Recent trends on nanocomposites based on Cu, Ag and Au clusters: A closer look

Nanocomposite materials based on metal nanoparticles (NPs, guest) in/on oxide matrices (host) have attracted increasing attention thanks to their intriguing chemico-physical properties that can be tailored as a function of NP size, shape and mutual interactions. The possibility to obtain a controlled dispersion of metal particles in/on suitable oxides (inside- and outside-cluster systems, respectively) paves the way to a broad spectrum of technological applications, ranging from heterogeneous catalysis, to gas sensing and non-linear optics. The control of functional performances relies on tailoring the system properties by design through a suitable choice of the synthesis and processing routes. In this context, the present review provides a synoptic overview on our recent research activity concerning nanocomposites containing 11th group metal clusters (Cu, Ag and Au), dispersed in/on oxide matrices (SiO2, TiO2, Al2O3). We begin by briefly outlining the interest and size-dependent properties of such systems. Subsequently, the attention is switched to a survey on the preparation strategies previously adopted in the literature, focusing in particular on the use of soft methods, such as sol-gel (SG), RF-sputtering and their innovative combination. The most relevant results on M'/MxOy nanocomposites (where M' = Cu, Ag, An and M = Si, Ti, Al) obtained by these routes are then comparatively discussed, highlighting analogies and differences between them. Finally, the most attractive research perspectives in the field are briefly presented. (c) 2005 Elsevier B.V. All rights reserved.