Structure and electronic properties of supported noble metal clusters

Abstract

The use of noble metal nanoparticles such as silver clusters in future applications requires detailed knowledge about their structure and electronic properties. These properties alter significantly with size and shape of the clusters as well as with the properties of the environment. Especially the properties of supported noble metal clusters are of great interest since for most applications the clusters are in contact with a surface or embedded in a matrix material. In this thesis the structure and electronic properties of Ag clusters on SiO2 silica glass, in a polydimethylsiloxane (PDMS) matrix and in a SiO2 aerogel matrix are investigated utilizing optical spectroscopy in the UV/VIS to measure the plasmon resonance of the clusters and x-ray absorption near edge structure (XANES) spectroscopy of the Ag L-edges to gain insight into the structure of the clusters and effects such as electromagnetic coupling and coalescence. Additionally the possible formation of an oxide layer around the clusters after exposure to air was investigated. By ab-initio simulating the x-ray absorption signals with the software package FEFF9 and comparison to the measured data it was possible not only to achieve first information on the geometrical structure of the supported clusters but also to approximate the size of the investigated clusters.