Akkerman Hylke B, Kronemeijer Auke J, van Hal Paul A, de Leeuw Dago M, Blom Paul W M, de Boer Bert
Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747AG Groningen, The Netherlands.
Small. 2008 Jan;4(1):100-4. doi: 10.1002/smll.200700623.
The orientation of alkanedithiol molecules in self-assembled monolayers (SAMs) is of vital importance for their transport properties in molecular junctions. It is demonstrated that a too-low concentration of long alkanedithiols in ethanol leads to the formation of looped molecules, resulting in a 50-fold increase of the current through the SAM. X-ray photoelectron spectroscopy measurements show that high-concentration dithiol solutions result in a preferential standing-up phase. To obtain an almost full standing-up phase of 1,14-tetradecanedithiol (C14) a 30 mM concentration in ethanol is required, whereas a 0.3 mM concentration leads to a highly looped monolayer. The conduction through the full standing-up phase of C14 and C16 is in accordance with the exponential dependence on molecule length as obtained from shorter alkanedithiols.
自组装单分子层（SAMs）中链烷二硫醇分子的取向对于其在分子结中的传输特性至关重要。结果表明，乙醇中长链烷二硫醇浓度过低会导致环状分子的形成，从而使通过自组装单分子层的电流增加50倍。X射线光电子能谱测量表明，高浓度二硫醇溶液会导致优先的直立相。为了获得1,14-十四烷二硫醇（C14）几乎完全的直立相，乙醇中需要30 mM的浓度，而0.3 mM的浓度会导致高度环状的单分子层。通过C14和C16完全直立相的传导符合从较短链烷二硫醇获得的对分子长度的指数依赖性。
