Measurement of core electron binding energies of silver nanoparticles and their modeling with electron propagator calculations of silver clusters

Silver nanoparticles were synthesized by ionic exchange with zeolites and further reduction with hydrogen flux. Core electron binding energies were determined by X-ray photoelectron spectroscopy at different times of the reduction process. Electron propagator calculations of core electron binding energies were performed including scalar relativistic effects using effective core potentials and zero order regular approximation. Theoretical results were compared to the experiment to get insight into the origin of the experimental signals for carbon, oxygen, silicon, aluminum and silver. Small model molecules and zeolite fragments were used for the calculation of core electron binding energies. It is evidenced that although binding energies tend to converge, fluctuations of more than 1 eV are found for non-symmetric structures in neutral and cationic silver clusters. Detailed analysis shows that these fluctuations originate on the different coordination numbers of ionized silver atoms and charge fluctuations.