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Scannning Tunneling Microscopy Based on Chemically Modified Tips

基于化学修饰尖端的扫描隧道显微镜

基本信息

批准号：
10554044
负责人：
UMEZAWA Yoshio
金额：
$ 0.96万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Monolayers of-mono-and diethers were studied with scanning tunneling microscopy (STM) as a new example for the chemical modification of STM tips for functional groups recognition. Bright lines revealing the positions of the ether oxygens of the monolayers were observed in STM images with tips modified with 4-mercaptobenzoic acid (4MBA) which can form hydrogen bond with ether oxygens. Such bright lines, however, were absent with unmodified tips or tips modified with thiophenol, which has no functional groups available for hydrogen bond formation. In the STM images of diethers, the brightness of the ether oxygens observed with 4MBA-modified tips was modulated depending upon the orientation of the ether oxygens. These results support that selective contrast enhancements are associated with hydrogen bond formation between sample and tip. It is demonstrated that chemical modification of STM tips allows not only selective recognition but also orientation-sensitive observation of functional groups.Chemical modification of scanning tunneling microscopy (STM) gold tips with 4-mercaptopyridine (4MP) was used for STM measurements of 5,15-bis(4-octadecyloxyphenyl) porphyrin (Por-H2) and its zinc(II) (Por-Zn) and nickel(II) complexes (Por-Ni). Monolayers of these compounds spontaneously form at the solution-HOPG (highly oriented pyrolytic graphite) interface. STM images of porphyrin centers measured with 4MP-modified tips exhibited bright spots while those measured with unmodified tips exhibited the porphyrin centers as dark depressions. The brightness of porphyrin centers seems to result from facilitated electron tunneling due to hydrogen bond interactions for Por-H2 and due to coordination interaction for Por-Zn and Por-Ni. Interestingly, the centers of Por-Zn were brighter than those of Por-H2 and Por-Ni. In addition, STM measurements with 4MP-modified tips allowed to distinguish Por-Zn from Por-H2 or Por-Ni in mixed monolayers.

使用扫描隧道显微镜 (STM) 研究了单醚和双醚的单层，作为 STM 尖端化学修饰用于官能团识别的新示例。在 STM 图像中观察到揭示单层醚氧位置的亮线，其尖端经过 4-巯基苯甲酸 (4MBA) 修饰，可与醚氧形成氢键。然而，未修饰的尖端或用苯硫酚修饰的尖端不存在这种亮线，苯硫酚不具有可用于形成氢键的官能团。在二醚的 STM 图像中，用 4MBA 改性尖端观察到的醚氧的亮度根据醚氧的方向进行调节。这些结果支持选择性对比度增强与样品和尖端之间的氢键形成有关。结果表明，STM 尖端的化学修饰不仅可以选择性识别，还可以对官能团进行方向敏感观察。用 4-巯基吡啶 (4MP) 对扫描隧道显微镜 (STM) 金尖端进行化学修饰，用于 5,15-双(4-十八烷氧基苯基)卟啉 (Por-H2) 及其锌 (II) 的 STM 测量 (Por-Zn) 和镍 (II) 络合物 (Por-Ni)。这些化合物的单层在溶液-HOPG（高度定向热解石墨）界面处自发形成。使用 4MP 修饰的尖端测量的卟啉中心的 STM 图像显示出亮点，而使用未修饰的尖端测量的卟啉中心的 STM 图像则显示为黑色凹陷。卟啉中心的亮度似乎是由于 Por-H2 的氢键相互作用以及 Por-Zn 和 Por-Ni 的配位相互作用而促进的电子隧道效应所致。有趣的是，Por-Zn 的中心比 Por-H2 和 Por-Ni 的中心更亮。此外，使用 4MP 改良尖端的 STM 测量可以区分混合单层中的 Por-Zn 与 Por-H2 或 Por-Ni。