Analytical TEM observation of Au nano-particles on cerium oxide

The structure changes of Au nanoparticles supported on CeO2 were observed by using an analytical transmission electron microscope (TEM). The rapid shape change of a Au particle was observed during TEM observation, such as shrinking layer by layer down to a mono-atomic layer on the CeO2 substrate with no large change of a contact diameter. The electron beam irradiation experiment revealed that the shape change of a Au particle is concerning with the oxidation state or the density of oxygen vacancies of CeO2, where the rapid desorption and adsorption of oxygen and the ordering of oxygen vacancies were precisely identified. It was also found that the reduction by strong electron beam irradiation and subsequent oxidation generate the encapsulation of Au particles by CeO2-x. (C) 2006 Elsevier B.V. All rights reserved.