纳米晶的结构形貌控制及生长机理研究

综述了纳米晶研究的最新进展，着重介绍了纳米晶形貌、尺寸和结构控制的新方法，评述了纳米晶的相转变及生长机理研究的新发现和新观点，对其生长规律做了新的概述。诸如气氛、羟基、蛋白质等个别不被人们注意的因素有可能是影响纳米晶结构形貌的关键。STM等技术像温度、压力一样能够诱导纳米晶体的相转变。一种鲜为人知的现象在纳米晶合成研究中被揭示出来，即纳米晶在一定条件下存在着叠合生长现象，晶体的初始位错起源于纳米晶的叠合生长。     

原位生成法制备单分散的纳米氧化锌分散液

用ZnCl2作原料,PVP作分散剂,在160℃下采用原位生成法制得单分散、具有良好晶体结构和规则外形的ZnO纳米单晶分散液,用透射电子显微镜、X射线衍射、紫外/可见分光光度计等测试手段对其进行了表征.讨论了工艺条件对纳米ZnO尺寸和形貌的影响,并对其生长机理做了初步探讨.     

八面体形状的重钼酸钠纳米晶的制备及生长机制

采用热蒸发方法,以红外烧结炉为制备仪器,在玻璃衬底上制备了空心的八面体纳米晶。利用扫描电子显微镜、X射线衍射谱、透射电子显微镜及选区电子衍射分析产物的形貌、尺寸、成分及结构,并对纳米晶的形成机理进行了探讨分析。     

Ag(TCNQ)纳米晶须的生长机理

本文采用真空饱和蒸汽反应法在相对较低的温度下制备了一系列一维纳米结构的金属有机配合物Ag(TCNQ).用多晶XRD谱表征了样品的成份和晶体结构,通过SEM观察到了不同生长阶段的形貌.纳米晶须的生长分别经历了溶解、结晶和单向生长三个阶段.在此基础上,利用VLS模型初步解释了其生长机理.     

Controlled Growth and Thickness-Dependent Conduction-Type Transition of 2D Ferrimagnetic Cr2S3 Semiconductors

2D magnetic materials have attracted intense attention as ideal platforms for constructing multifunctional electronic and spintronic devices. However, most of the reported 2D magnetic materials are mainly achieved by the mechanical exfoliation route. The direct synthesis of such materials is still rarely reported, especially toward thickness-controlled synthesis down to the 2D limit. Herein, the thickness-tunable synthesis of nanothick rhombohedral Cr₂S₃ flakes (from ≈1.9 nm to tens of nanometers) on a chemically inert mica substrate via a facile chemical vapor deposition route is demonstrated. This is accomplished by an accurate control of the feeding rate of the Cr precursor and the growth temperature. Furthermore, it is revealed that the conduction behavior of the nanothick Cr₂S₃ is variable with increasing thickness (from 2.6 to 4.8 nm and >7 nm) from p-type to ambipolar and then to n-type. Hereby, this work can shed light on the scalable synthesis, transport, and magnetic properties explorations of 2D magnetic materials.     

晶体生长用TiO2纳米晶的改良工艺研究

针对晶体生长的具体应用,分别以硫酸氧钛铵（ATS）和改良硫酸氧钛铵（M－ATS）为原料,采用高温焙烧法制备了TiO2纳米晶,用XRD分析了原料和纳米晶的物相,用SEM分析了纳米晶的形貌,结果表明虽然两种原料具有相似的物相结构,但所得纳米晶的性状不同,M－ATS焙烧所得纳米晶分散性更高,均匀性更好,此外,研究了焙烧温度,保温时间,急烧,缓烧等工艺条件对纳米晶形貌,物相的影响,并给出了批量制备TiO2纳米晶粉体的最佳工艺条件。     

纳米晶体光电子性质研究进展

本文综述了近年来国内外纳米晶体光电子性质研究领域某些方面的进展情况，着重介绍了纳米晶体在光吸收、光致发光、非线性光学效应和电导率等方面的独特性能，这些研究表明，对于０￣３ｎｍ晶体（纳米晶粒处于分散介质中）来说，量子尺寸效应是产生晶体光电子性质突变的主要原因之一。对纳米晶体结构和性能的深入研究，能为光电子材料的发展提供新的途径和思路。     

Crucial Role of Anions on Arrangement of Cu2S Nanocrystal Superstructures

Both of the arrays of Cu₂S nanowires and the superlattices of Cu₂S nanoparticles are obtained by the solventless thermolysis of copper thiolate in the presence of laurate. For the first time, the types of anions in the reaction system, which are generally neglected in previous studies, are found to determine the structure of the final assembly products. Furthermore, experimental results shows in the presence of Cl^‐ ions, Cl^‐ ions participate in the self‐assembly process and promote the formation of Cu₂S nanowire arrays. Finally, the content of Cl‐ ions is gradually decreased with assembly reaction proceeding. Therefore, duiring the process, Cl^‐ ions play a role of ‘catassembly’ in the formation of Cu₂S nanocrystal superstructures.     

Electronic Doping Controlled Migration of Dislocations in Polycrystalline 2D WS2

Migration of dislocations not only determines the durability of large‐scale nanoelectronic and opto‐electronic devices based on polycrystalline 2D transition‐metal dichalcogenides (TMDCs), but also plays an important role in enhancing the performance of novel memristors. However, a fundamental question of the migration dependence on the electronic effects, which are inevitable in practical field‐effect transistors based on 2D TMDCs, and its interplay with different dislocations, remains unexplored. Here, taking WS₂ as an example, first‐principle calculations are used to show that the electronic contributions arising from defect states can greatly influence the migration barriers of dislocations. The barrier height can be reduced by as much as 50%, which is mainly attributed to the change in electronic occupation and the band energy of defect levels controlled by electronic chemical potential (Fermi level). The reduced barriers in turn lead to significantly enhanced migration, and thus the plasticity. Since defect levels from dislocations locate deep inside the bandgap, the doping‐induced tuning of barrier height can be achieved at relatively low doping concentration through either chemical doping or electrode gating. The effective electromechanical coupling in 2D TMDCs can provide new opportunities in material engineering for various potential applications.