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, Au 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.