Chemically imaging nanostructures formed by the covalent assembly of molecular building blocks on a surface with ultrahigh vacuum tip-enhanced Raman spectroscopy
Chemically imaging nanostructures formed by the covalent assembly of molecular building blocks on a surface with ultrahigh vacuum tip-enhanced Raman spectroscopy
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DOI：
10.1088/1361-648x/ac57d8
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
J. Schultz;Linfei Li;Sayantan Mahapatra;Nan Jiang
中科院分区：
文献类型：
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作者：
J. Schultz;Linfei Li;Sayantan Mahapatra;Nan Jiang
表面结合反应已经成为一种可行的方法，通过自下而上的组装，以接近原子的精度开发纳米结构。然而，自下而上地在表面上制造纳米结构需要仔细考虑前驱体和衬底的固有性质，以及在非均相二维(2D)系统中出现的任何相互作用的复杂相互作用。因此，有必要考虑这些系统，其表征方法对这些属性敏感，并具有合适的空间分辨率。利用低温超高真空扫描隧道显微镜(STM)和尖端增强拉曼光谱(TERS)研究了四(4-溴苯基)卟啉(Br4TPP)分子在Ag(100)衬底上通过偶联反应形成二维共价网络的过程。通过STM形貌成像和TERS振动指纹图谱的结合，了解了分子前驱体在底物上的构象。在热激活偶联反应之后，STM和TERS成像证实了2D网络的共价性质，并表明明显的无序源于分子的柔性。
Surface-bound reactions have become a viable method to develop nanoarchitectures through bottom-up assembly with near atomic precision. However, the bottom-up fabrication of nanostructures on surfaces requires careful consideration of the intrinsic properties of the precursors and substrate as well as the complex interplay of any interactions that arise in the heterogeneous two-dimensional (2D) system. Therefore, it becomes necessary to consider these systems with characterization methods sensitive to such properties with suitable spatial resolution. Here, low temperature ultrahigh vacuum scanning tunneling microscopy (STM) and tip-enhanced Raman spectroscopy (TERS) were used to investigate the formation of 2D covalent networks via coupling reactions of tetra(4-bromophenyl)porphyrin (Br4TPP) molecules on a Ag(100) substrate. Through the combination of STM topographic imaging and TERS vibrational fingerprints, the conformation of molecular precursors on the substrate was understood. Following the thermally activated coupling reaction, STM and TERS imaging confirm the covalent nature of the 2D networks and suggest that the apparent disorder arises from molecular flexibility.