High refractive index dielectric coating on plasmonic nanoantennas for strong visible light absorption in small transition metal nanoparticle reactors.

ABSTRACT

A more practical model for plasmonic core@shell-satellite antenna-reactor photocatalysts is promoted. In contrast to the mainstream view, total light absorption in the Pt nanoparticle (NP) reactors can be further improved by 70% after coating a 10-nm-thick high refractive index TiO2 shell on the large Ag antenna as a result of more Pt NPs undergoing high absorption enhancement. The enhancement effect is maximized at the electric quadrupole (EQ) resonance. Considering the high refractive index of the TiO2 coating and the embedding of the Pt NPs, the underlying physics is addressed within classical electrodynamics, making a necessary supplement to the conventional plasmonic near-field enhancement mechanism. These findings provide a general strategy for developing novel, to the best of our knowledge, visible light photocatalysts made of transition metals directly.