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Ru is a metal of interest in catalysis. Monodisperse Ru 3 clusters as catalytic sites are relevant for the development of catalysts because clusters use significantly lower amounts of precious materials for forming active sites due to the small size of the cluster. However, retaining the mono-dispersity of the cluster size after deposition is a challenge because surface energy could drive both agglomeration and encapsulation of the clusters. In the present work Ru 3 clusters are deposited by chemical vapor deposition (CVD) of Ru 3 (CO) 12 and cluster source depositions of bare Ru 3 onto radio frequency sputter-deposited TiO 2 (RF-TiO 2 ) substrates, TiO 2 (100), and SiO 2 . When supported on RF-TiO 2 , bare Ru 3 is encapsulated by a layer of titania substrate material during deposition with a cluster source. Ligated Ru 3 (CO) 12 is also encapsulated by a layer of titania when deposited onto sputter-treated RF-TiO 2 , but only through heat treatment which is required to remove most of the ligands. The titania overlayer thickness was determined to be 1-2 monolayers for Ru 3 (CO) 12 clusters on RF-TiO 2 , which is thin enough for catalytic or photocatalytic reactions to potentially occur even without clusters being part of the very outermost layer. The implication for catalysis of the encapsulation of Ru 3 into the RF-TiO 2 is discussed. Temperature-dependent X-ray photoelectron spectroscopy (XPS), angle-resolved XPS, and temperature-dependent low energy ion scattering (TD-LEIS) are used to probe how the cluster-surface interaction changes due to heat treatment and scanning transmission electron microscopy (STEM) was used to image the depth of the surface from side-on.

Small Ru clusters are efficient catalysts for chemical reactions such as CO hydrogenation. In this study 3-atom Ru 3 clusters were deposited onto radio frequency (RF)-deposited TiO 2 which is an inexpensive, nanoparticulate form of TiO 2 . TiO 2 substrates are notable in that they form strong metal-substrate interactions with clusters. Using temperature programmed desorption to probe Ru-CO binding sites, and X-ray photoelectron spectroscopy to provide chemical information on clusters, differences in cluster-support interactions were studied for Ru 3 deposited using both an ultra-high vacuum cluster source and chemical vapour deposition of Ru 3 (CO) 12 . The TiO 2 was treated with different Ar + sputter doses prior to cluster depositions, and SiO 2 was also used as a comparison substrate. For cluster source-deposited Ru 3 , heating to 800 K caused cluster agglomeration on SiO 2 and oxidation on non-sputtered TiO 2 . For cluster source-deposited Ru 3 on sputtered TiO 2 substrates, all Ru-CO binding sites were blocked as-deposited and it was concluded that for the binding sites to be preserved for potential catalytic benefit, sputtering of TiO 2 before cluster deposition cannot be applied. Conversely, for Ru 3 (CO) 12 on sputtered TiO 2 the clusters were protected by their ligands and Ru-CO binding sites were only blocked once the sample was heated to 723 K. The mechanism for complete blocking of CO sites on sputtered TiO 2 could not be directly determined; however, comparisons to the literature indicate that the likely reasons for blocking of the CO adsorption sites are encapsulation into the TiO x layer reduced through sputtering and also partial oxidation of the Ru clusters., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Graphene supported transition metal clusters are of great interest for potential applications, such as catalysis, due to their unique properties. In this work, a simple approach to deposit Au 101 (PPh 3 ) 21 Cl 5 (Au 101 NC) on reduced graphene oxide (rGO) via an ex situ method is presented. Reduction of graphene oxide at native pH (pH ≈ 2) to rGO was performed under aqueous hydrothermal conditions. Decoration of rGO sheets with controlled content of 5 wt% Au was accomplished using only pre-synthesised Au 101 NC and rGO as precursors and methanol as solvent. High resolution scanning transmission electron microscopy indicated that the cluster size did not change upon deposition with an average diameter of 1.4 ± 0.4 nm. It was determined that the rGO reduction method was crucial to avoid agglomeration, with rGO reduced at pH ≈ 11 resulting in agglomeration. X-ray photoelectron spectroscopy was used to confirm the deposition of Au 101 NCs and show the presence of triphenyl phosphine ligands, which together with attenuated total reflectance Fourier transform infrared spectroscopy, advocates that the deposition of Au 101 NCs onto the surface of rGO was facilitated via non-covalent interactions with the phenyl groups of the ligands. Inductively coupled plasma mass spectrometry and thermogravimetric analysis were used to determine the gold loading and both agree with a gold loading of ca . 4.8-5 wt%. The presented simple and mild strategy demonstrates that good compatibility between size-specific phosphine protected gold clusters and rGO can prevent aggregation of the metal clusters. This work contributes towards producing an agglomeration-free synthesis of size-specific ligated gold clusters on rGO that could have wide range of applications., Competing Interests: The authors have no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The photocatalytic properties of titania (TiO 2 ) have prompted research utilising its useful ability to convert solar energy into electron-hole pairs to drive novel chemistry. The aim of the present work is to examine the properties required for a synthetic method capable of producing thin TiO 2 films, with well defined, easily modifiable characteristics. Presented here is a method of synthesis of TiO 2 nanoparticulate thin films generated using RF plasma capable of homogenous depositions with known elemental composition and modifiable properties at a far lower cost than single-crystal TiO 2 . Multiple depositions regimes were examined for their effect on overall chemical composition and to minimise the unwanted contaminant, carbon, from the final film. The resulting TiO 2 films can be easily modified through heating to further induce defects and change the electronic structure, crystallinity, surface morphology and roughness of the deposited thin film., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Metal clusters typically consist of two to a few hundred atoms and have unique properties that change with the type and number of atoms that form the cluster. Metal clusters can be generated with a precise number of atoms, and therefore have specific size, shape, and electronic structures. When metal clusters are deposited onto a substrate, their shape and electronic structure depend on the interaction with the substrate surface and thus depend on the properties of both the clusters and those of the substrate. Deposited metal clusters have discrete, individual electron energy levels that differ from the electron energy levels in the constituting individual atoms, isolated clusters, and the respective bulk material. The properties of clusters with a focus on Au and Ru, the methods to generate metal clusters, and the methods of deposition of clusters onto substrate surfaces are covered. The properties of cluster-modified surfaces are important for their application. The main application covered here is catalysis, and the methods for characterization of the cluster-modified surfaces are described., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)