| Summary: | 碩士 === 國立臺北科技大學 === 化學工程研究所 === 96 === Part I：Nanostructured TiO2 films were prepared onto screen-printed carbon electrode (SPE) and indium tin oxide coated electrode (ITO) by using potentiostat method. Resulting, TiO2 film coated electrode used to immobilize flavin adenine dinucleotide (FAD). Flavin enzyme firmly attached onto metal oxide surface and this modified electrode showed promising electrocatalytic activities towards reduction of hydrogen peroxide (H2O2) in physiological condition. The electrochemistry of FAD confined in the oxide film was investigated. The immobilized FAD displayed a pair of redox peaks with a formal potential of −0.42 V in pH 7.0 oxygen-free phosphate buffers at scan rate of 50 mV s−1. The FAD in the nanostructured-TiO2 film retained its bioactivity and could catalyze the reduction of H2O2. The immobilized FAD exhibited excellent electrocatalytic response to the reduction of H2O2, based on which mediated biosensor for H2O2 was achieved. The linear range for determination of H2O2 was from 10×10−6 to 2.0×10−4M with a detection limit of 2.0×10−7M at a signal-to-noise ratio of 3. In addition, atomic force microscopy and scanning electron microscopy are used for surface analysis and results are revealed that the FAD/TiO2 films are nanostrctured. The stability, repeatability and selectivity of the biosensor were also discussed.
Part II：Here, we report a simple method for preparation of biocomposite electrode based on nanostructured titanium dioxide (TiO2) and deoxyribonucleic acid (DNA). First step, Nano-TiO2 particles were electrochemically synthesized and used for modification of Glassy carbon electrode (GCE). Second step, DNA layer was electrochemically deposited onto Nano-TiO2/GCE. This bilayer (DNA/Nano-TiO2/GCE) film modified electrode used for loading of thionin (TN) dye molecules, cyclic voltammetry results indicated that strong and irreversible loading of TN. X-ray diffraction analysis, atomic force microscope and scanning electron microscope results revealed that TiO2 particles are composed mainly of anatase and TN/DNA/Nano-TiO2 film layer is nanocomposite, respectively. TN/DNA/Nano-TiO2/GCE shows a stable and reversible redox peak in the pH range of 1- 13. In neutral buffer solution, TN/DNA/Nano-TiO2/GCE biosensor exhibited excellent electrocatalytic activity towards reduction of hydrogen peroxide (H2O2) and oxygen (O2). This biosensor employed for detection H2O2 in wide linear range between 0.2 – 22.3mM with detection limit of 0.05mM (S/N=3). In addition with, determination of H2O2 in real samples was carried out and satisfactory results were obtained. The stability and reproducibility for biosensor also discussed in detail.
Part III：Copper nanoparticles (Cunano) have been prepared on polymer template and applied for the fabrication of H2O2 sensor with highly enhanced sensitivity. Cunano particles were directly electrodeposited onto pre-polymer coated electrodes by linear sweep voltammetry. Poly(o-phenylenediamine) (pOPD) electrochemically deposited onto electrode surface as plat form for Cunano particles deposition. The structures and morphologies of pOPD and Cunano/pOPD nancompsoites were characterized by X-ray diffraction, atomic force microscopy and scanning electron microscopy. The direct electrocatalytic reduction of H2O2 and oxygen in neutral medium at Cunano/pOPD nanocompsoite modified electrodes has been investigated in detail. Compared to a bare pOPD modified and bare electrode, a substantial decrease in the overvoltage of the H2O2 reduction and O2 were observed at the Cunano/pOPD nanocompsoite modified electrodes with reduction starting at cc. -0.30 V vs. Ag/AgCl (saturated KCl). At an applied potential of -0.30 V, Cunano/pOPD nanocompsoite electrodes produce high and reproducible sensitivity to H2O2 with 0.49 mA/mmol dm23. Linear responses were obtained over a concentration range from 1µM to 1.0 mM with a detection limit of 0.1 µM (S/N = 3). The Cunano/pOPD nanocompsoite modified electrode allows highly sensitive, low working potential, stable, and fast amperometric sensing of H2O2, thus is promising for the future development of non-enzymatic H2O2 sensors. In addition with, Cunano/pOPD nanocompsoite electrode showed excellent electrocatalytic activity towards nitrite and employed for its detection in acidic medium.
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