Study Of Electrochemical Biosensor Based On Nano Manganese Dioxide

Biosensor has attracted lots of attentions in the world due to hisabundant applications in clinical, military, food industry, environmentaltreatments and so on. However, the protein-based biosensors have theirown disadvantages, such as instability, high cost of enzymes, andcomplicated immobilization procedures. Furthermore, the activity of theproteins can be easily affected by around microenvironment, containingtemperature, pH, and toxic substances. Therefore, the development ofenzyme-free sensors with low detection limit and wide response rangehas become a trend. Modified electrodes based on nanostructured MnO₂combined with high surface area and good electrochemistry abilities canlargely improved electrical responses and the detection sensitivity, and itsactivity for the oxidation of H₂O₂has found several applications assensors. However, some of sensors have displayed the drawbacks of lowsensitivity, poor selectivity and complex procedure. In this paper, wereport a facile hydrothermal method for synthesizing cryptomelane-typeα-MnO₂nanofibrous andδ-MnO₂spongelike microspheres based on δ-MnO₂nanosheets. We investigated the electrochemical properties andthe applications in amperometric Determination of HydrogenPeroxide．The main contents of the thesis are given as follows：High dispersion of nanofibrous cryptomelane-type manganesedioxide was synthesized by a facile hydrothermal reduction route. Themorphological characterization was examined by scanning electronmicroscopy （SEM） and transmission electron microscopy （TEM）. Thestructure and electrochemical properties of manganese dioxide werecharacterized by X-ray diffraction （XRD） and an electrochemicalworkstation （EW）. Glassy carbon electrode （GCE） modifed with thenanostructured cryptomelane-type manganese dioxide was investigatedfor amperometric detection of hydrogen peroxide （H₂O₂） in phosphatebuffer solution with a pH7.4at an open-circuit-potentials of0.2V. Theamperometric signals are linearly proportional to H₂O₂concentration inthe range1.0-15.0×10^-4M with a correlation coefficient of0.996withthe GCE modified with0.1wt%cryptomelane-type manganese oxides.The sensor is sensitive and its significant electrocatalytic activity resultsfrom the nanostructure of cryptomelane-type manganese oxides. Inaddition, the sensor has a good reproducibility. These results demonstratethat this material with high electrocatalytic activity offers great promisefor new class of nanostructure electrode for biosensor.A novel sensor for hydrogen peroxide （H₂O₂） was fabricated using-MnO₂spongelike microspheres based on-MnO₂nanosheets on aglassy carbon electrode （GCE）. The hierarchical microspheres wereobtained by a hydrothermal method and characterized by scanningelectron microscopy（SEM）, transmission electron microscopy （TEM） andX-ray diffraction（XRD）. Electrochemical workstation （EW） was used toevaluate the electrochemical performance of the modified GCE. Thesensor also exhibits excellent catalytic activity toward the oxidation ofH₂O₂. The amperometric signals are linearly proportional to H₂O₂concentration in the range5-100×10^-4M with a correlation coefficient of0.993with the GCE modified with1wt%-MnO₂in phosphate buffersolution with a pH7.4at an open-circuit-potentials of0.2V.