Chemically-synthesised, atomically-precise gold clusters deposited and activated on titania

Abstract

Synchrotron XPS was used to investigate a series of chemically-synthesised, atomically-precise gold clusters Au_n(PPh₃)_y (n = 8, 9, 11 and 101, with y depending on cluster size) immobilized on titania nanoparticles. The gold clusters were washed with toluene at 100 °C or calcined at 200 °C to remove the organic ligand. From the position of the Au 4f_7/2 peak it is concluded that cluster size is not altered through the deposition. From the analysis of the phosphorous spectra, it can be concluded that the applied heat treatment removes the organic ligands. Washing and calcination leads to partial oxidation and partial agglomeration of the clusters. Oxidation of the clusters is most likely due to the interaction of the cluster core with the oxygen of the titania surface after removal of ligands. The position of the Au 4f_7/2 peak indicates that the size of the agglomerated clusters is still smaller than that of Au₁₀₁.