【作者】 赵志慧；

【导师】 杨柏；

【作者基本信息】 吉林大学 ， 高分子化学与物理， 2010， 博士

【摘要】 自组装一直是合成新型材料的有效且具有发展前景的重要方法。近年来,用纳米晶作为构筑基元来制备自组装超晶体成为人们的研究热点。本论文的主要工作就是形貌、尺寸可控纳米晶的制备,以及用纳米晶作为构筑基元来制备结构新颖的超晶体。本论文从三个方面开展工作：首先,首先,制备了一系列多面体形硫化铅纳米晶,通过简单地控制反应物浓度来调节纳米晶的尺寸和形貌。这些纳米晶尺寸分布窄、形貌均一,具有很好的自组装性质。然后,以硫化铅纳米晶作为构筑基元,通过溶剂挥发法,在硅基底的不同区域得到了维度、形貌和超晶格结构各异的超晶体,我们对形成超晶体的影响因素和推动力进行了分析。最后,利用垂直沉积技术,在硅片、ITO和PDMS基底上得到了大面积二维有序超晶体膜。通过控制实验条件,可以在一定程度内调节超晶体的形貌和结构。更多还原

【Abstract】 Self-assembly has become a very effective and promising approach to synthesize a wide range of novel materials. In the past decades, with the quick development of nanotechnology, self-assembled nanoscale materials have attracted many fundamental and technological interests. Due to their physical and chemical functional specificity and selectivity, nanocrytals (NCs) become ideal building blocks for self-assembled structures, which are called "supercrystals (SCs)". Well-defined SCs provide new opportunities for optimizing, tuning, and/or enhancing the properties and performance of the materials. Recently, researchers have successfully fabricated plentiful SCs, using spherical NCs as building blocks. In addition, many methods have been developed to generate SCs of non-spherical building blocks, such as solvent evaporation, LB technique, controlled crystallization in oversaturated solution and self-assemble under specific conditions, etc. Since the monodispersity of size and shape of NCs is one of the preconditions of self-assembly, many efforts have been paid to prepare size and shape selected and controlled NCs. In this thesis, attention is paid on the preparation and self-assembly of polyhedral PbS NCs with different sizes and shapes. SCs are obtained through controlled solvent evaporation and vertical deposition method, respectively.In chapter 2, PbS NCs with different sizes and shapes have been prepared by controlling the thermal decomposition of TAA in aqueous solution of Pb(Ac)2, with the help of cetyltrimethylammonium bromide (CTAB) as surfactant. It follows the regulation that the increase of TAA concentration leads firstly to decrease in the particle size and then to gradual changes of the particle shape from octahedral to cubic. Furthermore, on the basis of our investigating into the influences of concentrations of CTAB and Pb(Ac)2, a reasonable growth mechanism has been proposed, which must be very helpful in predicting the final architecture of NCs and preparing NCs with unique properties. In addition, optical properties and phase transition behavior under high pressure of PbS NCs are investigated.In chapter 3, large-scale preparation of dimension-controllable SCs of octahedral PbS NCs was achieved first through a solvent-evaporation approach. Applying the capillary flow of the drying droplet,2D close-packed SCs,3D faceted SCs and 3D bulk SCs were identified from the central region to the edge of the substrate, which have different shapes and superlattice structures, due to the interaction between NC and the substrate. Moreover, the supperlattice structures of SCs were tuned by using truncated octahedrons as building blocks under similar experimental conditions, demonstrating the importance of shape effect in NC self-assembly, while size is proved to have less effect on self-assembly. Nanoscale forces are investigated and the formation of SCs is believed to be a entropy-driven process. What is more, the influence of experimental conditions on self-assembly is discussed.In chapter 4, SCs are prepared by vertical deposition method.2D monolayered SC is generated on Si substrate with specific hydrophilia through two-substrate vertical deposition and 2D SCs with several layers are fabricated on ITO and PDMS film through one-substrate vertical deposition. In addition, patterned SCs are obtained with patterned substrates.更多还原