Gold clusters structures

In this chapter, two new approaches for the synthesis of metal-polymer nanocomposite materials have been described. The first method allows the preparation of contact-free dispersions of passivated gold clusters in polystyrene, and it is based on a traditional technique for the colloidal gold synthesis—that is, the alcoholic reduction of tetrachloroauric acid in presence of poly(vinyl pyrrolidone) as polymeric stabilizer. The primary function of the stabilizer is to avoid cluster sintering, but it also allows us to isolate clusters by co-precipitation. It has been found that the obtained polymer-protected nanometric gold particles can be dissolved in alkane-thiol alcoholic solutions to yield thiol-derivatized gold clusters by thiol absorbtion on the metal surface. Differently from other approaches for thioaurite synthesis available in the literature, this method allows complete control over the passivated gold cluster structure since a number of thiol molecules can be equivalently used and the... 

Clarke, L., et al. 1997. Transport in gold cluster structures defined by electron-beam Kthography. Appl Phys Lett 71 617. 

It came as a surprise, however, that Aug prefers a trigonal planar D3h structure in the gas phase [16] and is not octahedral as one might assume, suggesting that gold clusters do not follow the usual pattern of typical Lennard-Jones, Morse or Gupta systems, which all favor a maximum number of close atom-atom contacts. The preferred planarity of small gold cluster compounds is due to relativistic effects [17]. 

Bravo-Perez, G., Garzon, I.L. and Novaro, O. (1999) Ab initio study of small gold clusters. Journal of Molecular Structure THEOCHEM, 493, 225-231. 

Gorling, A., Rosch, N., Ellis, D.E. and Schmidbaur, H. (1991) Electronic structure of main-group-element-centered octahedral gold clusters. Inorganic Chemistry, 30, 3986-3994. 

Slovokhotov, Yu.L. and Struchkov, Yu.T (1984) X-ray crystal structure of a distorted tetrahedral cluster in the salt [(Ph P)4Au4N] BF4 . Geometrical indication of stable electronic configurations in post-transition metal complexes and the magic number 18-e in centred gold clusters. Journal of Organometallic Chemistry, 177, 143-146. 

Gilb, S., Weis, P., Furche, F., Ahlrichs, R. and Kappes, M.M. (2002) Structures of small gold cluster cations (Au u< 14) Ion mobility measurements versus density functional calculations. Journal of Chemical Physics, 116, 4094—4101. 

Fernandez, E.M., Soler, J.M. and Baibas, L.C. (2006) Planar and cagelike structures of gold clusters Density-functional pseudopotential calculations. Physical Review B - Condensed Matter, 73, 235433-1-235433-8. 

Wang, J.L., Jellinek, J., Zhao, J., Chen, Z.F., King, R.B. and Schleyer, P.V. (2005) Hollow Cages versus Space-Filling Structures for Medium-Sized Gold Clusters The Spherical Aromaticity of the Au o Cage. The Journal of Physical Chemistry A, 109, 9265-9269. 

Bonacic-Koutecky, V., Burda, J., Mitric, R., Ge, M., Zampella, G. and Fantucci, P. (2002) Density functional study of structural and electronic properties of bimetallic silver - gold clusters Comparison with pure gold and silver clusters./oumol of Chemical Physics, 117, 3120-3131. 

Rousseau, R., Dietrich, G., Kruckeberg, S., Lutzenkirchen, K., Marx, D., Schweikhard, L. and Walther, C. (1998) Probing cluster structures with sensor molecules methanol adsorbed onto gold clusters. Chemical Physics Letters, 295, 41-46. 

Kruger, D., Fuchs, H., Rousseau, R., Marx, D. and Parinello, M. (2001) Interaction of short-chain alkane thiols and thiolates with small gold clusters Adsorption structures and energetics. Journal of Chemical Physics, 115, 4776-4786. 

Molecular-dynamics simulations also showed that spherical gold clusters is stable in the form of FCC crystal structure in a size range of = 13-555 [191]. This is more likely a key factor in developing extremely high catalytic activity on reducible Ti02 as a support material. Thus, it controls the electronic structure of Au nanoparticles (e.g. band gap and BE shift of Au 4f7/2 band) and thereby the catalytic activity. 

Figure 13. CO oxidation over 13 atoms gold clusters having different three-dimensional structures supported on Mg(OH)2 [30].

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