Mechanism of transition metal interaction with graphene sheet reflected in its plasmonic excitations: Effect of gas adsorption phenomena studied by a combination of solid state and molecular orbital approaches

In this study, plasmonic properties of transition metal atoms (Sc-Zn, Pd, Pt) adsorbed on various sites of graphene sheets were investigated before and after CO adsorption by density functional theory (DFT). To this aim, Electron Energy Loss Spectroscopy (EELS) of these systems were obtained by periodic DFT. The results indicated that the highest in-plane plasmon peaks undergo blue shifts after CO adsorption, in such a way that Co-graphene system demonstrates the highest blue shift of 2.42 eV from Visible to UV region. Also, out-of-plane plasmons do not exhibit significant sensitivity to CO adsorption. For deeper understanding of electronic structure of metalgraphene systems, appropriate molecular models were considered, and natural bond orbital (NBO) analysis applied. Comparison of solid-state net charges with the NBO charges showed that CO adsorption has more nonlocal characteristics, while the metal atom adsorption on bare graphene surface has more local nature. Moreover, Jahn-Teller distortion of metal adatom strongly depends on the net charges of nearest-neighbor C atoms on the surface. In addition, spin distribution on metal 3d orbitals plays a role to some extent. These results can be useful for experimental researchers who want to construct the sensors and optical devices based on metal-graphene interactions.

Automated summary

Plasmonic properties of transition metal atoms on graphene surfaces were studied, showing blue shifts of in-plane plasmon peaks after CO adsorption and different characteristics between metal adatom and CO adsorption.