Mechanical properties of TiO/carboxylic-acid interfaces from first-principles calculations.

Nature forms structurally complex materials with a large variation of mechanical and physical properties from only very few organic compounds and minerals. Nanocomposites made from TiO and carboxylic-acids, two substances that are available to nature as well as materials engineers, can be seen as representative of a huge class of natural and bio-inspired materials. The hybrid interfaces between the two components are thought to determine the overall properties of the composite.

Surface structure of magnetite (111) under oxidizing and reducing conditions.

We report on differences in the magnetite (111) surface structure when prepared under oxidizing and reducing conditions. Both preparations were done under UHV conditions at elevated temperatures, but in one case the sample was cooled down while keeping it in an oxygen atmosphere. Scanning tunneling microscopy after each of the preparations showed a different apparent morphology, which is discussed to be an electronic effect and which is reflected in the necessity of using opposite bias tunneling voltages in order to obtain good images.

Heterogeneous Adsorption and Local Ordering of Formate on a Magnetite Surface.

We report a novel heterogeneous adsorption mechanism of formic acid on the magnetite (111) surface. Our experimental results and density functional theory (DFT) calculations give evidence for dissociative adsorption of formic acid in quasibidentate and chelating geometries. The latter is induced by the presence of iron vacancies at the surface, making oxygen atoms accessible for hydrogen atoms from dissociated formic acid.