Department of Chemistry and the Texas Center for Superconductivity, University of Houston , Houston, Texas 77204-5003.
Langmuir. 2013 Nov 19;29(46):14108-16. doi: 10.1021/la401899q. Epub 2013 Nov 4.
Tridentate cyclohexyl-based alkanethiolate SAMs generated from a series of adsorbates of the form R3C6H6(CH2SH)3, where R = -(CH2)nH and n = 3, 8, and 13 (3CnCyTSH), were examined. Characterization of the SAMs by X-ray photoelectron spectroscopy (XPS) revealed that all sulfur atoms of the tridentate adsorbates were bound to the surface of gold, and that the tailgroups were in general less densely packed than the SAM derived from octadecanethiol (C18SH). For each of the SAMs, the relative molecular coverage on the surface was estimated from the XPS-derived C1s/Au4f ratios. The trend in conformational order for these SAMs as determined by the surface interactions with contacting liquids and the relative crystallinity of the alkyl chains as revealed by the PM-IRRAS spectra were found to decrease as follows: C18SH >> 3C13CyTSH > 3C8CyTSH > 3C3CyTSH. A preliminary study of the thermal stability of the SAMs as evaluated by XPS indicates that the SAM generated from the cyclohexyl-based adsorbate with the longest alkyl chain, 3C13CyTSH, is markedly more stable than the SAM generated from C18SH. Overall, the results suggest that the stability of the SAMs are influenced by both the length of the alkyl chains and the chelate effect associated with the tridentate adsorbates.
研究了一系列形式为 R3C6H6(CH2SH)3 的吸附剂生成的三齿环己基烷硫醇自组装单分子膜（SAM），其中 R = -(CH2)nH，n = 3、8 和 13（3CnCyTSH）。通过 X 射线光电子能谱（XPS）对 SAMs 进行了表征，结果表明，三齿吸附剂的所有硫原子都与金表面结合，并且尾基团通常比十八烷硫醇（C18SH）衍生的 SAM 排列得更不紧密。对于每个 SAM，通过 XPS 衍生的 C1s/Au4f 比值估算了表面上的相对分子覆盖率。通过与接触液体的表面相互作用以及 PM-IRRAS 光谱揭示的烷基链的相对结晶度确定的这些 SAM 的构象有序性趋势表明，如下所示，依次降低：C18SH >> 3C13CyTSH > 3C8CyTSH > 3C3CyTSH。通过 XPS 评估的 SAM 热稳定性的初步研究表明，由具有最长烷基链的环己基吸附剂生成的 SAM 比由 C18SH 生成的 SAM 明显更稳定。总的来说，结果表明 SAM 的稳定性受到烷基链长度和三齿吸附剂相关的螯合效应的影响。
