Preparation Of ZnM (M=O, Se, S) Quasi-One-Demetional Nanostructures

Through low-cost chemical vapor deposition routes, ZnM (M=O, Se, S) with one-dimensional nanostructures, including nanowire/needle and tetrapod structures, have been successfully synthesized by using nitrate/sulfide/selenide of transition metal like nickel as the catalysts. The following major achievements were obtained.1. ZnO nanowires have been successfully prepared in the mixture of O₂Ar gas (O₂: ²0ppm, v/v) with Ni(NO₃)2 as the growth catalyst. The average diameter of ZnO nanowires was 50nm, and the length was about 20μm. At the beginning of ZnO nanowires growth, their diameters reduced rapidly, and then turned to constant in the subsequent process. It was found that the morphologies of ZnO nanostructures strongly depended on the oxygen content. According to our analysis, a combined mechanism of redox and VLS mechanism was proposed to understand the growth of the ZnO nanowires. In addition, other growth conditions were also investigated. Firstly, Ni(NO₃)₂ was replaced by AgNO₃, and ZnO nanowires with the same diameters but only several microns in length were synthesized. Their growth was governed by the classical VLS mechanism, and the low density was related to the activity of Ag. When pure nitrogen was used, tetrapod ZnO nanostructures were obtained according to the octahedral twin mechanism, but Ag damaged the morphology of tetrapod structures.2. According to the redox mechanism, ZnSe nanoneedles with high crystalline quality have been synthesized at about 700℃ by using NiSe nanocrystals as the source materials. Meanwhile, we successfully controlled the diameters of ZnSe nanoneedles by adjusting NiSe particle sizes, and found a suitable route for the preparation of one-dimensional ZnSe nanomaterials. When NiSe₂/NiSe or CuSe/Se nanocrystals were used, ZnSe nanowires and micro-whiskers were achieved according to the combined mechanism of redox and VLS mechanism. The mixed sources of NiSe₂/NiSe or CuSe/Se can be used to control Se partial pressure in the traditional CVD reaction system.3. Finally, ZnS nanowires have been preliminarily synthesized by using NiS as the catalyst at 600-800 °C. They were 50⁸0nm in diameters and ¹0um in lengths.