Electrochemical Sensors Based On Spinel-type Bimetallic Oxide And Its Composite

Spinel-type bimetallic oxides（AB₂O₄）have excellent magnetic properties,biocompatibility,and catalytic properties,and are widely used in environmental analysis and medical testing.In this thesis,the related references were firstly reviewed.Then,various electrochemical sensors were constructed based on spinel-type bimetallic oxides and their composites.The analytical performances of these sensors in the detection of hydrogen peroxide,glucose and NO₂^-were systematically investigated.Finally,the practical application of these sensors was discussed.The main research contents are as follows:1.Spherical zinc ferrite（ZnFe₂O₄）was prepared by solvothermal method using Zn（NO₃）₂·6H₂O,Fe（NO₃）₃·9H₂O,glycerol and isopropanol as raw materials;Flake graphite carbon nitride（g-C₃N₄）was prepared by high temperature calcination from melaminel;ZnFe₂O₄/g-C₃N₄composite material was prepared by adding different amounts of g-C₃N₄during the preparation of ZnFe₂O₄.The morphologies of composites were characterized by XRD,SEM,and FT-IR.The electrochemical behaviors of the modified electrode were studied in neutral H₂O₂solution and alkaline glucose solution,respectively.The results showed that the combination of ZnFe₂O₄and g-C₃N₄could significantly improve the electrical conductivity of composite.The synergistic electrocatalytical effects on the electrochemical oxidation of H₂O₂and glucose were obtained,resulting in strong electrochemical response.Cyclic voltammetric and chronoamperometric techniques were used in the sensitive detection of H₂O₂and glucose.Under the optimal conditions,H₂O₂could be detected in the range of 5 to 200μmol L^-1with a detection limit of 1μmol L^-1,while glucose could be detected in the range of 0.05 to 2 mmol L^-1with a detection limit of 30μmol L^-1.The modified electrode had good repeatability and stability,and showed potential application in actual sample detection.2.Copper gallate nanoparticles were prepared by hydrothermal-calcination method using Ga（NO₃）_3·9H₂O and Cu（NO₃）₂·3H₂O as raw materials.The morphology of nanomaterial was characterized by XRD,SEM,HRTEM and EDS,respectively.The electrochemical behaviors of Cu Ga₂O₄nanoparticle modified electrode were studied in neutral H₂O₂solution and alkaline glucose solution.The experimental results showed that Cu Ga₂O₄nanoparticles exhibited obvious electrocatalytic effects on the reduction of H₂O₂and the oxidation of glucose.Therefore,cyclic voltammetry and chronoamperometry techniques can be used for sensitive detection of H₂O₂and glucose.Under the optimal conditions,the detection range of H₂O₂was obtained from5 to 200μmol L^-1with a detection limit of 5μmol L^-1,while the detection range of glucose was determined from 0.05 to 2 mmol L^-1with a detection limit of 25μmol L^-1.The modified electrode had good repeatability and stability,and could be used in the detection of actual samples.The results revealed the potential application of gallate spinel oxide nanomaterials in electrochemical sensors.3.Spherical CdGa₂O₄nanomaterials were prepared by solvothermal-calcination method using Ga（NO₃）₃·9H₂O,Cd（NO₃）₂·3H₂O,glycerol and isopropanol as raw materials.The morphologies of nanomaterials were characterized by XRD,SEM and TEM,respectively.The electrochemical behavior of nitrite（NO₂^-）was studied at the CdGa₂O₄nanomaterial modified electrode.The experimental results showed that CdGa₂O₄nanomaterials exhibited obvious electrocatalytic effect on the oxidation of NO₂^-.Cyclic voltammetry and chronoamperometry techniques were used for the sensitive detection of NO₂^-.Under the optimal conditions,the detection range of NO₂^-was obtained from 5 to 200μmol L^-1,and the detection limit was determined as 1μmol L^-1.The modified electrode had good repeatability and stability,and was successfully applied in the detection of nitrite in real sample.