The Formation of Gold Clusters Supported on Mesoporous Silica Material Surfaces: A Molecular Picture

The interaction of gold particles with a silica surface is investigated using a combination of theoretical and experimental techniques. It is found that the physisorption strength of gold on silica decreases with increasing chloride concentration at the surface, with increasing cluster size, and with decreasing oxidation state of gold. However, the gold precursor is adsorbed more strongly than the corresponding precursor fragments and this via an H-bond network. It is also found that chemisorbed, grafted species may coexist on a silica surface, depending on the experimental conditions. From the vibrational frequencies and especially by the presence of a band at 3650 cm(-1), it is found that the gold species after calcination are probably present under the form of digrafted chemisorbed species. This information enables us to propose a scenario for the formation of gold clusters at the silica surface.