Nanoporous Gold: Novel Catalytic and Sensor Applications

Abstract

New materials are sought for applications in catalysis, sensing, optics, electronics and other emerging fields. With the event of nanotechnology, innovations greatly profit from the access to new nano-sized materials with novel properties of materials simply resulting from the reduction of size. In this dissertation nanoporous gold (np-Au) is investigated with respect to its surface mediated applications in catalysis and actuation technology. Additionally the influence of adsorbates on the stability of the nanostructure during annealing is investigated. The np-Au material is found to be highly active for the oxidation of CO at low temperatures as well as the highly selective oxidation of methanol. Although most of the catalytic performance can be assigned to the surface chemistry of gold, small Ag residues - leftovers from manufacturing procedure - are shown to facilitate the activation of molecular oxygen. In a further set of experiments it is shown that surface chemistry of high surface area materials such as np-Au can lead to a macroscopic strain response. By using ozone to efficiently oxidize the surface and CO as reducing agent np-Au cubes could be strained up to 0.5 %, a value comparable to that of commercial piezo ceramics.