TiO2 on Gold Nanostars Enhances Photocatalytic Water Reduction in the Near-Infrared Regime

The growth of a conformal layer of crystalline TiO2 on gold nanostars was achieved by a simple hydrothermal route preserving the large aspect ratio of the protruding spikes of the nanostar and enabled the photocatalytic evolution of hydrogen under near-infrared (NIR) illumination. The delicate structure of the underlying nanostars is otherwise extremely sensitive to atom migration. It has been revealed that the (101) crystal plane of anatase TiO2 grows epitaxially on the surface of gold, and TiO2 layer thickness and crystallinity can be controlled by varying synthesis conditions. TiO2-coated gold nanostars (AuNS@TiO2) displayed significantly enhanced photocatalytic activity under visible-NIR illumination compared with reported TiO2-coated gold nanoparticles and commercially available TiO2 nanoparticles. The high photocatalytic activity is attributed to effective hot electron generation via absorption of radiation via localized surface plasmon resonance modes of the spikes and further injection to the conduction band of the TiO2 shell across the gold nanoparticle-TiO2 interface.