A Nanoscale Model Catalyst Preparation: Solution Deposition of Phosphine-stabilized Gold Clusters onto a Planar TiO₂(110) Support
Agglomeration of noble metal particles has been a long-standing obstacle in the preparation of planar, finely dispersed, metal cluster-oxide support model catalyst systems. A solution deposition method was devised. Six-atom gold clusters, in the form of [Au6(PPh3)6] [BF4]2 (Au6L6), were deposited onto a TiO2(110) single crystal after an acetone pretreatment of the substrate and examined with scanning tunneling microscopy (STM), high-resolution electron energy loss spectroscopy (HREELS), and X-ray photoelectron spectroscopy (XPS). STM revealed single-unit entities of clusters ca. 1 nm in height, corresponding to the six-atom Au center with the triphenyl phosphine ligands attached. As a check on the success of the homogeneous dispersion, electron-stimulated desorption (ESD) was performed, irradiating the TiO2(110) surface with a 0.12 C cm-2 electron beam flux followed by STM, HREELS, and XPS. Evidence for ligand removal was shown by a pronounced reduction in height in the STM, a disappearance of the aromatic v(C-H) intensity at ca. 3000 cm-1 in the HREEL spectra, and a +0.4 eV shift in the XPS Au 4f7/2 core level.
C. C. Chusuei et al., "A Nanoscale Model Catalyst Preparation: Solution Deposition of Phosphine-stabilized Gold Clusters onto a Planar TiO₂(110) Support," Langmuir, American Chemical Society (ACS), Jan 2001.
The definitive version is available at http://dx.doi.org/10.1021/la001684r
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