Monolayers of trimesic and isophthalic acid on Cu and Ag: the influence of coordination strength on adsorption geometry
Monolayers of trimesic and isophthalic acid on Cu and Ag: the influence of coordination strength on adsorption geometry
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DOI：
10.1039/c3sc52137k
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发表时间：
2013-01-01
期刊：
影响因子：
8.4
通讯作者：
Buck, Manfred
中科院分区：
文献类型：
--
作者：
Cebula, Izabela;Lu, Hao;Buck, Manfred
采用欠电位沉积法（UPD）在Au（111）/云母基底上制备了均苯三甲酸（IPA）和均苯三甲酸（TMA）的自组装膜。通过扫描隧道显微镜（STM）、基于同步加速器的X射线光电子能谱（XPS）和近边X射线吸收精细结构（NEXAFS）光谱的非原位分析揭示了（1 x 1）Cu和（1 x 1）Ag掺杂改性的Au（111）/云母基底的明显不同的膜结构。在Cu上，IPA和TMA形成具有特征行结构的高度结晶的相称层，芳环从表面法线和涉及两个羧酸酯部分的分子的双足吸附几何形状的类似50度的显著倾斜。相比之下，一个显着较小的倾斜角，类似于20度和单足吸附的几何形状被发现对银。即使在Ag上也观察到TMA的行结构，但它缺乏在Cu上发现的规则性和因此的可折叠性。对比其他系统，产生分子分辨STM图像，没有横向顺序是看到在IPA自组装膜，尽管事实上，这两个IPA和TMA层上的银具有类似的结构，基本上相同的苯环的倾斜角。IPA和TMA在Ag上的差异可以通过用于通过分子间氢键稳定层的羧基数量的差异来解释。
Self-assembled monolayers (SAMs) of isophthalic acid (IPA) and trimesic acid (TMA) were prepared from solution using Au(111)/mica substrates modified by underpotential deposition (UPD) of Cu and Ag. Ex situ analysis by scanning tunneling microscopy (STM), synchrotron based X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy reveals pronouncedly different film structures for the (1 x 1) Cu and (1 x 1) Ag UPD-modified Au(111)/mica substrates. On Cu, both IPA and TMA form highly crystalline commensurate layers with a characteristic row structure, a significant tilt of the aromatic ring by similar to 50 degrees from the surface normal and a bipodal adsorption geometry of the molecules involving two carboxylate moieties. In contrast, a significantly smaller tilt angle of similar to 20 degrees and a monopodal adsorption geometry is found on Ag. Even though a row structure is also observed for TMA on Ag, it lacks the regularity and, thus, commensurability found on Cu. Contrasting the other systems which yield molecularly resolved STM images, no lateral order is seen in the IPA SAMs despite the fact that both the IPA and TMA layers on Ag have analogous structures with essentially the same tilt angle of the benzene ring. The difference between IPA and TMA on Ag is explained by the difference in the number of carboxyl groups available for stabilising the layer via intermolecular hydrogen bonds.