Plasmonic Nanocrystal Assembly–Semiconductor Hybrids for Boosting Visible to Near-Infrared Photocatalysis

Plasmonic metal-semiconductor hybrid photocatalysts have received much attention because of their wide light harvesting range and efficient charge carrier generation capability originating from plasmon energy transfer. Here, we introduce a plasmonic metal-semiconductor hybrid nanostructure consisting of a Au core-satellite assembly and crystalline TiO₂. The formation of Au@TiO₂-Au core-satellite assemblies using TiO₂ as a spacer and the subsequent growth of outer TiO₂ shells on the core-satellite assemblies, followed by calcination, successfully generated Au core-satellite assembly@TiO₂ nanostructures. Exquisite control over the growth of the TiO₂ interlayer enabled the regulation of the gap distance between the core and satellite Au nanocrystals within the same hybrid morphology. Due to the structural controllability of the present approach, the gap-distance-dependent plasmonic and photocatalytic properties of the hybrid nanostructures could be explored. The nanostructures possessing the most closely arranged Au nanocrystals showed high photocatalytic activity under visible to near-infrared light irradiation, which can be attributed to strong plasmon coupling between the core and satellite Au nanocrystals that can expedite the formation of intense plasmon energy and its transfer to TiO₂.