Well-definedAu−TiO 2 materials were synthesized by deposition of triphenylphosphine-protected Au 9 clusters on TiO 2 (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 PPh 3 ligand shell was removed upon deposition even before post-treatment, coinciding with some cluster aggregation. However, clusters deposited on TiO 2 treated using H 2 SO 4 and H 2 O 2 showed remarkable resistance to aggregation, even after high-temperature calcination, while clusters on H 2 -treated TiO 2 showed the greatest resistance to aggregation under ozonolysis.

Crystalline titanium dioxide was synthesised under mild conditions by the thermal degradation of peroxotitanic acid in the presence of a number of fluoride-containing surface modifying agents (NH 4 F, NH 4 BF 4 , NH 4 PF 6 , NBu 4 F, NBu 4 BF 4 , NBu 4 PF 6). The resulting materials were characterised by PXRD, SEM, HRTEM, XPS and NEXAFS. Particle phase, size, and surface area were noticeably affected by the choice of surface modifying agent. Both the cation and anion comprising the modifying agent affect the surface Ti 3+ population of the materials, with two apparent trends observed: F À > BF 4 À > PF 6 À and NBu 4 + > NH 4 +. All materials displayed evidence of fluorine doping on their surfaces, although no evidence of bulk doping was observed.

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