Well-Ordered Domains of 4-Fluorobenzenethiol Self-Assembled Monolayers on Au(111) Guided by a Displacement Reaction

Displacement processes of pre-covered cyclohexanethiol (CHT) self-assembled monolayers (SAMs) by 4-fluorobenzenethiol (4-FBT) on Au(111) were examined as a function of displacement time by scanning tunneling microscopy (STM) and water static contact angle (CA) measurements. STM imaging revealed that the adsorption of 4-FBT on Au(111) in a 1 mM ethanol solution at room temperature for 24 h generated disordered SAMs, whereas well-ordered 4-FBT SAMs with a (4√6 × √3)R5° packing structure were formed over the entire Au(111) surfaces via the displacement of pre-covered CHT SAMs by 4-FBT molecules. The CA measurements also showed that CA values increase with increasing displacement time, reflecting that the displacement reaction took place and the resulting SAMs had greater hydrophobicity compared with CHT SAMs. In this study, we found that the displacement technique using CHT SAMs as a molecular template is very useful in obtaining 4-FBT SAMs with a high degree of structural order and large ordered domains.