Willey Trevor M, Fabbri Jason D, Lee Jonathan R I, Schreiner Peter R, Fokin Andrey A, Tkachenko Boryslav A, Fokina Nataliya A, Dahl Jeremy E P, Carlson Robert M K, Vance Andrew L, Yang Wanli, Terminello Louis J, van Buuren Tony, Melosh Nicolas A
Materials Science and Technology Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
J Am Chem Soc. 2008 Aug 13;130(32):10536-44. doi: 10.1021/ja711131e. Epub 2008 Jul 19.
Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 +/- 0.05 and 0.16 +/- 0.04 eV, respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different degrees of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond nanoparticles.
金刚烷类化合物是具有立方金刚石笼状结构的碳氢化合物分子，具有独特的性质，在纳米技术领域具有潜在价值。这种特殊类型的纳米金刚石材料的可得性以及选择性功能化的能力，为表面改性、分子电子学中的高效场发射体、金刚石生长的籽晶或坚固的机械涂层开辟了新的可能性。因此，金刚烷类化合物自组装单分子层（SAMs）的性质对于各种新兴应用具有根本重要性。本文利用近边X射线吸收精细结构光谱（NEXAFS）和X射线光电子能谱（XPS），研究了硫醇取代位置和聚金刚烷顺序对金表面金刚烷类化合物SAMs的影响。提出了一种通过NEXAFS确定分子倾斜和扭曲的框架，该框架揭示了高度有序的金刚烷类化合物SAMs，其分子取向由硫醇位置控制。在金表面，金刚烷硫醇的C 1s和S 2p结合能分别比烷烃硫醇低0.67±0.05和0.16±0.04 eV。这些结合能随金刚烷类化合物单分子层结构和硫醇取代位置而变化，这与空间位阻应变程度以及与底物的电子相互作用不同相一致。这项工作展示了对组装的控制，特别是对取向和电子结构的控制，为利用这类令人兴奋的新型金刚石纳米颗粒灵活设计表面性质提供了可能。
