Guo Quanmin, Li Fangsen
School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT, UK.
Phys Chem Chem Phys. 2014 Sep 28;16(36):19074-90. doi: 10.1039/c4cp00596a.
The surface properties of metals and metal oxides can be modified by adding a single layer of organic molecules. A most popular route for depositing such a molecular layer is via the formation of self-assembled monolayers (SAMs). The molecules that form SAMs have a functionality which binds to the surface and the adsorption is self-regulated to terminate at exactly one single molecular layer. The very first example, which has become the most widely studied system, of SAMs on metal surfaces consists of chemisorbed alkylthiolate on gold. Despite the simplicity in the preparation of alkanethiol SAMs and the seemingly straightforward structure of such SAMs, the detailed bonding between the sulfur head group and gold is still subject to debate. Experimental and theoretical effort in the last six years has led to a much improved understanding of this classical system of SAMs. In this review, we will highlight the most recent progress in the study of the interfacial structure of alkanethiol SAMs on gold. We focus on the important phenomenon of phase transition that occurs from n-propanethiol to n-butanethiol, and propose a unified structural model to explain how the (3 × 4) phase for short chain alkanethiol monolayers (methyl-, ethyl- and propylthiolate monolayers) changes into the (3 × 2√3)-rect./c(4 × 2) phase for long chain molecular monolayers.
通过添加单分子层有机分子，可以改变金属和金属氧化物的表面性质。沉积这种分子层最常用的途径是通过形成自组装单分子层（SAMs）。形成SAMs的分子具有与表面结合的官能团，并且吸附是自我调节的，最终恰好形成一个单分子层。金属表面上SAMs的第一个例子，也是研究最广泛的体系，是金表面化学吸附的烷基硫醇盐。尽管烷硫醇SAMs的制备简单，且其结构看似直接，但硫端基与金之间的详细键合仍存在争议。过去六年的实验和理论研究使人们对这个经典的SAMs体系有了更好的理解。在这篇综述中，我们将重点介绍金表面烷硫醇SAMs界面结构研究的最新进展。我们关注从正丙硫醇到正丁硫醇发生的重要相变现象，并提出一个统一的结构模型来解释短链烷硫醇单分子层（甲基、乙基和丙基硫醇盐单分子层）的(3×4)相如何转变为长链分子单分子层的(3×2√3)-rect./c(4×2)相。
