E-Mail
IMAGE: Using the modified tip of an atomic force microscope, individual atoms in the surface can be probed. view more
Credit: TU Wien
The degree of acidity or alkalinity of a substance is crucial for its chemical behavior. The decisive factor is the so-called proton affinity, which indicates how easily an entity accepts or releases a single proton. While it is easy to measure this for molecules, it has not been possible for surfaces. This is important because atoms on surfaces have very different proton affinities, depending on where they sit.
Researchers at TU Wien have now succeeded in making this important physical quantity experimentally accessible for the first time: Using a specially modified atomic force microscope, it is possible to study the proton affinity of individual atoms. This should help to analyze catalysts on an atomic scale. The results have been published in the scientific journal
E-Mail
IMAGE: A scattering-invariant mode of light is generated by sending a laser beam onto a judiciously configured spatial light modulator (see quadratic pixel array on the left). This modulated beam then. view more
Credit: Allard Mosk/Matthias Kühmayer
Why is sugar not transparent? Because light that penetrates a piece of sugar is scattered, altered and deflected in a highly complicated way. However, as a research team from TU Wien (Vienna) and Utrecht University (Netherlands) has now been able to show, there is a class of very special light waves for which this does not apply: for any specific disordered medium such as the sugar cube you may just have put in your coffee tailor-made light beams can be constructed that are practically not changed by this medium, but only attenuated. The light beam penetrates the medium, and a light pattern arrives on the other side that has the same shape as if the medium were not there at all.
Electric current is deflected by a magnetic field - this leads to the so-called Hall effect. A surprising discovery has now been made at TU Wien: an exotic metal was examined and a giant Hall effect was found to be produced by the material, in the total absence of any magnetic field.
E-Mail
Metals such as gold or platinum are often used as catalysts. In the catalytic converters of vehicles, for example, platinum nanoparticles convert poisonous carbon monoxide into non-toxic CO2. Because platinum and other catalytically active metals are expensive and rare, the nanoparticles involved have been made smaller and smaller over time. Single-atom catalysts are the logical end point of this downsizing: The metal is no longer present as particles, but as individual atoms that are anchored on the surface of a cheaper support material. Individual atoms can no longer be described using the rules developed from larger pieces of metal, so the rules used to predict which metals will be good catalysts must be revamped - this has now been achieved at TU Wien. As it turns out, single atom catalysts based on much cheaper materials might be even more effective. These results have now been published in the journal