铜原子掺杂对金表面三聚氰胺自组装结构的调控
发布时间：2018-09-08 20:37
【摘要】：分子自组装膜由于其自发性、高度有序性、以及可设计性等特点,长期以来被认为是一种自下而上构筑纳米结构的有效方法。大量的分子自组装研究均以金属单质表面作为衬底,这与实际应用中广泛存在的多组分金属表面即合金化表面相差甚远。实际上,表面合金结构往往展现出有别于单组分金属表面的各种性质,在催化等领域应用广泛。然而目前人们对合金体系的表面科学基础研究仍然比较有限,所涉及的分子吸附及反应也多限于CO、O2等小分子,而对具有广泛应用前景的各种功能性有机分子在合金表面的吸附组装及反应研究则几乎是空白。故此,我们选择了有重要应用背景的Au-Cu合金体系,并在前期详细研究Cu/Au(111)薄膜结构与性质的基础上,进一步制备了只有一到几个原子层厚度的Au/Cu(111)薄膜。我们进而利用扫描隧道显微镜(STM)结合同步辐射及x射线光电子能谱技术(PES)详细研究了这些金薄膜的原子结构与电子性质以及三聚氰胺分子在其表面的吸附组装行为。研究发现:(1)3层及以下的Au薄膜的原子晶格小于Au(111)表面晶格而大于Cu(111)表面晶格,且随着层数增加而增大;4层及以上的Au薄膜才回归到Au(111)晶格。各层Au薄膜的电子性质也基本上按照原子晶格的变化规律而逐渐回归至Au(111)表面性质。(2)PES研究表明,衬底Cu原子渗析到Au薄膜表面,并随着Au膜厚度的增加而减少。直至7层金膜表面仍能观察到一定量的Cu。(3)三聚氰胺分子优先吸附在裸露的衬底Cu(111)表面并形成与纯净Cu(111)表面一致的组装结构,至饱和后才开始在金薄膜表面吸附。(4)三聚氰胺在Au膜上的组装结果受到渗析至金薄膜表面的Cu原子的影响而形成新颖的组装结构,其结构花样随着Au薄膜厚度即表面Cu原子的数量而变化,最终回归Au(111)表面的组装结果。作为对照,我们还在预吸附有三聚氰胺自组装薄膜的Au(111)表面蒸镀Cu原子。通过控制Cu原子的蒸镀量,实现了将三聚氰胺组装结构逐步调变至在Au/CU(111)表面形成的多种组装结构。经过两个体系的对比研究,进一步佐证了Cu原子的掺杂对三聚氰胺分子在金薄膜表面组装结构的调控作用。在本论文的最后一部分,我们尝试研究了另外一种有望制备二维共价网格结构的1,3,5-苯三腈分子,表征并分析了其在Cu(111)和Au(111)表面的自组装结构,为进一步研究其在Cu/Au(111)、Au/Cu(111)薄膜表面的吸附组装以及制备高度有序的二维共价有机框架结构打下了基础。
[Abstract]:Molecular self-assembled films have long been considered as an effective way to construct nanostructures from the bottom up due to their characteristics of spontaneity, high order and designability. A large number of molecular self-assembly studies have been carried out on a single metal substrate, which is far from the multicomponent metal surface, i.e. alloying surface, which is widely used in practical applications. As a matter of fact, the structure of surface alloys often shows a variety of properties different from that of single component metals, and is widely used in catalysis and other fields. However, at present, the basic research on surface science of alloy system is still limited, and the molecular adsorption and reaction involved are limited to small molecules such as CO,O2. However, the adsorption, assembly and reaction of various functional organic molecules with wide application prospects on the alloy surface are almost blank. Therefore, we have selected the Au-Cu alloy system with important application background, and on the basis of detailed investigation of the structure and properties of Cu/Au (111) thin films, we have further prepared Au/Cu (111) thin films with only one or several atomic layers. Furthermore, the atomic structure and electronic properties of these gold thin films and the adsorption and assembly behavior of melamine molecules on their surface have been studied in detail by scanning tunneling microscope (STM) combined with synchrotron radiation and X-ray photoelectron spectroscopy (PES). It is found that (1) the atomic lattice of Au thin films with layers 3 and below is smaller than that of Au (111) and is larger than that of Cu (111), and the Au films with 4 or more layers increase with the increase of the number of layers before returning to Au (111) lattices. The electronic properties of each layer of Au thin films are also gradually regressed to the surface properties of Au (111) according to the variation of atomic lattice. (2) PES study shows that the Cu atoms on the substrate are dialyzed to the surface of Au films and decrease with the increase of the thickness of Au films. Cu. (3) melamine molecules were preferentially adsorbed on the Cu (111) surface of the bare substrate and formed an assembly structure consistent with that of the pure Cu (111) surface. (4) the results of melamine assembly on Au films were influenced by the Cu atoms on the surface of gold films, and formed a novel assembly structure. The structure pattern changes with the thickness of the Au film, that is, the number of Cu atoms on the surface, and finally returns to the assembly result of the Au (111) surface. As a control, we also vaporized Cu atoms on the surface of Au (111) on which melamine self-assembled films were preadsorbed. By controlling the amount of vaporization of Cu atoms, the melamine assembly structure was gradually adjusted to a variety of assembly structures formed on the surface of Au/CU (111). Through the comparative study of the two systems, the effect of doping of Cu atoms on the structure of melamine molecules on the surface of gold films was further verified. In the last part of this thesis, we try to study another kind of molecule which is expected to prepare two-dimensional covalent lattice structure, and characterize and analyze its self-assembly structure on the surface of Cu (111) and Au (111). The results provide a basis for the further study of the adsorption and assembly on the surface of Cu/Au (111) au / Cu (111) films and the preparation of highly ordered two-dimensional covalent organic frameworks.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.2;O641.3
