Department of Scanning Probe Microscopy, Institute for Molecules and Materials, Radboud University Nijmegen, P.O. Box 9010, 6500GL Nijmegen, The Netherlands.
Langmuir. 2010 May 4;26(9):6357-66. doi: 10.1021/la9038057.
By using the nanografting method, well-defined nanoscale patches of alkanethiols were constructed in a self-assembled monolayer (SAM) matrix on an atomically flat gold (Au(111)) surface. A series of nanografted patches, composed of alkanethiols with different end groups (-CH(3), -CF(3), -OH, -SH, -COOH, and -NH(2)), were analyzed in detail by a combination of atomic force microscopy (AFM) height and quantitative lateral friction measurements. By constructing a series of nanografted patches of methyl-terminated thiols with various chain lengths, it was shown that the absolute friction of the nanografted patches was always smaller than that of the surrounding SAM matrix, demonstrating that, because of the spatially confined self-assembly during nanografting, SAMs show less defects. In addition, the friction gradually increased for decreasing alkane chain length as expected, although a subtle odd-even effect was observed. The study of thiols with functionalized end groups (-CF(3), -OH, -SH, -COOH, and -NH(2)) gave specific insights in orientation, packing, and structure of the molecules in the SAMs. Depending on the thiol end groups, these nanografted patches exhibited large and specific differences in lateral friction force, which offers the unique possibility to use the friction as a molecular recognition tool for thiol-based self-assembled monolayers.
通过使用纳米嫁接方法，在原子级平整的金（Au(111)）表面的自组装单分子层（SAM）基质中构建了具有明确纳米尺度的烷硫醇纳米级补丁。通过原子力显微镜（AFM）高度和定量横向摩擦测量的组合，详细分析了由具有不同末端基团（-CH(3)、-CF(3)、-OH、-SH、-COOH 和 -NH(2)）的烷硫醇组成的一系列纳米嫁接补丁。通过构建具有各种链长的甲基末端硫醇的一系列纳米嫁接补丁，表明纳米嫁接补丁的绝对摩擦力始终小于周围 SAM 基质的摩擦力，这表明由于空间受限的自组装在纳米嫁接过程中，SAM 显示出较少的缺陷。此外，如预期的那样，随着烷烃链长度的减小，摩擦力逐渐增加，尽管观察到微妙的奇偶效应。对具有官能化末端基团（-CF(3)、-OH、-SH、-COOH 和 -NH(2)）的硫醇的研究提供了有关 SAM 中分子取向、堆积和结构的具体见解。根据硫醇的末端基团，这些纳米嫁接补丁在横向摩擦力方面表现出很大且特定的差异，这为使用摩擦作为基于硫醇的自组装单层的分子识别工具提供了独特的可能性。
