Formation and nanostructures of organic self-assembled monolayers on Au(111)

Abstract

The discovery of molecular assemblies by the spontaneous adsorption of organic thiols on gold surfaces has proven to be a major advance for chemists and surface scientists in the research fields ranging from biomedicine, wetting, corrosion inhibition, molecular sensors, and nanopatterning.1-3 One of drawback of this technique is the propensity of organic thiols to oxidize to disulfides, which is especially frustrating in the case of aromatic thiols. To overcome this obstacle, new classes of SAMs on gold surfaces were fabricated by using organic compounds attached to other surface active head-groups such as alkylthiosulfates, aryl thioacetates, and alkylisocyanides in stead of thiol head-groups. We have demonstrated that these molecules can form ordered self-assembled monolayers with specific nano-domain structures by scanning tunneling microscopy (STM), which are comparable to those of conventional thiol SAMs. For examples, it was found, for the first time, that the adsorption of pentylisocyanide on Au(1111) provides SAMS having interesting small ordered domains with clear domain boundaries. In addition, there are few vacancy islands in the domains, suggesting that isocyanide group would not strongly affect the lattice of gold atoms during self-assembly processes compared with thiol.