Variations in the Photoexcitation Mechanism of an Adsorbed Molecule on a Gold Nanocluster Governed by Interfacial Contact

We performed first-principles calculations on the optical response of a Au147azobenzene complex to elucidate the role of the interfacial contact between Au147 and azobenzene. Our calculations of photoexcited electron dynamics for different configurations of azobenzene adsorbed on the Au147 nanocluster revealed that the optical properties of the azobenzene moiety change markedly by the interfacial contact, even if the electronic structure in the ground state is almost unchanged. The optical absorption measured for isolated azobenzene weakens when the Au147-azobenzene interaction increases, while the absorption measured using the light field along the Au147-azobenzene alignment strengthens. The electronic excitation analysis showed that the mechanism of the charge-transfer excitation between Au147 and azobenzene changes remarkably depending on the strength of the interfacial interaction. We revealed that the optical property can be governed by the atomic-scale difference in the adsorption structure of azobenzene on a Au147 nanocluster. This study affords novel insights that could enable the photoexcitation mechanism to be controlled by designing the interface between a metal nanoparticle and a molecule.

Automated summary

We performed first-principles calculations to investigate the optical response of an Au147azobenzene complex and found that the interfacial contact between Au147 and azobenzene plays a significant role in modulating the optical properties of azobenzene. The absorption of isolated azobenzene weakens with an increase in the Au147-azobenzene interaction, while the absorption measured with light field along the Au147-azobenzene alignment strengthens. The charge-transfer excitation mechanism between Au147 and azobenzene also changes remarkably depending on the strength of the interfacial interaction.