Surface Modification of Small Platinum Nanoclusters with Alkylamine and Alkylthiol: An XPS Study on the Influence of Organic Ligands on the Pt 4f Binding Energies of Small Platinum Nanoclusters

Platinum nanoclusters of average size 1.3 nm, modified with alkylamine, and alkylthiol, were prepared by a simple phase-transfer method using a small Pt nanocluster stabilized by glycol and OH− as a building block. Transmission electron microscopy, thermogravimetric analysis, 1H NMR, and X-ray photoelectron spectroscopy analyses were carried out on these metal nanoclusters. It was observed that the Pt 4f binding energies in the same-sized Pt nanoclusters modified with alkylamine, alkylthiol, PVP, PVA, or PPh3 increase by 0.5–0.8 eV relative to those of bulk Pt. The shifts in the binding energies are caused by a size effect of the small Pt core and a ligand effect from the modifiers. By deducing the small size effect, the ligand effect on the Pt 4f binding energies was studied.