Self-assembled monolayers of butanethiol adsorbed onto highly uniform Au/mica films have been studied using in-air scanning tunneling microscopy (STM) and infrared spectroscopy. STM images taken of fully equilibrated films show molecularly resolved features that are believed to correspond to the methyl terminations of the organic surface. Large domains of organized adsorbates and a variant of the previously reported p× 3 superlattice structure are observed on these surfaces; using this nomenclature, the basic repeat unit of the structure reported herein corresponds to 7× 3. Lateral variations in the elevations of striped structures are tentatively assigned to thiolates bound into fcc sites of the Au(111) substrate. We have also observed molecular structure in regions of the superlattice that were structureless in UHV-STM studies. These observations suggest that the filling factor of the fully equilibrated surfaces is highly sensitive to the manner of sample preparation and storage. Large-scale desorption of thiolates does not appear to be a necessary step in the formation of highly organized films of these short-chain systems when equilibrated in thiol/methanol solutions, and the sample processing history may have significant effects on the ultimate surface topology.

Evaporated gold films are frequently used as substrates for the study of biomolecular adsorbates, nanoparticle systems, amd partial and full monolayer films. These studies often benefit from a predeposition cleaning of the surface that removes adventitiously adsorbed material from laboratory contaminants. Scanning tunneling microscopy (STM) is used in this study to explore the microscopic consequences of two pretreatment protocols used in literature reports of self-assembled monolayers, based on sulfochromic and piranha acid solutions. These measurements show that treatment of the Au/mica surface with piranha acid can lead to extensive and uncontrolled etching of the surface and severe disruption of the surface topography; extended exposure causes the precipitation of crystallites on the surface that are highly mobile during STM imaging processes. Exposure of Au/mica surfaces to sulfochromic acid leads to the formation of permanent etch pits of the surface that are exclusively one Au layer deep; extended exposure leads to progressive etching and oxidation of the surface, ultimately leading to the formation of 0.33-0.36 nm high islands on the otherwise flat Au/mica surface. The piranha acid solutions are significantly more likely to cause the Au film to delaminate from the mica support than are the sulfochromic acid solutions. These results show that sulfochromic surface preparation is a direct and reliable method for the elimination of organic residues from Au(111)-textured surfaces, while causing a minimum of structural and chemical surface damage.

A new centrosymmetric alkaline-earth metal borate, Ba2B10O17, has been successfully synthesized through high-temperature solid-state reactions. The single-crystal X-ray structural analysis shows that Ba2B10O17 crystallizes in the triclinic space group P1[combining macron]. The parameters of the triclinic unit cell are a = 6.7128(3) Å, b = 9.8698(4) Å, c = 9.9998(4) Å, α = 76.860(3)°, β = 83.200(3)°, γ = 73.332(3)°, and Z = 2. The title compound features a [B10O17]∞ three-dimensional anionic framework with infinite channels in which the Ba(2+) cations are located. Ba2B10O17 possesses a large experimental band gap of 6.29 eV and a short cut-off edge lower than 180 nm proved by the transmission spectrum on a single crystal sample 0.5 mm in thickness. The calculated band structures and the density of states of Ba2B10O17 suggest that its indirect energy gap is 5.97 eV which agrees with the experimental result. The thermal behavior and the IR spectrum of Ba2B10O17 are also reported in this work.