Shewchuk Dwayne M, McDermott Mark T
Department of Chemistry and National Institute for Nanotechnology, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
Langmuir. 2009 Apr 21;25(8):4556-63. doi: 10.1021/la8040083.
The reduction of diazonium salts to produce aryl films on surfaces has expanded in application from carbon electrodes to a variety of conducting materials. The increasing interest in this method for modifying gold surfaces has motivated us to directly compare the structure and stability of nitrobenzene films derived from diazonium salts with monolayers formed from the corresponding thiol. We employ spectroscopic and microscopic techniques to characterize the structure and thickness of the as-formed layers. As a means of assessing stability, the nitrobenzene films were subjected to rigorous sonication, refluxing solvents, and chemical displacement by octadecanethiol. Infrared reflection-absorption spectroscopy and electrochemical blocking were used to assess the stabilities of the films generated by the two methods. Sonication and refluxing both remove more material from the diazonium-derived film relative to the thiol monolayer. However, a significant amount of each layer remains bonded to the surface following these treatments. Immersion in octadecanethiol solution results in complete displacement of the thiol derived nitrobenzene monolayer. Importantly, a significant fraction of the diazonium derived films cannot be displaced by octadecanethiol. These findings show that under certain conditions aryl films formed from the reduction of diazonium salts are more strongly bonded to gold surfaces compared to the thiol analogue.
通过重氮盐还原在表面制备芳基薄膜的应用已从碳电极扩展到多种导电材料。人们对这种修饰金表面的方法兴趣日增，促使我们直接比较由重氮盐衍生的硝基苯薄膜与由相应硫醇形成的单分子层的结构和稳定性。我们采用光谱和显微镜技术来表征所形成层的结构和厚度。作为评估稳定性的一种方法，对硝基苯薄膜进行了严格的超声处理、回流溶剂处理以及用十八烷硫醇进行化学置换。利用红外反射吸收光谱和电化学阻断来评估这两种方法所生成薄膜的稳定性。相对于硫醇单分子层，超声处理和回流处理从重氮盐衍生的薄膜中去除的物质更多。然而，经过这些处理后，每层仍有大量物质与表面结合。浸入十八烷硫醇溶液会导致硫醇衍生的硝基苯单分子层被完全置换。重要的是，相当一部分重氮盐衍生的薄膜不能被十八烷硫醇置换。这些发现表明，在某些条件下，与硫醇类似物相比，由重氮盐还原形成的芳基薄膜与金表面的结合更强。
