Interatomic Coupling of Au Molecular Clusters and Er3+ Ions in Silica

To unveil the mechanisms of energy transfer between Au-N nanostructures and Er3+ ions in silica is of paramount importance for the possible use of Au molecular clusters as sensitizing agents of the rare-earth luminescence in photonic devices. In the present work a phenomenological model was developed that allowed us to estimate the most important photophysical parameters as the sensitization cross-section, the fraction of sensitized Er ions, and the coupling distance of the energy transfer. The results demonstrate that in spite of very large sensitization cross-sections (more than 3 orders of magnitude higher than the intrinsic Er excitation cross-section in silica) only a limited fraction of Er ions (<1%) are indirectly excited by the Au-N nanoclusters, and the energy transfer occurs via short-range coupling at interatomic distances, in the range 0.4-0.8 nm