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Adsorption Au clusters Chemical modification Dopants Electronic
properties Oxide films Wet impregnation
Abstract:
Small Au particles have been shown to exhibit interesting catalytic
properties. In an attempt to parallel catalytic studies on powder supports we have
undertaken a series of model studies using oxide films as support. We address the
formation of Au aggregates as a function of size starting from Au atoms to clusters
and islands of larger size and as a function of the support. In addition we have
studied different support materials such as alumina and iron oxide and we compare
ultrathin and thicker oxide films of the same material (MgO). From a comparison of
charge transfer through ultrathin films with the situation encountered in thicker
films, we propose the use of dopants in bulk materials to control particle shape.We
include the study of carbon monoxide adsorption on Au clusters of varying size. It is
demonstrated how chemical modification (hydroxylation) of oxide supports influence
particle growth and properties. Finally, we report on effects to study the
processes involved in particle growth by wet impregnation in order to bridge the
gap to catalyst preparation under realistic conditions. On that basis one may now
compare properties of supported particles prepared in ultrahigh vacuum using
physical vapor deposition with those prepared by wet impregnation.
