Leaflike Structured Multilayer Assembly of Dimercaptothiadiazole on Gold Surface

Adsorption of a heteroaromatic dithiol, 2,5-dimercapto-1,3,4-thiadiazole (DMT), on Au surface from a completely deaerated aqueous solution leads to the formation of a multilayer assembly via hydrogen bonding with water molecules, whereas adsorption from acetonitrile, ethanol, dimethyl sulfoxide, and chloroform solutions leads to the formation of a monolayer. Cyclic voltammetry (CV), attenuated total reflectance (ATR) infrared spectroscopy, Raman spectroscopy, high-resolution X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were used to characterize the monolayer and multilayer assemblies of DMT on Au surface. Since DMT contains two S−H groups, it chemisorbs on Au surface through one of its two S−H groups, while the other S−H group is pointing away from the surface. The presence of free S−H groups on the Au surface was confirmed by CV, ATR-FT-IR, and XPS. It is presumed that the free S−H groups of DMT on the Au surface form a hydrogen bond with the water molecules. Subsequentl...