Central metal dependence of conformation and self-assembly of porphyrins on Ag(110)

Intercalating Single-Atom Metal Centers into an Organic Monolayer with a Full-Sample Coverage

Thiolate self-assembled monolayers (SAMs) have been widely used as a straightforward method to functionalize the surface of a common substrate with selective organic functional groups. Here we describe a process that further introduces isolated metal centers into an organic SAM using solutions of metallic porphyrin so that different organic groups and metal single-atoms can be simultaneously exposed on top of the surface. The entire process employs only common laboratory equipment and mild-temperature (<100 °C) incubation to create a full-sample (>cm²) SAM coverage. Each step in this process is closely monitored and discussed using nm-scale scanning tunneling microscopy (STM) images. This work can be straightforwardly adopted by research groups interested in such a diversely customizable surface but without access to a vacuum-based deposition technology. The porphyrin molecules are shown to intercalate among closely packed thiolate SAM domains, and STM characterization shows that the entire mixed monolayer is stable in an ambient condition. This process also does not involve any tip-assisted desorption or lithography procedure and can thus be applied toward substrates of other shapes beyond a flat surface.

Coverage induced structural transformations of tetracene on Ag(110)

Self-assembly of tetracene on an anisotropic surface of Ag(110) has been investigated using scanning tunneling microscopy and low-energy electron diffraction. We observe multistage structural transformations of the self-assembled tetracene on Ag(110) as a function of molecular coverages, which are accompanied by the changes in molecular orientations. They are analyzed by a balance between multiple molecule-molecule and anisotropic substrate-molecule interactions.

Adsorption and self-assembled structures of sexithiophene on the Si(111)-√3×√3-Ag surface

The adsorption and self-assembled structures of α-sexithiophene (α-6T) have been investigated on a Si(111)-Ag surface using scanning tunneling microscopy (STM), low-energy electron diffraction, and density functional theory calculations. The adsorbed α-6T molecules are arranged into unidirectional molecular rows with a side-by-side orientation. The molecular rows reveal three kinds of appearances in the filled-state STM images, which reflect the distinct adsorption sites. From tunneling spectroscopy, we find that the filled-state STM images of α-6T should be influenced by the surface states of Si(111)-Ag. At one monolayer coverage, sequentially ordering of the triple molecular rows results in the close-packed arrangement of the α-6T overlayer.