Two-dimensional Molecular Arrangements of Tolanethioacetate Self-Assembled Monolayers on Au(111) in Catalytic Tetrabutylammonium Cyanide Solution

Abstract

Surface structures and adsorption conditions of tolanethioacetate (TTA) self-assembled monolayers (SAMs) on Au(111) formed in catalytic tetrabutylammonium cyanide (TBACN) solution were examined by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). We found that SAM formation by TTA on Au(111) strongly depends on experimental conditions for the deprotection of acetyl group. Molecular-scale STM imaging revealed that TTA molecules on Au(111) can form well-ordered SAMs in TBACN catalytic medium compared to in pure solvent. TTA SAMs on Au(111) formed in catalytic TBACN solution contain an unique ordered phase consisting rod-like domains, which can be described as a (√3 × √11) R8° structure. We also found that that the concentration of catalytic TBACN strongly affects the formation of two-dimensional TTA SAMs. In addition, XPS measurements showed a strong S 2p peak at 162 eV for TTA SAMs on Au(111), implying that the SAMs were formed via chemical reactions between the sulfur atoms and gold surfaces.