ABSTRACT

This paper presents an investigation of atomic force microscopy (AFM) in the force-distance mode for self-assembled monolayers (SAM) by means of molecular dynamics modeling methods. A model system of SAM of biphenyldithiol (BPDT) on a gold substrate and a gold tip with a diameter of 10 nm were used. This work has reproduced the general behavior of force–distance curves in similar systems observed in experimental studies. The impact of the structural order (i.e., standing up ordered, disordered and striped phases) on the attractive and repulsive molecular interactions and conformations were revealed. The ordered SAM in standing up phase has the highest adhesive force and the striped phase has the lowest. The adhesive forces as a function of the tip-surface distance exhibit some unique and distinct features. An AFM induced ordering for both disordered and striped phases is reported.

摘要

本文通过分子动力学建模方法对自组装单分子层 (SAM) 的力-距离模式下的原子力显微镜 (AFM) 进行了研究。使用了在金基板和直径为 10 nm 的金尖端上的联苯二硫醇 (BPDT) SAM 模型系统。这项工作再现了在实验研究中观察到的类似系统中力-距离曲线的一般行为。揭示了结构顺序（即直立有序、无序和条纹相）对吸引和排斥分子相互作用和构象的影响。直立相的有序SAM具有最高的粘附力，而条纹相的粘附力最低。作为尖端表面距离的函数的粘附力表现出一些独特和明显的特征。