本文编号：2231630
[Abstract]:Molecular self-assembled films have long been considered as an effective way to construct nanostructures from the bottom up due to their characteristics of spontaneity, high order and designability. A large number of molecular self-assembly studies have been carried out on a single metal substrate, which is far from the multicomponent metal surface, i.e. alloying surface, which is widely used in practical applications. As a matter of fact, the structure of surface alloys often shows a variety of properties different from that of single component metals, and is widely used in catalysis and other fields. However, at present, the basic research on surface science of alloy system is still limited, and the molecular adsorption and reaction involved are limited to small molecules such as CO,O2. However, the adsorption, assembly and reaction of various functional organic molecules with wide application prospects on the alloy surface are almost blank. Therefore, we have selected the Au-Cu alloy system with important application background, and on the basis of detailed investigation of the structure and properties of Cu/Au (111) thin films, we have further prepared Au/Cu (111) thin films with only one or several atomic layers. Furthermore, the atomic structure and electronic properties of these gold thin films and the adsorption and assembly behavior of melamine molecules on their surface have been studied in detail by scanning tunneling microscope (STM) combined with synchrotron radiation and X-ray photoelectron spectroscopy (PES). It is found that (1) the atomic lattice of Au thin films with layers 3 and below is smaller than that of Au (111) and is larger than that of Cu (111), and the Au films with 4 or more layers increase with the increase of the number of layers before returning to Au (111) lattices. The electronic properties of each layer of Au thin films are also gradually regressed to the surface properties of Au (111) according to the variation of atomic lattice. (2) PES study shows that the Cu atoms on the substrate are dialyzed to the surface of Au films and decrease with the increase of the thickness of Au films. Cu. (3) melamine molecules were preferentially adsorbed on the Cu (111) surface of the bare substrate and formed an assembly structure consistent with that of the pure Cu (111) surface. (4) the results of melamine assembly on Au films were influenced by the Cu atoms on the surface of gold films, and formed a novel assembly structure. The structure pattern changes with the thickness of the Au film, that is, the number of Cu atoms on the surface, and finally returns to the assembly result of the Au (111) surface. As a control, we also vaporized Cu atoms on the surface of Au (111) on which melamine self-assembled films were preadsorbed. By controlling the amount of vaporization of Cu atoms, the melamine assembly structure was gradually adjusted to a variety of assembly structures formed on the surface of Au/CU (111). Through the comparative study of the two systems, the effect of doping of Cu atoms on the structure of melamine molecules on the surface of gold films was further verified. In the last part of this thesis, we try to study another kind of molecule which is expected to prepare two-dimensional covalent lattice structure, and characterize and analyze its self-assembly structure on the surface of Cu (111) and Au (111). The results provide a basis for the further study of the adsorption and assembly on the surface of Cu/Au (111) au / Cu (111) films and the preparation of highly ordered two-dimensional covalent organic frameworks.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.2;O641.3
【参考文献】
相关期刊论文 前2条
1 张建祥,赵彦巧,陈吉祥,王日杰,张继炎;CO_2加氢合成甲醇及二甲醚研究进展[J];天然气化工;2004年06期
2 高俊文,张勇,霍尚义;国内外合成甲醇催化剂研究进展[J];工业催化;1999年05期
，本文编号：2231630
本文链接：https://www.wllwen.com/guanlilunwen/gongchengguanli/2231630.html
