硫化锌硫化镉微纳米材料的液相控制合成及表征

【作者】 韩健；

【导师】 杨延钊；

【作者基本信息】 山东大学 ， 无机化学， 2008， 博士

【摘要】 纳米材料的制备工艺路线对于它们的应用非常重要，如何探索和发展纳米材料的设计与合成的新途径、新方法始终是纳米材料研究领域中的一个重要课题。目前合成纳米材料的方法虽然很多，但获得尺寸可控、粒度均匀的纳米材料仍然存在一定的困难，因此探索一种设计简单、操作方便、成本低、产率高的方法，来实现对纳米材料的尺寸大小、粒径分布以及晶体结构和形貌的控制仍然是化学家和材料学家关心的课题之一。ZnS和CdS等半导体纳米粉末在光、电、磁、催化和力学等方面有着特殊的性能，这与其具有多种晶体形态和不同形貌紧密相关，而制备可控粒度、形状、取向的ZnS和CdS半导体纳米粉末，研究其形貌的影响因素，同时解释晶体的生长机理是实现形貌和尺寸控制的一个重要途径，对材料付诸于工业应用具有十分重要的意义。本文选取了Ⅱ-Ⅵ族硫属化合物中的硫化锌和硫化镉为研究对象，对它们的制备以及形貌的控制方法进行了研究，论文的主要工作总结如下：1、水热分解法制备硫化锌微纳米材料以硫脲为硫源，与乙酸锌在水热条件下，通过改变不同的反应物配比、反应温度及时间，得到了硫化锌微米球及纳米粒子，通过TEM及SEM对产物的观察，发现硫化锌微米球是由小的纳米粒子聚集而成。当反应物摩尔比Zn²⁺：Tu=1：4，且反应温度为180℃，反应时间大于等于10h的条件下，得到粒径为100nm左右的硫化锌纳米粒子；而反应温度小于180℃且反应时间小于10h时，或者当反应物的摩尔比Zn²⁺：Tu<1：4时，得到的产物均为3-5μm的微米球。以硫氰酸铵为硫源，与氯化锌在水热条件下反应制备出了分散性良好，粒径为30-50nm的硫化锌球状纳米粒子。随着反应温度的升高，其粒径逐渐增大，并发现反应物的摩尔比对硫化锌产物形貌的影响较小，因此可以通过改变反应温度就可以控制硫化锌纳米粒子的粒径。2、水热分解法制备硫化镉有序微结构材料以硫脲为硫源，以氯化镉为镉源，采用水热分解的合成方法，在水热体系中，制备了具有有序微结构的CdS晶体，并考察了反应温度及反应物的摩尔配比对产物形貌的影响，实验结果显示反应物Cd^2-／Tu的摩尔配比是影响产物形貌的关键因素。初步讨论了其形成过程及可能的反应机理，硫脲在反应中可能起到了两种作用，一是作为硫源，与氯化镉反应生成硫化镉；二是作为配合物模板从而起到对硫化镉有序微结构的形貌控制的作用。以硫氰酸铵作为硫源，研究了改变反应温度和反应物的配比对产物形貌的影响，实验结果发现改变反应物Cd²⁺／NH₄SCN的摩尔配比同样是控制产物硫化镉形貌的关键因素。3、表面活性剂辅助水热法制备硫化锌硫化镉纳米粒子选取十二烷基硫酸钠在溶液中形成的胶束作为软模板，在水热条件下，利用乙酸锌和硫代乙酰胺反应，制备出了分散性良好的硫化锌纳米粒子，考察了十二烷基硫酸钠的浓度对产物的影响，并讨论了可能的机理。初步研究了由常温常压下制得的无规则形貌的硫化镉通过加入表面活性剂十二烷基硫酸钠、十二烷基磺酸钠以及十六烷基三甲基溴化铵，然后在180℃下进行水热处理，并与未加表面活性剂时的产物进行了对比，讨论了表面活性剂在水热处理中起到的修饰作用。4、微乳液水热法制备硫化锌硫化镉纳米材料选用十二烷基硫酸钠（SDS）／正庚烷/正己醇／水（盐溶液）组成的微乳液体系，结合水热法在120℃时，利用硫代乙酰胺的分解与乙酸锌反应制备出了硫化锌纳米空心球，主要考察了反应体系中w值以及反应温度对产物形貌的影响。实验结果发现可以通过调整w值可以控制产物的粒径，同时当反应体系达到一个较高的温度即180℃时，微乳体系被破坏而不能形成纳米空心球。选用十六烷基三甲基溴化铵（CTAB）／正戊醇／环己烷／水（盐溶液）组成的微乳液体系，结合水热法在140℃时，利用硫代乙酰胺的分解与氯化镉反应成功制备出了硫化镉纳米多边锥结构。更多还原

【Abstract】 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,Ⅱ-Ⅵmetal 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.更多还原