The Fabrication And Characterization Of Nanowires And Nanoelectrode Formed By The Template Technique And The Evaluation Of Nanoelectrode

A great deal of attention has been paid to the fabrication and characterization of one-dimensional nanostructnie materials. These materials have significant potential applications in many important advanced technologies, such as solar energy conversion, chemical sensor, catalyst, absorption and nanoelectrode, and they also have some novel electrical, optical, magnetic and chemical properties. Microclcctrodc has a number of advantages for its small dimension, for example, high mass transport, low iR drop, high signal to noise ratio, high current density, low time constant. Therefore, microelectrode is one of the front fields of electrochemistry and electroanalytical chemistry. In addition to possessing the properties of microelectrode, nanoelectrode should have properties for the nanostructure of its own. The advantages and applications in dynamics of electrochemistry, cyclic voltammctric detection, modified electrode, sensor, imaging lip and detection of single molecule of nanoeleclrode show a wider potential future. Consequently, nanoelectrode has generated a tremendous amount of interests in fundamental and potential promising applications.In this thesis, we have prepared the self-organi/ed anodic aluminum oxide (AAO) templates, which provides a hexagonally ordered array of nanopores with very uniform pore diameters. The nanowircs of Pt and An were prepared by the template technique using electrochemical methods. The morphology and crystal structures of these obtained nanowires were systemically characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Scanning electron microscopy (SEM). Nanoelectrode arrays were fabricated through these obtained nanowires. Voltammetric experiments were conducted to measure the capacitive currents and the Faradaic currents of the nanoelectrode.(1) Under appropriate anodic conditions, for example, the temperature, the electrolyte and the potential, we have successfully prepared the porous anodic aluminum oxide (AAO) templates, which provide a hexagonally ordered array of nanopores with very uniform pore diameters (20nm and 50nm). And we also successfully prepared porous anodic aluminum oxide (AAO) templates with large interpore space whose pore diameter is 100nm or so.(2) Uniform Pt and Au nanowire arrays with controllable lengths have been fabricated by constant voltage electrodeposition in the AAO templates with Ag as their conductive substrates. It is found that the nanowires are dense and continuous, with uniform diameters. The nanowires with the diameters of 20nm, 50nm and lOOnm, and the lengths from lum to 12j.im have been obtained. SEM, TEM and XRD were used to investigate the morphology and crystal structure of the nanowires.(3) A new procedure for fabrication of nanoelectrode has been developed. This procedure is simple and quick and requires only routine inexpensive electrochemical instruments. SEM was used to characterize the morphology of the nanoelectrode. The capacitive current of nanoelectrode is very low, that is to say the double-layer capacitance is low, which can improve the ratio of signal to noise. Cyclic vollammetric experiments were conducted to measure the capacitive currents and the Faradaic currents of the nanoelectrode. Under varying scanning rates, cyclic voltammetry was used to explore the Faradaic currents. At low scan rate, the diffusion will be dominated by transport in the thick linear zone. Indeed, the currents observed will be identical to currents obtained for the same solution at a macroelectrode of equivalent geometric area. As the scan rale increases, the faradic current will be dominated by the transport in the nonlinear zone. The peak of the Vollammogram becomes small and the Voltammogram appears a sigmoidal shape.