Investigation of phosphine ligand protected Au₁₃ clusters on defect rich titania

Abstract

Atomically precise chemically synthesized gold clusters protected by diphenylphosphine ligands [(Au₁₃(dppe)₅Cl₂)Cl₃] (dppe = 1,2-bis(diphenylphosphino)ethane) were deposited onto a defect-rich, atomic layer deposited titania surface prepared by heating and subsequently sputtering the titania under ultrahigh vacuum (UHV). The gold clusters deposited onto the pretreated titania were heated at 200 °C for 20 min under UHV with the aim to remove the ligands protecting the gold core of the clusters. The change in the electronic structure and the chemical composition after deposition after aforementioned heat treatment was investigated using metastable induced electron spectroscopy (MIES) and X-ray photoelectron spectroscopy (XPS). The MIES data allow identification of the density of states (DOS) of the deligated Au₁₃ clusters on the titania to be made. The DOS of the Au₁₃ are found to be similar to those previously found for Au₉ clusters on sputtered ALD titania but have shifted binding energies. The differences in DOS of Au₁₃ and Au₉ are discussed.