| AVS 54th International Symposium | |
| Nanometer-scale Science and Technology | Tuesday Sessions |
| Session NS-TuP |
| Session: | Nanometer-scale Science and Technology Poster Session I |
| Presenter: | A. Wittstock, University Bremen, Germany |
| Authors: | A. Wittstock, University Bremen, Germany J. Biener, Lawrence Livermore National Laboratory M. Biener, Lawrence Livermore National Laboratory D. Kramer, Forschungszentrum Karlsruhe, Germany J. Weissmueller, Forschungszentrum Karlsruhe, Germany M. Baeumer, University Bremen, Germany V. Zielasek, University Bremen, Germany |
| Correspondent: | Click to Email |
In recent years there has been a rising interest in nanoporous gold sponges due to their promising features in low temperature heterogeneous catalysis. Preparation by selectively leaching silver from a gold-silver alloy with acid or a combination of applied voltage and acid leads to a sponge-like morphology with structures in the range of only a few nanometers. Model studies on Au(111) single crystals show a strong interaction of atomic oxygen with the gold surface.1 The chemisorbed oxygen extracts Au atoms from the surface leading to gold-oxygen complexes on top of it . Inspired by this work we treat nanoporous gold-sponges with atomic oxygen under an ozone-containing ambient atmosphere. We show that in contrast to molecular oxygen the atomic oxygen reacts strongly with the surface leading to a macroscopically detectable shrinking. Measurement of shrinking depending on the concentration of ozone is carried out with a dilatometer. We detect a change of length of nearly 0.5 % of the edge size. The process was accompanied by a black staining which affirms that the oxygen reacts with gold and leads to the formation of gold oxide clusters in the range of a few nanometers on top of the surface. Staining and shrinking can be changed reversibly by reduction with carbon monoxide. In catalytic measurements it is shown that the surface oxygen produced by ozone reacts immediately with carbon monoxide leading to the product of oxidation, the carbon dioxide. These results provide fundamental insight into the allocation of reactive oxygen on catalytically active gold surfaces, the key step of the oxidation reaction on gold catalysts. Furthermore, ozone detection is of great interest in the context of environmental monitoring. Our experiments show that application of gold sponges as chemical gas sensors for determination of ozone is an interesting and promising possibility.
1 Min, BK; Alemozafar, AR; Biener, MM; Biener, J.; Friend, CM, Top. Catal., 2005, 36, 77.