthesized by hydrothermal method.The morphology and composition of the materials were characterized by scanning electron microscopy（SEM）,energy dispersive spectroscopy（EDS）and X-ray diffraction（XRD）.A novel electroactive interface（Er PO₄/CPE）for the detection of DA and UA was fabricated based on a carbon paste electrode（CPE）loaded with Er PO₄nanoparticles.Electrochemical behavior studies showed that Er PO₄nanoparticles could be used as conductive carriers for electron transport at the electrode/electrolyte interface,and the redox reaction mechanism of the electrode surface was discussed.Er PO₄/CPE showedxiugai surprising electrocatalytic activity for DA and UA.The detection limits（LOD）of DA and UA were 0.02μM and 0.004μM and linear relationships were satisfied in the concentration range of 0.07-78μM and 0.01-66μM,respectively.In addition,Er PO₄/CPE exhibited excellent selectivity in the simultaneous determination of DA and UA.The method had been successfully applied to the analysis of DA and UA in actual samples.Erbium doped cadmium tungstate nanomaterials（Er-Cd WO₄）were successfully synthesized by hydrothermal synthesis without template.The composition,structure and morphology of erbium doped samples with different content of Er were studied by XRD,SEM,EDS and other characterization methods.Then,Er-Cd WO₄was further utilized to prepare a novel electrochemical sensor（Er-Cd WO₄/CPE）.Electrochemical impedance spectroscopy（EIS）and cyclic voltammetry（CV）results showed that 0.5 wt%Er-Cd WO₄/CPE had the most excellent electrocatalytic performance for BPA,and its catalytic ability was 12 times higher than that of bare CPE.The reaction kinetics were studied at different p H and sweep speeds,revealed that the electrochemical process was mainly controlled by diffusion and it was a two-electron and two-proton transfer reaction.The 0.5 wt%Er-Cd WO₄/CPE showed a lower detection limit of 0.003μM（S/N=3）with a linear range of 0.01-6μM using differential pulse voltammetry（DPV）.At the same time,the newly proposed sensor also exhibited ideal anti-interference ability,stability and repeatability.It was expected to be used for the routine analysis of BPA.The new core-shell nanocomposites（ZnAlCe LDH@ZIF-8）were successfully prepared by in-situ growth of ZnAlCe layered double hydroxide（LDH）on the surface of the zeolitic imidazolate framework（ZIF-8）via the metal organic framework（MOF）derivatization method.Based on the material,a novel electrochemical sensor for the detection of BPA was fabricated.The composites were characterized by XRD,SEM and EDX mapping.The electron transfer ability and electrocatalytic ability of ZnAlCe LDH@ZIF-8 in potassium ferricyanide were studied by EIS and CV.Electrode reaction kinetics confirmed that the reaction was a typical diffusion controlled process.The electrocatalytic activity of ZnAlCe LDH@ZIF-8 was investigated by amperometric response（i-t）using BPA as a molecular probe.The results showed that there was an ideal linear relationship between the peak current and BPA concentration on ZnAlCe LDH@ZIF-8/CPE,and the detection limit was 0.03μM（S/N=3）.At the same time,the anti-interference test and actual sample analysis were carried out with good results.