Plasmonic Photocatalysis with Anisotropic Nanoparticles

Abstract

The energy stored in a photoexcited metal nanoparticle is capable of bringing out various chemical and physical transformations, which forms the basis of plasmonic photocatalysis. The interference from different nonradiative relaxation processes such as charge carrier generation and local heating is often observed during plasmonic photocatalysis. A fine-control on the factors governing the nonradiative relaxation pathways is essential to gain a better understanding on the mechanism of plasmonic photocatalysis. We studied the influence of interband vs intraband photo excitations on the photocatalytic activities of gold nanorods in two model reactions in plasmonic photocatalysis: (i) reduction of ferricyanide and (ii) NADH regeneration. Results from both systems indicate the predominant role of interband hot electrons in the photocatalytic reduction of substrates. During the reduction of ferricyanide, we observed a wavelength dependent etching of gold nanorods. Interband hot charge carriers enhanced etching the most, which also corroborates the predominant contribution of hot electrons. Likewise, wavelength dependent NADH regeneration studies conclusively proved the role of hot charge carriers in plasmonic photocatalysis. Our study resolves a long-standing gap in understanding the mechanistic details of plasmonic catalysis. We believe that this opens up numerous possibilities to custom engineer photocatalysts with unprecedented efficiency, amenable to easily modulated reaction conditions.