Synchrotron XPS was used to investigate a series of chemically synthesised, atomically precise gold clusters Au(n)(PPh3)y (n = 8, 9 and 101, y depending on the cluster size) immobilized on anatase (titania) nanoparticles. Effects of post-deposition treatments were investigated by comparison of untreated samples with analogues that have been heat treated at 200 °C in O2, or in O2 followed by H2 atmosphere. XPS data shows that the phosphine ligands are oxidised upon heat treatment in O2. From the position of the Au 4f(7/2) peak it can be concluded that the clusters partially agglomerate immediately upon deposition. Heating in oxygen, and subsequently in hydrogen, leads to further agglomeration of the gold clusters. It is found that the pre-treatment plays a crucial role in the removal of ligands and agglomeration of the clusters.

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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