Controllable Preparation And Properties Investigation Of Semiconductor Nanomaterials SnO₂and Cu₂O

Semiconductor nanomaterials are an important member with a special status in the family of nanomaterials. Obtaining semiconductor nanostructures with adjustable morphology and controlled size is the key of comprehensive studying their special properties and potential applications. Thus, controllable synthesis on the morphology and size of the semiconductor nanomaterials and study the relationship between nanostructures and their properties not only have important theoretical significance but also broaden the scope of applications of semiconductor nanomaterials. In this dissertation, semiconductor SnO2and Cu2O were chosen as the target and several kinds of simple liquid methods were conducted to prepare SnO2and Cu2O nanostructures with adjustable morphology and controlled size by adjusting various reaction conditions and using metal inorganic salts as the precursors.The obtained products were characterized by XRD, FESEM, TEM， HRTEM, UV-Vis, et al. The formation mechanisms of the obtained nanostructures were discussed and their properties were also investigated. The main work is summarized as follows:(1) Single-crystalline SnO2nanorods were obtained via a solvothermal approach in a mixed solution of diethylene glycol and distilled water. Diethylene glycol was crucial in this anisotropic growth process and believed to act both as a solvent and a surfactant. The preferred growth direction of the nanorods was along [112]. By just simply adjusting the volume ratio of diethylene glycol and distilled water (VD:VW), individual nanorods with different size and flower-like nanorod clusters could be obtained. The photocatalytic properties of SnO2nanocrystals prepared under the above conditions were studied and the main conclusions are as follows:①It has been demonstrated that under UV irradiation, the photocatalytic activity of SnO2nanocrystals depends on its crystal size, specific surface area, exposed crystal surfaces, morphology and so on.②The sample SnO2exhibits optimal photocatalytic activity for the degradation of Rhodamine B under UV irradiation which was prepared in a mixed solution of diethylene glycol and distilled water with the volume ratio (VD:VW) of10:1. The degradation of RhB reaches96.4%within180min when50mg of the SnO2photocatalysts were dispersed in50mL of10mg/L RhB solution and irradiated by a300W high-pressure mercury lamp. Moreover, in order to further regulate the morphology and size of SnO2crystal, various additives were introduced into in a mixed solution of diethylene glycol and distilled water with the volume ratio (VD:VW) of6:1. The photocatalytic properties of SnO2nanocrystals prepared in the presence of different additives were studied and the main conclusions are as follows:①Additives have a significant effect on the morphology and size of SnO2crystal.②The sample SnO2exhibits the best photocatalytic activity for the degradation of Rhodamine B under UV irradiation which was obtained under the condition of NH4F as additives. The degradation of RhB reaches96.3%within180min when50mg of the SnO2photocatalysts were dispersed in50mL of10mg/L RhB solution and irradiated by a300W high-pressure mercury lamp. Compared to the sample prepared in the absence of any additives, the degradation of RhB increases28.1%.(2) Using SnCl4·5H2O as raw material, tin oxide nanoparticles with a diameter of10.0nm were synthesized with oleic acid as solvent. Afterwards according to the effect of the nature of the different solvents on the crystal growth process, another solvent composition was introduced into the above system to control the morphology of SnO2crystal. Thus earthworm-like nanorod clusters and nanorods with average diameter of3.6nm were prepared in different non-aqueous systems which oleic acid-ethanol and oleic acid-glacial acetic acid were used as solvent respectively. At the same time, the photocatalytic activity of SnO2nanocrystals with various morphologies was examined. The SnO2photocatalysts which were prepared in oleic acid-ethanol system exhibit optimal photocatalytic activity for the degradation of Rhodamine B under UV irradiation. The degradation of RhB reaches92.5%within210min when50mg of the SnO2photocatalysts were dispersed in50mL of10mg/L RhB solution and irradiated by a300W high-pressure mercury lamp.(3) Using polyethylene polyamine as auxiliaries, Cu2O nanospheres with average particle size of about259nm were synthesized in low temperature water bath via reducing the copper-polyethylene polyamine complex solution with D-(+) glucose at80℃. UV-visible absorption spectrum of the as-prepared Cu2O nanospheres show that compared with bulk Cu2O, its absorption band edge displays blue shift, but it don’t reveal quantum effects. In addition, the preparation and the formation process of Cu2O nanospheres were systematically studied by changing reaction temperature, the amount of auxiliaries and reducing agent, reaction time and introducing surfactant. The results show that the reaction temperature would influence the product purity and its particle size, while the amount of auxiliaries would not only affect the product phase but also affect its morphology. As for additives PVP, it could make Cu2O nanospheres become more uniform and smaller. It also could make Cu2O nanospheres be well dispersed simultaneously.Finally, the main experimental results and innovations in this dissertation were summarized and the following expectations were proposed.