【作者】 曹红亮；

【导师】 钱雪峰； 朱子康；

【作者基本信息】 上海交通大学 ， 材料学， 2007， 博士

【摘要】 金属硫族半导体纳米材料由于其独特的物理和化学性能,在许多领域具有广泛的应用前景。而且他们也可作为微/纳米器件的组装单元,对微/纳米器件的性能起到决定性的作用,因此研究半导体纳米材料的结构、形貌及控制合成技术具有重要的意义。由于铜的硫族化合物(如氧化亚铜、硫化铜、硒化铜)、氧化锌及铅的硫族化合物(硫化铅、硒化铅和碲化铅)等材料在催化、光电转化、发光、压电、气敏、热电等有着广泛的应用前景而成为材料化学等领域的研究热点之一。以往的研究表明材料的性能和应用不仅取决于其本身的结构、晶型及组成,而且其尺寸和形貌对材料的性能和应用也起到决定性的作用,因而对半导体纳米材料的尺寸和形貌进行可控的合成不仅具有理论上的意义而且可拓宽纳米材料的应用范围。在本文的研究中,我们使用简单而且温和的水溶液湿化学反应方法,控制合成了具有规整形貌和结构的氧化亚铜纳米/微米晶体,并以此为基础通过简单的化学转化制备了具有新颖拓扑结构的硫化铜多面体中空纳米晶和多种形貌的硒化铜中空微/纳米晶,进一步使用温和的乙醇湿化学反应合成了直径小于10纳米的一维纳米氧化锌单晶材料并研究了其光学性能,最后通过微波辐照辅助法制备了具有枝形结构的硫化铅、硒化铅和碲化铅的树枝形微晶。本文的主要研究内容包括:1.不同形貌和粒径的Cu2O模板物微/纳米材料的可控合成。制备了具有立方体、八面体、球形多孔和一维纳米结构的Cu2O纳米/微米材料。当以抗坏血酸作还原剂制备Cu2O立方体时,随PVP的增加,立方体的颗粒的大小变小。而且,随着加入的NaOH的浓度的增加,Cu2O纳米颗粒的尺寸也相应的增加。使用盐酸羟胺作还原剂时,得到八面体的Cu2O微晶,改变反应条件得到一维和立方体Cu2O的混合物及多孔颗粒。2.中空笼状硫化铜和硒化铜多面体的模板牺牲法控制合成及形成机理。基于以上工作的基础,以Cu2O立方体模板首次通过模板牺牲法合成了具有高度对称结构的Cu7S4十八面体中空半导体材料,并通过反应参数的控制,成功地通过化学“雕刻”技术得到了具有窗口结构的十八面体中空硫化铜多面体,研究表明我们可以在不同尺度的纳米表面进行化学“打孔”。论文进一步以立方体、八面体和球形形貌的Cu2O作为模板牺牲物,合成了具有立方体、八面体及球形结构的中空Cu2-xSe晶体。基于Kirkendall效应和晶体生长理论对其中空结构和多面体结构的形成机理进行了讨论。这些工作已经先后以快讯发表在JACS和Chem. Commun.,JACS审稿人给予较高评价,认为该工作是一项原创性的工作,可排在功能材料合成前20(top20)。3.具有极小直径的一维ZnO纳米材料的合成及光学性能研究。在室温条件下制备了直径为5-10纳米,长径比可调的一维ZnO纳米材料,研究了反应时间和反应物浓度等对产物形貌的影响。研究表明一维氧化锌纳米颗粒的长径比随反应时间的延长而变大,随着NaOH含量的增加,产物的长径比相应的有所增加。其光学性能研究表明所制备的一维ZnO具有完美的晶体结构。论文进一步通过水热合成法制备了直径约为10纳米的一维ZnO纳米材料,并且讨论了不同溶剂、反应温度、反应物的比例对形貌的影响。研究表明乙醇胺的加入有助于该一维材料的自组转。相关研究发表在Nanotechnology,并获当月下载top10。4.三维结构PbE(E=S,Se,Te)的微波合成。以硫脲为硫源成功制备了三维结构的PbS树枝晶,对比实验表明PbS树枝晶的形成过程受动力学条件控制,反应前驱物的浓度对形貌有着非常大的影响。如果反应前驱物浓度低,可得到立方体和四边形片状纳米颗粒;提高反应前驱物的浓度可观察到从立方体到树枝晶的转变过程。用硒粉和碲粉为前驱物,在外加还原剂的条件下,首次制备了PbSe和PbTe树枝晶。更多还原

