Template Synthesis Of Metal And Oxide Nanowire Arrays And Investigation Of Their Applications

A great deal of attention has been paid to one-dimensional nanostructural materials due to their novel electrical, optical, magnetic and chemical properties. They have significant potential applications in many important advanced technologies, such as solar energy conversion, chemical sensor, catalysis, absorption and separation. So the synthesis of one-dimensional nanostructural materials attracted much more interest and become the focus of a rapidly growing scientific community. Anodic aluminium oxide (AAO) membrane, which is usually fabricated by anodic oxide of Al, has uniform parallel pores and high pore density. Furthermore, the pore diameter is controllable according to practical needs. These characteristics allow the use of AAO as a template to synthesize one-dimensional nanostructural materials. In this thesis, several kinds of nanowires were prepared by using anodic aluminium oxide (AAO) template. The morphology, chemical compositions, crystal structures of these obtained nanowires were systemically characterized. In addition, the Ag nanowire array electrode was also assembled and its electrochemical performances were measured for methylene blue.This thesis consists of four sections as follows:(1) The preparation and characterization of porous anodic alumina.Template is the effective tools for preparing nanowires arrays. In this paper, the fabricating process of AAO template was described in details. AAO templates with different pore diameter were produced in different electrolytes (oxalic acid and phosphoric acid) by different methods (two-step anodic oxidation, one-step anodic oxidation). The anodic oxide film was characterized by using an atomic force microscope (AFM), the scanning electron microscopy (SEM), a transmission electron microscope (TEM), and furthermore the its crystal conversion was also analyzed by the X-ray diffraction (XRD). The results show that AAO template prepared in oxalic acid have high ordered pore arrays, which consist of the separated nanopores perpendicular to the film surface, parallel to each other and with uniform pore diameter. The pores are about 60 nm in diameters and 1.1×10¹⁰ pores/cm² in density, while AAO template produced in phosphoric acid have pore arrays in less order and pores with about 120 nm in diameters. Because of the above features, the AAO template obtained in 0.3M oxalic acid by controlling anodic voltage was used as a desirable template to fabricate nanowire arrays or freestanding nanowires.(2) Template synthesis of Ag ordered nanowire arrays.Silver has high electrical and thermal conductions, and exhibits conspicuous catalysis for a lot chemical reactions. The one-dimensional nanostructures of silver are expected to be used as interconnectors and functional units of devices with nanoscale dimensions. Besides, they could play an important role in chemical catalysis and electrocatalysis due to their peculiar structure and high surface activation.Ordered flawless Ag nanowires arrays were fabricated using an effective method, in which Ag ions and glycol react to form silver nanonuclei inside the nanochannels of AAO templates, and then grow into Ag nanowire by confining growth. The nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). The TEM images show that Ag nanowires are abundant and uniform, and the diameter of the Ag nanowires is about 60 nm, which correspond to the pore sizes of the templates used. The SEM images show that the Ag nanowires are abundant and well-ordered in large-area, and up to 10μm in length. The data of X-ray diffraction indicate that the silver nanowire have face-centered-cubic structure.(3) Preparation and electrocatalytic activities of Ag nanowire array electrodeOrdered Ag nanowires arrays were generated by electroless deposition in AAOtemplates. Ag nanowire array electrode was prepared by assembling Ag nanowires arrays onto the surface of kryptol. Electrocatalytic activities of Ag nanowire array electrode for methylene blue was investigated by means of cyclic voltammertry, in which Ag nanowire array electrode was used as the working electrode. Cyclic voltammograms exhibits high electrocatalytic activities of methylene blue on the Ag nanowire array electrode.(4) Template synthesis of Sr₂CeO₄ ordered nanowire arrays.Ordered Sr₂CeO₄ nanowire arrays embedded in AAO templates were fabricated by a converse transport technique that precipitations were shaped into one dimension structure in the hexagonally ordered nanochannels of the AAM and changed into the Sr₂CeO₄ nanowire by the subsequent treatment. The nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy images (SEM), transmission electron microscopy (TEM). The TEM images show that Sr₂CeO₄ nanowires are about 60 nm in diameter and up to 20μm in length. The SEM images show that the Sr₂CeO₄ nanowires are abundant and uniform.