有机分子组装体系的扫描隧道显微镜研究

利用长链烷烃取代基与石墨表面的较强相互作用,可以获得烷基取代的有机小分子(酞菁、卟啉、碱基)的高分辨STM图像。理论分析表明,这些分子的吸附稳定性来源于长链烷基与石墨间较强的范德华相互作用,以及长链烷烃链间的二维结晶能。分子在表面的吸附组装结构受到分子与基底间、吸附分子间,以及溶剂与分子间作用的共同影响。对于长链烷基取代的碱基分子在石墨表面的组装结构中,分子的排列方式不仅受到烷基链与石墨间较强的取向匹配的作用,碱基分子间形成的多个氢键以及芳环离域π键的作用也会影响分子的排列方式,并且是造成烷基取代碱基分子组装结构多样性的原因。扫描隧道谱研究表明,硫醇在Au表面的自组装分子膜对电流的整流作用,来自于分子中巯基与Au表面形成的双电层,而不对称取代的NtBuPc分子在石墨表面的LB膜的电流整流行为,来源于分子内部的不对称电子结构

Scanning Tunnelling Microscopic Investigation of Organic Molecular Assembling Systems

Self assembled organic molecules, including alkylated phthalocyanines, porphyrin and adenine, physisorbed on graphite surface have been stabilized and dispersed on the basal plane of graphite by using linear alkyl substituents as molecular anchors, and have been systematically studied under ambient conditions, with the combination of scanning tunnelling microscopy and molecular mechanics simulation. In addition, scanning tunnelling microscopy measurements have been performed to characterize the conductance behaviour of thiol/Au and phthalocyanines LB films/HOPG, as well as the capillary condensed liquid meniscus formed around tip substrate contact.