Azzam Waleed, Subaihi Abdu, Rohwerder Michael, Zharnikov Michael, Bashir Asif
Department of Chemistry, Tafila Technical University, P.O. Box 179, Tafila, 66110, Jordan.
Department of Chemistry, University College in Al-Qunfudah, Umm Al-Qura University, 1109, Makkah, Al-Mukarramah, Saudi Arabia.
Chemphyschem. 2022 Oct 6;23(19):e202200347. doi: 10.1002/cphc.202200347. Epub 2022 Jul 20.
Self-assembled monolayers (SAMs) of 4-fluorobenzenemethanethiol (p-FBMT) on Au(111), prepared by immersion procedure (1 mM ethanolic solution; 60 °C; 18 h), were characterized by scanning tunneling microscopy (STM). The data suggest the formation of highly ordered monolayer with a commensurate structure, described by the unit cell. The STM appearance of this cell occurs, however, in two different forms, with either well-localized individual spots or splitting of these spots in two components. These components are assigned to the tunneling through the entire molecule or sulfur docking group only. The respective spots correspond then to the terminal fluorine atom and sulfur docking group, manifesting, thus, building-block-resolving STM imaging. The accessibility of the docking group for direct tunneling is most likely related to a specific molecular organization for one of the two possible internal structures of the unit cell. The above results represent a showcase for potential of STM for imaging of upright-arranged and densely packed molecular assemblies, such as SAMs.
通过浸渍法（1 mM乙醇溶液；60°C；18小时）在Au(111)上制备的4-氟苯甲硫醇（p-FBMT）自组装单分子层（SAMs），用扫描隧道显微镜（STM）进行了表征。数据表明形成了具有匹配结构的高度有序单分子层，由晶胞描述。然而，这个晶胞的STM外观以两种不同形式出现，要么是定位良好的单个斑点，要么是这些斑点分裂成两个组分。这些组分分别对应于通过整个分子的隧穿或仅通过硫对接基团的隧穿。相应的斑点则对应于末端氟原子和硫对接基团，从而体现了基于结构单元分辨的STM成像。对接基团对于直接隧穿的可及性很可能与晶胞两种可能内部结构之一的特定分子组织有关。上述结果展示了STM对直立排列且紧密堆积的分子组装体（如SAMs）成像的潜力。
