Optical Activity of Metal Nanoclusters Deposited on Regular and Doped Oxide Supports from First-Principles Simulations

• Published in: Molecules (Basel, Switzerland) Vol. 26; no. 22; p. 6961
• Main Authors: Sementa, Luca, Stener, Mauro, Fortunelli, Alessandro
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 18.11.2021; MDPI
• Subjects: Absorption; Absorption spectra; Alternative energy sources; Charge injection; cluster/oxide interface; Computer applications; Copper; Density functional theory; Doppler effect; Excitation; First principles; first-principles modeling; Magnesium; Magnesium oxide; metal clusters; Metals; Nanoclusters; Nanoparticles; optical photo-absorption; photo-enhanced processes; Point defects; Red shift; Simulation; Substrates; Superconductors (materials); Surface charge; Time-Dependent Density-Functional Theory (TDDFT); Transition metals; cluster/oxide interface; optical photo-absorption; Time-Dependent Density-Functional Theory (TDDFT); first-principles modeling; metal clusters; photo-enhanced processes
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules26226961

We report a computational study and analysis of the optical absorption processes of Ag and Au clusters deposited on the magnesium oxide (100) facet, both regular and including point defects. Ag and Au are taken as models of metal nanoparticles and their plasmonic response, MgO as a model of a simple oxide support. We consider oxide defects both on the oxygen anion framework (i.e., a neutral oxygen vacancy) and in the magnesium cation framework (i.e., replacing Mg with a transition metal: Cu or Co ). We relax the clusters' geometries via Density-Functional Theory (DFT) and calculate the photo-absorption spectra via Time-Dependent DFT (TDDFT) simulations on the relaxed geometries. We find that the substrate/cluster interaction induces a broadening and a red-shift of the excited states of the clusters, phenomena that are enhanced by the presence of an oxygen vacancy and its localized excitations. The presence of a transition-metal dopant does not qualitatively affect the spectral profile. However, when it lies next to an oxygen vacancy for Ag , it can strongly enhance the component of the cluster excitations perpendicular to the surface, thus favoring charge injection.