Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
J Am Chem Soc. 2011 Apr 6;133(13):4930-9. doi: 10.1021/ja110358t. Epub 2011 Mar 8.
This Article reports a systematic study on the formation of self-assembled monolayers (SAMs) of conjugated molecules for molecular electronic (ME) devices. We monitored the deprotection reaction of acetyl protected dithiols of oligophenylene ethynylenes (OPEs) in solution using two different bases and studied the quality of the resulting SAMs on gold. We found that the optimal conditions to reproducibly form dense, high-quality monolayers are 9-15% triethylamine (Et(3)N) in THF. The deprotection base tetrabutylammonium hydroxide (Bu(4)NOH) leads to less dense SAMs and the incorporation of Bu(4)N into the monolayer. Furthermore, our results show the importance of the equilibrium concentrations of (di)thiolate in solution on the quality of the SAM. To demonstrate the relevance of these results for molecular electronics applications, large-area molecular junctions were fabricated using no base, Et(3)N, and Bu(4)NOH. The magnitude of the current-densities in these devices is highly dependent on the base. A value of β=0.15 Å(-1) for the exponential decay of the current-density of OPEs of varying length formed using Et(3)N was obtained.
本文报道了对共轭分子自组装单层（SAM）在分子电子（ME）器件中的形成进行的系统研究。我们使用两种不同的碱监测了聚乙炔基二硫醇（OPEs）的乙酰保护基在溶液中的脱保护反应，并研究了在金上得到的 SAM 的质量。我们发现，在 THF 中重复形成致密、高质量单层的最佳条件是 9-15%三乙胺（Et（3）N）。脱保护碱四丁基氢氧化铵（Bu（4）NOH）导致 SAM 密度降低，并将 Bu（4）N 掺入单层中。此外，我们的结果表明溶液中二硫醇盐的平衡浓度对 SAM 的质量非常重要。为了证明这些结果与分子电子学应用的相关性，使用无碱、Et（3）N 和 Bu（4）NOH 制造了大面积分子结。这些器件中的电流密度值高度依赖于基底。使用 Et（3）N 形成的不同长度的 OPEs 的电流密度呈指数衰减，得到了β=0.15 Å（-1）的值。
