Toward control of gold cluster aggregation on TiO₂ via surface treatments

Abstract

Well-defined Au–TiO₂ materials were synthesized by deposition of triphenylphosphine-protected Au₉ clusters on TiO₂ (Aeroxide P-25), pre-treated in eight different ways and subsequently exposed to two post-treatments. X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectroscopy studies showed that in most cases the PPh₃ ligand shell was removed upon deposition even before post-treatment, coinciding with some cluster aggregation. However, clusters deposited on TiO₂ treated using H₂SO₄ and H2O₂ showed remarkable resistance to aggregation, even after high-temperature calcination, while clusters on H₂-treated TiO₂ showed the greatest resistance to aggregation under ozonolysis.