Chemically-synthesised, atomically-precise gold clusters deposited and activated on titania

David P Anderson,Jason F Alvino,Lars Thomsen,Vladimir B Golovko,Alexander Gentleman,Gunther G Andersson,Hassan Al Qahtani,Gregory F Metha,Matthew I J Polson

doi:10.1039/c3cp44005b

Abstract

Synchrotron XPS was used to investigate a series of chemically-synthesised, atomically-precise gold clusters Au(n)(PPh(3))(y) (n = 8, 9, 11 and 101, with y depending on cluster size) immobilized on titania nanoparticles. The gold clusters were washed with toluene at 100 °C or calcined at 200 °C to remove the organic ligand. From the position of the Au 4f(7/2) peak it is concluded that cluster size is not altered through the deposition. From the analysis of the phosphorous spectra, it can be concluded that the applied heat treatment removes the organic ligands. Washing and calcination leads to partial oxidation and partial agglomeration of the clusters. Oxidation of the clusters is most likely due to the interaction of the cluster core with the oxygen of the titania surface after removal of ligands. The position of the Au 4f(7/2) peak indicates that the size of the agglomerated clusters is still smaller than that of Au(101).

Highlights

Immobilization of colloids and clusters onto supports is an important step in the fabrication of heterogeneous catalysts
The molecular clusters (n = 8, 9, 11) used in this study contain atomically precise, ideally monodisperse metal cores protected by phosphine ligands, while Au101 particles have narrow particle size distribution centered around 1.5 nm
The crystal structures of Au11, Au9 and Au8 clusters are shown in Fig. 1, confirming that the cluster metal core contain exactly 8, 960 and 11 atoms of gold respectively, with all the gold atoms involved in forming the metal–metal bonded cluster core

Summary

Introduction

Immobilization of colloids and clusters onto supports is an important step in the fabrication of heterogeneous catalysts. In some cases catalytic activity is attributed to intact clusters on the support, i.e. clusters from which ligands have not been removed.[19] Detailed studies of the effects of the activation processes on the morphology and electronic properties of the supportimmobilized nanoparticles are required to understand the nature of such catalysts. Support-immobilization of atomically-precise chemically-synthesised clusters offers an opportunity to control the active site of the heterogeneous. This journal is c the Owner Societies 2013. Detailed understanding of the deposition of atomically precise gold clusters and the effect of activation processes is important for the development of better strategies for fabrication of heterogeneous catalysts

Objectives

Results

Conclusion