Optical absorption of magnesia-supported gold clusters and nanoscale catalysts: Effects due to the support, clusters, and adsorbants

Abstract

Polarization-resolved optical spectra of magnesia-supported gold clusters ${\mathrm{Au}}_N∕\mathrm{Mg}\mathrm{O}$ $(N=1,2,4,8)$, bound at a surface color center $F_s$ of the MgO(100) face, are calculated from the time-dependent density functional theory. The optical lines for $N=1,2$ are dominated by transitions that involve strong hybridization between gold and $F_s$ states whereas for $N=4,8$ intracluster transitions dominate. The theoretical optical spectra are sensitive to cluster structure and adsorbants (here CO and ${\mathrm{O}}_2$ molecules on ${\mathrm{Au}}_8∕F_s@\mathrm{Mg}\mathrm{O}$) which suggests polarization-resolved optical spectroscopy as a powerful tool to investigate structures and functions of chemically active, supported clusters.