Self-assembly behavior and monolayer characteristics of dodecylamine on Au (111) surface

Abstract

BackgroundSelf-assembly monolayers (SAMs) had been used widely to tailor the surface properties; and alkanthiols were the most common molecules which have been intensively studied. However, the assembly behavior of amine molecules and the characteristics of the SAMs are not well understood. MethodIn this study, dodecylamine (DDA) is used as a model molecule to study the self-assembly behavior of amine molecules from HClO4 solution onto an Au(111) surface. The adsorption process and the SAM characteristics are studied via cyclic voltammetry (CV), in-situ surface-enhanced infrared absorption spectroscopy (SEIRAS) and scanning tunneling microscopy (STM). Significant findingsThe CV spectra show that the current densities of Fe+2/Fe+3 redox reaction decrease slightly after the treatment of DDA, implying the formation of a DDA adlayer. The in-situ SEIRAS spectra demonstrate that the adsorption of DDA performed slowly. These results imply a weak interaction of DDA with the gold surface. The STM observation in the HClO4 solution demonstrates that the adsorbed molecules arranged in an orderly manner, forming a flat-lying orientation. The lift-off orientation commonly found for thiol molecules doesn't occur for the DDA adlayer. On the basis of this study, the self-assembly ability of DDA on a gold surface is confirmed, and a weak DDA-Au interaction is verified.