Electrochemical Preparation And Characterization Of Nanowires Formed By The Template Technique

A great deal of attention has been paid to the preparation and characterization of one-dimensional nanostructrue. These materials have significant potential applications in many important advanced technologies, such as solar energy conversion, chemical sensor, catalysis, absorption and separation, and they also have some novel electrical, optical, magnetic and chemical properties. In this thesis, several new kinds of nanowires were prepared by the template technique using electrochemical methods. The morphology, chemical compositions, crystal structures and some properties of these obtained nanowires were systemically characterized. Because of their novel properties and unique structures, one-dimensional nanostructrue semiconductor materials have generated a tremendous amount of interests in fundamental and potential promising applications in electronic and photoelectronic devices. We fabricated CdSe, Te and CdTe nanowires by direct current (dc) electrodeposition in porous anodic aluminum oxide (AAO) templates. (1) CdSe thin film has been produced by electrochemical method on conductive glass in dimethylsulfoxide (DMSO) system under 130℃, 140℃, 150℃, 160℃, 170℃ and 185℃, and characterized by scanning electron microscopy (SEM), X-ray photoelectron spectrum (XPS), powder X-ray diffraction (XRD), and optical absorption measurement. The effects of bath temperature and heat treatment on the morphology, chemical compositions, crystal structures and optical properties have been discussed. (2) Uniform CdSe nanowire arrays with controllable lengths have been fabricated by dc electrodeposition in the AAO templates with Ag as their conductive substrates from DMSO system under different temperature. The nanowires with the diameters from 10nm to 50nm, and the lengths from 1(m to 20(m have been obtained. SEM, transmission electron microscopy (TEM), X-ray energy-dispersion analysis (EDAX), XRD, electron diffraction (ED) and high-resolution electron microscopy (HREM) were used to investigate the morphology, atomic composition and crystal structure of the nanowires. The hexagonal CdSe nanowires with single crystal structure have been obtained in DMSO under 140℃. (3) Semiconductor Te and CdTe nanowires embedded in AAO templates were fabricated for the first time by dc electrodeposition in ethylene glycol. SEM and TEM with EDAX assisted were used to study the morphology and chemical compositions of the nanowires. The diameters and lengths of the nanowiers are uniform. XRD, ED and HREM shows that hexagonal Te and CdTe nanowires were obtained in the experiments, and they both have a single crystal structure with uniform (001) growth direction. Much interest has focused, in recent years, on the developments of magnetoresistance in various multistructures, especially on the giant magnetoresistance of multilayered nanowires. Fe20Ni80/Ag multilayered nanowires were successfully obtained for the first time by pulse electrodeposition in the AAO templates, and their morphologies were characterized by SEM and TEM. In addition, we use spectrophotometric to study the compositions of nickel-iron alloy prepared by electrodeposition, and the main results are as follows: Iron(Ⅲ) forms a stable deep purple complex with ethylenediaminetetraacetic acid disodium salt (EDTA) and hydrogen peroxide in aqueous solution at PH=10.7-11.3; Nickel(Ⅱ) forms a red complex with dlacetyl dioxime in aqueous ammonia when an oxidation (iodine) exists; thus the amount of iron(Ⅲ) and nickel(Ⅱ) can be determinated by the absorption of their complexes at 519nm and 538nm respectively.