【Abstract】 Binary metal chalcogenide semiconductors have attracted much attention due to their unique physical, chemical properties and the widely applications in many fields, such as electronics, magnetics, optics, etc. If applied as basic building blocks, they also play an important role on the properties of assembling nano-/micro- apparatus. Therefore, it was important to investigate the structures, morphologies and synthetical technologies of nano semiconductors. As typical materials of binary semiconductors, copper chalcogenides (e.g. Cu2O, copper sulfide and copper selenide), ZnO and lead chalcogenides (e.g. PbS, PbSe and PbTe) have attracted considerable attention owing to their wide applications in catalysts, photoelectric transition, luminescence, piezoelectricity, gas sensor, thermoelectricity materials, etc. It was well known that the properties of materials were mainly determined by composition, structure of crystal itself according to previous studies, however, the size and shape of materials also played important roles to determine their applications and properties. Thus, controlled synthesis on the size and shape of nano-semiconductors will largely increased their scientific significances and widen the corresponding technical applications. In this study, we managed to produce Cu2O nanocrystals with uniform shapes via facile and warmly wet-chemical methods, and then transferred Cu2O nanocrystals into Cu7S4 and Cu2-xSe with novel hollow polyhedral morphologies. In addition, we prepared ZnO nanorod of small diameter (<10nm) with varied aspect ratio in ethanol solution under ambient temperature condition or low temperature hydrothermal condition. In the end, dendrites of lead chalcogenides (PbS, PbSe and PbTe) were synthesized by microwave-assistant heating routes. The main contents of this dissertation could be summarized in four sections:1. Shape- and size-controlled synthesis of Cu2O nano-/ micro-crystals.Cubic, octahedral, sphere-like and fiber-like of Cu2O particles have been prepared under different reaction conditions. The shape and size of Cu2O particles were strongly dependent on different reaction parameters, for example, the precursor’s concentration, the type of reductive regent, the concentration of PVP and NaOH, even the mixing sequence of reaction component.2. The synthesis of copper sulfide and copper selenide nano/micro hollow cages with uniform polyhedral and sphere shapes.Firstly, hollow single-crystal semiconductor of Cu7S4 with high symmetric 18-facet polyhedron structure was prepared by reacting cubic Cu2O template with Tu. Then, 18-facet polyhedra of Cu7S4 with hollow window structure and various sizes were synthesized at high temperature hydrothermal condition. Finally, cubic-like, octahedral-like and sphere-like Cu2-xSe hollow cages were successfully fabricated from shape-controlled Cu2O as sacrificial cores, precursors or templates by a single technique at room temperature. A plausible formation mechanism of these hollow structures could be based on the Kirkendall effect. These studies were published by JACS and Chem. Commun. The reviewers of JACS gave high comments about the study of Cu7S4 polyhedron.“The authors present valuable results of an original research in the area of chemical synthesis of functional materials, and I believe this paper fell within top 20% in this field.”3. Preparation of ZnO nanorods with various aspect ratios.We studied the reactive time and concentration effect on morphologies of ZnO nanorods at room temperature. It was found that the aspect ratio would be increased if the reactive time was prolonged or the reactant concentration was increased. The optical properties showed that the ZnO nanorods possess perfect crystalline structure. We also discussed the effect of different solvent, reactive temperature and reactant ratio on morphologies of ZnO nanorods.4. Dendrites of lead chalcogenides (PbS, PbSe and PbTe)Dendrite of PbS with 3-D structure was synthesized by microwave assistant heating method in EG solution. It was found that the formation of PbS was dependent on the kinetics condition, and the precursor concentration also played an important role on the morphologies of PbS. The cubic or plate-like PbS nanoparticles would be obtained if low concentration of precursor was used. The transferred process from cube to dendrite of PbS would be clearly observed when increasing the concentration of precursors. We also synthesized the dendrites of PbSe and PbTe if Se and Te powder replaced sulfur source and another reducing agent was added in this system.更多还原