A dimeric structure of eosin molecules on Au(1 1 1) surface

In situ scanning tunneling microscopy (STM) and cyclic voltammetry have been employed to investigate the adsorption of eosin molecules on Au(1 1 1) in aqueous HClO4 solution. The eosin molecules are found to form a highly ordered adlayer on the well-defined Au(1 1 1) surface. A dimeric structure of eosin molecules is clearly resolved in high-resolution STM image. Based on the STM observation and theoretical calculation, a structural model is tentatively proposed. The interaction between the bromide atoms is assumed to be responsible for the formation of the dimeric structure.