characterization and catalysis
Gold nano clusters were prepared by two different
growth procedures. In the first, the clusters were prepared by
direct deposition (DD) of gold atoms on amorphous SiO2
substrates. The second growth mode is based on initial evaporation
of gold atoms on top of amorphous solid water as a buffer layer at
100K that separates the small gold seed clusters from the substrate.
Subsequent annealing to 300K desorbs the water molecules, resulting
in aggregation and growth and (cold) deposition of nano-clusters on
the substrate in a Buffer Layer Assisted Growth (BLAG) mechanism.
In order to increase the BLAG clusters density we
introduced a Multi-Cycle BLAG procedure (MC-BLAG). By repeating the
BLAG procedure up to seven times consequently, the cluster density
can be increased by 5 fold while the clusters size is almost
unchanged. BLAG clusters are more 3D in nature, have larger height
to diameter ratio than DD clusters, yet their interaction with CO is
very similar to DD clusters. This is reflected by the practically
identical CO stretch observed on both clusters at 2106±2cm-1.
TPD measurements have shown that interaction of CO molecules with
BLAG clusters is somewhat weaker than with DD clusters. As the BLAG
cluster size is increased the interaction with adsorbed CO molecules