Investigation of Phosphine Ligand Protected Au₁₃ Clusters on Defect Rich Titania

Abstract

Atomically precise chemically synthesized gold clusters protected by diphenylphosphine ligands [(Au 13 (dppe) 5 Cl 2 )Cl 3 ] (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 Au 13 clusters on the titania to be made. The DOS of the Au 13 are found to be similar to those previously found for Au 9 clusters on sputtered ALD titania but have shifted binding energies. The differences in DOS of Au 13 and Au 9 are discussed.

Sub-monolayer Au9cluster formationviapulsed nozzle cluster deposition

“…It has been determined through previous studies that ligated Au 9 clusters have a 4f 7/2 peak with characteristic binding energy (BE) at 84.9 AE 0.3 eV contrasting with the same peak for agglomerated clusters found at the binding energy for bulk gold at 84 AE 0.2 eV. 16,23 For samples A4, A5, B2-5, agglomeration is fairly consistent at a ratio around 70/30 cluster/bulk, as shown in Fig. S5 † for sample A4.…”

“…These measurement conditions have been shown not to damage samples of this type. 16 High-resolution XP spectra of the C 1s, O 1s, P 2p, Ti 2p and Au 4f regions were collected at 10 eV pass energy. All XP spectra were analysed with Casa XPS using a Shirley background and a hybrid Gaussian (30%) and Lorentzian (70%) function to t all peaks in a method described previously.…”

“…The total amount of solvent attaching to the surface through the deposition method thus is signicantly less than when depositing clusters by dipping the substrate into solution. 13,16 The circular feature identied on some heavily deposited surfaces in AFM (Fig. S4 †) may be accounted for by vacuum degradation over lengthy depositions affecting the solvent evaporation rate.…”

“…While vacuum generated nanoclusters can be deposited directly onto treated substrates for further analysis, 14,15 chemically synthesised nanoclusters have required any deposition to take place outside of vacuum, thus introducing contamination through the exposure to of the surface to atmosphere and solvents from solution based deposition methods and potentially affecting any surface treatments made in vacuum. 16,17 Thus, a method of depositing chemically synthesised nanoclusters directly onto a substrate under vacuum conditions would have the advantage to strongly reduce contaminations through exposure to air and solvents.…”

Composition and properties of RF-sputter deposited titanium dioxide thin films

“…Many photocatalytic systems require a robust substrate-catalyst electronic interaction to prevent changes in the performance of the catalyst due to agglomeration; one method proposed to achieve this is defect rich surfaces [21,22]. Ti 3+ defects have been explored as promising binding sites for heterogeneous catalysts that offer strong electronic interaction to prevent agglomeration [23,24].…”