Zhu Zihua, Daniel Thomas A, Maitani Masato, Cabarcos Orlando M, Allara David L, Winograd Nicholas
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Am Chem Soc. 2006 Oct 25;128(42):13710-9. doi: 10.1021/ja060084x.
The penetration behavior of thermally evaporated Au on S(CH(2))(15)CH(3), S(CH(2))(15)CO(2)CH(3), S(CH(2))(15)CO(2)H, K-modified S(CH(2))(15)CO(2)CH(3), and K-modified S(CH(2))(15)CO(2)H self-assembled monolayers (SAM) on Au substrates is investigated. Gold is a particularly interesting metal since vapor-deposited Au atoms are known to pass through alkanethiolate SAMs on Au{111} substrates at room temperature. Here we show that it is possible to control Au penetration by adjusting the interactions between terminal groups. It is found that Au atoms evenly penetrate into the CH(3) and CO(2)CH(3) films, forming smooth buried layers below the organic thin films. For the CO(2)H film, although Au atoms can still penetrate through it, filaments and mushroomlike clusters form due to H-bonding between film molecules. In the case of the K-modified CO(2)CH(3) or CO(2)H films, however, most Au atoms form islands at the vacuum interface. These results suggest that van der Waals forces and H-bonds are not strong enough to block Au from going through but that ionic interactions are able to block Au penetration. The measurements were performed primarily using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM). The combination of these highly complementary probes provides a very useful strategy for the study of metal atom behavior on SAMs.
研究了热蒸发金在金基底上的S(CH₂)₁₅CH₃、S(CH₂)₁₅CO₂CH₃、S(CH₂)₁₅CO₂H、K修饰的S(CH₂)₁₅CO₂CH₃和K修饰的S(CH₂)₁₅CO₂H自组装单分子层（SAM）上的渗透行为。金是一种特别有趣的金属，因为已知气相沉积的金原子在室温下能穿过金{111}基底上的烷硫醇盐SAM。在此我们表明，通过调节端基之间的相互作用可以控制金的渗透。发现金原子均匀地渗透到CH₃和CO₂CH₃薄膜中，在有机薄膜下方形成光滑的掩埋层。对于CO₂H薄膜，尽管金原子仍能穿过它，但由于薄膜分子之间的氢键作用，会形成细丝状和蘑菇状簇。然而，在K修饰的CO₂CH₃或CO₂H薄膜的情况下，大多数金原子在真空界面处形成岛状结构。这些结果表明，范德华力和氢键不足以阻止金穿过，但离子相互作用能够阻止金的渗透。测量主要使用飞行时间二次离子质谱（ToF-SIMS）和原子力显微镜（AFM）进行。这些高度互补的探针的组合为研究SAM上的金属原子行为提供了一种非常有用的策略。
