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S. Pollitt, N. Barrabés-Rabanal, G. Rupprechter:
"Reactivity and Stability of supported Au38(SR)24 clusters on oxides in gas and liquid phase reactions";
Talk: 17. Österreichische Chemietage 2017, Salzburg; 09-25-2017 - 09-28-2017; in: "17. Österreichische Chemietage 2017", (2017).

Heterogenous catalysis by metal nanoparticle supported on oxides, are often limited in their activity/sensitivity, due to variations in metal particle size, surface structure and bonding to the support. In contrast thiolate-protected Au nanoclusters can be synthesized with precise atomic numbers (<100 metal atoms). When deposited on support materials, the ligands can be successively thermally removed to expose the metal atoms for a truly monodisperse heterogenous catalyst. Furthermore [Aux(SR)]z dispersed in solution show catalytic activity in several types of oxidation and hydrogenation processes. Although their stability under harder conditions are limited, fact that has been overcome by supporting the clusters on solid materials [1,2].
Different levels of ligand removal by thermal treatments (oxidation process under different temperatures) of Au38(SR)24 on CeO2 and Al2O3 support have been investigated in means of cluster stability, ligand removal mechanism and effect on catalytic activity in cyclohexane and CO oxidation. Structural studies during ligand removal processes were performed by operando XAFS at Au L3-edge at SuperXAS beamline (SLS), additional ex situ XAFS studies on fresh and used catalysts in a cyclohexane oxidation reaction were performed at CLAESS beamline (ALBA) in S K-edge. Results obtained together with UV-vis diffuse reflectance, HRTEM, XRD and XPS revealed the change of the electronic structure and slight size growth of the Au38 after reaction. The most interesting point is the different interaction of the thiol ligands depending on the support material after thermal treatment and reaction, observed for the first time.
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[1] Yamazoe, S.; Koyasu, K.; Tsukuda, T. Acc. Chem. Res. 2014, 47, 816.
[2] Shivhare, A.; Chevrier, D. M.; Purves, R. W.; Scott, R. W. J. J. Phys.Chem. C. 2013, 117, 20007.
[3] Zhang, B.; Kaziz, S.; Li H.; Hevia, M.G.; Wodka, D.; Mazet, C.; Bürgi, T.; Barrabés, N. J. Phys.Chem. C. 2015, 119, 11193