Clusters 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 is weakened.
