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二联吡啶衍生物分子表面自组装结构调控的STM研究
王熠
学位类型硕士
导师王富、袁群惠
2016-05-24
学位授予单位中国科学院大学
学位授予地点北京
学位专业材料工程
关键词二联吡啶 表面配位 物理吸附 扫描隧道显微镜(Stm) 自组装 高定向裂解石墨(Hopg)
摘要

具有多元化、低维度结构的分子薄膜在先进功能纳米器件领域具有潜在的应用。近年来的研究发现,表界面分子组装或表面化学反应是一种得到这类薄膜结构的简单且行之有效的方法。为满足功能性纳米器件在性能上的要求,在制备功能分子自组装薄膜时,需要对功能分子的排列方式进行适当的调控。目前,研究表界面上功能分子自组装结构的构筑和调控已成为推进纳米器件发展的研究热点之一。已知有机分子在基底材料表面的自组装过程中会受到分子-分子间以及分子-基底间的相互作用力。此外,外界因素如溶剂、温度、基底类型、光照和电磁场等也会对分子的自组装过程有一定的影响。因此,通过合理的分子设计和对于影响组装过程因素的调控,研究者有望获得具有目标组装结构的功能性分子薄膜。本论文借助扫描隧道显微镜(STM)技术系统地研究了侧链长度、配位方式以及配位金属离子等因素对二联吡啶衍生物分子自组装结构的调控作用。 本论文的研究内容及结果如下: 1. 侧链长度对二联吡啶衍生物自组装结构的调控。利用STM得到了4, 4’-二壬基-2, 2’-联吡啶(9-bpy)和4,4’-二十四基-2,2’-联吡啶(14-bpy)的分子自组装结构图像。实验结果表明:两个分子的吡啶环均以平躺的方式吸附在高定向裂解石墨(HOPG)表面,且烷基链以尾对尾、无交叉的方式排列。二者结构的不同点在于吡啶环与其相应烷基链的夹角。其原因可能是由于9-bpy和14-bpy分子在HOPG表面吸附时与基底点阵匹配程度不同以及不同的吸附能所造成的。 2. 金属中心(Zn2+、Cu2+)对二联吡啶衍生物自组装结构的调控。通过使用Zn2+、Cu2+分别与同一种二联吡啶衍生物分子配位,得到相应的组装结构并分析得出,不同的金属离子对二联吡啶衍生物自组装结构有很大影响。例如,9-bpy与Zn2+原位配位,其配合物组装结构表现为烷基链部分交叉,而与Cu2+原位配位后,其配合物烷基链完全交叉。其原因可能是由于不同金属离子配位性能不同造成的。 3. 配位方法(原位、非原位)对二联吡啶衍生物自组装结构的调控。实验结果表明,经过原位和非原位两种方式配位后的组装结构具有很大差异。例如,9-bpy与Zn2+原位配位后,其烷基链出现了不同程度的交叉。经过非原位配位后,9-bpy/Zn2+配合物的组装结构表现为烷基链完全交叉。其原因可能是由于原位的配位过程为吸附-脱附-再吸附的过程,而非原位配位过程只有吸附的过程。 本论文研究表明,二联吡啶衍生物的二维自组装结构可以通过调控侧链、配位方法和金属离子种类等参数而达到对目标分子组装结构进一步调控的目的。

其他摘要

The diverse low-dimensional molecular motif attracts growing interest for its potential applications in the field of the nanodevices with advanced function. Recent studies found that self-assembling route or on-surface chemistry strategy is an effective way to gain the needed molecular motifs. For achieving the wanted performance of the nanodevice that incorporated with the functional molecular motifs, appropriate control of the spatial arrangement of every building block is required. Therefore, the fabrication of self-assembly motifs with special performances is becoming a hot topic in the development of nanodevices. The formation and structure of self-assembled monolayer on surface/at interface is mainly influenced by the subtle balance between molecule–molecule and molecule–substrate interactions. In addition, environmental factors such as solvent, temperature, substrate, illumination, and electromagnetic field are also playing important roles. Therefore, the desired on-surface architectures may be achieved by designing the structures of building blocks and the environmental factors during self-assembling processes. The thesis have systematically studied the self-assembled motifs of the bipyridine derivatives with different length of substituent group via in-situ and ex-situ coordination by scanning tunnelling microscopy (STM). The main contents and results of experiments are as following: 1.The adjustment of the length of periphera alkyl chains for the self-assembly of bipyridine derivatives. We have investigated the self-assembly structures of 4, 4'-dinonyl-2, 2'-bipyridine (9-bpy) and 4, 4'-ditetradecyl-2, 2'-bipyridine (14-bpy) by STM. The results demonstrate that the 9-bpy and 14-bpy all adopt flat-lying orientations with their substituted alkyl chains in tail-to-tail arrangements in their corresponding arryas. The difference in the adsorption structures of 9-bpy and 14-bpy is the including angle between aromatic rings and corresponding alkyl chains. The reasons may be due to their different matching status with the substrate as well as the varied adsorption energies. 2.The adjustment of the metal centers for the self-assembly structure of bipyridine derivatives. We have used Zn(II) and Cu(II) for on-surface coordination with 9-bpy and 14-bpy molecules. The experimental data show that the motif transition in a self-assembled monolayer of bipyridine derivatives depends on the metal centers. For example, upon in-situ coordination, the alkyl chains of 9-bpy/Zn(II) complex appear to be partly interdigitated in the ensembles, while the alkyl chains of 9-bpy/Cu(II) complex is fully interdigitated in the on-surface arrays. These results indicate that the metal centers may play important roles in adjusting the self-assembled coordinated motifs of bipyridine derivative/metal complexes. 3.The adjustment of the coordination modes including in-situ and ex-situ for the self-assembled motifs of bipyridine derivatives. The results indicate that a great discrepancy existed in the coordination modes between in-situ and ex-situ coordinations. For example, the aliphatic chains of the formed 9-bpy/Zn(II) complexes arrays via in-situ coordination were partly interdigitated, while they were fully interdigitated in the pre-organized 9-bpy/Zn(II) complexes arrays which defined as the ex-situ coordination. The reason may due to the on-surface complexes arrays formed via the in-situ coordination mode including both desorption and re-adsorption processes, while the ex-situ coordination just go through the adsorption process. These results demonstrate that the desired on-surface coordination motifs can be achieved by adjusting the length of side-group of bpys, the metal centers, as well as the coordination modes.

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4577
专题环境科学与技术研究室
作者单位中国科学院新疆理化技术研究所
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王熠. 二联吡啶衍生物分子表面自组装结构调控的STM研究[D]. 北京. 中国科学院大学,2016.
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