Otero Roberto, Lukas Maya, Kelly Ross E A, Xu Wei, Laegsgaard Erik, Stensgaard Ivan, Kantorovich Lev N, Besenbacher Flemming
Interdisciplinary Nanoscience Center, Centre for DNA Nanotechnology and Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C, Denmark.
Science. 2008 Jan 18;319(5861):312-5. doi: 10.1126/science.1150532. Epub 2007 Dec 13.
Nonsymmetrical organic molecules adsorbed on solid surfaces may assemble into random networks, thereby providing model systems for organic glasses that can be directly observed by scanning tunneling microscopy (STM). We investigated the structure of a disordered cytosine network on a gold(111) surface created by thermal quenching, to temperatures below 150 K, of the two-dimensional fluid present on the surface at room temperature. Comparison of STM images to density functional theory calculations allowed us to identify three elementary structural motifs (zigzag filaments and five- and six-membered rings) that underlie the whole supramolecular random network. The identification of elementary structural motifs may provide a new framework for understanding medium-range order in amorphous and glassy systems.
吸附在固体表面的非对称有机分子可能会组装成随机网络，从而为有机玻璃提供可通过扫描隧道显微镜（STM）直接观察的模型系统。我们研究了通过将室温下表面存在的二维流体热猝灭至150 K以下而在金（111）表面形成的无序胞嘧啶网络的结构。将STM图像与密度泛函理论计算进行比较，使我们能够识别出构成整个超分子随机网络基础的三种基本结构单元（锯齿状细丝以及五元环和六元环）。基本结构单元的识别可能为理解非晶态和玻璃态系统中的中程有序提供一个新的框架。
