纳米尺度的表面化学在薄膜材料与表面工程中的应用

Application of Nanoscale Surface Chemistry in Growth of Thin Film Materials and Surface Engineering

纳米尺度的表面化学定义为在纳米及其以下尺度研究表面与界面的结构与化学以用于精确控制材料合成与应用中发生在表面与界面的弱的相互作用力或强的化学键合。通常,新的功能材料的合成涉及到分子间弱的相互作用或新的化学键的产生。文中简要评论了有机分子在固体表面的自组装或通过表面化学反应而实现的定向组装以引证说明研究纳米尺度的表面化学对新材料合成与对材料性能理解的重要性。基于对这些组装过程的原子尺度的理解,新的纳米有机结构材料合成方法如固体表面二维纳米网格得以讨论。对通过弱的非键作用而实现的分子自组装薄膜,分子–基体间相互作用可能引起分子构型的变化甚至使分子产生手性。分子与分子之间相互作用特别是分子之间的官能团相互作用以最大化自组装薄膜的稳定性,从而决定分子在薄膜中的排布结构。有机分子在固体表面的定向排布是通过分子的活性官能团与固体表面活性场进行表面化学反应而实现的。因而分子在定向组装的薄膜中的排布主要取决于不同官能团参与表面反应的竞争与选择以及固体表面活性场的分布。用有机分子在Si(100)与Si(111)–7×7表面的反应为例对分子定向组装形成薄膜进行原子尺度的理解,并讨论了有机分子在硅表面定向组装的反应机理。研究表明在纳米以下尺度对分子在固体表面自组装和定向组装的理解对发展具有广泛应用前景的二维与三维固体表面功能材料具有重要意义。

The study of surface and interfacial structure and chemistry at nanoscale for precisely controlling these weak interactions and/or strong chemical binding occurred at interface in synthesis and application of new functional materials, is termed nanoscale surface chemistry. In general, the syntheses of new materials involve weak intermolecular interactions and/or the formation of new chemical bonds. The self-assembly and directed-assembly of organic thin films on different solid surfaces were briefly reviewed for demonstrating the significance of nanoscale surface chemistry in synthesis of new materials and understanding of materials functions. On the basis of the atomic-level understanding of these assemblies, new synthetic methodologies for nanostructured organic architectures such as 2-D nanomeshesusing these techniques were also created. For molecular self-assembly on solid surfaces through weak noncovalent interactions, molecule-substrate interactions could induce distortion of molecular configuration and even chirality Molecule-molecule interactions, particularly interactions between functional groups determine the molecular packing pattern by maximizing stability of the self-assembled monolayers, and could possibly be used to create macroscale 2-D chiral materials. Directed-assembled organic thin films are formed through strong chemical binding between reactive sites of a substrate and molecular active functional groups. Molecular packing is dominated by competition and selectivity of different functional groups and the geometrical arrangement of reactive sites on the solid surface. Directed assemblies of organic molecules on Si （100） and Si （111） - 7×7 were taken as examples for mechanistically understanding directed-assembly at the atomic level Reaction mechanisms of the directed assembly on silicon surfaces were discussed. The understanding of molecular self- assembly and directed-assembly at nanoscale will definitely aid the development of new 2-D and 3-D organic architectures on solid surfaces for significant applications in a wide spectrum of technological fields