The Liquid Phase Of The Zns Cds Micro-nano-materials Control The Synthesis And Characterization

The synthesis processes of nanomaterials are very important for their application. Up to now, it is still an important task in the field of materials that how to develop a new method for preparing nanomaterials. Although there are many methods reported for preparing nanomaterials, it is still difficult to obtain materials with controllable morphologies and sizes. Therefore, it is attracting a great deal of attention of the chemists and materials researchers to explore a new method for obtaining low-cost mild reaction.ZnS and CdS semiconductor nanoparticles have special properties in some fields such as photoelectricity, magnetism, catalyses and energetics and so on, which is closely related to their different structures and morphologies. So it is very necessary for the industrialization to prepare ZnS and CdS semiconductor nanoparticles with controllable particle size, shape and crystallinity and their assemble products.In this dissertation,â…¡-â…¥metal chalcogenides ZnS and CdS are choosen to prepare, and the methods of controlling the morphology of ZnS and CdS are studied. The main work of this paper was summarized are as follows:1. Preparation of micro- and nanocrystalline ZnS by a hydrothermal decompostion method. ZnS microspheres and nanoparticles have been prepared by a hydrothermal decomposition method, which thiourea(Tu) was selected as a sulfur source and Zn(Ac)2 as zinc source. The reaction conditions of different reactant mol ratio, temperature and time were also study to control the morphology of products.lt has been found that ZnS microspheres are assembled by nanoparticles through TEM and SEM tests. The appropriate reaction conditions of preparing nanoparticles are reactant mol ratio of Zn^2- Tu be at 14, hydrothermal temperature be at 180℃, and hydrothermal treatment time≥10 hours TEM and SEM results show the nanoparticles are well-crystallized and diameter is about 100nm When hydrothermal temperature<180℃, and hydrothermal treatment time<10hours, or reactant mol ratio of Zn^2- Tu <1 4, 3-5μm microspheres are obtained In addition. well dispersed ZnS nanoparticles of 30-50nm have been prepared by a hydrothermal decomposition method, which NH4SCN was selected as a sulfur source and ZnCl₂ as zinc source. It has been found that the diameter of ZnS increases with hydrothermal temperature increasing and reactant mol ratio has little effect on the morphology of the products. So the diameter can be controlled by changing reaction temperature.2. Preparation of hierarchical microstructure CdS by a hydrothermal decomposition method. Hierarchical microstructure CdS has been prepared by a hydrothermal decomposition method, which thiourea(Tu) was selected as a sulfur source and CdCl₂ as cadmium source. The effect of reaction temperature and reactant molar ratio on morphology of products was studied. It has been found that reactant molar ratio of Cd²⁺/Tu is the key factor to control the morphology of products. The possible formation mechanism of CdS microstructure was investigated as well. In the reaction, thiourea acts two parts, one of which reacts with CdCl₂ as a sulfur source and the other is the complex template controlling the morphology of the CdS products. The effect of different reactant Cd²⁺/NH4SCN mol ratio and hydrothermal temperature were also studied on the CdS morphology with NH4SCN as sulfur source. It is found that reactant Cd²⁺/NH₄SCN mol ratio is the key factor to control the morphology of products as well.3. Preparation of ZnS and CdS nanoparticles with surfactant by a hydrothermal method. The micelle formed by SDS (sodium dodecyl sulfate) was chosen as the soft template. Well dispersed ZnS nanoparticles were prepared with the reaction of Zn(Ac)2 and thioacetamide(TAA) under the hydrothermal condition. Then the effect of different SDS concentration on the product was studied, and the possible mechanism was investigated as well. Amorphous cadmium sulfide prepared at normal temperature and pressure was treated under the hydrothermal condition by adding sodium dodecyl sulfate, sodium dodecyl sulfonate and cetyltrimethylammonium bromide (CTAB) respectively at 180℃. The made products were contrasted with that of no surfactants, and the modification effect that the surfactant played in the hydrothermal process was discussed.4. Preparation of ZnS and CdS nanomaterials by a microemulsion hydrothermal method. ZnS hollow nanospheres were prepared in quaternary micrormulsion system containing SDS/n-heptane/n-hexanol/water, combined with the hydrothermal method. In the reaction, TAA was decomposed at 120℃to react with Zn(Ac)₂. The effect of the value of w ([H₂O]/[SDS]) and the reaction temperature on morphology of ZnS was studied. The result showed that particle diameter was controlled by tuning the value of w. Meanwhile, when the reaction temperature was as high as 180℃, nanospheres can't be obtained for the microemulsion was destroyed. CdS nano-multilateral cones were prepared in quaternary micrognulsion system containing cetyltrimethylammonium bromide(CTAB)/n-pentanol/cyclohexane/water, combined with the hydrothermal method at 140℃and in the reaction, TAA was decomposed at 140℃to react with CdCl₂.