Introduction to XPS studies of metal and metal-oxide nanosystems

Metal and metal-oxide based nanosystems are intriguing candidates for a plethora of advanced applications thanks to their diversified chemico-physical properties, that can be further tailored by the use of proper synthesis procedures. Among the different preparation techniques, Chemical Vapor Deposition (CVD), RF-sputtering and Sol-Gel (SG) display promising features for the design and control of nanosystem characteristics even beyond thermodynamical predictions, thanks to the soft synthetic conditions that enable nucleation to prevail over the subsequent particle agglomeration. In this context, a direct feedback between the nanosystem synthesis and characterization represents a unique tool for the optimization of the process. In particular, XPS spectroscopy plays an outstanding role for the investigation of surface and in-depth chemical composition of thin films as a function of the experimental conditions.In this paper, the attention is devoted to the XPS analysis of different kinds of nanosystems, from nanostructured thin films (LaCoO3) to oxide clusters in silica matrices (HfO2 and HfO2-ZrO2 in SiO2) and metal cluster-based composites (Au/graphite, Au/TiO2, Ag/SiO2). This introduction provides an overview of the data presented in the collected papers, focusing in particular on the interest in these systems and on the most relevant results obtained by XPS investigations.