Template Synthesis Of Nanowire Arrays

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. 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, which is attractive for synthesis of one-dimensional nanostructural materials. In this thesis, several new kinds of nanowires were prepared by the AAO template technique. The morphology, chemical compositions, crystal structures and some properties of these obtained nanowires were systemically characterized.This thesis consists of three sections as follows:First, the preparation and characterization of porous anodic alumina. Template is the effective tools for preparing nanowire arrays. In this dissertation, the fabricating process of AAO template was discribed in details. We have got porous alumina in the aqueous solution of oxalic acid with appropriate concentration through two-step anodic oxidation. The resultant porous alumina membranes have relatively ordered hexagonal pore arrays, which consist of separated nanopores perpendicular to the film surface, parallel to each other and with uniform pore diameter. The pore diameter can be controlled by varieties of immersion time in acid. Because of the above features, the porous alumina was used as a desirable template to fabricate ordered nanowire arrays. In our experiments, the template with pore diameters of 60 nm, and with a pores density of l.lxlO10 has been obtained in 0.3 M oxalic acid. The anodic oxide film was observed by using an atomic force microscope (AFM), the scanning electron microscopy (SEM), a transmission electron microscope (TEM) and the X-ray diffraction (XRD).Second, template synthesis of CeO2 ordered nanowire arrays. Rare earth elements have unique properties and extensive applications owing to their special electronic configuration. In order to further understand the movement regularity of 4f electrons and to make rare earth materials have new and better practical value, research on synthesis, electronic construction,functional properties and applications of rare earth compound nanomaterials is urgent and important. CeO22 is used as optical materials, polishing agents, ultraviolet absorption materials, the cleaning catalyst of car's waste gases, chemical decolorant of glass, radiation-resisting glass permanent magnet, electronic ceramics etc. If it is processed into nanoparticles, it will exhibit some novel properties led to varied applications. For example, CeO22 nanocrystal is a better promoter of cytochrome C and the stabilizer of ZrO22 ceramics. Because of its high index of refraction and good stability, it is used to produce reduced reflection film. In conclusion, it is important to synthesize CeO22 nanoparticles because of its extensive use.Ordered CeO2 nanowire arrays embedded in anodic aluminium oxide (AAO) membrane were fabricated by a novel technique, in which anions and cations conversely migrate into the hexagonally ordered nanochannels of the AAO and react inside the channels to form one-dimensional nanostructures. The transmission electron microscopy (TEM) images show that CeO2 nanowires are about 60 nm in diameter, which correspond to the pore sizes of the membranes used. The selected-area electron diffraction (SAED) pattern indicates that the nanowires selected are single crystals. The scanning electron microscopy (SEM) images show that the resultant nanowires are abundant and uniform. The X-ray diffraction (XRD) spectra indicate that the CeO2 nanowires are cubic crystalline structure. The X-ray photoelectron spectroscopy (XPS) spectra data demonstrate that stoichiometric CeO2 is formed. It is found that the...