Kang Hungu, Jang Chang-Hyun, Hara Masahiko, Noh Jaegeun
Department of Chemistry, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea.
J Nanosci Nanotechnol. 2009 Dec;9(12):7085-9. doi: 10.1166/jnn.2009.1621.
Two-dimensional ordered structures of cyclohexanethiol (CHT) self-assembled monolayers (SAMs) on Au(111) formed from different solution concentrations were investigated using scanning tunneling microscopy (STM). Molecular-scale STM imaging clearly revealed the 2D phase transitions of CHT SAMs from a (2 x 4 square root of 2)R20 degrees structure to a (5 x 2 square root of 3)R35 degrees structure via a intermediate phase of a (5 x square root of 15)R25 degrees structure depending on solution concentration used for SAM fabrication. The (5 x 2 square root of 3)R35 degrees phase was observed for high concentrations, after deposition at low temperature or after long-time immersion. Based on these results, we confirmed that the molecular packing arrangement can be regarded as a fully covered SAM structure. In addition, 2D SAM formation of CHT SAMs is markedly different from that of alkanethiol SAMs, which is a result of structural dynamics of the CHT ring in the process of molecular self-assembly. The molecular-scale STM results for CHT SAMs on Au(111) can provide very useful information on understanding structural behaviors of cyclic thiol SAMs.
利用扫描隧道显微镜（STM）研究了由不同溶液浓度形成的环己烷硫醇（CHT）自组装单分子层（SAMs）在Au(111)上的二维有序结构。分子尺度的STM成像清楚地揭示了CHT SAMs的二维相变，即从(2×4√2)R20°结构通过(5×√15)R25°结构的中间相转变为(5×2√3)R35°结构，这取决于用于制备SAMs的溶液浓度。在高浓度、低温沉积后或长时间浸泡后观察到(5×2√3)R35°相。基于这些结果，我们证实分子堆积排列可被视为完全覆盖的SAM结构。此外，CHT SAMs的二维SAM形成与链烷硫醇SAMs明显不同，这是分子自组装过程中CHT环结构动力学的结果。Au(111)上CHT SAMs的分子尺度STM结果可为理解环状硫醇SAMs的结构行为提供非常有用的信息。
